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ABSTRACT: Foraging, defense and waste disposal are essential for sustaining social insect colonies. Hence, their nest generally has an open structure, wherein specialized castes called workers and soldiers perform these tasks. However, some social aphids form completely closed galls, wherein hundreds to thousands of insects grow and reproduce for several months in isolation. Why these social aphids are not drowned by accumulated honeydew has been an enigma. Here we report a sophisticated biological solution to the waste problem in the closed system: the gall inner surface is specialized for absorbing water, whereby honeydew is promptly removed via the plant vascular system. The water-absorbing closed galls have evolved at least twice independently among social aphids. The plant-mediated waste removal, which entails insect's manipulation of plant morphogenesis and physiology, comprises a previously unknown mechanism of nest cleaning, which can be regarded as 'extended phenotype' and 'indirect social behavior' of the social aphids.
Nature Communications 11/2012; 3:1187. · 7.40 Impact Factor
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ABSTRACT: Mealybugs (Homoptera: Coccoidea: Pseudococcidae) possess a large bacteriome consisting of a number of bacteriocytes whose cytoplasm is populated by endosymbiotic bacteria. In many mealybugs of the subfamily Pseudococcinae, a peculiar endosymbiotic configuration has been identified: within the bacteriocytes, the primary betaproteobacterial endosymbiont Tremblaya princeps endocellularly harbor secondary gammaproteobacterial endosymbionts in a nested manner. Meanwhile, some mealybugs of the subfamily Phenacoccinae are associated only with a betaproteobacterial endosymbiont, designated as Tremblaya phenacola, which constitutes a distinct sister clade of T. princeps. However, cytological configuration of the endosymbiotic system in the phenacoccine mealybugs has not been established. Here, we investigated the endosymbiotic systems of the azalea mealybugs Crisicoccus azaleae (Pseudococcinae) and Phenacoccus azaleae (Phenacoccinae) living on the same host plants. Crisicoccus azaleae possessed a nested endosymbiotic system with T. princeps within the bacteriocyte cytoplasm and itself endocellularly harboring gammaproteobacterial cells, whereas P. azaleae exhibited a simple endosymbiotic system in which T. phenacola cells are localized within the bacteriocytes without additional gammaproteobacterial associates. Considering that these mealybugs live on the identical plant phloem sap, these different endosymbiotic consortia likely play similar biological roles for their host insects. The findings presented here should be helpful for future functional and comparative genomics toward elucidating evolutionary pathways of mealybugs and their endosymbionts.
FEMS Microbiology Ecology 07/2012; · 3.41 Impact Factor
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ABSTRACT: Many insects are associated with obligate symbiotic bacteria, which are localized in specialized cells called bacteriocytes, vertically transmitted through host generations via ovarial passage, and essential for growth and reproduction of their hosts. Although vertical transmission is pivotal for maintenance of such intimate host-symbiont associations, molecular and cellular mechanisms underlying the process are largely unknown. Here we report a cellular mechanism for vertical transmission of the obligate symbiont Buchnera in the pea aphid Acyrthosiphon pisum. In the aphid body, Buchnera cells are transmitted from maternal bacteriocytes to adjacent blastulae at the ovariole tips in a highly coordinated manner. By making use of symbiont-manipulated strains of A. pisum, we demonstrated that the facultative symbiont Serratia is, unlike Buchnera, not transmitted from maternal bacteriocytes to blastulae, suggesting a specific mechanism for Buchnera transmission. EM observations revealed a series of exo-/endocytotic processes operating at the bacteriocyte-blastula interface: Buchnera cells are exocytosed from the maternal bacteriocyte, temporarily released to the extracellular space, and endocytosed by the posterior syncytial cytoplasm of the blastula. These results suggest that the selective Buchnera transmission is likely attributable to Buchnera-specific exocytosis by the maternal bacteriocyte, whereas both Buchnera and Serratia are nonselectively incorporated by the endocytotic activity of the posterior region of the blastula. The sophisticated cellular mechanism for vertical transmission of Buchnera must have evolved to ensure the obligate host-symbiont association, whereas facultative symbionts like Serratia may coopt the endocytotic component of the mechanism for their entry into the host embryos.
