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Identifying the core microbial community in the gut of fungus-growing termites
Abstract
Gut microbes play a crucial role in decomposing lignocellulose to fuel termite societies, with protists in the lower termites and prokaryotes in the higher termites providing these services. However, a single basal subfamily of the higher termites, the Macrotermitinae, also domesticated a plant biomass-degrading fungus (Termitomyces), and how this symbiont acquisition has affected the fungus-growing termite gut microbiota has remained unclear. The objective of our study was to compare the intestinal bacterial communities of five genera (nine species) of fungus-growing termites to establish whether or not an ancestral core microbiota has been maintained and characterizes extant lineages. Using 454-pyrosequencing of the 16S rRNA gene, we show that gut communities have representatives of 26 bacterial phyla and are dominated by Firmicutes, Bacteroidetes, Spirochaetes, Proteobacteria, and Synergistetes. A set of 42 genus-level taxa was present in all termite species and accounted for 56–68% of the species-specific reads. Gut communities of termites from the same genus were more similar than distantly related species, suggesting that phylogenetic ancestry matters, possibly in connection with specific termite genus-level ecological niches. Finally, we show that gut communities of fungus-growing termites are similar to cockroaches, both at the bacterial phylum level and in a comparison of the core Macrotermitinae taxa abundances with representative cockroach, lower termite, and higher non-fungus-growing termites. These results suggest that the obligate association with Termitomyces has forced the bacterial gut communities of the fungus-growing termites towards a relatively uniform composition with higher similarity to their omnivorous relatives than to more closely related termites.This article is protected by copyright. All rights reserved.
... Our understanding of how host development directs changes in microbiomes predominantly comes from work on mammals, but non-mammal animals also experience marked shifts in diet at critical stages in life. For example, the tripartite fungus-farming termite (Macrotermitinae) symbiosis involves complex microbiomes 15,16 and a cultivated basidiomycete fungus as a sole food source for the termite host 17 . In most species, the fungal cultivar is absent for the rst several months of colony life, after which termite hosts transition to a fungal biomass diet. ...
... Termitomyces exhibits some degree of complementarity in degradative capabilities to the termites and their gut microbiota 22 and exhibits considerable phylogenetic congruence with termite hosts 17,24 , implying co-adaptation over millions of years of coevolution. In mature colonies, both termite guts and fungus combs host complex communities of bacterial symbionts 15,16 that are distinct between termite castes re ecting division of labour 25 to serve complementary roles to their termite and fungal host 22 . These bacterial communities are dominated by Firmicutes, Bacteroidetes, Spirochaetes, Proteobacteria, and Synergistetes 15,16 . ...
... In mature colonies, both termite guts and fungus combs host complex communities of bacterial symbionts 15,16 that are distinct between termite castes re ecting division of labour 25 to serve complementary roles to their termite and fungal host 22 . These bacterial communities are dominated by Firmicutes, Bacteroidetes, Spirochaetes, Proteobacteria, and Synergistetes 15,16 . A core set of bacterial genera are shared across species of fungus-farming termites 15 , and their functions are substantially different from those of other termites 26 , being reduced in plant degrading enzymes and enriched in fungal cell wall degrading enzymes 22,26,27 . ...
Microbiome assembly critically impacts the ability of hosts to access beneficial symbiont functions. Fungus-farming termites have coevolved with a fungal symbiont for plant biomass degradation and complex gut microbiomes that complement termite and fungal metabolism. A large subset of the bacterial community residing within termite guts are inherited (vertically transmitted) from the parental colony, while the fungal symbiont is, in most termite species, acquired from the environment (horizontally transmitted). It has remained unknown how the gut microbiota sustains incipient colonies prior to the acquisition of the fungal cultivar, and how, if at all, microbial functions are modulated by fungus garden establishment. Here we test this by determining the composition and predicted functions of the gut microbiome using metabarcoding and shotgun metagenomics, respectively. We focus our functional predictions on bacterial carbohydrate-active enzyme and nitrogen cycling genes and verify compositional patterns of the former through enzyme activity assays. Our findings reveal that the vast majority of microbial functions are encoded in the inherited microbiome, and that the establishment of fungal gardens incurs only minor modulations of predicted bacterial capacities for CAZy and N-metabolism. While we cannot rule out that other symbiont functions are obtained post-fungus garden establishment, our findings suggest that farming termite hosts are equipped with a near-complete set of gut microbiome functions at the earliest stages of colony life, likely contributing to the high extent of specificity and coevolution observed between termite hosts, gut microbiomes, and the fungal cultivar.
... Here, we assess vertical transmission from parent to offspring colonies for the first time by tracking bacterial strains across pedigrees of the fungus-farming termite Macrotermes natalensis. As in other termites, fungus-farming termites (Termitidae: Macrotermitinae) host a specific [32], consistent [33,34], and co-evolved gut microbiome [35,36]. Given the consistent complexity of the microbiome and evolutionary patterns of mixed-mode transmission [11,27], we first hypothesized that a subset of the colony microbiome would be vertically transmitted and contain a conserved diverse set of microbes. ...
... Pedigree-specific ASVs accounted for many of these genera (electronic supplementary material, table S3), and ASV diversity within genera was also comparable (figure 2b). Thus, pedigrees inherit a diverse and congruent set of microbes, including multiple taxa that are consistently associated with fungus-farming termites [31,34], implying that offspring colonies have predictable access to co-adapted symbionts. ...
... By contrast, 13 genera that increased in abundance in founding reproductives completed vertical transmission across all pedigrees (figure 3b; electronic supplementary material, table S4). These genera thus appear critical for hosts, consistent with findings that several have diversified with termite hosts [11,27] and are members of the core microbiome [34]. The subsequent transfer to offspring colonies did not drastically alter the inherited microbiome, but some inherited genera either significantly royalsocietypublishing.org/journal/rspb Proc. ...
Mutualistic coevolution can be mediated by vertical transmission of symbionts between host generations. Termites host complex gut bacterial communities with evolutionary histories indicative of mixed-mode transmission. Here, we document that vertical transmission of gut bacterial strains is congruent across parent to offspring colonies in four pedigrees of the fungus-farming termite Macrotermes natalensis. We show that 44% of the offspring colony microbiome, including more than 80 bacterial genera and pedigree-specific strains, are consistently inherited. We go on to demonstrate that this is achieved because colony-founding reproductives are selectively enriched with a set of non-random, environmentally sensitive and termite-specific gut microbes from their colonies of origin. These symbionts transfer to offspring colony workers with high fidelity, after which priority effects appear to influence the composition of the establishing microbiome. Termite reproductives thus secure transmission of complex communities of specific, co-evolved microbes that are critical to their offspring colonies. Extensive yet imperfect inheritance implies that the maturing colony benefits from acquiring environmental microbes to complement combinations of termite, fungus and vertically transmitted microbes; a mode of transmission that is emerging as a prevailing strategy for hosts to assemble complex adaptive microbiomes.
... Only phylotypes discussed in the text are presented with different colors at the phylum level: blue, Pseudomonoadota; magenta, Bacillota; orange, Actinomycetota; green, Bacteroidota; grey, Mycoplasmatota; and black, other phyla. References are indicated in square brackets [38,[48][49][50][51][52][53][54][55]. Average and standard deviation are calculated assuming a Gaussian distribution of the population. ...
... This termite group, consisting only of the subfamily Macrotermitinae, cultivates symbiotic fungi on the plant material, which is partially degraded by the fungi and provided to the termites [93,103]. Gut bacterial communities of nine fungus-growing termite species are highly dominated by Bacteroidota and Bacillota, followed by Spirochaetota, Pseudomonadota, and Synergistota formerly "Synergistetes" (average 32,34,9,9, and 7% of relative abundance, respectively) ( Figure 1C) [53]. In those phyla, the most abundantly and prevalently detected genera are Alistipes 1 (Bacteroidota, 10.9% of relative abundance), Treponema 1a (Spirochaetota, 5.6%), Ruminococcaceae Gut Cluster 1 (Bacillota, 4.3%), Ca. ...
... Comparable results have been observed in several studies [95,102,104]. The dominance of Bacteroidota and Bacillota and the relatively high abundance of Synergistota in Macrotermitinae are similar characteristics to those of omnivorous cockroaches rather than in other termites, suggesting that the unique deeding habits rather than host phylogeny shape gut microbiota of these insects [53]. ...
Simple Summary
It is increasingly recognized that gut microbiota plays crucial roles in host health and function. Various ecological and physiological factors influence the structure of the gut microbial community, resulting in, for example, the formation of enterotypes or the development of inflammatory disease by dysbiosis in humans. Social insects, such as bees, ants, and termites, are known to harbor unique but stable gut microbiota among individuals, which can be a good model to understand how gut microbial communities are shaped and stably maintained in host populations. This review summarizes current knowledge regarding structures of gut microbiota in social insects. Microbes colonizing those insect guts and differentially abundant among host castes are mainly featured.
Abstract
Gut bacterial communities assist host animals with numerous functions such as food digestion, nutritional provision, or immunity. Some social mammals and insects are unique in that their gut microbial communities are stable among individuals. In this review, we focus on the gut bacterial communities of eusocial insects, including bees, ants, and termites, to provide an overview of their community structures and to gain insights into any general aspects of their structural basis. Pseudomonadota and Bacillota are prevalent bacterial phyla commonly detected in those three insect groups, but their compositions are distinct at lower taxonomic levels. Eusocial insects harbor unique gut bacterial communities that are shared within host species, while their stability varies depending on host physiology and ecology. Species with narrow dietary habits, such as eusocial bees, harbor highly stable and intraspecific microbial communities, while generalists, such as most ant species, exhibit relatively diverse community structures. Caste differences could influence the relative abundance of community members without significantly altering the taxonomic composition.
... We assessed vertical transmission from parent to offspring colonies in four distinct termite pedigrees of the fungus-farming termite Macrotermes natalensis (Seite et al., 2022). Fungus-farming termites host a speci c (Dietrich et al., 2014), consistent (Otani et al., 2016;Otani et al., 2014), and co-evolved gut microbiome (Hu et al., 2019;Poulsen et al., 2014), and recently, offspring colonies were shown to maintain a substantial portion of microbes inherited from founding reproductives (Diouf et al., 2023). ...
... We assessed vertical transmission from parent to offspring colonies in four distinct termite pedigrees of the fungus-farming termite Macrotermes natalensis (Seite et al., 2022). Fungus-farming termites host a speci c (Dietrich et al., 2014), consistent (Otani et al., 2016;Otani et al., 2014), and co-evolved gut microbiome (Hu et al., 2019;Poulsen et al., 2014), and recently, offspring colonies were shown to maintain a substantial portion of microbes inherited from founding reproductives (Diouf et al., 2023). ...
... Further, pedigree-speci c ASVs accounted for many of these genera ( Figure 2 -source data 1), and ASV diversity within genera was comparable across pedigrees ( Figure 2B). Thus, pedigrees inherit a diverse and congruent set of microbes, including multiple taxa that are consistently associated with fungus-growing termites (Otani et al., 2014) and known to be maintained in offspring colonies (Diouf et al., 2023). Microbiome consistency in transmission ensures that offspring colonies have predictable access to bene cial co-adapted symbionts. ...
Mutualistic co-evolution can be mediated by vertical transmission of symbionts between host generations. Organisms exhibit adaptations that ensure optimal microbial inheritance, yet the extent to which this applies to social insects, such as termites that have co-evolved with gut microbes, is poorly resolved. Here, we document consistent vertical transmission across colony generations of fungus-farming termites. Inherited bacteria comprise 44% of the microbiome, over 80 genera, and strains that are specific to termite pedigrees. We show that the superorganism, consisting of reproductives and workers, analogous to gametes and soma of an organism, is adapted to vertically transmit a distinct microbial community with high fidelity. Microbial inheritance is achieved because colony-founding reproductives are endowed with a set of non-random, environmentally-sensitive, and termite-specific gut microbes derived from their colonies of origin. Reproductives biparentally transmit these symbionts to offspring colony workers, where priority effects dictate the composition of the forming colony microbiome. Superorganismal gametes, the reproductives, are thus adapted to secure transmission of entire communities of specific, co-evolved microbes that are critical to the colony microbiome later retained by workers. Extensive vertical transmission aligns with evolutionary patterns of termite-bacterial co-diversification. This colony-level inheritance extends models of transmission from individual organisms to superorganisms, both of which demonstrate adaptations to retain symbiotic fidelity and mixed-mode transmission conducive to mutualism.
... Synergistota are considered amino acid-degrading bacteria (41). Spirochaetota are generally infrequent in fungus-growing termites (49,50), but they may be involved in reductive acetogenesis and nitrogen fixation (51). Despite this, we have a generally poor understanding of where different plant components are targeted during the stages in the decomposition process and the presence and hence potential importance of specific bacterial community members in the processes. ...
... Breznakia blatticola and Breznakia pachnodae are considered fermenters of glucose to formate, ethanol, and acetate (63,64). The increased abundance of the genus "Candidatus Tammella" has also been recorded in the gut of Macrotermitinae (37,50) and dry wood termites (65), and it has been suggested that some members of this genus are involved in amino acid fermentation (65). ...
... The fresh comb showed increased amounts of lignin units, cellulose, and hemicellulose, while it showed reduced amounts of simple sugars. Previous reports also documented the enrichment of Dysgonomonas (36,50) and Treponema (40) in the fungus comb. Metagenomic analysis of Macrotermes annandalei and other termites revealed that some members of Dysgonomonas have the capacity to break down cellulose (67), and Treponema isolates play a key role in nitrogen fixation, reductive acetogenesis, hemicellulose degradation (68), and aromatic ring cleavage (69). ...
Fungus-growing termites are efficient in degrading and digesting plant substrates, achieved through the engagement of symbiotic gut microbiota and lignocellulolytic Termitomyces fungi cultivated for protein-rich food. Insights into where specific plant biomass components are targeted during the decomposition process are sparse. In this study, we performed several analytical approaches on the fate of plant biomass components and did amplicon sequencing of the 16S rRNA gene to investigate the lignocellulose digestion in the symbiotic system of the fungus-growing termite Odontotermes formosanus (Shiraki) and to compare bacterial communities across the different stages in the degradation process. We observed a gradual reduction of lignocellulose components throughout the process. Our findings support that the digestive tract of young workers initiates the degradation of lignocellulose but leaves most of the lignin, hemicellulose, and cellulose, which enters the fresh fungus comb, where decomposition primarily occurs. We found a high diversity and quantity of monomeric sugars in older parts of the fungus comb, indicating that the decomposition of lignocellulose enriches the old comb with sugars that can be utilized by Termitomyces and termite workers. Amplicon sequencing of the 16S rRNA gene showed clear differences in community composition associated with the different stages of plant biomass decomposition which could work synergistically with Termitomyces to shape the digestion process. IMPORTANCE Fungus-farming termites have a mutualist association with fungi of the genus Termitomyces and gut microbiota to support the nearly complete decomposition of lignocellulose to gain access to nutrients. This elaborate strategy of plant biomass digestion makes them ecologically successful dominant decomposers in (sub)tropical Old World ecosystems. We employed acid detergent fiber analysis, high-performance anion-exchange chromatography (HPAEC), high-performance liquid chromatography (HPLC), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), pyrolysis gas chromatography-mass spectrometry (Py-GC-MS), and amplicon sequencing of the 16S rRNA gene to examine which lignocellulose components were digested and which bacteria were abundant throughout the decomposition process. Our findings suggest that although the first gut passage initiates lignocellulose digestion, the most prominent decomposition occurs within the fungus comb. Moreover, distinct bacterial communities were associated with different stages of decomposition, potentially contributing to the breakdown of particular plant components.
... Bacterial colonies were isolated on the basis of morphology and subcultured until isolated colonies were obtained for further use. To identify these cultures, DNA from individual bacterial colonies was extracted with CTAB buffer and amplified with the primer set 341F/806R [30] for a portion of the 16S rRNA gene (supplementary methods S1). Further selection of these strains was done based on their sequence similarity so that each of these 38 selected strains differ from each other by at least a single SNP in their 16S rRNA gene sequence. ...
... To identify the microbiota present within termite castes and fungus combs, the V3-V4 region of the 16S rRNA gene was amplified using primers 341F/806R [30]. Six different DNA samples (major worker, minor worker, nymph, male alate, female alate and comb) were prepared for pan-microbiome analysis on the Nanopore platform ( supplementary methods S1). ...
... To test how representative these communities are across different species of Odontotermes, a comparison was done with the data obtained in this study with previously published data from nineteen different species of Odontotermes [30,40,41] using weighted principal coordinate analysis (PCoA) in phyloseq package of R. The microbial abundance datasets obtained from this study were combined with all the six different samples and a consolidated list of bacterial genera was made for comparison. We also analyzed the caste specific compositional differences in bacterial communities across different fungus-growing termite genera [28,30,40,41] using weighted PCoA in R. ...
