No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Spore release in Acrochaetium sp. (Rhodophyta) is bacterially controled.
Abstract
The facultative red algal epiphyte Acrochaetium sp. liberated spores preferentially and recruited more successfully in laboratory cultures when its host Gracilaria chilensis C. J. Bird, McLachlan et E. C. Oliveira was present. The same effect was also induced by cell-free medium from G. chilensis, suggesting it contained a molecular signal. Antibiotics prevented spore release in Acrochaetium sp., even when G. chilensis was present, suggesting a prokaryotic origin of the signal. Simultaneous application of N-butyl-homoserine-lactone (BHL) restored the spore-release capacity, which demonstrated that spore release was not directly inhibited by the antibiotics and indicated that bacterially generated N-acyl-homoserine-lactones (AHLs) regulate spore release. An involvement of AHL was further indicated by the fact that two different halofuranone inhibitors of AHL receptors also inhibited spore release when they were applied at relatively low concentrations. Of seven different AHLs tested, only BHL induced the effect. However, BHL was only active at relatively high concentrations (100 μM), and it was not detected in spore-release-inducing medium of G. chilensis. Another water-soluble AHL or an AHL structure analog is therefore probably the active compound in G. chilensis cultures. The data presented demonstrate that life cycle completion in Acrochaetium sp. strongly depends on bacteria, which are not always present in sufficient numbers on the alga itself. Exogenous bacteria that are associated with G. chilensis or with other potential substrates may therefore trigger timely spore liberation in Acrochaetium sp., provided that the necessary concentration of AHL is reached. This first finding of AHL perception in a red alga confirms that AHL signalling is more widespread among eukaryotes than was thought until recently. However, spore release of a second red alga, Sahlingia subintegra (Rosenv.) Kornmann, was unaffected by AHL, and the reaction observed is therefore not universal.
... Spore survival was low in the drying experiments. A limiting factor for algal spore development is the availability of suitable substrata (Weinberger et al, 2007) therefore, shaking the glass vials may have prevented development and survival explaining why petri dishes were used in the osmotic shock experiment. ...
... Olpidiopsis pyropiae has caused millions of dollars of damage to Pyropia spp. The presence of epiphytes can reduce the quality of biomass for consumption and extractable components (Weinberger et al, 2007). Epiphytic growth was observed in KI, CH3OH and control samples in Experiment 2 showing that although treatments were not damaging the P. palmata, other species were also insensitive. ...
... A. secundatum grows epiphytically on spores of P. palmata in laboratory conditions (Figure 3.6) which is likely to be due to the presence of the epiphyte on the parent tissue. Spore release in Acrochaetium spp. is controlled bacterially and the use of antibiotics can prevent its sexual reproduction (Weinberger et al, 2007). As this was a common contaminant in the samples in Experiment 2 the use of antibiotics on parent tissue or released spores could be trialled in future experiments. ...
Abstract
Palmaria palmata is an edible seaweed in high demand due to its many health benefits and uses in pharmaceuticals and cosmetics. Cultivation of P. palmata has been unsuccessful in the past due to poor spore survival, poor attachment to substrates, slow growth and degradation of biomass in tanks. This project aimed to find methods of growing P. palmata from spores and vegetatively for the development of a commercial crop. Initially, methods of spore release were trialled and spore survival was observed. Epiphytic growth was observed on spores for which a number of chemical treatments were then investigated. Vegetative propagation of meristematic tissue was also trialled alongside decontamination treatments. These experiments were subsequently up-scaled to flask culture and at-sea experiments. The main observation from the spore experiments was that an oomycete infection is highly prevalent and limits the production of this species. However, resistant spores were identified which have potential to be grown to adult sized plants to create a starting crop based around these strains. The growth of meristematic tissue was unsuccessful however, potassium iodide was identified as a potential decontamination treatment as it did not have a negative effect on the P. palmata tissue whereas sodium hypochlorite and methanol decreased the survival of the samples. In the flask cultures, Von Stosch media encouraged significantly enhanced vegetative growth compared to KTH media as did the use of potassium iodide and germanium dioxide in combination, compared to controls. A doubling in biomass of whole P. palmata fronds was achieved within four weeks. The at-sea investigation was ineffective due to the time of year as the biomass was heavily fouled with epiphytes. There is potential for this species to be grown commercially if further research takes place to overcome the persisting problems described in this thesis.
... For example, nitrogen fixation activity of some associated bacterial strains significantly influences growth of the green and red seaweeds (Chisholm et al. 1996;Singh et al. 2011a). Bacterial biofilm and their extracellular polymeric substance and chemical compounds are found to be important for settling zoospores in Ulvaceae (Tait et al. 2005;Singh et al. 2013) and releasing spores in Gracilariaceae (Weinberger et al. 2007;Singh et al. 2015). Moreover, bacteria are thought to protect macroalgal surfaces from biofouling pressure via the production of both general and specific biological active chemical metabolites (i.e. ...