Proceedings of the National Academy of Sciences 04/2012; 109(20):E1230-7. · 9.68 Impact Factor
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ABSTRACT: Here we report a novel clade of secondary endosymbionts associated with insects and other arthropods. Seed bugs of the genus Nysius (Hemiptera: Lygaeidae) harbor the primary gammaproteobacterial symbiont Schneideria nysicola within a pair of bacteriomes in the abdomen. Our survey of Nysius species for their facultative bacterial associates consistently yielded a novel type of alphaproteobacterial 16S rRNA gene sequence in addition to those of Wolbachia. Diagnostic PCR survey of 343 individuals representing 24 populations of four Nysius species revealed overall detection rates of the alphaproteobacteria at 77.6% in Nysius plebeius, 87.7% in Nysius sp. 1, 81.0% in Nysius sp. 2, and 100% in Nysius expressus. Further survey of diverse stinkbugs representing 24 families, 191 species, and 582 individuals detected the alphaproteobacteria from an additional 12 species representing six families. Molecular phylogenetic analysis showed that the alphaproteobacteria from the stinkbugs form a distinct and coherent monophyletic group in the order Rickettsiales together with several uncharacterized endosymbionts from fleas and ticks. The alphaproteobacterial symbiont clade was allied to bacterial clades such as the endosymbionts of acanthamoebae, the endosymbionts of cnidarians, and Midichloria spp., the mitochondrion-associated endosymbionts of ticks. In situ hybridization and electron microscopy identified small filamentous bacterial cells in various tissues of N. plebeius, including the bacteriome and ovary. The concentrated localization of the symbiont cells at the anterior pole of oocytes indicated its vertical transmission route through host insect generations. The designation "Candidatus Lariskella arthropodarum" is proposed for the endosymbiont clade.
Applied and environmental microbiology 04/2012; 78(12):4149-56. · 3.69 Impact Factor
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ABSTRACT: Bat flies of the family Nycteribiidae are known for their extreme morphological and physiological traits specialized for ectoparasitic blood-feeding lifestyle on bats, including lack of wings, reduced head and eyes, adenotrophic viviparity with a highly developed uterus and milk glands, as well as association with endosymbiotic bacteria. We investigated Japanese nycteribiid bat flies representing 4 genera, 8 species and 27 populations for their bacterial endosymbionts. From all the nycteribiid species examined, a distinct clade of gammaproteobacteria was consistently detected, which was allied to endosymbionts of other insects such as Riesia spp. of primate lice and Arsenophonus spp. of diverse insects. In adult insects, the endosymbiont was localized in specific bacteriocytes in the abdomen, suggesting an intimate host-symbiont association. In adult females, the endosymbiont was also found in the cavity of milk gland tubules, which suggests uterine vertical transmission of the endosymbiont to larvae through milk gland secretion. In adult females of Penicillidia jenynsii, we discovered a previously unknown type of symbiotic organ in the Nycteribiidae: a pair of large bacteriomes located inside the swellings on the fifth abdominal ventral plate. The endosymbiont genes consistently exhibited adenine/thymine biased nucleotide compositions and accelerated rates of molecular evolution. The endosymbiont genome was estimated to be highly reduced, ~0.76 Mb in size. The endosymbiont phylogeny perfectly mirrored the host insect phylogeny, indicating strict vertical transmission and host-symbiont co-speciation in the evolutionary course of the Nycteribiidae. The designation 'Candidatus Aschnera chinzeii' is proposed for the endosymbiont clade.