Insects that farm monocultures of fungi are canonical examples of nutritional symbiosis as well as independent evolution of agriculture in non-human animals. But just like in human agriculture, these fungal crops face constant threat of invasion by weeds which, if unchecked, take over the crop fungus. In fungus-growing termites, the crop fungus (Termitomyces) faces such challenges from the weedy fungus Pseudoxylaria. The mechanism by which Pseudoxylaria is suppressed is not known. However, evidence suggests that some bacterial secondary symbionts can serve as defensive mutualists by preventing the growth of Pseudoxylaria. However, such secondary symbionts must possess the dual, yet contrasting, capabilities of suppressing the weedy fungus while keeping the growth of the crop fungus unaffected. This study describes the isolation, identification, and culture-dependent estimation of the roles of several such putative defensive mutualists from the colonies of the wide-spread fungus-growing termite from India, Odontotermes obesus. From the 38 bacterial cultures tested, a strain of Pseudomonas showed significantly greater suppression of the weedy fungus than the crop fungus. Moreover, a 16S rRNA pan-microbiome survey, using the Nanopore platform, revealed Pseudomonas to be a part of the core microbiota of O. obesus. A meta-analysis of microbiota composition across different species of Odontotermes also confirms the widespread prevalence of Pseudomonas within this termite. These lines of evidence indicate that Pseudomonas could be playing the role of defensive mutualist within Odontotermes.
... A dilution series (1x -10 -6 x) of these homogenates were then plated on Luria Bertani Agar (LBA) and Tryptic Soya Agar (TSA) for any bacterial growth at 30˚C for 24 hrs. For strain identi cation, DNA from individual bacterial colonies was extracted with CTAB buffer and ampli ed with the primer set 341F/806R [31] for a portion of the 16S rRNA gene (supplementary methods S1). The sequences thus obtained were used to identify the bacterial strains by a BLAST search in NCBI. ...
... Sample preparation, running the Nanopore platform and obtaining sequences To identify the microbiota present within termite castes and fungus combs, the V3-V4 region of the 16S rRNA gene was ampli ed using primers 341F/806R [31]. Six different DNA samples (major worker, minor worker, nymph, male alate, female alate and comb) were prepared for pan-microbiome analysis on the Nanopore platform ( supplementary methods S1). ...
... We compared the gut and comb microbiota from the other known Odontotermes sp. [31,40,41] with the results obtained from this study using weighted principle coordinate analysis (PCoA) in phyloseq package of R. Nineteen different microbiota were used for the similarity analysis as these also ampli ed the same 16S rRNA gene region and used the same reference database. ...
Insects that farm monocultures of fungi are canonical examples of nutritional symbiosis as well as independent evolution of agriculture in non-human animals. But just like in human agriculture, these fungal crops face constant threat of invasion by weeds which, if unchecked, takes over the crop fungus. In fungus-growing termites, the crop fungus ( Termitomyces ) faces such challenges from the parasitic fungus Pseudoxylaria . The mechanism by which Pseudoxylaria is suppressed is not known. However, evidence suggests that some bacterial secondary symbionts can serve as defensive mutualists by preventing the growth of Pseudoxylaria . However, such secondary symbionts must possess the dual, yet contrasting, capabilities of suppressing the weedy fungus while keeping the growth of the crop fungus unaffected. This study describes the isolation, identification and culture-dependent estimation of the roles of several such putative defensive mutualists from the colonies of the wide-spread fungus-growing termite from India, Odontotermes obesus . From the 38 bacterial cultures tested, a strain of Pseudomonas showed significantly greater suppression of the weedy fungus than the crop fungus. Moreover, a 16S rRNA pan-microbiome survey, using the Nanopore platform, revealed Pseudomonas to be a part of the core microbiota of Odontotermes obesus . A meta-analysis of microbiota composition across different species of Odontotermes also confirms the wide-spread prevalence of Pseudomonas within this termite. These evidence indicate that Pseudomonas could be playing the role of defensive mutualist within Odontotermes .
... We also identified 97 abundant bacterial OTUs that are predominantly associated with termite bodies (referred to as body-associated bacteria), termite galleries (referred to as galleryassociated bacteria), or control wood samples (referred to as gallery-depleted bacteria). Consequently, our results show that termites not only shape the bacterial communities inside their gut (6,7,40) but also those in their environment. ...
... The bacterial communities associated with termite galleries are more diverse than (5)(6)(7)40), indicating that the majority of bacterial OTUs associated with termite bodies are gut specialists. The termite gut is a highly specialized habitat, with extreme physicochemical properties, in some species having a pH of Ͼ12 (41), and is largely populated by bacteria found nowhere else (3)(4)(5). ...
... We found that the bacterial communities associated with termite galleries are specific to termite species and differ from those of termite bodies and wood controls. These results concur with previous studies that found that bacterial communities associated with nests differ from those of surrounding soil and wood samples (7,34,37,38). Exclusion experiments have also shown that termites influence the bacterial communities in wood pieces (33). Importantly, our results show that the differences between galleries of different termite species and wood control samples are subtler than those found for gut bacterial communities, suggesting that the gallery-associated bacteria are loosely associated with termites. ...
All termites have established a wide range of associations with symbiotic microbes in their guts. Some termite species are also associated with microbes that grow in their nests, but the prevalence of these associations remains largely unknown. Here, we studied the bacterial communities associated with the termites and galleries of three wood-feeding termite species by using 16S rRNA gene amplicon sequencing. We found that the compositions of bacterial communities among termite bodies, termite galleries, and control wood fragments devoid of termite activities differ in a species-specific manner. Termite galleries were enriched in bacterial operational taxonomic units (OTUs) belonging to Rhizobiales and Actinobacteria , which were often shared by several termite species. The abundance of several bacterial OTUs, such as Bacillus , Clostridium , Corynebacterium , and Staphylococcus , was reduced in termite galleries. Our results demonstrate that both termite guts and termite galleries harbor unique bacterial communities.
IMPORTANCE As is the case for all ecosystem engineers, termites impact their habitat by their activities, potentially affecting bacterial communities. Here, we studied three wood-feeding termite species and found that they influence the composition of the bacterial communities in their surrounding environment. Termite activities have positive effects on Rhizobiales and Actinobacteria abundance and negative effects on the abundance of several ubiquitous genera, such as Bacillus , Clostridium , Corynebacterium , and Staphylococcus . Our results demonstrate that termite galleries harbor unique bacterial communities.
... Their gut microbiome was reported crucial in multiple ecological processes, including growth promotion, nutrient acquisition, energy harvest and stress tolerance (Claesson et al., 2012). For example, the hindguts of termites have been reported as microbial bioreactors in the metabolic processes and cellulose digestion (Otani et al., 2014;Brune, 2014). Moreover, researchers have demonstrated a range of antimicrobial activities in gut microbiome of soil invertebrates possibly relating to nutrition or defense against pathogens (Gibson et al., 2015;Bahrndorff et al., 2018;Agamennone et al., 2019). ...
... Lett., 2024, 6(1): 230195 together, and microbial ecology are dictated by environmental factors and microbial interactions with the host and among microbes (Ellegaard and Engel, 2019). Microorganisms form a complex gut niche together through competition and symbiosis (Otani et al., 2014;Callegari et al., 2021). As other microbiome components are not well characterized in invertebrate guts, more studies are needed to help clarify these complex interactions to deepen our understanding on ecological associations in gut microbiome. ...
The unique gut habitat led to a core intestinal microbiome in diverse soil ecosystems.
The collembolan guts may help eliminate soil pathogens.
Host-selection carried more weight on community assembly of gut microbiome.
Soil invertebrates are widely distributed in the ecosystem and are essential for soil ecological processes. Invertebrate gut microbiome plays an important role in host health and has been considered as a hidden microbial repository. However, little is known about how gut microbiome in soil invertebrates respond to diverse soil ecosystems. Based on a laboratory microcosm experiment, we characterized the assembling of microbiome of soil collembolans (Folsomia candida) from six representative regions of the soil ecosystem which they inhabit. Results showed that collembolan gut microbial communities differed significantly from their surrounding soil microbial communities. A dominant core gut microbiome was identified in gut habitat. Community analyses indicated that deterministic process dominated in the community assembly of collembolan gut microbiome. The results further demonstrate a dominant contribution of host selection in shaping gut microbiome. It is also worthy to mention that pathogens, such as common agricultural phytopathogenic fungi Fusarium, were involved in core microbiome, indicating that collembolans could act as vectors of pathogens. Our results unravelled the existence of gut core microbiome of collembolans in soil ecosystems and provided new insights for understanding the crucial role of gut microbiome of soil fauna in maintaining microbial biodiversity and stability of soil ecosystems.
... Possible reasons for this are that the gut environment limits the production of secondary metabolites by actinomycetes or that actinomycetes require a period of response time in response to Metarhizium and the production of secondary metabolites takes some time to be effective. Hosts are usually associated with a specific group of microorganisms: 78.6% of the core microbiota of higher termites are distributed in the phyla Bacteroides and Firmicutes, and we also found alterations in the abundance of the core microorganism Firmicutes (Otani et al., 2014). Bacteroidetes and Firmicutes ( Figure 3E) are associated with fungal cell wall degradation, and it has been proposed that they are able to adapt bacteria to the gut environment through DNA transfer between themselves and other bacteria (Ning et al., 2013). ...
... It has been found that termite hosts are closely associated with a specific group of microorganisms, which are called core microbiota. Most of the core taxa of cultivated termites are distributed in the Bacteroidetes and Firmicutes, and the need for a link between the composition and function of the gut flora has been described (Otani et al., 2014). The changes in diversity and composition that we observed responded functionally to the reduction of relevant pathways at 12 h post-infection, indicating the beginning of changes in the gut environment. ...
The crosstalk between gut microbiota and host immunity has emerged as one of the research foci of microbiome studies in recent years. The purpose of this study was to determine how gut microbes respond to fungal infection in termites, given their reliance on gut symbionts for food intake as well as maintaining host health. Here, we used Metarhizium robertsii , an entomopathogenic fungus, to infect Odontotermes formosanus , a fungus-growing termite in the family Termitidae, and documented changes in host gut microbiota via a combination of bacterial 16S rDNA sequencing, metagenomic shotgun sequencing, and transmission electron microscopy. Our analyses found that when challenged with Metarhizium , the termite gut showed reduced microbial diversity within the first 12 h of fungal infection and then recovered and even surpassed pre-infection flora levels. These combined results shed light on the role of gut flora in maintaining homeostasis and immune homeostasis in the host, and the impact of gut flora dysbiosis on host susceptibility to infection.
... 14,28,29 The two gut passages (inoculation and nal consumption) place the termite gut central in the symbiosis, and guts harbour diverse and distinct bacterial communities, containing 100s of bacterial lineages, predominantly in the phyla Firmicutes, Bacteroidetes, and Proteobacteria. 13,30,31 Dominant members are distinct from those of other termitesand the ancestral cockroachesimplying that community shis in compositions and functions have been associated with the transition from a plant to a fungal biomassbased diet of the termite host. 30,31 Across termite species within the fungus-growing termite sub-family, conserved gut community compositions suggest specicities in association for reasons Fig. 1 The fungus-farming termite cooperation and origins of the natural products. ...
... 13,30,31 Dominant members are distinct from those of other termitesand the ancestral cockroachesimplying that community shis in compositions and functions have been associated with the transition from a plant to a fungal biomassbased diet of the termite host. 30,31 Across termite species within the fungus-growing termite sub-family, conserved gut community compositions suggest specicities in association for reasons Fig. 1 The fungus-farming termite cooperation and origins of the natural products. (A) Nymph and worker termite from a Macrotermes bellicosus colony from Côte d'Ivoire (Nick Bos). ...
Covering: September 1972 to December 2020Explorations of complex symbioses have often elucidated a plethora of previously undescribed chemical compounds that may serve ecological functions in signalling, communication or defence. A case in point is the subfamily of termites that cultivate a fungus as their primary food source and maintain complex bacterial communities, from which a series of novel compound discoveries have been made. Here, we summarise the origins and types of 375 compounds that have been discovered from the symbiosis over the past four decades and discuss the potential for synergistic actions between compounds within the complex chemical mixtures in which they exist. We go on to highlight how vastly underexplored the diversity and geographic distribution of the symbiosis is, which leaves ample potential for natural product discovery of compounds of both ecological and medical importance.
... Lastly, Actinobacteria are consistently present and more abundant in fungus combs (14) than guts (Fig. 1C). Thus, Actinobacteria contributions are conceivably in fungus combs, while their presence in termite guts is more likely due to ingestion from the plant substrate, soil, or the comb (14,28,29). ...
... The persistent similarities in genomes irrespective of their origin being from termite colonies or free living suggest that the termite-obtained Actinobacteria do not display unique genomic signatures that point to specialized biomass decomposition or antimicrobial production. This could suggest that they may randomly colonize fungus combs or termites from the substrate harvested by the termites, from ingested soil (14,28,29,48), or from contact with the surrounding soil. Although the net positive (mutualistic) benefit to the termites is currently not known, their presence implies potential effects in the comb environment, and considering that they are not removed by the termites, it makes it unlikely that they negatively impact the termite-Termitomyces association. ...
Actinobacteria, one of the largest bacterial phyla, are ubiquitous in many of Earth’s ecosystems and often act as defensive symbionts with animal hosts. Members of the phylum have repeatedly been isolated from basidiomycete-cultivating fungus-farming termites that maintain a monoculture fungus crop on macerated dead plant substrate. The proclivity for antimicrobial and enzyme production of Actinobacteria make them likely contributors to plant decomposition and defense in the symbiosis. To test this, we analyzed the prophylactic (biosynthetic gene cluster [BGC]) and metabolic (carbohydrate-active enzyme [CAZy]) potential in 16 (10 existing and six new genomes) termite-associated Actinobacteria and compared these to the soil-dwelling close relatives. Using antiSMASH, we identified 435 BGCs, of which 329 (65 unique) were similar to known compound gene clusters, while 106 were putatively novel, suggesting ample prospects for novel compound discovery. BGCs were identified among all major compound categories, including 26 encoding the production of known antimicrobial compounds, which ranged in activity (antibacterial being most prevalent) and modes of action that might suggest broad defensive potential. Peptide pattern recognition analysis revealed 823 (43 unique) CAZymes coding for enzymes that target key plant and fungal cell wall components (predominantly chitin, cellulose, and hemicellulose), confirming a substantial degradative potential of these bacteria. Comparison of termite-associated and soil-dwelling bacteria indicated no significant difference in either BGC or CAZy potential, suggesting that the farming termite hosts may have coopted these soil-dwelling bacteria due to their metabolic potential but that they have not been subject to genome change associated with symbiosis. © 2021 Murphy et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license.
... Both cultivate specific fungi as colony food source and their bacterial mutualists produce antifungals to protect the cultivar. Some 30 Ma Macrotermitinae termites (of which there are some 350 species) evolved the cultivation of basidiomycetes within the genus Termitomyces as their primary food source [35][36][37]. Termitomyces is subject to parasitism by opportunistic fungi belonging to the genus Pseudoxylaria spp. and competition from fungi such as Trichoderma or Beauveria [38][39][40][41]. ...
... It is likely that the Macrotermitinae employ multiple strategies to control such antagonists and production of antifungals is one of them [38,40]. So far, seven prokaryotic phyla have been identified in the Macrotermitinae's gut flora [35]. Among them, Bacillus strains are dominant and can produce antifungals. ...
Arthropods can produce a wide range of antifungal compounds, including specialist proteins, cuticular products, venoms and haemolymphs. In spite of this, many arthropod taxa, particularly eusocial insects, make use of additional antifungal compounds derived from their mutualistic association with microbes. Because multiple taxa have evolved such mutualisms, it must be assumed that, under certain ecological circumstances, natural selection has favoured them over those relying upon endogenous antifungal compound production. Further, such associations have been shown to persist versus specific pathogenic fungal antagonists for more than 50 million years, suggesting that compounds employed have retained efficacy in spite of the pathogens' capacity to develop resistance. We provide a brief overview of antifungal compounds in the arthropods' armoury, proposing a conceptual model to suggest why their use remains so successful. Fundamental concepts embedded within such a model may suggest strategies by which to reduce the rise of antifungal resistance within the clinical milieu.
... These 10 core families made up an average of 84% of the total gut bacteria for all individuals. A large proportion of these families were anaerobic, fermentative bacteria, from the phyla Firmicutes and Bacteroidetes, including the families Ruminococcaceae and Lachnospiraceae, known to degrade complex plant material (37), and Rikenellaceae, which is common in fungus-cultivating termites and cockroaches and aids with the digestion of proteins (38)(39)(40). Fifteen percent of the gut bacteria were anaerobic, sulfate-reducing bacteria from the family Desulfovibrionaceae (Proteobacteria-Deltaproteobacteria), a family also found in the digestive tracts of fungus-cultivating termites, cockroaches, and humus-feeding scarab larvae (11,38,39). Five percent of the gut community of Cephalodesmius were from the phylum Planctomycetes, a phylum also found in detritivorous species (39,41,42), but not recorded in dung beetles, with the exception of a single detritivorous species that eats decaying leaves (27). ...
... A large proportion of these families were anaerobic, fermentative bacteria, from the phyla Firmicutes and Bacteroidetes, including the families Ruminococcaceae and Lachnospiraceae, known to degrade complex plant material (37), and Rikenellaceae, which is common in fungus-cultivating termites and cockroaches and aids with the digestion of proteins (38)(39)(40). Fifteen percent of the gut bacteria were anaerobic, sulfate-reducing bacteria from the family Desulfovibrionaceae (Proteobacteria-Deltaproteobacteria), a family also found in the digestive tracts of fungus-cultivating termites, cockroaches, and humus-feeding scarab larvae (11,38,39). Five percent of the gut community of Cephalodesmius were from the phylum Planctomycetes, a phylum also found in detritivorous species (39,41,42), but not recorded in dung beetles, with the exception of a single detritivorous species that eats decaying leaves (27). ...