... Cross kingdom communication through QS exists between bacteria and macroalgae. AHL molecules increase zoospore settlement in green macroalgae (Joint et al. 2002) and promote carpospore liberation in some red macroalgae (Weinberger et al. 2007;Singh et al. 2015). Joint et al. (2002) demonstrated that zoospores of Enteromorpha species respond to biofilm of the Vibrio anguillarum. ...
... The effect of AHL is not only restricted to green algae but has also been observed in red algal species such as Gracilaria and Acrochaetium species. In these macroalgae, C 4 -and C 6 -HSLs have been shown to control carpospore liberation (Weinberger et al. 2007;Singh et al. 2015). Furthermore, sodium dodecyl sulphate-polyacrylamide gel electrophoresis analysis of total protein of C 4 -and C 6 -HSL-treated cystocarps of G. dura revealed the induction of specific polypeptide bands of approximate molecular weights 50 and 60 kDa (Singh et al. 2015). ...
Macroalgae belong to a diverse group of photosynthetic organisms that play an essential role in marine ecosystems. These ecosystem engineers contribute significantly to global primary production and are the major habitat formers on rocky shores in temperate waters, providing food and shelter for marine life. Macroalgae harbour a rich diversity of associated microorganisms with varied functions related to host performance and defence. In particular, epiphytic bacterial communities have been reported as essential for normal morphological development of the algal host. Moreover, bacteria with antifouling properties are thought to protect chemically undefended macroalgae from detrimental, secondary colonization by other microscopic and macroscopic epibiota. This tight relationship suggests that macroalgae and epiphytic bacteria interact as an integrated functional entity or “holobiont”. Many of these interactions are controlled via chemical signalling systems in a type of interkingdom communication. Indeed recent studies have demonstrated that chemical signalling molecules from bacteria regulate important functions in green algae such as reproduction and host defence.
... On the interface between the seawater and the inner tissue of the seaweed, epibiota form a dynamic biofilm, which has also been termed the 'second skin', and influences the host physiologically, chemically and biologically (Wahl et al. 2012). These epibiota include (opportunistic) pathogens but also beneficial microbes that promote the host's development and fitness, such as, for example, sporulation (Weinberger et al. 2007) or morphogenesis (Weiss et al. 2017, reviewed in Egan et al. 2013, pathogen recognition and chemically mediated defence mechanisms (Li et al. 2022;Longford et al. 2019;Rao et al. 2007;Saha and Weinberger 2019). ...
... Besides the environment, also the host undergoes metabolic, physiological and reproductive changes which can be season dependent (Liu et al. 2017 and references therein). Cycles in the host can also coincide with microbial life cycles, such as, for example, in the brown alga Ascophyllum nodosum, whose reproductive cycles are synchronised with the fungal symbiont Stigmidium ascophylli (Stanley 1992) or in Acrochaetium (Rhodophyta), in which bacterial metabolites (N-acyl-homoserine-lactones) regulate spore release (Weinberger et al. 2007). In this context, an interesting observation is that functional and taxonomic composition of the bacterial communities associated with G. vermiculophylla oscillated seasonally with similar intensity, whereas pronounced taxonomic differences between sites were hardly reflected by similar functional differences. ...
Seasonality is an important natural feature that drives cyclic environmental changes. Seaweed holobionts, inhabiting shallow waters such as rocky shores and mud flats, are subject to seasonal changes in particular, but little is known about the influence of seasonality on their microbial communities. In this study, we conducted a three-year time series, sampling at two-month intervals, to assess the seasonality of microbial epibiota in the seaweed holobiont Gracilaria vermiculophylla. Our results reveal pronounced seasonal shifts that are both taxonomic and functional, oscillating between late winter and early summer across consecutive years. While epibiota varied taxonomically between populations, they were functionally similar, indicating that seasonal variability drives functional changes, while spatial variability is more redundant. We also identified seasonal core mi-crobiota that consistently (re)associated with the host at specific times, alongside a permanent core that is present year-round, independent of season or geography. These findings highlight the dynamic yet resilient nature of seaweed holobionts and demonstrate that their epibiota undergo predictable changes. Therewith, this research offers important insights into the temporal dynamics of seaweed-associated microbiota and demonstrates that the relationship between seaweed host and its epibiota is not static but naturally subject to an ongoing seasonal succession process.
... Studies by Weinberger et al. (2007) on Acrochaetium sp., showed that the spore release is controlled by bacteria. He reported that suppression of bacterial epiphytes with antibiotics prevented spore release of Acrochaetium sp. ...
... They suggested that the life cycle completion in Acrochaetium sp. strongly depends on bacteria (Weinberger et al. 2007). ...