The ISME Journal 09/2011; 6(3):577-87. · 7.38 Impact Factor
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ABSTRACT: We investigated seed bugs of the genus Nysius (Insecta: Hemiptera: Lygaeidae) for their symbiotic bacteria. From all the samples representing 4 species, 18 populations and 281 individuals, specific bacterial 16S rRNA gene sequences were consistently identified, which formed a distinct clade in the Gammaproteobacteria. In situ hybridization showed that the bacterium was endocellularly localized in a pair of large bacteriomes that were amorphous in shape, deep red in color, and in association with gonads. In the ovary of adult females, the endosymbiont was also localized in the 'infection zone' in the middle of each germarium and in the 'symbiont ball' at the anterior pole of each oocyte, indicating vertical transmission of the endosymbiont through the ovarial passage. Phylogenetic analyses based on bacterial 16S rRNA, groEL and gyrB genes consistently supported a coherent monophyly of the Nysius endosymbionts. The possibility of a sister relationship to 'Candidatus Kleidoceria schneideri', the bacteriome-associated endosymbiont of a lygaeid bug Kleidocerys resedae, was statistically rejected, indicating independent evolutionary origins of the endosymbionts in the Lygaeidae. The endosymbiont genes consistently exhibited AT-biased nucleotide compositions and accelerated rates of molecular evolution, and the endosymbiont genome was only 0.6 Mb in size. The endosymbiont phylogeny was congruent with the host insect phylogeny, suggesting strict vertical transmission and host-symbiont co-speciation over evolutionary time. Based on these results, we discuss the evolution of bacteriomes and endosymbionts in the Heteroptera, most members of which are associated with gut symbiotic bacteria. The designation 'Candidatus Schneideria nysicola' is proposed for the endosymbiont clade.
The ISME Journal 08/2011; 6(2):397-409. · 7.38 Impact Factor
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ABSTRACT: A novel aerobic, chemoheterotrophic bacterium, strain YO-36(T), isolated from the rhizoplane of an aquatic plant (a reed, Phragmites australis) inhabiting a freshwater lake in Japan, was morphologically, physiologically and phylogenetically characterized. Strain YO-36(T) was Gram-negative and ovoid to rod-shaped, and formed pinkish hard colonies on agar plates. Strain YO-36(T) grew at 20-40 °C with optimum growth at 30-35 °C, whilst no growth was observed at 15 °C or 45 °C. The pH range for growth was 5.5-8.5 with an optimum at pH 6.5. Strain YO-36(T) utilized a limited range of substrates, such as sucrose, gentiobiose, pectin, gellan gum and xanthan gum. The strain contained C(16 : 0), C(16 : 1), C(14 : 0) and C(15 : 0) as the major cellular fatty acids and menaquinone-12 as the respiratory quinone. The G+C content of the genomic DNA was 62.4 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain YO-36(T) belonged to the candidate phylum OP10 comprised solely of environmental 16S rRNA gene clone sequences except for two strains, P488 and T49 isolated from geothermal soil in New Zealand; strain YO-36(T) showed less than 80 % sequence similarity to strains P488 and T47. Based on the phylogetic and phenotypic findings, a new genus and species, Armatimonas rosea gen. nov., sp. nov., is proposed for the isolate (type strain YO-36(T) = NBRC 105658(T) = DSM 23562(T)). In addition, a new bacterial phylum named Armatimonadetes phyl. nov. is proposed for the candidate phylum OP10 represented by A. rosea gen. nov., sp. nov. and Armatimonadaceae fam. nov., Armatimonadales ord. nov., and Armatimonadia classis nov.
INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY 06/2011; 61(Pt 6):1442-7. · 2.11 Impact Factor
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ABSTRACT: Microbiological characterization of gut symbiotic bacteria in a limited number of stinkbugs of the families Acanthosomatidae, Plataspidae, Pentatomidae, Scutelleridae, Parastrachiidae, Alydidae and Pyrrhocoridae has shown symbiotic association with midgut bacteria to be common in phytophagous taxa of these heteropteran insects. Here we investigated the midgut bacterial symbiont of Eucorysses grandis, a stinkbug of the family Scutelleridae. A specific gammaproteobacterium was consistently identified in insects from five different geographic origins. The bacterium was detected in 64 of 64 insects sampled from three host populations. Phylogenetic analyses revealed that the bacterium constitutes a distinct lineage in the Gammaproteobacteria, neither closely related to the gut symbiont of another scutellerid stinkbug, Cantao ocellatus, nor to gut symbionts of other stinkbugs. Diagnostic PCR, in situ hybridization and electron microscopy demonstrated that the bacterium is located extracelluarly, in the midgut fourth section, which possesses crypts. These results indicate that the primary gut symbionts have multiple evolutionary origins in the Scutelleridae. A Sodalis-allied facultative symbiont was also identified in some insects from natural populations. Biological aspects of the primary gut symbiont and the secondary Sodalis-allied symbiont are discussed.