Gut microbes play an important role in the biology and evolution of insects. Australian native dung beetles (Scarabaeinae) present an opportunity to study gut microbiota in an evolutionary context as they come from two distinct phylogenetic lineages and some species in each lineage have secondarily adapted to alternative or broader diets. In this study, we characterised the hindgut bacterial communities found in 21 species of dung beetles across two lineages using 16S rRNA sequencing. We found that gut microbial diversity was more dependent on host phylogeny and gut morphology than specific dietary preferences or environment. In particular, gut microbial diversity was highest in the endemic, flightless genus Cephalodesmius that feeds on a broad range of composted organic matter. The hindgut of Cephalodesmius harbours a highly conserved core set of bacteria suggesting that the bacteria are symbiotic. Symbiosis is supported by the persistence of the core microbiota across isolated beetle populations and between species in the genus. A co-evolutionary relationship is supported by the expansion of the hindgut to form a fermentation chamber and the fermentative nature of the core microbes. In contrast, Australian species of the widespread dung beetle genus Onthophagus, specialise on a single food resource such as dung or fungus, exhibit minimal food processing behaviour, have a short, narrow hindgut and a variable gut microbiota with relatively few core bacterial taxa. A conserved, complex gut microbiota is hypothesised to be unnecessary for this highly mobile genus.
IMPORTANCE
Dung beetles are a very important part of an ecosystem because of their role in the removal and decomposition of vertebrate dung. It has been suspected that symbiotic gut bacteria facilitate this role, a hypothesis that we have explored with high throughput barcoding. We found that differences in hindgut morphology had the greatest effect on the bacterial community composition. Species with a hindgut fermentation chamber harboured a distinctly different hindgut community compared to those species with a narrow, undifferentiated hindgut. Diet and phylogeny were also associated with differences in gut community. Further understanding of the relationships between dung beetles and their gut microbes will provide insights into the evolution of their behaviours and how gut communities contribute to their fitness.
... Termites of the subfamily Macrotermitinae are an intriguing exception to this rule, because they uniquely rely on cultivated external fungal symbionts for the breakdown of lignocellulose. Their unique diet composed of lignocellulose and fungal biomass, is richer in nitrogen compared to typical wood-feeding termites [48] , and positions them closer to detritivores, a trait also mirrored in their gut microbiome structure [49][50][51] . Regardless, these symbiotic interactions mesh the insect's own adaptations with the contributions of microbial symbionts to achieve an efficient extraction of nutrients from this complex resource. ...
Decaying wood, while an abundant and stable resource, presents considerable nutritional challenges due to its structural rigidity, chemical recalcitrance, and low nitrogen content. Despite these challenges, certain insect lineages have successfully evolved saproxylophagy (consuming and deriving sustenance from decaying wood), impacting nutrient recycling in ecosystems and carbon sequestration dynamics. This study explores the uneven phylogenetic distribution of saproxylophagy across insects and delves into the evolutionary origins of this trait in disparate insect orders. Employing a comprehensive analysis of gut microbiome data, from both saproxylophagous insects and their non-saproxylophagous relatives, including new data from unexplored wood-feeding insects, this Hypothesis paper discusses the broader phylogenetic context and potential adaptations necessary for this dietary specialization. The study proposes the “Detritivore-First Hypothesis,” suggesting an evolutionary pathway to saproxylophagy through detritivory, and highlights the critical role of symbiotic gut microbiomes in the digestion of decaying wood.
... Exploring core and differentially abundant gut microbiome communities in lepidopteran insect is a key to understanding how different host plants affect their development, behavior, adaptation, and preference (Paniagua Voirol et al., 2018;Zhang et al., 2022). The core microbial communities support conserved biological processes, and transient bacteriomes provide quick and plastic metabolic competencies against extrinsic disturbances or host switches (Otani et al., 2014;Jones et al., 2019;Chakraborty et al., 2020;Näsvall et al., 2021;Oliveira et al., 2022). Host feeding is a crucial factor underlying the gut microbial assemblage (Gayatri Priya et al., 2012;Jones et al., 2019;Lv et al., 2021;Malacrinò, 2022). ...
Diet composition is vital in shaping gut microbial assemblage in many insects. Minimal knowledge is available about the influence of transgenerational diet transition on gut microbial community structure and function in polyphagous pests. This study investigated transgenerational diet-induced changes in Spodoptera littoralis larval gut bacteriome using 16S ribosomal sequencing. Our data revealed that 88% of bacterial populations in the S. littoralis larval gut comprise Proteobacteria, Firmicutes, Actinobacteria , and Bacteroidetes . The first diet transition experiment from an artificial diet (F0) to a plant diet (F1), cabbage and cotton, caused an alteration of bacterial communities in the S. littoralis larval gut. The second transgenerational diet switch, where F1 larvae feed on the same plant in the F2 generation, displayed a significant variation suggesting further restructuring of the microbial communities in the Spodoptera larval gut. F1 larvae were also challenged with the plant diet transition at the F2 generation (cabbage to cotton or cotton to cabbage). After feeding on different plant diets, the microbial assemblage of F2 larvae pointed to considerable differences from other F2 larvae that continued on the same diet. Our results showed that S. littoralis larval gut bacteriome responds rapidly and inexplicably to different diet changes. Further experiments must be conducted to determine the developmental and ecological consequences of such changes. Nevertheless, this study improves our perception of the impact of transgenerational diet switches on the resident gut bacteriome in S. littoralis larvae and could facilitate future research to understand the importance of symbiosis in lepidopteran generalists better.
... The most representative taxon in the fungal community is the lichen Myriospora smaragdula, which is well adapted to an exposed environment characterised by harsh conditions and adopts a photolithoautotrophic strategy for survival (Purvis et al., 2000;Rosa et al., 2020). The rocky and harsh characteristics of the soil outside the cushions are also reflected in the presence of psychrotolerant Ascomycota of the genus Pseudogymnoascus (Villanueva et al., 2021) and prokaryotic organisms such as those of the genus Dyella (Wang et al., 2021), which are typical of rocky environments, bacteria of the genus Crossiella (Labeda, 2015), which are more abundant in cold environments, and Tundrisphaera, which are psychrotolerant and associated with lichens (Kulichevskaya Interestingly, bacteria of the phylum Bacteroidota also proliferate under the canopy and are often associated with termite guts in a three-way symbiosis (Otani et al., 2014). ...
Question
Cushion‐forming vascular plants are adapted to alpine environments and act as ecosystem engineers by moderating microclimate and creating a fertility island under their canopy. Most of the available studies on cushion ecology have been devoted to plant facilitation, but none used a holistic approach that considers the response of co‐existing plant species with other key ecosystem players. Here, we quantified the biogenic effect and facilitation capacity of Astragalus siculus , a spiny nitrogen‐fixing cushion plant, and test the hypothesis that the facilitation effect would increase with elevation as stress gradient.
Location
Mount Etna, the highest active volcano in the Mediterranean Basin.
Methods
We combined chemical characterization of the soil with a description of the soil microbiota by high‐throughput sequencing of bacterial and eukaryotic rRNA gene markers carried out at three elevations, that is 1650, 1900 and 2210 m a.s.l. In addition, we analysed the microclimate outside and inside the Astragalus canopy to assess the linkages between above‐ and below‐ground ecosystem compartments and quantified the occurrence of co‐existing vascular plants.
Results
Astragalus cushions have strong biogenic effects on above‐ and below‐ground conditions by dramatically increasing soil organic carbon and total nitrogen stocks at 1900 and 2210 m elevation. Moreover, a buffering of soil temperature and moisture regimes was recorded, with lower temperatures in summer but higher in winter inside the cushions. Cushions harbour a specific bacterial and fungal microbiota compared to external bare soil. Stem density and cushion height increase significantly with altitude, as does the nurse effect of the cushion on the growth and survival of co‐existing vascular plants.
Conclusions
As a result of cushion biogenic environmental changes, the effect of Astragalus on some of the co‐existing species shifted from negative or null at 1650 m to facilitative along the elevation gradient. Furthermore, our data show a relationship between Astragalus morphological traits and soil biogenic changes related to soil chemistry and microbiota that affect plant interaction and coexistence.
... The bacterial symbionts act as "microbial brokers" that enable the hosts to overcome the activities that are either low or absent in the host [21,22], thereby providing additional capabilities to the termites [23]. During the last three decades, a plethora of information has been generated related to the presence and functions of bacteria in termite gut systems through high throughput sequencing techniques involving omics [24]. However, the major drawback of these omics methods is the lacunae in terms of details about the contribution of individual bacterial strains. ...
Fungus-growing termites are eusocial insects that represent one of the most efficient and unique systems for lignocellulose bioconversion, evolved from a sophisticated symbiosis with lignocellulolytic fungi and gut bacterial communities. Despite a plethora of information generated during the last century, some essential information on gut bacterial profiles and their unique contributions to wood digestion in some fungus-growing termites is still inadequate. Hence, using the culture-dependent approach, the present study aims to assess and compare the diversity of lignocellulose-degrading bacterial symbionts within the gut systems of three fungus-growing termites: Ancistrotermes pakistanicus, Odontotermes longignathus, and Macrotermes sp. A total of 32 bacterial species, belonging to 18 genera and 10 different families, were successfully isolated and identified from three fungus-growing termites using Avicel or xylan as the sole source of carbon. Enterobacteriaceae was the most dominant family represented by 68.1% of the total bacteria, followed by Yersiniaceae (10.6%) and Moraxellaceae (9%). Interestingly, five bacterial genera such as Enterobacter, Citrobacter, Acinetobacter, Trabulsiella, and Kluyvera were common among the tested termites, while the other bacteria demonstrated a termite-specific distribution. Further, the lignocellulolytic potential of selected bacterial strains was tested on agricultural waste to evaluate their capability for lignocellulose bioconversion. The highest substrate degradation was achieved with E. chengduensis MA11 which degraded 45.52% of rice straw. All of the potential strains showed endoglucanase, exoglucanase, and xylanase activities depicting a symbiotic role towards the lignocellulose digestion within the termite gut. The above results indicated that fungus-growing termites harbor a diverse array of bacterial symbionts that differ from species to species, which may play an inevitable role to enhance the degradation efficacy in lignocellulose decomposition. The present study further elaborates our knowledge about the termite-bacteria symbiosis for lignocellulose bioconversion which could be helpful to design a future biorefinery.
... The complex web of interactions involving insects , their fungal crops Otani et al., 2019), specialized pathogens (Guo et al., 2016), symbiotic fungus (Xu et al., 2020), and symbiotic bacteria has become both a model system for chemical ecology and a source of naturally occurring small molecules. We are still a long way from identifying additional antifungal compounds in this system and understand thoroughly the chemical basis of symbiotic or antagonistic associations among termites, fungal cultivar, cultivar competitors, entomopathogenic fungi and antibioticproducing actinomycetes. ...
The book is the collection of articles submitted to the research topic Antimicrobials in Wildlife and the Environment.
... There are a large number of archaea, bacteria, and fungi in termites and their nests (Brune, 2014). Bacteroidetes, Proteobacteria, Firmicutes, Spirochaetes, and Actinobacteria were the core bacterial flora in fungal combs, also the core gut microbiota of fungus-growing termite species (Hu et al., 2019;Liang et al., 2020;Mathew et al., 2012;Otani et al., 2014Otani et al., , 2016Shinzato et al., 2007). Our results were consistent with these findings ( Figure S2b). ...
Fungus‐growing termites cultivate the fungal mutualist Termitomyces as their main food source; however, how fungus‐growing termites protect Termitomyces from threats is still unclear. In this study, we investigated the actinobacterial communities in Odontotermes formosanus individuals and their fungal combs.
Moreover, the antifungal activities of the isolated actinobacteria were tested. 16 S rRNA gene sequencing results indicated that the actinobacteria in O. formosanus and its fungal combs belong to 5 classes, 17 orders, 40 families, and 84 genera.
The relative abundance of Coriobacteriia in the nymphs, young workers, old workers, and soldiers was higher than that in the queens and fungal combs, and the relative abundance of class Actinobacteria in the queens and the fungal combs was higher than that in the nymphs, young workers, old workers, and soldiers.
Based on antifungal bioassays, 3 strains of Amycolatopsis and 2 strains of Streptomyces isolated from old workers had strong inhibitory activity against Xylaria angulosa but weak inhibitory activity against Termitomyces sp.
These results indicated that the actinobacteria of O. formosanus may contribute to protecting termite fungal food via their asymmetric antifungal activities.
... The termites probably use a variety of tactics to manage such antagonists, with the production of antifungals being one among them (Um et al., 2013). The gut flora of the (2011-present Macrotermitinae has so far been found to contain seven different bacterial phyla (Otani et al., 2014). Bacillus strains are the most prevalent and can produce antifungals among them. ...
Excessive antibiotic prescriptions as well as their misuse in agriculture are the main causes of antimicrobial resistance which poses a growing threat to public health. It necessitates the search for novel chemicals to combat drug resistance. Since ancient times, naturally occurring medicines have been employed and the enormous variety of bioactive chemicals found in nature has long served as an inspiration for researchers looking for possible therapeutics. Secondary metabolites from microorganisms, particularly those from actinomycetes, have made it incredibly easy to find new molecules. Different actinomycetes species account for more than 70% of naturally generated antibiotics currently used in medicine, and they also produce a variety of secondary metabolites, including pigments, enzymes, and anti-inflammatory compounds. They continue to be a crucial source of fresh chemical diversity and a crucial component of drug discovery. This review summarizes some uncommon sources of antifungal metabolites and highlights the importance of further research on these unusual habitats as a source of novel antimicrobial molecules.
... Wood-feeding termites harboring specialized gut microbial symbionts are among the most capable organisms for lignocellulose degradation (Brune, 2014;Brune and Dietrich, 2015;Liu et al., 2019;Otani et al., 2014). Most of the higher termite species rely on the microbial communities in their gut environment for plant polymer digestion (Brune, 2014;He et al., 2013;Zhou et al., 2019). ...
Fungus-cultivating termite Odontotermes badius developed a mutualistic association with Termitomyces fungi for the plant material decomposition and providing a food source for the host survival. The mutualistic relationship sifted the microbiome composition of the termite gut and Termitomyces fungal comb. Symbiotic bacterial communities in the O. badius gut and fungal comb have been studied extensively to identify abundant bacteria and their lignocellulose degradation capabilities. Despite several metagenomic studies, the species-wide metabolic interaction pattern of bacterial communities in termite gut and fungal comb remains unclear. The bacterial species metabolic interaction network (BSMIN) has been constructed with 230 bacteria identified from the O. badius gut and fungal comb microbiota. The network portrayed the metabolic map of the entire microbiota and highlighted several inter-species biochemical interactions like cross-feeding, metabolic interdependency, and competition. Further, the reconstruction and analysis of the bacterial influence network (BIN) quantified the positive and negative pairwise influences in the termite gut and fungal comb microbial communities. Several key macromolecule degraders and fermentative microbial entities have been identified by analyzing the BIN. The mechanistic interplay between these influential microbial groups and the crucial glycoside hydrolases (GH) enzymes produced by the macromolecule degraders execute the community-wide functionality of lignocellulose degradation and subsequent fermentation. The metabolic interaction pattern between the nine influential microbial species has been determined by considering them growing in a synthetic microbial community. Competition (30%), parasitism (47%), and mutualism (17%) were predicted to be the major mode of metabolic interaction in this synthetic microbial community. Further, the antagonistic metabolic effect was found to be very high in the metabolic-deprived condition, which may disrupt the community functionality. Thus, metabolic interactions of the crucial bacterial species and their GH enzyme cocktail identified from the O. badius gut and fungal comb microbiota may provide essential knowledge for developing a synthetic microcosm with efficient lignocellulolytic machinery.
... The DNA extractions from the subsamples were mixed in equal proportions in a single sample, thus obtaining three samples per glacier forefield and one per microbial mat. The 16S rRNA gene was amplified by PCR using primers set 341F (5 -CCT AYGGGRBG-CASCAG -3 ) and 806R (5 -GGACTACNNGGG TATCTAAT -3 ) targeting the V3-V4 hypervariable regions (Otani et al. 2014), and primers specific for cyanobacteria with ample use in the literature (CYA359F/CYA781Ra and CYA781Rb) following reaction mix and PCR conditions from Nübel et al. (1997). The pool of samples with the prepared libraries was sequenced by the Illumina MiSeq platform. ...