ZOOLOGICAL SCIENCE 03/2011; 28(3):169-74. · 0.95 Impact Factor
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ABSTRACT: The stinkbug Parastrachia japonensis (Hemiptera: Parastrachiidae) is known for its prolonged prereproductive nonfeeding period, maternal care of eggs in an underground nest, and maternal collection and provisioning of food (fruits) for nymphs. A previous study suggested that a bacterial symbiont is involved in uric acid recycling in this insect during the nonfeeding period, but the identity of this symbiont has not been determined. Here we characterized a novel bacterial symbiont obtained from P. japonensis. Molecular phylogenetic analyses based on 16S rRNA, gyrB, and groEL gene sequences consistently indicated that this symbiont constituted a distinct lineage in the Gammaproteobacteria that has no close relatives but is allied with gut symbionts of acanthosomatid and plataspid stinkbugs, as well as with endocellular symbionts of sharpshooters, tsetse flies, and aphids. The symbiont genes had a remarkably AT-biased nucleotide composition and exhibited significantly accelerated molecular evolution. The symbiont genome was extremely reduced; its size was estimated to be 0.85 Mb. These results suggest that there has been an intimate host-symbiont association over evolutionary time. The symbiont was localized in swollen crypts in a posterior part of the midgut, which was a specialized symbiotic organ. The possibility that the symbiont is involved in uric acid recycling is discussed. The designation "Candidatus Benitsuchiphilus tojoi" is proposed for the symbiont.
Applied and environmental microbiology 07/2010; 76(13):4130-5. · 3.69 Impact Factor
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ABSTRACT: A microbial fuel cell (MFC) was inoculated with a random transposon insertion mutant library of Shewanella oneidensis MR-1 and operated with lactate as the sole fuel to select for mutants that preferentially grew in it. Agar plate cultivation of the resultant MFC enrichment culture detected an increased number of colonies exhibiting rough morphology. One such isolate, strain 4A, generated 50% more current in an MFC than wild-type MR-1. Determination of the transposon insertion site in strain 4A followed by deletion and complementation experiments revealed that the SO3177 gene, encoding a putative formyltransferase and situated in a cell surface polysaccharide biosynthesis gene cluster, was responsible for the increased current. Transmission electron microscopy showed that a layered structure at the cell surface, stainable with ruthenium red, was impaired in the SO3177 mutant (DeltaSO3177), confirming that SO3177 is involved in the biosynthesis of cell surface polysaccharides. Compared to the wild type, DeltaSO3177 cells preferentially attached to graphite felt anodes in MFCs, while physicochemical analyses revealed that the cell surface of DeltaSO3177 was more hydrophobic. These results demonstrate that cell surface polysaccharides affect not only the cell adhesion to graphite anodes but also the current generation in MFCs.