Cyanobacteria are key organisms in the Antarctic ecosystem, but the primary succession of its communities in recently deglaciated soils remains poorly understood. In this study, we surveyed the primary succession of cyanobacterial communities with an in-depth Next Generation Sequencing approach in three Antarctic recently glacier forefields. Despite the similar physicochemical characteristics of the soils, we did not find a common pattern in the distribution of the cyanobacterial communities at the finest level of taxonomic resolution. However, the metabarcoding analysis revealed a common community of 14 cyanobacterial identical sequences in all the studied soils, whose lineages were not restricted to polar or alpine biotopes. These ASVs comprised a relative abundance within the cyanobacterial community of 51.5–81.7% among the three locations and were also found in two cyanobacterial mats from the Antarctic Peninsula. Our results suggest that (micro)biotic interactions act as a key driver of the community composition and dynamics of Cyanobacteria during the early stages of succession in recently deglaciated soils of Antarctica. A few common genera might play a key role in the ecosystem, due to its ubiquitous presence not only in these soils but also in microbial mats, conforming probably the most widely disperse and dominant single genotypes in Antarctic soils.
... 30 MY. The adoption of a primarily fungal diet remodeled farming termite gut bacterial community compositions [9][10][11], shifting the prominent role of plant biomass degradation from the gut to Termitomyces. Consequently, fungus-farming termite gut bacteria encode fewer lignocellulose-degrading enzymes, but are enriched in enzymes targeting the fungal cell wall [9]. ...
Fungus-farming termites host gut microbial communities that contribute to the pre-digestion of plant biomass for manuring the fungal mutualist, and potentially to the production of defensive compounds that suppress antagonists. Termite colonies are characterized by complex division of labor and differences in diet between termite size (minor and major) and morphological (worker and soldier) castes, and this extends to the composition of their gut microbial communities. We hypothesized that gut metabolomes should mirror these differences and tested this through untargeted LC-MS/MS analyses of three South African species of fungus-farming termites. We found distinct metabolomes between species and across castes, especially between soldiers and workers. Primary metabolites dominate the metabolomes and the high number of overlapping features with the mutualistic fungus and plant material show distinct impacts of diet and the environment. The identification of a few bioactive compounds of likely microbial origin underlines the potential for compound discovery among the many unannotated features. Our untargeted approach provides a first glimpse into the complex gut metabolomes and our dereplication suggests the presence of bioactive compounds with potential defensive roles to be targeted in future studies.
... Fukuda et al. [81] studied the symbiotic relationship between arthropod and bacteria (Pseudonocardia sp.) and found that bacteria provide chemical weapons against the pathogenic fungi, and in return, they are fed by the host. Otani et al. [82], identified seven different bacterial phyla in Macrotermitinae gut, in which the Bacillus sp. strain was dominant and could produce secondary metabolites (polyene polyketide and bacillaene) to inhibit the growth of Trichoderma, Pseudoxylaria, Coriolopsis, Fusarium, and Umbelopsis. ...
The world is constantly facing threats, including the emergence of new pathogens and antibiotic resistance among extant pathogens, which is a matter of concern. Therefore, the need for natural and effective sources of drugs is inevitable. The ancient and pristine ecosystems of caves contain a unique microbial world and could provide a possible source of antimicrobial metabolites. The association between humans and caves is as old as human history itself. Historically, cave environments have been used to treat patients with respiratory tract infections, which is referred to as speleotherapy. Today, the pristine environment of caves that comprise a poorly explored microbial world is a potential source of antimicrobial and anticancer drugs. Oligotrophic conditions in caves enhance the competition among microbial communities, and unique antimicrobial agents may be used in this competition. This review suggests that the world needs a novel and effective source of drug discovery. Therefore, being the emerging spot of modern human civilization, caves could play a crucial role in the current medical crisis, and cave microorganisms may have the potential to produce novel antimicrobial and anticancer drugs.
... William (1965) suggested that microbial diversity is moreover due to deficiency of enzymes responsible to digest major diet components such as cellulose and lignin. Gut content analysis in higher fungus feeding termite M. gilvus revealed the predominance of Bacteroidales (phylum Bacteroidetes) and Clostridales (phylum Firmicutes) in their gut Otani et al. 2014); whereas, Fibrobacteres and TG3 phylum members are present in large proportions in wood-feeding species N. takasagoensis (Hongoh et al. 2006a, b). In humus feeding termite Termes comis, the gut content was found to be rich in Clostridia and Bacilli (Thongaram et al. 2005) and in case of soil feeding termite, Cubitermes niokoloensis, Firmicutes and Proteobacteria phyla dominated the gut section of the termites (Fall et al. 2007). ...
This article explores the symbiotic role of microorganisms (bacteria, fungi and protozoans) associated with xylophagous termites. Members of the subfamily Macrotermitinae belonging to the family Termitidae have evolved symbiosis with fungi, which belong to the genus Termitomyces. The function of Termitomyces varies for different termite groups depending on their feeding behaviour. In some termites, the primary function of Termitomyces fungi is the degradation of lignin to its simpler form and to make cellulose available to termites; however, these fungi also serve as nutrient rich food sources to other groups of termites. The subsequent breakdown of ingested cellulose in termite gut is further facilitated and controlled by the action of various groups of enzymes secreted by gut-borne microflora and micro-fauna. Understanding the function, significance and management of these diverse microbial symbionts associated with pestiferous higher termites may help in developing their effective bio-control.
... The higher termites forage a wide variety of lignocellulosic biomass and materials such as wood, dry grass, herbivore dung, lichen, plant litter, organic matter, and soil (Hongoh 2011;Brune 2014;Mikaelyan et al. 2015). Therefore, they play a vital role in general plant decomposition, carbon cycling of organic matters, and recycling nutrients of ecosystems (König et al. 2013;Otani et al. 2014). ...
Boontanom P, Chantarasiri A. 2021. Diversity and cellulolytic activity of culturable bacteria isolated from the gut of higher termites (Odontotermes sp.) in eastern Thailand. Biodiversitas 22: 3349-3357. Cellulolytic bacteria are vital symbionts associated with the gut of all higher termites. Odontotermes termites are a higher termite widely found in Thailand. However, information concerning the diversity of cellulolytic bacteria in this termite gut remains inadequate. The aim of this study is to isolate and identify the culturable cellulolytic bacteria from the Odontotermes gut collected from eastern Thailand. The crude cellulases produced from the most active cellulolytic bacterium were further characterized. Thirty-two cellulolytic bacteria were isolated and subsequently classified by PCR-RFLP of the 16S rRNA gene. A total of 10 different RFLP patterns were obtained belonging to five bacterial genera, namely Acinetobacter, Bacillus, Citrobacter, Paenibacillus, and Serratia. The B. cereus strain TWV503 was considered to be the most active cellulolytic bacterium based on the CMC agar method. B. cereus strain TWV503 showed CMCase activity at 2.190 0.063 U/mL of CMCase and 0.276 0.031 U/mL of FPase. The optimum temperature and pH for CMCase activity were 50C and the neutral pH ranging from 7.0 to 8.0, respectively. CMCase activity remained stable at up to 70C and neutral pH ranging from 7.0 to 8.0 for 24 hours of incubation. This study revealed novel information related to cellulolytic bacteria isolated from the gut of Odontotermes termites collected from Thailand.
... Numerous studies on the gut microbiota of higher termites have been published in the last two decades (Warnecke et al., 2007;Otani et al., 2014;Mikaelyan et al., 2015;Rahman et al., 2015;Santana et al., 2015;Su et al., 2016, Bourguignon et al., 2018. Knowing the factors that shape the structure of the microbial communities has become an increasing focus of interest. ...
The termite gut microbiome is dominated by lignocellulose degrading microorganisms. This study describes the intestinal microbiota of four Argentinian higher termite species with different feeding habits: Microcerotermes strunckii (hardwood), Nasutitermes corniger (softwood), Termes riograndensis (soil organic matter/grass) and Cornitermes cumulans (grass) by deep sequencing of amplified 16S rRNA and ITS genes. In addition, we have performed a taxonomic and gut community structure comparison incorporating into the analysis the previously reported microbiomes of additional termite species with varied diets. The bacterial phylum Spirochaetes was dominant in the guts of M. strunckii, N. corniger and C. cumulans, whereas Firmicutes predominated in the T. riograndensis gut microbiome. A single bacterial genus, Treponema (Spirochaetes), was dominant in all termite species, except for T. riograndensis. Both in our own sequenced samples and in the broader comparison, prokaryotic a-diversity was higher in the soil/grass feeders than in the wood feeders. Meanwhile, the β-diversity of prokaryotes and fungi was highly dissimilar among strict wood-feeders, whereas that of soil-and grass-feeders grouped more closely. Ascomycota and Basidiomycota were the only fungal phyla that could be identified in all gut samples, because of the lack of reference sequences in public databases. In summary, higher microbial diversity was recorded in termites with more versatile feeding sources, providing further evidence that diet, along with other factors (e.g., host taxonomy), influences the microbial community assembly in the termite gut.
... DNA concentrations were determined in a NanoDrop ND 1000 spectrophotometer (Thermo Fisher Scientific TM ). The 16S rRNA gene was amplified by PCR using barcoded primers set 341F (5 -CCT AYGGGRBGCASCAG -3 ) and 806R (5 -GGACTACNNGGG TATCTAAT -3 ) targeting the V3-V4 hypervariable regions (Otani et al., 2014). This universal primer set is for bacterial community and the archaeal community was not included in the study. ...
Ice-free areas represent less than 1% of the Antarctic surface. However, climate change models predict a significant increase in temperatures in the coming decades, triggering a relevant reduction of the ice-covered surface. Microorganisms, adapted to the extreme and fluctuating conditions, are the dominant biota. In this article we analyze the diversity and composition of soil bacterial communities in 52 soil samples on three scales: (i) fine scale, where we compare the differences in the microbial community between top-stratum soils (0–2 cm) and deeper-stratum soils (5–10 cm) at the same sampling point; (ii) medium scale, in which we compare the composition of the microbial community of top-stratum soils from different sampling points within the same sampling location; and (iii) coarse scale, where we compare communities between comparable ecosystems located hundreds of kilometers apart along the Antarctic Peninsula. The results suggest that in ice-free soils exposed for longer periods of time (millennia) microbial communities are significantly different along the soil profiles. However, in recently (decades) deglaciated soils the communities are not different along the soil profile. Furthermore, the microbial communities found in soils at the different sampling locations show a high degree of heterogeneity, with a relevant proportion of unique amplicon sequence variants (ASV) that appeared mainly in low abundance, and only at a single sampling location. The Core90 community, defined as the ASVs shared by 90% of the soils from the 4 sampling locations, was composed of 26 ASVs, representing a small percentage of the total sequences. Nevertheless, the taxonomic composition of the Core80 (ASVs shared by 80% of sampling points per location) of the different sampling locations, was very similar, as they were mostly defined by 20 common taxa, representing up to 75.7% of the sequences of the Core80 communities, suggesting a greater homogeneity of soil bacterial taxa among distant locations.
... Next, we exposed both groups of nymphs to microbial inocula from their own species (conspecific) or from another species (allospecific) (cockroach versus termite) and the corresponding diets of the two species (omnivorous versus specialized fungus). We chose these species because termites are social cockroaches and fungus-growing termites share many cockroach gut bacterial lineages (23,46). In doing so, we show that ecological interactions are important for microbial assemblage and that removing the initial microbiome, even if later reinoculated, will strongly affect microbiome consistency, even if most microbes are shared. ...
A multitude of factors affect the assemblies of complex microbial communities associated with animal hosts, with implications for community flexibility, resilience, and long-term stability; however, their relative effects have rarely been deduced. Here, we use a tractable lab model to quantify the relative and combined effects of parental transmission (egg case microbiome present/reduced), gut inocula (cockroach versus termite gut provisioned), and varying diets (matched or unmatched with gut inoculum source) on gut microbiota structure of hatchlings of the omnivorous cockroach Shelfordella lateralis using 16S rRNA gene (rDNA) amplicon sequencing. We show that the presence of a preexisting bacterial community via vertical transmission of microbes on egg cases reduces subsequent microbial invasion, suggesting priority effects that allow initial colonizers to take a strong hold and which stabilize the microbiome. However, subsequent inoculation sources more strongly affect ultimate community composition and their ecological networks, with distinct host-taxon-of-origin effects on which bacteria establish. While this is so, communities respond flexibly to specific diets in ways that consequently impact predicted community functions. In conclusion, our findings suggest that inoculations drive communities toward different stable states depending on colonization and extinction events, through ecological host-microbe relations and interactions with other gut bacteria, while diet in parallel shapes the functional capabilities of these microbiomes. These effects may lead to consistent microbial communities that maximize the extended phenotype that the microbiota provides the host, particularly if microbes spend most of their lives in hostassociated environments. © 2021. Renelies-Hamilton et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license. All Rights Reserved.
... DNA extraction, PCR, and high-throughput sequencing DNA was extracted by the lysozyme-SDS-phenol/chloroform method (Mikhailov et al., 2019). The V3-V4 region of the 16S rRNA gene was amplified using universal primers 341F (5′-CCTAYGGGRBGCASCAG-3′) and 806R (5′-GGACTACNNGGGTATCTAAT-3′) (Otani et al., 2014), and the V4 region of the 18S rRNA gene was amplified with forward 3NDF (5′-GGCAAGTCTGGTGCCAG-3′) and V4 (5′-ACGGTATCT(AG)ATC(AG)TCTT CG-3′) broad eukaryotic primers (Bråte et al., 2010). PCR reactions (95°C for 2 min, followed by 35 cycles at 95°C for 30 s, 55°C for 30 s, and 72°C for 45 s and a final extension at 72°C for 10 min) were performed in a triplicate 20 μL mixture containing 4 μL of 5 × FastPfu Buffer, 2 mL of 2.5 mM dNTPs, 0.8 μL of each primer (5 mM), 0.4 μL of FastPfu Polymerase and 10 ng of template DNA. ...
Microbial communities are a large component of abyssal and hadal benthic environments, especially in deep-sea areas like Yap Trench, they provide a continuous source of nutrients and energy in their unique ecosystems. However, due to sampling difficulties, these microbial communities are relatively understudied. In the summer of 2017, sediment samples were collected from 21 stations around Yap Trench in the Western Pacific Ocean (mostly in the West Caroline Basin), at depths ranging from 3156 to 7837 m. Sediment samples from deep water depths and shallow water depths differed in organic matter content, median grain size, silt-clay content, and biodiversity. The structure of the microbial communities in the surface sediments had distinct relationships with environmental factors and their co-occurrence networks exhibited a clear spatial pattern. In addition, for both prokaryotes or eukaryotes, a combination of variables including silt-clay content, organic matter content, median grain size, and depth had the greatest impact on community structure. It was notable that Fungi played important roles in the co-occurrence networks of deep water depth sediment samples while bacteria dominated those of shallow water depth samples. The differences in structure and ecological niches in the different networks were due to differences in sediment texture and organic matter content. Since clay had a positive effect on the diversity of bacteria, it had an indirect positive effect on fungi, leading to differences in biodiversity among different groups. More organic matter meant more nutrients were available for the growth and reproduction of microbes, which led to fewer niche overlaps. This study conducted an extensive and systematic sequencing survey of surface sediments around Yap Trench in the Western Pacific Ocean, providing insight into microbial responses to environmental heterogeneity in deep-sea benthic ecosystems.
... Gut microbiota is closely related to host health, metabolism and immunity as well as soil decomposition processes. Growing evidence supports that gut microbiota plays an important role in nutrition utilization, pathogen defense and cellulose digestion, and has ability to modulate host metabolism, maintain intestinal homeostasis and regulate the development of various functions of host immune system (Hooper et al., 2012;Khan et al., 2017;Otani et al., 2014). Several studies have reported that various of environment pollutants (e.g., arsenic, tetracycline and triclosan) can induce gut microbiota dysbiosis, alter the mucus layer, and even result in inflammation in organisms (Ma et al., 2017;Pass et al., 2015;Raymann et al., 2017). ...
As an emerging pollutant in terrestrial ecosystem, studies on the effects of microplastics on the gut microbiota of terrestrial organisms are relatively little even though gut microbiota is closely related to host health, metabolism and immunity as well as soil decomposition processes. In this study, earthworms Metaphire guillelmi were exposed to soil amended with 0.25% (w/w) high-density polyethylene (HDPE, 25 μm) or polypropylene (PP, 13 μm) microplastics for 28 d. The ingestion of HDPE and PP microplastics by M. guillelmi was clearly demonstrated by Nile Red fluorescence staining method. There were significant differences for the microbiota between the M. guillelmi gut and the surrounding soil, which may result from the influence of specific conditions in the gut habitat. HDPE and PP microplastics exposure did not induce gut microbiota dysbiosis in M. guillelmi. However, PP microplastics exposure significantly reduced bacterial diversity and altered bacterial community structure in the soil. Specifically, the relative abundance of Aeromonadaceae and Pseudomonadaceae significantly increased while the relative abundance of Nitrososphaeraceae and two unidentified families affiliated with Proteobacteria significantly decreased. This study broadens our understanding of the ecotoxicity of microplastics on the soil and gut microbiota of terrestrial organisms.
... [35e40] and as ectosymbionts of nematodes living in the cockroach digestive system [41], as well as in the hindguts of phylogenetically related termites [42e46]. Dysgonomonas have been identified as core microbiota of both higher [47] and lower [48] termites, including Reticulitermes flavipes [49]. There is growing interest in Dysgonomonas due to their prevalence in biotechnological processes such as lignocellulose degradation and bioconversion of polysaccharides for biofuel development [50,51], microbial fuel and electrolysis cells [52e59], wastewater bioreactors [60,61], biodegradation of food waste [62,63] and pharmaceutical compounds [60,64e66]. ...