Applied and environmental microbiology 07/2010; 76(13):4151-7. · 3.69 Impact Factor
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ABSTRACT: Symbiotic associations with midgut bacteria have been commonly found in diverse phytophagous heteropteran groups, where microbiological characterization of the symbiotic bacteria has been restricted to the stinkbug families Acanthosomatidae, Plataspidae, Pentatomidae, Alydidae, and Pyrrhocoridae. Here we investigated the midgut bacterial symbiont of Cantao ocellatus, a stinkbug of the family Scutelleridae. A specific gammaproteobacterium was consistently identified from the insects of different geographic origins. The bacterium was detected in all 116 insects collected from 9 natural host populations. Phylogenetic analyses revealed that the bacterium constitutes a distinct lineage in the Gammaproteobacteria, not closely related to gut symbionts of other stinkbugs. Diagnostic PCR and in situ hybridization demonstrated that the bacterium is extracellularly located in the midgut 4th section with crypts. Electron microscopy of the crypts revealed a peculiar histological configuration at the host-symbiont interface. Egg sterilization experiments confirmed that the bacterium is vertically transmitted to stinkbug nymphs via egg surface contamination. In addition to the gut symbiont, some individuals of C. ocellatus harbored another bacterial symbiont in their gonads, which was closely related to Sodalis glossinidius, the secondary endosymbiont of tsetse flies. Biological aspects of the primary gut symbiont and the secondary Sodalis-allied symbiont are discussed.
Applied and environmental microbiology 06/2010; 76(11):3486-94. · 3.69 Impact Factor
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ABSTRACT: Many insects are dependent on bacterial symbionts that provide essential nutrients (ex. aphid-Buchnera and tsetse-Wiglesworthia associations), wherein the symbionts are harbored in specific cells called bacteriocytes that constitute a symbiotic organ bacteriome. Facultative and parasitic bacterial symbionts like Wolbachia have been regarded as evolutionarily distinct from such obligate nutritional mutualists. However, we discovered that, in the bedbug Cimex lectularius, Wolbachia resides in a bacteriome and appears to be an obligate nutritional mutualist. Two bacterial symbionts, a Wolbachia strain and an unnamed gamma-proteobacterium, were identified from different strains of the bedbug. The Wolbachia symbiont was detected from all of the insects examined whereas the gamma-proteobacterium was found in a part of them. The Wolbachia symbiont was specifically localized in the bacteriomes and vertically transmitted via the somatic stem cell niche of germalia to oocytes, infecting the incipient symbiotic organ at an early stage of the embryogenesis. Elimination of the Wolbachia symbiont resulted in retarded growth and sterility of the host insect. These deficiencies were rescued by oral supplementation of B vitamins, confirming the essential nutritional role of the symbiont for the host. The estimated genome size of the Wolbachia symbiont was around 1.3 Mb, which was almost equivalent to the genome sizes of parasitic Wolbachia strains of other insects. These results indicate that bacteriocyte-associated nutritional mutualism can evolve from facultative and prevalent microbial associates like Wolbachia, highlighting a previously unknown aspect of the parasitism-mutualism evolutionary continuum.
Proceedings of the National Academy of Sciences 01/2010; 107(2):769-74. · 9.68 Impact Factor
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ABSTRACT: Here we investigated the bacterial endosymbionts of weevils of the genus Curculio. From all four species of Curculio weevils examined, a novel group of bacterial gene sequences were consistently identified. Molecular phylogenetic analyses demonstrated that the sequences formed a distinct clade in the Gammaproteobacteria, which was not related to previously known groups of weevil endosymbionts such as Nardonella spp. and Sodalis-allied symbionts. In situ hybridization revealed that the bacterium was intracellularly harbored in a bacteriome associated with larval midgut. In adult females, the bacterium was localized in the germalia at the tip of each overiole, suggesting vertical transmission via ovarial passage. Diagnostic PCR surveys detected high prevalence of the bacterial infection in natural host populations. Electron microscopy identified the reduced cell wall of the bacterial cells, and the bacterial genes exhibited AT-biased nucleotide composition and accelerated molecular evolution, which are suggestive of a long-lasting endosymbiotic association. On the basis of these results, we conclude that the novel endocellular bacteria represent the primary symbiont of Curculio weevils and proposed the designation "Candidatus Curculioniphilus buchneri." In addition to "Ca. Curculioniphilus," we identified Sodalis-allied gammaproteobacterial endosymbionts from the chestnut weevil, Curculio sikkimensis, which exhibited partial infection frequencies in host insect populations and neither AT-biased nucleotide composition nor accelerated molecular evolution. We suggest that such Sodalis-allied secondary symbionts in weevils might provide a potential source for symbiont replacements, as has occurred in an ancestor of Sitophilus grain weevils.
Applied and environmental microbiology 10/2009; 76(1):275-82. · 3.69 Impact Factor
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ABSTRACT: Giant scale insects (Drosicha: Coccoldea: Monophlebidae) were investigated for their symbiotic organs and bacterial endosymbionts. Two types of bacterial 16S rRNA gene sequences, flavobacterial and enterobacterial, were consistently detected in D. corpulenta and D. pinicola. The former sequences formed a compact clade in the Bacteroidetes, allied to the symbionts of cushion and armored scales. The latter sequences formed a robust clade in the gamma-Proteobacteria, allied to enteric bacteria like Enterobacter aerogenes and Escherichia coli. Another type of 16S sequence derived from Wolbachia was also detected in D. pinicola. In-situ hybridization demonstrated that the flavobacterial and enterobacterial symbionts were localized in a pair of huge bacteriomes in the abdomen, the former in uninucleated peripheral bacteriocytes and the latter in syncytial central bacteriocytes. Electron microscopy confirmed the endocellular locations of the pleomorphic flavobacterial symbiont and the rod-shaped enterobacterial symbiont, and also revealed the location and fine structure of the Wolbachia symbiont in D. pinicola. Infection frequencies of the flavobacterial and enterobacterial symbionts were consistently 100% in populations of D. corpulenta and D. pinicola, while the Wolbachia symbiont exhibited 0% and 100% infection frequencies in D. corpulente and D. pinicola, respectively. Neither the flavobacterial symbiont nor the enterobacterial symbiont exhibited AT-biased nucleotide composition or accelerated molecular evolution. The huge bacteriomes of Drosicha giant scales would provide a useful system for investigating biochemical, physiological, and genomic aspects of the host-symbiont and symbiont-symbiont interactions.
ZOOLOGICAL SCIENCE 08/2009; 26(7):448-56. · 0.95 Impact Factor
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ABSTRACT: Host-symbiont co-speciation and reductive genome evolution have been commonly observed among obligate endocellular insect symbionts, while such examples have rarely been identified among extracellular ones, the only case reported being from gut symbiotic bacteria of stinkbugs of the family Plataspidae. Considering that gut symbiotic communities are vulnerable to invasion of foreign microbes, gut symbiotic associations have been thought to be evolutionarily not stable. Stinkbugs of the family Acanthosomatidae harbor a bacterial symbiont in the midgut crypts, the lumen of which is completely sealed off from the midgut main tract, thereby retaining the symbiont in the isolated cryptic cavities. We investigated histological, ecological, phylogenetic, and genomic aspects of the unique gut symbiosis of the acanthosomatid stinkbugs.
Phylogenetic analyses showed that the acanthosomatid symbionts constitute a distinct clade in the gamma-Proteobacteria, whose sister groups are the obligate endocellular symbionts of aphids Buchnera and the obligate gut symbionts of plataspid stinkbugs Ishikawaella. In addition to the midgut crypts, the symbionts were located in a pair of peculiar lubricating organs associated with the female ovipositor, by which the symbionts are vertically transmitted via egg surface contamination. The symbionts were detected not from ovaries but from deposited eggs, and surface sterilization of eggs resulted in symbiont-free hatchlings. The symbiont-free insects suffered retarded growth, high mortality, and abnormal morphology, suggesting important biological roles of the symbiont for the host insects. The symbiont phylogeny was generally concordant with the host phylogeny, indicating host-symbiont co-speciation over evolutionary time despite the extracellular association. Meanwhile, some local host-symbiont phylogenetic discrepancies were found, suggesting occasional horizontal symbiont transfers across the host lineages. The symbionts exhibited AT-biased nucleotide composition, accelerated molecular evolution, and reduced genome size, as has been observed in obligate endocellular insect symbionts.
Comprehensive studies of the acanthosomatid bacterial symbiosis provide new insights into the genomic evolution of extracellular symbiotic bacteria: host-symbiont co-speciation and drastic genome reduction can occur not only in endocellular symbiotic associations but also in extracellular ones. We suggest that many more such cases might be discovered in future surveys.