Members of Dysgonomonas are Gram-stain-negative, non-motile, facultatively anaerobic coccobacilli originally described in relation to their isolation from stool and wounds of human patients (CDC group DF-3). More recently, Dysgonomonas have been found to be widely distributed in terrestrial environments and are particularly enriched in insect systems. Their prevalence in xylophagous insects such as termites and wood-feeding cockroaches, as well as in soil-fed microbial fuel cells, elicit interest in lignocellulose degradation and biofuel production, respectively. Their occurrence in mosquito and fruit fly have implications relating to symbiosis, host immunology and developmental biology. Additionally, their presence in termite, mosquito and nematode present novel opportunities for pest and vector control. Currently, the absolute growth requirements of Dysgonomonas are unknown, and they are commonly cultured under anaerobic conditions on complex media containing blood, peptones, tryptones, and yeast, plant or meat extracts. Restrictive and undefined culturing conditions preclude physiological and genetic studies, and thus further understanding of their metabolic potential. Here we describe the requirements for growth of termite-derived Dysgonomonas isolates and create parallel complex, defined and minimal media that permit vigorous and reliable aerobic growth. Furthermore, we show that these media can be used to easily enrich for Dysgonomonas isolates from densely-colonized and microbially-diverse environmental samples.
... Termites produce very few endogenous lignocellulosedegrading enzymes, and their gut microbiome is mainly responsible for their ability to capture nutrients and energy from plant biomass (14,15). Over the last decade, numerous metagenomics studies revealed enzyme arsenals of termite gut microbiomes and detected promising enzymes for industrial use (16)(17)(18)(19)(20). Notably, Gram-negative Bacteroidetes, the dominant phylum in many animal digestive systems (21)(22)(23)(24)(25), utilize finely tuned glycan utilization systems. ...
The functional screening of a Pseudacanthotermes militaris termite gut metagenomic library revealed an array of xylan degrading enzymes including Pm25, a multi-modular Glycoside Hydrolase (GH) family 10. Sequence analysis showed details of the unusual domain organization of this enzyme. It consists of one catalytic domain, which is intercalated by two Carbohydrate Binding Modules (CBMs) from family 4. The genes upstream of pm25 are susC-susD-unk suggesting Pm25 is a Xyn10C-like enzyme belonging to a polysaccharide utilization loci. The majority of Xyn10C-like enzymes shared the same interrupted domain architecture, and were vastly distributed in different xylan utilization loci found in gut Bacteroidetes, indicating its importance in glycan foraging for the gut microbiota. In order to understand its unusual multi-modularity and the possible role of the CBMs, a detailed characterization of the full length Pm25 and truncated variants was performed. Results revealed that the GH10 catalytic module is specific towards the hydrolysis of xylan. Ligand binding results indicate that the GH10 module and the CBMs act independently whereas the tandem CBM4s act synergistically with each other and improve enzymatic activity when assayed on insoluble polysaccharides. In addition, we show that the UNK protein upstream of Pm25 is able to bind arabinoxylan. Altogether, these findings contribute to a better understanding of the potential role of Xyn10C-like proteins in xylan utilization systems of gut bacteria.
IMPORTANCE
Xylan is the major hemicellulosic polysaccharide in cereals and contributes to the recalcitrance of the plant cell wall toward degradation. Bacteroidetes, one of the main phyla in Rumen and Human gut microbiota, have been shown to encode polysaccharide utilization loci (PUL) dedicated to the degradation of xylan. Here we present the biochemical characterization of a xylanase encoded by a bacteroidetes strain isolated from the termite gut metagenome. This xylanase is a multi-modular enzyme of which sequence is interrupted by the insertion of two CBM from family 4. Our results show that not only this enzyme resemble homologues that were shown to be important for xylan degradation in rumen or human diet but show that the CBM insertion in the middle of the sequence seems to be a common feature in xylan utilisation system. This study shed light on a better understanding toward xylan degradation and plant cell wall deconstruction which can conduct to several applications in food, feed and bioeconomy.
Specialized microbial communities in the fungus-farming termite gut and fungal comb microbiome help maintain host nutrition through interactive biochemical activities of complex carbohydrate degradation. Numerous research studies have been focused on identifying the microbial species in the termite gut and fungal comb microbiota, but the community-wide metabolic interaction patterns remain obscure. The inter-microbial metabolic interactions in the community environment are essential for executing biochemical processes like complex carbohydrate degradation and maintaining the host’s physicochemical homeostasis. Recent progress in high-throughput sequencing techniques and mathematical modeling provides suitable platforms for constructing multispecies genome-scale community metabolic models that can render sound knowledge about microbial metabolic interaction patterns. Here, we have implemented the genome-scale metabolic modeling strategy to map the relationship between genes, proteins, and reactions of 12 key bacterial species from fungal cultivating termite gut and fungal comb microbiota. The resulting individual genome-scale metabolic models (GEMs) have been analyzed using flux balance analysis (FBA) to optimize the metabolic flux distribution pattern. Further, these individual GEMs have been integrated into genome-scale community metabolic models where a heuristics-based computational procedure has been employed to track the inter-microbial metabolic interactions. Two separate genome-scale community metabolic models were reconstructed for the O. badius gut and fungal comb microbiome. Analysis of the community models showed up to ∼167% increased flux range in lignocellulose degradation, amino acid biosynthesis, and nucleotide metabolism pathways. The inter-microbial metabolic exchange of amino acids, SCFAs, and small sugars was also upregulated in the multispecies community for maximum biomass formation. The flux variability analysis (FVA) has also been performed to calculate the feasible flux range of metabolic reactions. Furthermore, based on the calculated metabolic flux values, newly defined parameters, i.e., pairwise metabolic assistance (PMA) and community metabolic assistance (CMA) showed that the microbial species are getting up to 15% higher metabolic benefits in the multispecies community compared to pairwise growth. Assessment of the inter-microbial metabolic interaction patterns through pairwise growth support index (PGSI) indicated an increased mutualistic interaction in the termite gut environment compared to the fungal comb. Thus, this genome-scale community modeling study provides a systematic methodology to understand the inter-microbial interaction patterns with several newly defined parameters like PMA, CMA, and PGSI. The microbial metabolic assistance and interaction patterns derived from this computational approach will enhance the understanding of combinatorial microbial activities and may help develop effective synergistic microcosms to utilize complex plant polymers.
Termites have co-evolved with a complex gut microbiota consisting mostly of exclusive resident taxa, but key forces sustaining this exclusive partnership are still poorly understood. The potential for primary reproductives to vertically transmit their gut microbiota (mycobiome and bacteriome) to offspring was investigated using colony foundations from field-derived swarming alates of Macrotermes subhyalinus. Metabarcoding based on the fungal internal transcribed spacer (ITS) region and the bacterial 16S rRNA gene was used to characterize the reproductives mycobiome and bacteriome over the colony foundation time. The mycobiome of swarming alates differed from that of workers of Macrotermitinae and changed randomly within and between sampling time points, highlighting no close link with the gut habitat. The fungal ectosymbiont Termitomyces was lost early from the gut of reproductives, confirming the absence of vertical transmission to offspring. Unlike fungi, the bacteriome of alates mirrored that of workers of Macroterminae. Key genera and core OTUs inherited from the mother colony mostly persisted in the gut of reproductive until the emergence of workers, enabling their vertical transmission and explaining why they were found in offspring workers. These findings demonstrate that the parental transmission may greatly contribute to the maintenance of the bacteriome and its co-evolution with termite hosts at short time scales.
Fungus‐farming termites are dominant decomposers and important ecosystem engineers in their natural sub‐Sahara African and Southeast Asian ecosystems. This is accomplished through integrated behavioral management of complex communities of fungal and bacterial symbionts by the termite host that facilitate plant biomass decomposition and production of defensive antimicrobial compounds. The extensive, near‐complete turnover of plant biomass, which is sustained for several years due to their disease‐free lifestyle, pivotally shapes ecosystems. The termites impact their immediate environment through enrichment of water and nutrients, which seep from the mound, and help sustain plant and animal communities, particularly in dry savannah ecosystems. Here, we summarize our understanding of the role microbial symbionts play in fungus‐farming termites and the implications of these processes for ecosystem services and impacts on humans.
Mutualistic co-evolution can be mediated by vertical transmission of symbionts between host generations. Organisms exhibit adaptations that ensure optimal microbial inheritance, yet it is unknown if this extends to superorganismal social insects that host co-evolved gut microbiomes. Here, we document consistent vertical transmission that preserves more than 80 bacterial genera across colony generations in a fungus-farming termite model system. Inheritance is governed by reproductives, analogous to organismal gametes, that found new colonies and are endowed with environmentally-sensitive and termite-specific gut microbes. These symbionts are then reliably passed on within the offspring colony, where priority effects dictate the composition of the forming colony microbiome. Founding reproductives thus play a central role in transmission. However, in sharp contrast to organismal inheritance of an endosymbiont within an egg, the multicellular properties of the superorganismal gametes allow for inheritance of entire communities of co-adapted microbes. Superorganismal inheritance aligns the reproductive interests of the host colony and a diverse set of microbes and clarifies a fundamental driver of millions of years of termite-bacterial co-diversification. Ultimately, the high symbiotic fidelity and host control favors mutualistic cooperation that should surpass that of other animals with complex microbiomes.
Feeding habits were the primary factor affecting the gut bacterial communities in Ensifera. However, the interaction mechanism between the gut microbiota and feeding characteristics is not precisely understood. Here, the gut microbiota of Ensifera with diverse feeding habits was analyzed by shotgun metagenomic sequencing to further clarify the composition and function of the gut microbiota and its relationship with feeding characteristics. Our results indicate that under the influence of feeding habits, the gut microbial communities of Ensifera showed specific characteristics. Firstly, the gut microbial communities of the Ensifera with different feeding habits differed significantly, among which the gut microbial diversity of the herbivorous Mecopoda niponensis was the highest. Secondly, the functional genes related to feeding habits were in high abundance. Thirdly, the specific function of the gut microbial species in the omnivorous Gryllotalpa orientalis showed that the more diverse the feeding behavior of Ensifera, the worse the functional specificity related to the feeding characteristics of its gut microbiota. However, feeding habits were not the only factors affecting the gut microbiota of Ensifera. Some microorganisms’ genes, whose functions were unrelated to feeding characteristics but were relevant to energy acquisition and nutrient absorption, were detected in high abundance. Our results were the first to report on the composition and function of the gut microbiota of Ensifera based on shotgun metagenomic sequencing and to explore the potential mechanism of the gut microbiota’s association with diverse feeding habits.
This study investigates microbiome assembly in the fungus-growing ant Trachymyrmex septentrionalis , showing how colony, caste, and lab adaptation influence the microbiome and revealing unique patterns of mollicute symbiont abundance. We find that ant microbiomes differ strongly between colonies but less so within colonies.
Phthalate esters (PAEs) are widely used as plasticizers and can be ubiquitously detected in environment. However, the toxic effects and mechanisms of diisononyl phthalate (DINP) on earthworms are still poorly understood. In this study, earthworms (Eisenia fetida) were exposed to DINP at various doses (0, 300, 600, 1200, and 2400 mg/kg) to investigate their subchronic toxicity. The results demonstrated that the reactive oxygen species (ROS) levels displayed an “increase-decrease” trend with the increasing DINP doses after DINP exposure on days 7, 14, 21, and 28. The malondialdehyde (MDA) content increased with increasing DINP doses on days 7, 14, and then decreased on days 21, 28. The values of superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST) showed similar variation patterns and reached a maximum level on 21 d. Moreover, on day 28, the SOD and CAT gene expression levels were upregulated, while the GST gene expression levels were downregulated. Meanwhile, 16S rRNA genes of E. fetida gut bacteria and surrounding soil bacteria were measured after 28 days of exposure to DINP. The Chao index of E. fetida gut bacteria decreased when the treatment with the highest concentration (2400 mg/kg) was applied. At the phylum level, the abundance of Chloroflexi was significantly lower in the gut of E. fetida. In addition, the abundance of Proteobacteria at the phylum level and Ottowia at the genus level significantly increased in the surrounding soil. Overall, our results shed light on the toxic mechanism of DINP at biochemical, molecular, and omics levels, and contributed to a better understanding of the ecotoxicity of DINP.
Termites are eusocial insects that host a range of prokaryotic and eukaryotic gut symbionts and can differentiate into a range of caste phenotypes. Soldier caste differentiation from termite workers follows two successive molts (worker-presoldier-soldier) that are driven at the endocrine level by juvenile hormone (JH). While physiological and eusocial mechanisms tied to JH signaling have been studied, the role of gut symbionts in the caste differentiation process is poorly understood. Here, we used the JH analog-methoprene in combination with the antibiotic kanamycin to manipulate caste differentiation and gut bacterial loads in Reticulitermes flavipes termites via four bioassay treatments: kanamycin, methoprene, kanamycin+methoprene, and an untreated (negative) control. Bioassay results demonstrated a significantly higher number of presoldiers in the methoprene, highest mortality in kanamycin+methoprene, and significantly reduced protist numbers in all treatments except the untreated control. Bacterial 16S rRNA gene sequencing provided alpha and beta diversity results that mirrored bioassay findings. From ANCOM analysis, we found that several bacterial genera were differentially abundant among treatments. Finally, follow-up experiments showed that if methoprene and kanamycin or untreated termites are placed together, zero or rescued presoldier initiation (respectively) occurs. These findings reveal that endogenous JH selects for symbiont compositions required to successfully complete presoldier differentiation. However, if the gut is voided before the influx of JH, it cannot select for the necessary symbionts that are crucial for molting. Based on these results we are able to provide a novel example of linkages between gut microbial communities and host phenotypic plasticity.
Background: While there have been a lot of studies on the termite gut microbiota, there has been very little research directly on the cellulose-degrading microbiota in termites or their soil environment. This study addresses this problem by profiling cellulose-degrading bacteria and archaea in the selective cellulose cultures of two samples of the eastern subterranean termite ( Reticulitermes flavipes ) and one soil sample collected at the same location as one of the termite samples.
Methods: All the cultures were examined for cell concentration and remaining cellulose after the culture was completed. The 16S rRNA pyrotag sequencing method was used to identify the prokaryotic microbiota for the three cultures and one termite colony without culture. The MOTHUR, SSU-ALIGN, RDPTools, phyloseq, and other R packages were used for sequence and statistical analyses.
Results: Biochemical analyses of the cultures suggested high efficiency of cellulose degradation. Comparative analyses between the cultured and uncultured termite gut microbiota revealed a significant difference. Proteobacteria and Firmicutes were found to be the two most abundant phyla of cellulose-degrading bacteria from the three cultures, but different classes within each phylum dominated the different samples. Shared and sample-specific cellulose-degrading taxa, including a core set of taxa across all the cultures, were identified.
Conclusions: Our study demonstrates the importance of using selective cellulose culture to study the cellulose-degrading microbial community. It also revealed that the cellulose-degrading microbiota in the eastern subterranean termite is significantly influenced by the microbiota in the surrounding soil environment. Biochemical analyses showed that the microbial communities enriched from all the selective cultures were efficient in degrading cellulose, and a core set of bacteria have been identified as targets for further functional analyses.
Spirochetes of the genus Treponema are surprisingly abundant in termite guts, where they play an important role in reductive acetogenesis. Although they occur in all termites investigated, their evolutionary origin is obscure. Here, we isolated the first representative of ‘termite gut treponemes’ from cockroaches, the closest relatives of termites. Phylogenomic analysis revealed that Breznakiella homolactica gen. nov. sp. nov. represents the most basal lineage of the highly diverse ‘termite cluster I’, a deep‐branching sister group of Treponemataceae (fam. ‘Termitinemataceae’) that was present already in the cockroach ancestor of termites and subsequently coevolved with its host. B. homolactica is obligately anaerobic and catalyzes the homolactic fermentation of both hexoses and pentoses. Resting cells produced acetate in the presence of oxygen. Genome analysis revealed the presence of pyruvate oxidase and catalase, and a cryptic potential for the formation of acetate, ethanol, formate, CO2 and H2 — the fermentation products of termite gut isolates. Genes encoding key enzymes of reductive acetogenesis, however, are absent, confirming the hypothesis that the ancestral metabolism of the cluster was fermentative, and that the capacity for acetogenesis from H2 plus CO2 — the most intriguing property among termite gut treponemes — was acquired by lateral gene transfer. This article is protected by copyright. All rights reserved.
Fungus-growing termites are engaged in a tripartite mutualism with intestinal microbes and a monocultivar (Termitomyces sp.) in the fungus garden. The termites are often plagued by entomopathogen (Metarhizium anisopliae) and fungus garden is always threatened by competitors (Xylaria spp.). Here, we aim to understand the defensive role of intestinal microbes, the actinomycetes which were isolated from the gut of Macrotermes barneyi. We obtained 44 antifungal isolates, which showed moderate to strong inhibition to Xylaria sp. HPLC analysis indicated that different types of polyenes (tetraene, pentene, and heptaene) existed in the metabolites of 10 strong antifungal Streptomyces strains. Two pentene macrolides (pentamycin and 1′14-dihydroxyisochainin) were firstly purified from Streptomyces strain HF10, both exhibiting higher activity against Xylaria sp. and M. anisopliae than cultivar Termitomyces. Subsequently, tetraene and heptaene related gene disruption assay showed that the mutant strains lost the ability to produce corresponding polyenes, and they also had significantly decreased activities against Xylaria sp. and M. anisopliae compared to that of wild type strains. These results indicate that polyene-producing Streptomyces from the guts of M. barneyi have strong inhibition to competitor fungus and polyenes contribute to inhibitory effects on Xylaria sp.
Laccase, an important oxidoreductase, is widely distributed in various organisms. Termites are known to decompose lignocellulose efficiently with the aid of gut microorganisms. However, few laccases have been characterized from termite or its gut microbes. We aimed to screen the strain capable of degrading lignocellulose from fungus-growing termites. In this study, Bacillus stratosphericus BCMC2 with lignocellulolytic activity was firstly isolated from the hindgut of fungus-growing termite Macrotermes barneyi. The laccase gene (BaCotA) was cloned both from the BCMC2 strain and termite intestinal metagenomic DNA. BaCotA was overexpressed in E. coli, and the recombinant BaCotA showed high specific activity (554.1 U/mg). BaCotA was thermostable with an optimum temperature of 70 °C, pH 5.0. Furthermore, BaCotA was resistant to alkali and organic solvents. The enzyme remained more than 70% residual activity at pH 8.0 for 120 min; and the organic solvents such as methanol, ethanol and acetone (10%) had no inhibitory effect on laccase activity. Additionally, BaCotA exhibited efficient decolorization ability towards indigo and crystal violet. The multiple enzymatic properties suggested the presented laccase as a potential candidate for industrial applications. Moreover, this study highlighted that termite intestine is a good resource for either new strains or enzymes.
Insects that farm monocultures of fungi are canonical examples of nutritional symbiosis as well as independent evolution of agriculture in non-human animals. But just like in human agriculture, these fungal crops face constant threat of invasion by weeds which, if unchecked, takes over the crop fungus. In fungus-growing termites, the crop fungus (Termitomyces) faces such challenges from the parasitic fungus Pseudoxylaria. The mechanism by which Pseudoxylaria is suppressed is not known. However, evidence suggests that some bacterial secondary symbionts can serve as defensive mutualists by preventing the growth of Pseudoxylaria. However, such secondary symbionts must possess the dual, yet contrasting, capabilities of suppressing the weedy fungus while keeping the growth of the crop fungus unaffected. This study describes the isolation, identification and culture-dependent estimation of the roles of several such putative defensive mutualists from the colonies of the wide-spread fungus-growing termite from India, Odontotermes obesus. From the 38 bacterial cultures tested, a strain of Pseudomonas showed significantly greater suppression of the weedy fungus than the crop fungus. Moreover, a 16S rRNA pan-microbiome survey, using the Nanopore platform, revealed Pseudomonas to be a part of the core microbiota of Odontotermes obesus. A meta-analysis of microbiota composition across different species of Odontotermes also confirms the wide-spread prevalence of Pseudomonas within this termite. These evidence indicate that Pseudomonas could be playing the role of defensive mutualist within Odontotermes.
Termitomyces species are wild edible mushrooms that possess high nutritional value and a wide range of medicinal properties. However, the cultivation of these mushrooms is very difficult because of their symbiotic association with termites. In this study, we aimed to examine the differences in physicochemical indices and microbial communities between combs with Termitomyces basidiomes (CF) and combs without Termitomyces basidiomes (CNF). High-performance liquid chromatography (HPLC), inductively coupled plasma optical emission spectrometry (ICP-OES), gas chromatography equipped with a flame ionization detector (GC-FID), some commercial kits, high-throughput sequencing of the 16s RNA, and internal transcribed spacer (ITS) were used. Humidity, pH, and elements, i.e., Al, Ba, Fe, Mn, Ni, S, Ca, and Mg were higher while amino acids particularly alanine, tyrosine, and isoleucine were lower in CF as compared to CNF. The average contents of fatty acids were not significantly different between the two comb categories. The bacterial genera Alistipes , Burkholderia , Sediminibacterium , and Thermus were dominant in all combs. Brevibacterium , Brevundimonas , and Sediminibacterium were significantly more abundant in CF. Basidiomycota and Ascomycota were also identified in combs. Termitomyces clypeatus , Termitomyces sp. Group3, and Termitomyces sp. were the most dominant species in combs. However, any single Termitomyces species was abundantly present in an individual comb.
Fungus‐growing termites are among the most successful herbivorous animals and improve crop productivity and soil fertility. A range of symbiotic organisms can be found inside their nests. However, interactions of termites with these symbionts are poorly understood. This review provides detailed information on the role of multipartite symbioses (between termitophiles, termites, fungi, and bacteria) in fungus‐growing termites for lignocellulose degradation. The specific functions of each component in the symbiotic system are also discussed. Based on previous studies, we argue that the enzymatic contribution from the host, fungus, and bacteria greatly facilitates the decomposition of complex polysaccharide plant materials. The host‐termitophile interaction protects the termite nest from natural enemies and maintains the stability of the microenvironment inside the colony.
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The data deluge rises in the absence of a framework for deciding which ones to sequence and for containing, organizing, and interpreting the data that result. The NIH-sponsored Human Microbiome Project (HMP), which samples and sequences microbial populations found in the human gut and other bodily sites, has already generated about a million times as much sequence data as did the initial Human Genome Project. To create a reference set of microbial gene sequences, the HMP began with a phase that funded four large-scale sequencing centers. The initiative will begin with the sequencing of up to 600 genomes from both cultured and uncultured bacteria, plus several non-bacterial microbes. The absence of a conceptual framework for interpreting HMP data becomes apparent when one asks which principles and well-tested theories in ecology can provide insight into the human microbiome. NIH could double down on its investment by sequencing more and more microbes and metagenomes in the hope that large enough data sets will speak for themselves and yield insights in response to the principles of ecology and other algorithms.
A strategy to understand the microbial components of the human genetic and metabolic landscape and how they contribute to normal physiology and predisposition to disease.
The interaction between termites and their gut symbionts has continued to attract the curiosity of researchers over time. The aim of this study was to characterize and compare the bacterial diversity and community structure in the guts of three termites (Odontotermes somaliensis, Odontotermes sp. and Microtermes sp.) using 16S rRNA gene sequencing of clone libraries. Clone libraries were screened by restriction fragment length polymorphism and representative clones from O. somaliensis (100 out of 330 clones), Odontotermes sp. (100 out of 359 clones) and Microtermes sp. (96 out 336 clones) were sequenced. Phylogenetic analysis indicated seven bacterial phyla were represented: Bacteroidetes, Spirochaetes, Firmicutes, Proteobacteria, Synergistetes, Planctomycetes and Actinobacteria. Sequences representing the phylum Bacteroidetes (>60 %) were the most abundant group in Odontotermes while those of Spirochaetes (29 %) and Firmicutes (23 %) were the abundant groups in Microtermes. The gut bacterial community structure within the two Odontotermes species investigated here was almost identical at the phylum level, but the Microtermes sp. had a unique bacterial community structure. Bacterial diversity was higher in Odontotermes than in Microtermes. The affiliation and clustering of the sequences, often with those from other termites' guts, indicate a majority of the gut bacteria are autochthonous having mutualistic relationships with their hosts. The findings underscore the presence of termite-specific bacterial lineages, the majority of which are still uncultured.
Macrotermitinae (fungus-cultivating termites) are major decomposers in tropical and subtropical areas of Asia and Africa. They have specifically evolved mutualistic associations with both a Termitomyces fungi on the nest and a gut microbiota, providing a model system for probing host-microbe interactions. Yet the symbiotic roles of gut microbes residing in its major feeding caste remain largely undefined. Here, by pyrosequencing the whole gut metagenome of adult workers of a fungus-cultivating termite (Odontotermes yunnanensis), we showed that it did harbor a broad set of genes or gene modules encoding carbohydrate-active enzymes (CAZymes) relevant to plant fiber degradation, particularly debranching enzymes and oligosaccharide-processing enzymes. Besides, it also contained a considerable number of genes encoding chitinases and glycoprotein oligosaccharide-processing enzymes for fungal cell wall degradation. To investigate the metabolic divergence of higher termites of different feeding guilds, a SEED subsystem-based gene-centric comparative analysis of the data with that of a previously sequenced wood-feeding Nasutitermes hindgut microbiome was also attempted, revealing that SEED classifications of nitrogen metabolism, and motility and chemotaxis were significantly overrepresented in the wood-feeder hindgut metagenome, while Bacteroidales conjugative transposons and subsystems related to central aromatic compounds metabolism were apparently overrepresented here. This work fills up our gaps in understanding the functional capacities of fungus-cultivating termite gut microbiota, especially their roles in the symbiotic digestion of lignocelluloses and utilization of fungal biomass, both of which greatly add to existing understandings of this peculiar symbiosis.
This paper presents data on the abundance, biomass and species richness of termites in the Mbalmayo Forest Reserve, southern Cameroon. Five plots of differing disturbance level (near primary forest, old secondary forest, young plantation, weeded Chromolaena fallow, and completely cleared forest) were sampled for termites in two successive years (July 1992 and July 1993, giving a total of ten sampling areas, plus one in the completely cleared plot in November 1992). A stratified sampling regime of soil pits, wood samples, mound samples and soil scrape samples was used. Estimated abundance and biomass were extremely high in the near primary and old secondary plot (maximum estimated abundance, old secondary sampling area 1, 10488 m-2, maximum biomass density, near primary sampling area 1, 123.2 g m-2). In all cases termite abundance was highly clumped. Disturbance had apparently little effect on termite abundances and biomass in forested plots, but there were clear reductions in abundance and biomass in the cleared plots. In the completely cleared plot, abundance and biomass fell sharply from year 1 to year 2, presumably because colonies left after clearance had dried out and died. There were large differences in the taxonomic-, nesting- and feeding-group composition of the plots, with soil feeding termites being especially strongly affected by disturbance. The sources of error associated with this sampling programme are discussed. It is argued that the near primary forest plot may have higher microhabitat and concomitant termite assemblage heterogeneity than the more disturbed plots. In most cases over 90% of the overall abundance in a sampling area was due to a few species; however, the same species were not dominant in all sampling areas. This may be due to the unpredictable dynamics of colony foundation and extinction, and will make estimations of the effect of termites on overall ecosystem processes (from abundance and biomass data alone) problematical. There is no evidence of immigration of savanna termites into the forest reserve, and thus cleared areas have depauperate forest assemblages. It is concluded that this is the most accurate estimation of termite assemblage parameters yet attempted.
Termites effectively feed on many types of lignocellulose assisted by their gut microbial symbionts. To better understand the microbial decomposition of biomass with varied chemical profiles, it is important to determine whether termites harbor different microbial symbionts with specialized functionalities geared toward different feeding regimens. In this study, we compared the microbiota in the hindgut paunch of Amitermes wheeleri collected from cow dung and Nasutitermes corniger feeding on sound wood by 16S rRNA pyrotag, comparative metagenomic and metatranscriptomic analyses. We found that Firmicutes and Spirochaetes were the most abundant phyla in A. wheeleri, in contrast to N. corniger where Spirochaetes and Fibrobacteres dominated. Despite this community divergence, a convergence was observed for functions essential to termite biology including hydrolytic enzymes, homoacetogenesis and cell motility and chemotaxis. Overrepresented functions in A. wheeleri relative to N. corniger microbiota included hemicellulose breakdown and fixed-nitrogen utilization. By contrast, glycoside hydrolases attacking celluloses and nitrogen fixation genes were overrepresented in N. corniger microbiota. These observations are consistent with dietary differences in carbohydrate composition and nutrient contents, but may also reflect the phylogenetic difference between the hosts.
Elucidating the spatial dynamic and core constituents of the microbial communities found in association with arthropod hosts is of crucial importance for insects that may vector human or agricultural pathogens. The hematophagous Cimex lectularius (Hemiptera: Cimicidae), known as the human bed bug, has made a recent resurgence in North America, as well as worldwide, potentially owing to increased travel, climate change and resistance to insecticides. A comprehensive survey of the bed bug microbiome has not been performed to date, nor has an assessment of the spatial dynamics of its microbiome. Here we present a survey of internal and external bed bug microbial communities by amplifying the V4-V6 hypervariable region of the 16S rDNA gene region followed by 454 Titanium sequencing using 31 individuals from eight distinct collection locations obtained from residences in Cincinnati, OH. Across all samples, 97% of the microbial community is made up of two dominant OTUs, previously identified as the α-proteobacterium Wolbachia and an unnamed γ-proteobacterium from the Enterobacteriaceae. Microbial communities varied among host locations for measures of community diversity and exhibited structure according to collection location. This broad survey represents the most in-depth assessment, to date, of the microbes that associate with bed bugs.
Termites, particularly the mound building, fungus growing Macrotermitinae, reach densities of up to 400 termites m−2 in soils of dry tropical Africa. The influence of Macrotermi tinae in increasing certain soil nutrients in mounds compared to adjacent soils has been documented, but the links between litter harvesting by termites, soil fertility, and global C cycling have not been explored. This study reviews the evidence from soil science, ecology and atmos pheric chemistry and generates hypotheses to explain the role of termites in dry tropical eco systems. It is suggested that termite activity exhaustively partitions litterfall among adjacent com peting colonies, where it is so thoroughly decomposed that little or no organic C is incorporated into the soils. Associated N, P, and cations build up in the mounds, but C apparently is emitted as CO2 and CH4 from the mounds. While not adequate to calculate nutrient fluxes through termites, the data available support the argument that termites contribute significantly to atmospheric fluxes of CO2 and CH4. Moreover, they suggest a coupling of regional soil forming processes and the global C budget.
Starting in 2003, numerous studies using culture-independent methodologies to characterize the gut microbiota of honey bees have retrieved a consistent and distinctive set of eight bacterial species, based on near identity of the 16S rRNA gene sequences. A recent study [Mattila HR, Rios D, Walker-Sperling VE, Roeselers G, Newton ILG (2012) Characterization of the active microbiotas associated with honey bees reveals healthier and broader communities when colonies are genetically diverse. PLoS ONE 7(3): e32962], using pyrosequencing of the V1-V2 hypervariable region of the 16S rRNA gene, reported finding entirely novel bacterial species in honey bee guts, and used taxonomic assignments from these reads to predict metabolic activities based on known metabolisms of cultivable species. To better understand this discrepancy, we analyzed the Mattila et al. pyrotag dataset. In contrast to the conclusions of Mattila et al., we found that the large majority of pyrotag sequences belonged to clusters for which representative sequences were identical to sequences from previously identified core species of the bee microbiota. On average, they represent 95% of the bacteria in each worker bee in the Mattila et al. dataset, a slightly lower value than that found in other studies. Some colonies contain small proportions of other bacteria, mostly species of Enterobacteriaceae. Reanalysis of the Mattila et al. dataset also did not support a relationship between abundances of Bifidobacterium and of putative pathogens or a significant difference in gut communities between colonies from queens that were singly or multiply mated. Additionally, consistent with previous studies, the dataset supports the occurrence of considerable strain variation within core species, even within single colonies. The roles of these bacteria within bees, or the implications of the strain variation, are not yet clear.
1. Gut content analysis of termites was undertaken using microscopical techniques. The 46 study species covered the entire range of taxonomic and feeding forms within the Order.
2. Inter-specific gut contents data were analysed using principal components analysis, placing species along a clear humification gradient based on variations in the amount of silica and plant tissue fragments in the gut.
3. Redundancy analysis was used to find morphological correlates of the observed variation in gut contents. A total of 22 morphological characters (out of 45 candidate characters) were correlated significantly with the gut contents.
4. Three of the 22 significantly correlated characters unambiguously defined feeding groups, which were designated groups I to IV in increasing order of humification of the feeding substrate. Group I contains lower termite dead wood and grass-feeders; group II contains Termitidae with a range of feeding habits including dead wood, grass, leaf litter, and micro-epiphytes; group III contains Termitidae feeding in the organic rich upper layers of the soil; group IV contains the true soil-feeders (again all Termitidae), ingesting apparently mineral soil. These groupings were generally supported statistically in a canonical covariance analysis, although group II apparently represents termite species with a rather wide range of feeding habits.
5. Using existing hypotheses of termite phylogenetic relationships, it seems probable that group I feeders are phylogenetically basal, and that the other groupings have arisen independently on a number of occasions. Soil-feeding (i.e. group III and group IV feeding) may have evolved due to the co-option of faecal material as a fungal substrate by Macrotermitinae-like ancestral forms. As a consequence, these forms would have been constrained to build nest structures from soil and would therefore have passed at least some soil through their guts.