BMC Biology 02/2009; 7:2. · 5.75 Impact Factor
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ABSTRACT: The anaerobic free-living ciliate, Trimyema compressum, is known to harbor both methanogenic archaeal and bacterial symbionts in the cytoplasm. To clarify their phylogenetic belongings, a full-cycle rRNA approach was applied to this symbiosis. Phylogenetic analysis showed that the methanogenic symbiont was related to Methanobrevibacter arboriphilicus, which was distantly related to symbionts found in other Trimyema species. This result suggested that Trimyema species do not require very specific methanogenic symbionts, and symbiont replacement could have occurred in the history of Trimyema species. On the other hand, the bacterial symbiont was located near the lineage of the family Syntrophomonadaceae in the phylum Firmicutes. The sequence similarity between the bacterial symbiont and the nearest species was 85%, indicating that bacterial symbionts may be specific to the Trimyema species. The elimination of bacterial symbionts from the ciliate cell by antibiotic treatment resulted in considerably decreased host growth. However, it was not restored by stigmasterol addition (<2 microg ml(-1)), which was different from the previous report that showed that the symbiont-free strain required exogenous sterols for growth. In addition, the decline of host growth was not accompanied by host metabolism shift toward the formation of more reduced products, which suggested that the contribution of bacterial symbionts to the host ciliate was not a dispose of excessive reducing equivalent arising from the host's fermentative metabolism as methanogenic symbionts do. This study showed that bacterial symbionts make a significant contribution to the host ciliate by an unknown function and suggested that interactions between bacterial symbionts and T. compressum are more complicated than hitherto proposed.
Microbial Ecology 12/2007; 54(4):627-36. · 2.91 Impact Factor
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ABSTRACT: In situ detection of methanogens within the family Methanobacteriaceae is sometimes known to be unsuccessful due to the difficulty in permeability of oligonucleotide probes. Pseudomurein endoisopeptidase (Pei), a lytic enzyme that specifically acts on their cell walls, was applied prior to 16S rRNA-targeting fluorescence in situ hybridization (FISH). For this purpose, pure cultured methanogens within this family, Methanobacterium bryantii, Methanobrevibacter ruminantium, Methanosphaera stadtmanae, and Methanothermobacter thermautotrophicus together with a Methanothermobacter thermautotrophicus-containing syntrophic acetate-oxidizing coculture, endosymbiotic Methanobrevibacter methanogens within an anaerobic ciliate, and an upflow anaerobic sludge blanket (UASB) granule were examined. Even without the Pei treatment, Methanobacterium bryantii and Methanothermobacter thermautotrophicus cells are relatively well hybridized with oligonucleotide probes. However, almost none of the cells of Methanobrevibacter ruminantium, Methanosphaera stadtmanae, cocultured Methanothermobacter thermautotrophicus, and the endosymbiotic methanogens and the cells within UASB granule were hybridized. Pei treatment was able to increase the probe hybridization ratio in every specimen, particularly in the specimen that had shown little hybridization. Interestingly, the hybridizing signal intensity of Methanothermobacter thermautotrophicus cells in coculture with an acetate-oxidizing H(2)-producing syntroph was significantly improved by Pei pretreatment, whereas the probe was well hybridized with the cells of pure culture of the same strain. We found that the difference is attributed to the differences in cell wall thicknesses between the two culture conditions. These results indicate that Pei treatment is effective for FISH analysis of methanogens that show impermeability to the probe.
Applied and Environmental Microbiology 12/2006; 72(11):6907-13. · 3.83 Impact Factor
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ABSTRACT: A Gram-negative, rod-shaped, motile, non-pigmented, facultative aerobe that grew optimally at pH 6.5 and 30 degrees C (strain PM1T) was isolated for its ability to completely degrade the gasoline additive methyl tert-butyl ether. Analysis of the 16S rRNA gene sequence indicated that this bacterium was a member of the class Betaproteobacteria in the Sphaerotilus-Leptothrix group. The 16S rRNA gene sequence identity to other genera in this group, Leptothrix, Aquabacterium, Roseateles, Sphaerotilus, Ideonella and Rubrivivax, ranged from 93 to 96 %. The chemotaxonomic data including Q-8 as the major quinone, C16 : 1omega7c and C16 : 0 as the major fatty acids and a DNA G+C content of 69 mol%, support the inclusion of strain PM1T in the class Betaproteobacteria. It differed from other members of the Sphaerotilus-Leptothrix group by being a facultative methylotroph that used methanol as a sole carbon source, and by also being able to grow heterotrophically in defined media containing ethanol, toluene, benzene, ethylbenzene and dihydroxybenzoates as sole carbon sources. On the basis of the morphological, physiological, biochemical and genetic information, a new genus and species, Methylibium petroleiphilum gen. nov., sp. nov., is proposed, with PM1T (=ATCC BAA-1232T=LMG 22953T) as the type strain.
International journal of systematic and evolutionary microbiology 06/2006; 56(Pt 5):983-9. · 2.27 Impact Factor
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ABSTRACT: The Japanese common broad-headed bugs Riptortus clavatus and Leptocorisa chinensis possess a number of crypts in the posterior region of the midgut, whose lumen contains a copious amount of bacterial cells. We characterized the gut symbiotic bacteria by using molecular phylogenetic analysis, light and electron microscopy, in situ hybridization, and PCR-based detection techniques. Restriction fragment length polymorphism analysis of 16S rRNA gene clones suggested that a single bacterium dominated the microbiota in the crypts of the both bug species. The predominant 16S rRNA gene sequences obtained from different individuals and species of the bugs were not identical but were very similar to each other. Homology searches in the DNA databases revealed that the sequences showed the highest levels of similarity (96% to 99%) to the sequences of Burkholderia spp. belonging to the beta subdivision of the class Proteobacteria. In situ hybridization with specific oligonucleotide probes confirmed the localization of the Burkholderia symbiont in the lumen of the midgut crypts. Electron microscopy showed that the lumen of the crypts was filled with rod-shaped bacteria of a single morphotype. Molecular phylogenetic analysis demonstrated that the Burkholderia symbionts of the bugs formed a well-defined monophyletic group, although the group also contained several environmental Burkholderia strains. The phylogenetic relationship of the Burkholderia symbionts did not reflect the relationship of the host bug species at all. The sequences from R. clavatus and the sequences from L. chinensis did not form clades but were intermingled in the phylogeny, suggesting that horizontal transmission of the symbiont might have occasionally occurred between populations and species of the bugs.
Applied and Environmental Microbiology 08/2005; 71(7):4035-43. · 3.83 Impact Factor
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ABSTRACT: In natural populations of the pea aphid Acyrthosiphon pisum, a facultative bacterial symbiont of the genus Rickettsia has been detected at considerable infection frequencies worldwide. We investigated the effects of the Rickettsia symbiont on the host aphid and also on the coexisting essential symbiont Buchnera. In situ hybridization revealed that the Rickettsia symbiont was specifically localized in two types of host cells specialized for endosymbiosis: secondary mycetocytes and sheath cells. Electron microscopy identified bacterial rods, about 2 mum long and 0.5 mum thick, in sheath cells of Rickettsia-infected aphids. Virus-like particles were sometimes observed in association with the bacterial cells. By an antibiotic treatment, we generated Rickettsia-infected and Rickettsia-eliminated aphid strains with an identical genetic background. Comparison of these strains revealed that Rickettsia infection negatively affected some components of the host fitness. Quantitative PCR analysis of the bacterial population dynamics identified a remarkable interaction between the coexisting symbionts: Buchnera population was significantly suppressed in the presence of Rickettsia, particularly at the young adult stage, when the aphid most actively reproduces. On the basis of these results, we discussed the possible mechanisms that enable the prevalence of Rickettsia infection in natural host populations in spite of the negative fitness effects observed in the laboratory.
Applied and Environmental Microbiology 08/2005; 71(7):4069-75. · 3.83 Impact Factor