We explore the microbiota of 18 body sites in over 200 individuals using sequences amplified V1-V3 and the V3-V5 small subunit ribosomal RNA (16S) hypervariable regions as part of the NIH Common Fund Human Microbiome Project. The body sites with the greatest number of core OTUs, defined as OTUs shared amongst 95% or more of the individuals, were the oral sites (saliva, tongue, cheek, gums, and throat) followed by the nose, stool, and skin, while the vaginal sites had the fewest number of OTUs shared across subjects. We found that commonalities between samples based on taxonomy could sometimes belie variability at the sub-genus OTU level. This was particularly apparent in the mouth where a given genus can be present in many different oral sites, but the sub-genus OTUs show very distinct site selection, and in the vaginal sites, which are consistently dominated by the Lactobacillus genus but have distinctly different sub-genus V1-V3 OTU populations across subjects. Different body sites show approximately a ten-fold difference in estimated microbial richness, with stool samples having the highest estimated richness, followed by the mouth, throat and gums, then by the skin, nasal and vaginal sites. Richness as measured by the V1-V3 primers was consistently higher than richness measured by V3-V5. We also show that when such a large cohort is analyzed at the genus level, most subjects fit the stool "enterotype" profile, but other subjects are intermediate, blurring the distinction between the enterotypes. When analyzed at the finer-scale, OTU level, there was little or no segregation into stool enterotypes, but in the vagina distinct biotypes were apparent. Finally, we note that even OTUs present in nearly every subject, or that dominate in some samples, showed orders of magnitude variation in relative abundance emphasizing the highly variable nature across individuals.
Increasing evidence suggests that environmental factors changing the normal colonisation pattern in the gut strongly influence the risk of developing autoimmune diabetes. The aim of this study was to investigate, both during infancy and adulthood, whether treatment with vancomycin, a glycopeptide antibiotic specifically directed against Gram-positive bacteria, could influence immune homeostasis and the development of diabetic symptoms in the NOD mouse model for diabetes.
Accordingly, one group of mice received vancomycin from birth until weaning (day 28), while another group received vancomycin from 8 weeks of age until onset of diabetes. Pyrosequencing of the gut microbiota and flow cytometry of intestinal immune cells was used to investigate the effect of vancomycin treatment.
At the end of the study, the cumulative diabetes incidence was found to be significantly lower for the neonatally treated group compared with the untreated group, whereas the insulitis score and blood glucose levels were significantly lower for the mice treated as adults compared with the other groups. Mucosal inflammation was investigated by intracellular cytokine staining of the small intestinal lymphocytes, which displayed an increase in cluster of differentiation (CD)4(+) T cells producing pro-inflammatory cytokines in the neonatally treated mice. Furthermore, bacteriological examination of the gut microbiota composition by pyrosequencing revealed that vancomycin depleted many major genera of Gram-positive and Gram-negative microbes while, interestingly, one single species, Akkermansia muciniphila, became dominant.
The early postnatal period is a critical time for microbial protection from type 1 diabetes and it is suggested that the mucolytic bacterium A. muciniphila plays a protective role in autoimmune diabetes development, particularly during infancy.
Higher termites are characterized by a purely prokaryotic gut microbiota and an increased compartmentation of their intestinal tract. In soil-feeding species, each gut compartment has different physicochemical conditions and is colonized by a specific microbial community. Although considerable information has accumulated also for wood-feeding species of the genus Nasutitermes, including cellulase activities and metagenomic data, a comprehensive study linking physicochemical gut conditions with the structure of the microbial communities in the different gut compartments is lacking. In this study, we measured high-resolution profiles of H(2), O(2), pH, and redox potential in the gut of Nasutitermes corniger termites, determined the fermentation products accumulating in the individual gut compartments, and analyzed the bacterial communities in detail by pyrotag sequencing of the V3-V4 region of the 16S rRNA genes. The dilated hindgut paunch (P3 compartment) was the only anoxic gut region, showed the highest density of bacteria, and accumulated H(2) to high partial pressures (up to 12 kPa). Molecular hydrogen is apparently produced by a dense community of Spirochaetes and Fibrobacteres, which also dominate the gut of other Nasutitermes species. All other compartments, such as the alkaline P1 compartment (average pH, 10.0), showed high redox potentials and comprised small but distinct populations characteristic for each gut region. In the crop and the posterior hindgut compartments, the community was even more diverse than in the paunch. Similarities in the communities of the posterior hindgut and crop suggested that proctodeal trophallaxis or coprophagy also occurs in higher termites. The large sampling depths of pyrotag sequencing in combination with the determination of important physicochemical parameters allow cautious conclusions concerning the functions of particular bacterial lineages in the respective gut sections to be drawn.
We present a new perspective for the role of Termitomyces fungi in the mutualism with fungus-growing termites. According to the predominant view, this mutualism is as an example of agriculture with termites as farmers of a domesticated fungus crop, which is used for degradation of plant-material and production of fungal biomass. However, a detailed study of the literature indicates that the termites might as well be envisioned as domesticates of the fungus. According to the “ruminant hypothesis” proposed here, termite workers, by consuming asexual fruiting bodies not only harvest asexual spores, but also lignocellulolytic enzymes, which they mix with foraged plant material and enzymes of termite and possibly bacterial origin. This mixture is the building material of the fungus garden and facilitates efficient degradation of plant material. The fungus garden thus functions as an external rumen for termites and primarily the fungi themselves benefit from their own, and gut-derived, lignocellulolytic enzymes, using the termites to efficiently mix these with their growth substrate. Only secondarily the termites benefit, when they consume the degraded, nitrogen-enriched plant-fungus mixture a second time. We propose that the details of substrate use, and the degree of complementarity and redundancy among enzymes in food processing, determine selection of horizontally transmitted fungal symbionts at the start of a colony: by testing spores on a specific, mechanically and enzymatically pre-treated growth substrate, the termite host has the opportunity to select specific fungal symbionts. Potentially, the gut-microbiota thus influence host-fungus specificity, and the selection of specific fungal strains at the start of a new colony. We argue that we need to expand the current bipartite insect-biased view of the mutualism of fungus-growing termites and include the possible role of bacteria and the benefit for the fungi to fully understand the division of labor among partners in substrate degradation.
We review the two known mutualistic symbioses between basidiomycete fungi and social insects: the attine ants and macrotermitine termites, comparing their origin, history and patterns of co-evolution, and stability. It is argued that ants are “specialised farmers of unspecialised crops”, whereas termites are “specialised farmers of specialised crops”. Furthermore, despite differences in symmetry and symbiont transmission mode, in both relationships there is a moderate specificity between partners. The unresolved debate about the main role of the symbiotic fungus in the fungus-growing termites is summarised and contrasted with the role in the fungus in attine ants, which is little debated. We compare colony foundation and structure, and the modes of symbiotic interaction between the two groups of social insects, highlighting gaps in our understanding of both systems. Finally, we discuss how these symbioses can be evolutionarily stable and the mechanisms by which the ant and termite symbionts ensure monopolies of host care. We conclude by identifying some lines of future research within the fungus-growing termite symbiosis.
Ants dominate many terrestrial ecosystems, yet we know little about their nutritional physiology and ecology. While traditionally viewed as predators and scavengers, recent isotopic studies revealed that many dominant ant species are functional herbivores. As with other insects with nitrogen-poor diets, it is hypothesized that these ants rely on symbiotic bacteria for nutritional supplementation. In this study, we used cloning and 16S sequencing to further characterize the bacterial flora of several herbivorous ants, while also examining the beta diversity of bacterial communities within and between ant species from different trophic levels. Through estimating phylogenetic overlap between these communities, we tested the hypothesis that ecologically or phylogenetically similar groups of ants harbor similar microbial flora. Our findings reveal: (i) clear differences in bacterial communities harbored by predatory and herbivorous ants; (ii) notable similarities among communities from distantly related herbivorous ants and (iii) similar communities shared by different predatory army ant species. Focusing on one herbivorous ant tribe, the Cephalotini, we detected five major bacterial taxa that likely represent the core microbiota. Metabolic functions of bacterial relatives suggest that these microbes may play roles in fixing, recycling, or upgrading nitrogen. Overall, our findings reveal that similar microbial communities are harbored by ants from similar trophic niches and, to a greater extent, by related ants from the same colonies, species, genera, and tribes. These trends hint at coevolved histories between ants and microbes, suggesting new possibilities for roles of bacteria in the evolution of both herbivores and carnivores from the ant family Formicidae.
The comparative structure of bacterial communities among closely related host species remains relatively unexplored. For instance, as speciation events progress from incipient to complete stages, does divergence in the composition of the species' microbial communities parallel the divergence of host nuclear genes? To address this question, we used the recently diverged species of the parasitoid wasp genus Nasonia to test whether the evolutionary relationships of their bacterial microbiotas recapitulate the Nasonia phylogenetic history. We also assessed microbial diversity in Nasonia at different stages of development to determine the role that host age plays in microbiota structure. The results indicate that all three species of Nasonia share simple larval microbiotas dominated by the γ-proteobacteria class; however, bacterial species diversity increases as Nasonia develop into pupae and adults. Finally, under identical environmental conditions, the relationships of the microbial communities reflect the phylogeny of the Nasonia host species at multiple developmental stages, which suggests that the structure of an animal's microbial community is closely allied with divergence of host genes. These findings highlight the importance of host evolutionary relationships on microbiota composition and have broad implications for future studies of microbial symbiosis and animal speciation.
Coevolution of mammals and their gut microbiota has profoundly affected their radiation into myriad habitats. We used shotgun sequencing of microbial community DNA and targeted sequencing of bacterial 16S ribosomal RNA genes to gain an understanding of how microbial communities adapt to extremes of diet. We sampled fecal DNA from 33 mammalian species and 18 humans who kept detailed diet records, and we found that the adaptation of the microbiota to diet is similar across different mammalian lineages. Functional repertoires of microbiome genes, such as those encoding carbohydrate-active enzymes and proteases, can be predicted from bacterial species assemblages. These results illustrate the value of characterizing vertebrate gut microbiomes to understand host evolutionary histories at a supraorganismal level.
Assortative mating, considered to be an early event in speciation, has been studied for decades in the context of divergent adaptation. In Drosophila it is commonly attributed to genetic elements in the flies that exhibit assortative mating. However, some cases have been reported where the genetic basis for these differences was unclear. In light of the Hologenome Theory of Evolution (Zilber-Rosenberg and Rosenberg, 2008), we considered the microbiota of Drosophila as an additional element, acting together with its host to better adapt to a changing environment. The microbiota of any organism is closely linked to its host. Many of the impacts of the microbiota on its host are known. New evidence shows an interesting, previously unknown, role of the microbiota in influencing its host’s behavior. In one case, as a result of adaptation to a new substrate, the microbiota changed with behavioral implications on its host flies. By changing its host’s mating preference, the microbiota has the potential of driving the evolution of its host. In this chapter, the mating process in Drosophila will be reviewed within the framework of the hologenome theory of evolution. Some conclusions and speculations on how microbes and their Drosophila host interact will be presented.
All of the enzymes required for the digestion of native cellulose, as well as of xylan and pectin, are present in the gut fluids of adult workers of the fungus-growing termite, Macrotermes natalensis. Activity levels are highest in the midgut, suggesting that this portion of the gut, rather than the paunch, is the major site of polysaccharide digestion in this higher termite. The Ci-enzymes, active against crystalline cellulose, are acquired by the termites when they feed upon the fungus nodules which grow on their fungus combs. The -enzymes, active against noncrystalline cellulose and soluble derivatives and degradation products of cellulose, are derived in part from ingested fungal material, and in part they are produced internally by the termite, being secreted both by the midgut epithelium and the salivary glands. The nutritional dependence of the termites on their fungus gardens is explained in terms of their reliance upon the fungus nodules as a source of the critical C₁-enzymes, which must be acquired before they are able to effect the digestion of cellulosic materials. It is proposed that a strategy of resource utilization based upon the acquisition of digestive enzymes which expand the range of natural substrates suitable for exploitation as nutrient sources may be a general one.
Termites are an extremely successful group of wood-degrading organisms and are therefore important both for their roles in carbon turnover in the environment and as potential sources of biochemical catalysts for efforts aimed at converting wood into biofuels. To contribute to the evolutional study of termite digestive symbiosis, a bacterial 16S rRNA gene clone library from the gut microbial community of the fungus-growing termite Macrotermes barneyi was constructed. After screening by restriction fragment length polymorphism (RFLP) analysis, 25 out of 105 clones with unique RFLP patters were sequenced and phylogenetically analyzed. Many of the clones (95%) were derived from three phyla within the domain bacteria: Bacteroidetes, Firmicutes andProteobacteria. In addition, a few clones derived from Deferribacteres, Actinobacteria andPlanctomycetes were also found. No one clone affiliated with the phylum Spirochaeteswas identified, in contrast to the case of wood-feeding termites. The phylogenetic analysis revealed that nearly half of the representative clones (11 phylotypes) formed monophyletic clusters with clones obtained from other termite species, especially with the sequences retrieved from fungus-growing termites. These results indicate that the presence of termite-specific bacterial lineages implies a coevolutional relationship of gut microbes and host termites. The remaining 14 clones formed a cluster, and there was very low sequence similarity (30 to 40%) to known 16S rRNA sequences. The 16S rRNA gene sequence data showed that the majority of the intestinal microflora of M. barneyiconsisted of new, uncultured species previously unknown to microbiologists.
Key words: Termite, bacteria, symbiosis, restriction, fragment, length, polymorphism.
The prime object of this book is to put into the hands of research workers, and especially of biologists, the means of applying statistical tests accurately to numerical data accumulated in their own laboratories or available in the literature.
Termites are an extremely successful group of wood-degrading organisms and are therefore important both for their roles in carbon turnover in the environment and as potential sources of biochemical catalysts for efforts aimed at converting wood into biofuels. To contribute to the evolutional study of termite digestive symbiosis, a bacterial 16S rRNA gene clone library from the gut microbial community of the fungus-growing termite Macrotermes barneyi was constructed. After screening by restriction fragment length polymorphism (RFLP) analysis, 25 out of 105 clones with unique RFLP patters were sequenced and phylogenetically analyzed. Many of the clones (95%) were derived from three phyla within the domain bacteria: Bacteroidetes, Firmicutes and Proteobacteria. In addition, a few clones derived from Deferribacteres, Actinobacteria and Planctomycetes were also found. No one clone affiliated with the phylum Spirochaetes was identified, in contrast to the case of wood-feeding termites. The phylogenetic analysis revealed that nearly half of the representative clones (11 phylotypes) formed monophyletic clusters with clones obtained from other termite species, especially with the sequences retrieved from fungus-growing termites. These results indicate that the presence of termite-specific bacterial lineages implies a coevolutional relationship of gut microbes and host termites. The remaining 14 clones formed a cluster, and there was very low sequence similarity (30 to 40%) to known 16S rRNA sequences. The 16S rRNA gene sequence data showed that the majority of the intestinal microflora of M. barneyi consisted of new, uncultured species previously unknown to microbiologists.
Termites digest lignocellulose with the help of their symbiotic gut microbiota. In the hindgut of evolutionary lower termites, a dense community of cellulolytic flagellates sequesters wood particles from the hindgut content into their digestive vacuoles. In higher termites (family Termitidae), which possess an entirely prokaryotic microbiota, the wood particles are available for bacterial colonization. Substantial particle-associated cellulase activities have been detected in the hindgut of Nasutitermes species, but the microorganisms responsible for these activities and their potential association with the wood fibers remain to be studied. Here, we used density-gradient centrifugation to separate wood fibers and adherent bacterial cells from cells freely suspended in the hindgut fluid. In Nasutitermes corniger, the fiber fraction contained 28% of the DNA and 45% of the cellulase activity in the luminal contents (P3 region). Community fingerprinting (T-RFLP) and pyrotag sequencing analysis of the bacterial 16S rRNA genes demonstrated that the wood fibers in the hindgut of both N. corniger and Nasutitermes takasagoensis are specifically colonized by members of Fibrobacteres, the TG3 phylum, and certain lineages of Spirochaetes characteristic of the gut microbiota of wood-feeding higher termites. We propose that the loss of flagellates in higher termites provided a new niche for fiber-associated cellulolytic bacteria.
Termites digest wood and other lignocellulosic substrates with the help of their intestinal microbiota. While the functions of the symbionts in the digestive process are slowly emerging, the origin of the bacteria colonizing the hindgut bioreactor is entirely in the dark. Recently, our group discovered numerous representatives of bacterial lineages specific for termite guts in a closely related omnivorous cockroach, but it remains unclear whether they derive from the microbiota of a common ancestor or were independently selected by the gut environment. Here, we studied the bacterial gut microbiota in 34 species of termites and cockroaches using pyrotag analysis of the 16S rRNA genes. Although the community structure strongly differed between the major host groups, with dramatic changes in the relative abundance of particular bacterial taxa, we found that the majority of sequence reads belonged to bacterial lineages that were shared among most host species. When mapped onto the host tree, the changes in community structure coincided with major events in termite evolution, such as acquisition and loss of cellulolytic protists and the ensuing dietary diversification. Unifrac analysis of the core microbiota of termites and cockroaches and phylogenetic treeing of individual genus-level lineages revealed a general host signal, whereas the branching order often did not match the detailed phylogeny of the host. It remains unclear whether the lineages in question were associated already with the ancestral cockroach since the early Cretaceous (cospeciation) or are diet-specific lineages that were independently acquired from the environment (host selection).
Their ability to degrade lignocellulose gives termites an important place in the carbon cycle. This ability relies on their partnership with a diverse community of bacterial, archaeal and eukaryotic gut symbionts, which break down the plant fibre and ferment the products to acetate and variable amounts of methane, with hydrogen as a central intermediate. In addition, termites rely on the biosynthetic capacities of their gut microbiota as a nutritional resource. The mineralization of humus components in the guts of soil-feeding species also contributes to nitrogen cycling in tropical soils. Lastly, the high efficiency of their minute intestinal bioreactors makes termites promising models for the industrial conversion of lignocellulose into microbial products and the production of biofuels.
Correlation between gut microbiota and host phylogeny could reflect codiversification over shared evolutionary history, or a selective environment that is more similar in related hosts. These alternatives imply substantial differences in the relationship between host and symbiont, but can they be distinguished based on patterns in the community data themselves? Here, we explore patterns of phylogenetic correlation in the distribution of gut bacteria among species of turtle ants (genus Cephalotes), which host a dense gut microbial community. We use 16S rRNA pyrosequencing from 25 Cephalotes species to show that their gut community is remarkably stable, from the colony to the genus level. Despite this overall similarity, the existing differences among species' microbiota significantly correlate with host phylogeny. We introduce a novel analytical technique to test whether these phylogenetic correlations are derived from recent bacterial evolution, as would be expected in the case of codiversification, or from broader shifts more likely to reflect environmental filters imposed by factors like diet or habitat. We also test this technique on a published dataset of ape microbiota, confirming earlier results while revealing previously undescribed patterns of phylogenetic correlation. Our results indicate a high degree of partner fidelity in the Cephalotes microbiota, suggesting that vertical transmission of the entire community could play an important role in the evolution and maintenance of the association. As additional comparative microbiota data become available, the techniques presented here can be used to explore trends in the evolution of host-associated microbial communities. This article is protected by copyright. All rights reserved.
Insect guts are often colonized by multi-species microbial communities that play integral roles in nutrition, digestion, and defense. Community composition can differ across host species with increasing dietary and genetic divergence, yet gut microbiota can also vary between conspecific hosts and across an individual's lifespan. Through exploration of such intraspecific variation and its correlates, molecular profiling of microbial communities can generate and test hypotheses on the causes and consequences of symbioses. In this study, we used 454 pyrosequencing and TRFLP to achieve these goals in an herbivorous ant, Cephalotes varians, exploring variation in bacterial communities across colonies, populations, and workers reared on different diets. C. varians bacterial communities were dominated by 16 core species present in over two-thirds of the sampled colonies. Core species comprised multiple genotypes, or strains, and hailed from ant-specific clades containing relatives from other Cephalotes species. Yet three were detected in environmental samples, suggesting the potential for environmental acquisition. In spite of their prevalence and long-standing relationships with Cephalotes ants, the relative abundance and genotypic composition of core species varied across colonies. Diet-induced plasticity is a likely cause, but only pollen-based diets had consistent effects, altering the abundance of two types of bacteria. Additional factors such as host age, genetics, chance, or natural selection must therefore shape natural variation. Future studies on these possibilities and on bacterial contributions to the use of pollen, a widespread food source across Cephalotes, will be important steps in developing C. varians as a model for studying widespread social insect-bacteria symbioses. This article is protected by copyright. All rights reserved.
Mammals have diversified into many dietary niches. Specialized myrmecophagous (ant- and termite-eating) placental mammals represent a textbook example of evolutionary convergence driven by extreme diet specialization. Armadillos, anteaters, aardvarks, pangolins and aardwolves thus provide a model system for understanding the potential role of gut microbiota in the convergent adaptation to myrmecophagy. Here, we expand upon previous mammalian gut microbiome studies by using high-throughput barcoded Illumina sequencing of the 16S rRNA gene to characterize the composition of gut microbiota in 15 species representing all placental myrmecophagous lineages and their close relatives from zoo- and field-collected samples. We confirm that both diet and phylogeny drive the evolution of mammalian gut microbiota, with cases of convergence in global composition, but also examples of phylogenetic inertia. Our results reveal specialized placental myrmecophages as a spectacular case of large-scale convergence in gut microbiome composition. Indeed, neighbour-net networks and beta-diversity plots based on UniFrac distances show significant clustering of myrmecophagous species (anteaters, aardvarks and aardwolves), even though they belong to phylogenetically distant lineages representing different orders. The aardwolf, which diverged from carnivorous hyenas only in the last 10 million years, experienced a convergent shift in the composition of its gut microbiome to become more similar to other myrmecophages. These results confirm diet adaptation to be a major driving factor of convergence in gut microbiome composition over evolutionary timescales. This study sets the scene for future metagenomic studies aiming at evaluating potential convergence in functional gene content in the microbiomes of specialized mammalian myrmecophages.
In order to investigate the role of the mutualistic fungus, Termitomyces sp., in the fungus-growing termite, Macrotermes gilvus, we applied CP/MAS 13C NMR and selected proximate analyses to fungus comb of different ages and degrees of maturation. We found evidence that lignin degradation took place progressively in the fungus comb. In vitro digestibility of cellulose in old fungus comb, on which the termites feed, was approximately 3-fold higher than that in the fresh part. These results confirm the ‘lignin degradation hypothesis’ that the role of the mutualistic fungi is to degrade lignin and enhance the digestibility of cellulose for the termites, suggesting the ability of the termite–fungus association to make extremely efficient use of plant material.
Diets shape the animal gut microbiota, although the relationships between diets and the structure of the gut microbial community are not yet well understood. The gut bacterial communities of Reticulitermes flavipes termites fed on four individual plant biomasses with different degrees of recalcitrance to biodegradation were investigated by 16S rRNA pyrosequencing analysis. The termite gut bacterial communities could be differentiated between grassy and woody diets, and among grassy diets (corn stover vs. sorghum). The majority of bacterial taxa were shared across all diets, but each diet significantly enriched some taxa. Interestingly, the diet of corn stover reduced gut bacterial richness and diversity compared to other diets, and this may be related to the lower recalcitrance of this biomass to degradation.
To investigate whether the role of symbiotic fungi in lignin degradation and food provision differs among fungus‐growing termites (four species of Macrotermes , three species of Odontotermes , Hypotermes makhamensis , Ancistrotermes pakistanicus and Pseudacanthotermes militaris ), the chemical composition of fungus combs of different ages and the chitinolytic activity in the gut of termites were analysed. In addition, the carbon stable isotope ratios (δ ¹³ C) in old combs, worker termite tissues and fungal nodules (aggregated conidia) were compared.
In Macrotermes spp., the carbohydrate : lignin ratio of the combs increased with increased comb age, but it decreased or remained the same in Odontotermes spp., H. makhamensis , A. pakistanicus and P. militaris. In contrast, the chitin : carbohydrate ratio and ash content increased more over time in the combs of Odontotermes spp., H. makhamensis , A. pakistanicus and P. militaris than in the combs of Macrotermes spp.
Chitinolytic activity in the gut of workers was higher in O. takensis , H. makhamensis and A. pakistanicus than in M. annandalei .
In all species examined, the δ ¹³ C value increased in the sequence: old combs < termites < fungal nodules. Based on a two‐source model of δ ¹³ C, the contribution of fungi to termite nutrition was considered higher in Odontotermes spp., H. makhamensis , A. pakistanicus and P. militaris than in Macrotermes spp.
These results suggest that symbiotic fungi play different roles among fungus‐growing termites. In Macrotermes spp., the main role of symbiotic fungi is to degrade lignin, so that the termites can utilize cellulose more efficiently, whereas in Odontotermes spp., H. makhamensis , A. pakistanicus and P. militaris , it is to serve as a food source.
1.1. The comparative study of digestive osidases in five fungus-growing species and its symbiotic fungus (Termitomyces sp.) brings new insight into the nutritive mode of these species, known to have a great impact in most African ecosystems.2.2. While this work stressed the importance and the variety of enzymatic activities detected in the termite workers digestive tract, our results clearly distinguished two main symbiotic mechanisms into termite nutrition, according to the ability for the symbiotic fungus to produce active enzymes.3.3. In the case of Macrotermes bellicosus, Odontotermes near pauperans and Pseudacanthotermes militaris, the metabolism of the fungi is characterized by a relatively higher enzymatic production (variable according to the substrates tested).4.4. These enzymes are ingested by the termite and the digestion is due to the combined action of the enzymes from the termite gut and from the fungus.5.5. In the case of Ancislrotermes cavithorax and Microtermes toumodiensis, one can question the role of the fungi as they exhibited very low enzymatic activities.6.6. The fungus protoplasm could then be a nutrition source for the termite. Possibly also, these fungi could degrade other substrates (chitin, lignin) not tested in our experiments.7.7. Our results showed also a very high oligosaccharidasic activity of Pseudacanthotermes militaris symbiotic fungus (Termitomyces striatus) which appear to coincide with a different behaviour of the termite towards its fungus comb.
Principal component analysis (PCA) is a multivariate technique that analyzes a data table in which observations are described by several inter‐correlated quantitative dependent variables. Its goal is to extract the important information from the table, to represent it as a set of new orthogonal variables called principal components, and to display the pattern of similarity of the observations and of the variables as points in maps. The quality of the PCA model can be evaluated using cross‐validation techniques such as the bootstrap and the jackknife. PCA can be generalized as correspondence analysis (CA) in order to handle qualitative variables and as multiple factor analysis (MFA) in order to handle heterogeneous sets of variables. Mathematically, PCA depends upon the eigen‐decomposition of positive semi‐definite matrices and upon the singular value decomposition (SVD) of rectangular matrices. Copyright © 2010 John Wiley & Sons, Inc.
This article is categorized under: Statistical and Graphical Methods of Data Analysis > Multivariate Analysis
Statistical and Graphical Methods of Data Analysis > Dimension Reduction
The symbiotic gut microbiota of termites plays important roles in lignocellulose digestion and nitrogen metabolism. Termites possess a dual cellulolytic system: in lower termites the cellulases are contributed by both the insect and its gut flagellates, whereas in higher termites, host cellulases and hindgut bacteria participate in fiber digestion. Commonly, the microbial feeding chain is driven by the primary fermentations of carbohydrates. However in soil-feeding taxa, which exploit the peptidic component of soil organic matter as a dietary resource and show pronounced differences in physiochemical conditions along their highly compartmented intestinal tract, amino acids are an important substrate for the microbiota. Hydrogen appears to be the central intermediate in the hindgut fermentations in all termites. In wood-feeding taxa, it is efficiently recycled by homoacetogenic spirochetes, which prevail over methanogenic archaea probably because of their ability to colonize the bulk volume of the hindgut, whereas methanogens are restricted to particular microniches at the hindgut wall or within the gut flagellates. As a general rule, the spatial separation of microbial populations and metabolic activities gives rise to steep gradients of metabolites. The continuous influx of oxygen into the hindgut affects microbial metabolism in the microoxic periphery, and the anoxic status of the gut center is maintained only by the rapid reduction of oxygen by both aerobic and anaerobic microorganisms. Lignin is not significantly mineralized during gut passage, but modification of polyphenols by processes yet uncharacterized may increase the digestibility of both lignocellulose and humic substances. In wood-feeding termites, gut microbiota fix and upgrade nitrogen and recycle nitrogenous waste products. The microorganisms responsible for these reactions are mostly unknown, but recent studies have indicated that bacterial ectosymbionts and endosymbionts of the gut flagellates play a major role in the nitrogen metabolism of lower termites.
Ancistrotermes guineensis (Silv.) colonies were reared in observation nests The timetable of development of the young colony is given. The construction of fungus comb from the faeces of the worker caste was observed; chewed wood was not used is constructing the comb. The fungus comb remained sterile until the correct species of Termitomyces was introduced. The symbiosis between termite and fungus would appear to be specific. It seems that the alates do not carry an inoculum of viable spores of the fungus from the parent colony, but that workers introduce basidiospores in early foraging. This may be an important factor controlling the abundance of the termites. The phylogeny of the Macrotermitinæ is reviewed in the light of the new evidence.
1.
Density of nests, population number, biomass, nitrogen and carbon content, calorific content and respiration rate of termites were studied at Pasoh Forest, West Malaysia mainly with four dominant species of epigeous nest builders, Macrotermes carbonarius, Dicuspiditermes nemorosus type-a, type-b and Homallotermes foraminifer, to reveal their role in the ecosystem.
2.
The density of nests or mounds was 15–41/ha in M. carbonarius, 60–110/ha in the two types of D. nemorosus and 85–165/ha in H. foraminifer.
3.
The population number per nest or mound was about 88,000 in M. carbonarius, 45,000 in D. nemorosus type-a, 47,000 in D. nemorosus type-b and 13,000 in H. foraminifer. The population number per hectare was about 1.8x106 for M. carbonarius, 4.3x106 for D. nemorosus type-a, 5.2x106 for D. nemorosus type-b and 2.1x106 for H. foraminifer.
4.
The ratio in number of workers to soldiers was 6.4 for M. carbonarius, 19.0 for D. nemorosus type-a, 23.1 for D. nemorosus type-b and 8.9 for H. foraminifer. The ratio in number of adults (workers plus soldiers) to larvae was 1.4 for M. carbonarius, 0.59 for D. nemorosus type-a, 1.76 for D. nemorosus type-b and 3.84 for H. foraminifer.
5.
The number of adults per nest of D. nemorosus type-a, type-b and H. foraminifer was linearly correlated with the weight of nest on the log-log coordinates.
6.
The ratio of dry body weight to live weight was 0.24–0.30 for workers, 0.19–0.29 for soldiers and 0.15–0.22 for larvae.
7.
The ash content of termite body was 26–66% for workers, 2–24% for soldiers and 1–4% for larvae.
8.
The carbon content ranged from 45% to 66% of ash-free dry weight and the nitrogen content from 5.6% to 12.6%.
9.
The mean calorific value of termite body was 5.3 gcal/mg in workers and soldiers on an ash-free weight basis, but was greater in nymphs and winged reproductives in the nest (6.7–6.9 gcal/mg) owing probably to their large fat storage.
10.
The relation of CO2 evolution rate to temperature in these termites was similar to what has been found in other insects.
11.
The total biomass of the four termite species was estimated at 6.01 kg ash-free dry weight/ha, equivalent to 0.55 kg nitrogen/ha and 3.09 kg carbon/ha.
12.
The role of the fungi cultivated by M. carbonarius on their fungus combs was discussed in relation to the nutrition of termites and the decomposition of leaf-litter with special reference to their nitrogen metabolism. The high nitrogen content of fungus spherules growing on fungus combs seemed to have an important bearing on the nutrition of termites.
13.
It was concluded that the termites played a very important role in the organic matter decomposition cycle of Pasoh Forest.
The bacteria in the fruitfly Drosophila melanogaster of different life stages was quantified by 454 pyrosequencing of 16S rRNA gene amplicons. The sequence reads were dominated by 5 operational taxonomic units (OTUs) at ≤ 97% sequence identity that could be assigned to Acetobacter pomorum, A. tropicalis, Lactobacillus brevis, L. fructivorans and L. plantarum. The saturated rarefaction curves and species richness indices indicated that the sampling (85,000-159,000 reads per sample) was comprehensive. Parallel diagnostic PCR assays revealed only minor variation in the complement of the five bacterial species across individual insects and three D. melanogaster strains. Other gut-associated bacteria included 6 OTUs with low %ID to previously reported sequences, raising the possibility that they represent novel taxa within the genera Acetobacter and Lactobacillus. A developmental change in the most abundant species, from L. fructivorans in young adults to A. pomorum in aged adults was identified; changes in gut oxygen tension or immune system function might account for this effect. Host immune responses and disturbance may also contribute to the low bacterial diversity in the Drosophila gut habitat.
The mutualistic symbiosis between fungus-growing termites and Termitomyces fungi originated in Africa and shows a moderate degree of interaction specificity. Here we estimate the age of the mutualism and test the hypothesis that the major splits have occurred simultaneously in the host and in the symbiont. We present a scenario where fungus-growing termites originated in the African rainforest just before the expansion of the savanna, about 31 Ma (19-49 Ma). Whereas rough age correspondence is observed for the four main clades of host and symbiont, the analysis reveals several recent events of host switching followed by dispersal of the symbiont throughout large areas and throughout different host genera. The most spectacular of these is a group of closely related fungi (the maximum age of which is estimated to be 2.4 Ma), shared between the divergent genera Microtermes, Ancistrotermes, Acanthotermes and Synacanthotermes (which diverged at least 16.7 Ma), and found throughout the African continent and on Madagascar. The lack of geographical differentiation of fungal symbionts shows that continuous exchange has occurred between regions and across host species.
Termites thrive on dead plant matters with the aid of microorganisms resident in their gut. The gut microbiota comprises protists (single-celled eukaryotes), bacteria, and archaea, most of which are unique to the termite gut ecosystem. Although this symbiosis has long been intriguing researchers of both basic and applied sciences, its detailed mechanism remains unclear due to the enormous complexity and the unculturability of the microbiota. In the effort to overcome the difficulty, recent advances in omics, such as metagenomics, metatranscriptomics, and metaproteomics have gradually unveiled the black box of this symbiotic system. Genomics targeting a single species of the unculturable microbial members has also provided a great progress in the understanding of the symbiotic interrelationships among the gut microorganisms. In this review, the symbiotic system organized by wood-feeding termites and their gut microorganisms is outlined, focusing on the recent achievement in omics studies of this multilayered symbiotic system.