Marine biomass production known as blue carbon sequestration now received global attention as 50% greenhouse gas (CO2) sinks into ocean. Most of the marine macroalgae (seaweeds) growing along the tidal, intertidal and subtidal regions of the coastal waters are edible and also used as a source for industrially important hydrocolloids (agar, carrageenan, and alginate), pigments and secondary metabolites used in food, pharmaceutical, cosmetics and allied industries. Gracilaria sps. belong to marine red algae have gained much attraction due to its ‘agar’ content and the major share of agar production as this polysaccharide has more demand in various food and pharmaceuticals industries. The increased utilization of agar increased the harvest from the natural stock that eventually led to a decrease in the biomass resource availability as well as species extinction. So considering the agar biomass demand several methods being practiced for cultivating the Gracilaria throughout the world are compiled. This mitigates global warming by blue carbon conversion. In this review, various methods of seaweed farming by focusing Gracilaria, different cultivation methods and practices and the potential role of associated bacteria for improving the algal growth are presented for wider access and dissemination.Keywords
Gracilaria
Seaweed cultivationBlue carbon sequestrationEndobiotic bacteria
... The amount of bacteria in the biofilm on surfaces (e.g., rocks) has a positive effect on the number of zoospores settling on the substrate [107], as does the age of the biofilm [108], thus facilitating the successful colonization of new surfaces by macroalgae and the formation of new holobionts [14]. In addition, the release of spores can be influenced by biofilms due to the secretion of secondary metabolites that act as a cue [73,109]. Finally, the biofilm has an important chemical function. ...
... By inoculating the axenic cultures with a particular set of microbes, or by supplying the hosts with seawater containing a selected microbial community (Figure 3), different experimental groups can be created. Those microbes can be chosen based on, for example, their function in morphogenesis [71], the potential to induce diseases [72], their function in immune system and production of compounds [73], or other functions of interest. Additionally, axenic cultures can be maintained under sterile conditions, and holobionts resembling in situ holobionts (realistic holobionts) can be created by supplying axenic hosts with nonsterilized natural seawater ( Figure 3). ...
When studying the effects of climate change on eukaryotic organisms we often oversee a major ecological process: the interaction with microbes. Eukaryotic hosts and microbes form functional units, termed holobionts, where microbes play crucial roles in host functioning. Environmental stress may disturb these complex mutualistic relations. Macroalgae form the foundation of coastal ecosystems worldwide and provide important ecosystem services – services they could likely not provide without their microbial associates. Still, today we do not know how environmental stress will affect the macroalgal holobiont in an increasingly changing ocean. In this review, we provide a conceptual framework that contributes to understanding the different levels at which the holobiont and environment interact, and we suggest a manipulative experimental approach as a guideline for future research.
... Marine microbes (Bacteria and Archaea) are numerous and diverse, with an estimated richness of a million species globally and abundance of 10 6 cells per milliliter of seawater (Azam et al., 1983; Whitman et al., 1998). Microbes serve beneficial ecosystem roles, cycling nutrients and providing carbon to higher trophic levels via the microbial loop (Azam et al., 1983; Arrigo, 2005). ...
... Acylated homoserine lactone molecules produced by microbes regulated spore release of red algae Acrochaetium sp. (Weinberger et al., 2007), and influenced zoospore settlement of green algae Ulva (Tait et al., 2005; Joint et al., 2007) through chemotactic or chemokinetic responses (Joint et al., 2002). Microbial communities are influencing the reproduction and recruitment of the genera of green and red macroalgal groups, and in this study we investigate the effects on brown algae recruits. ...
Marine microbes mediate key ecological processes in kelp forest ecosystems and interact with macroalgae. Pelagic and biofilm-associated microbes interact with macroalgal propagules at multiple stages of recruitment, yet these interactions have not been described for Macrocystis pyrifera. Here we investigate the influence of microbes from coastal environments on recruitment of giant kelp, M. pyrifera. Through repeated laboratory experiments, we tested the effects of altered pelagic microbial abundance on the settlement and development of the microscopic propagules of M. pyrifera during recruitment. M. pyrifera zoospores were reared in laboratory microcosms exposed to environmental microbial communities from seawater during the complete haploid stages of the kelp recruitment cycle, including zoospore release, followed by zoospore settlement, to gametophyte germination and development. We altered the microbial abundance states differentially in three independent experiments with repeated trials, where microbes were (a) present or absent in seawater, (b) altered in community composition, and (c) altered in abundance. Within the third experiment, we also tested the effect of nearshore versus offshore microbial communities on the macroalgal propagules. Distinct pelagic microbial communities were collected from two southern California temperate environments reflecting contrasting intensity of human influence, the nearshore Point Loma kelp forest and the offshore Santa Catalina Island kelp forest. The Point Loma kelp forest is a high impacted coastal region adjacent to the populous San Diego Bay; whereas the kelp forest at Catalina Island is a low impacted region of the Channel Islands, 40 km offshore the southern California coast, and is adjacent to a marine protected area. Kelp gametophytes reared with nearshore Point Loma microbes showed lower survival, growth, and deteriorated morphology compared to gametophytes with the offshore Catalina Island microbial community, and these effects were magnified under high microbial abundances. Reducing abundance of Point Loma microbes restored M. pyrifera propagule success. Yet an intermediate microbial abundance was optimal for kelp propagules reared with Catalina Island microbes, suggesting that microbes also have a beneficial influence on kelp. Our study shows that pelagic microbes from nearshore and offshore environments are differentially influencing kelp propagule success, which has significant implications for kelp recruitment and kelp forest ecosystem health.
... For example, in the red alga Gracilaria chilensis, AHLs produced by the epiphyte Acrochaetium sp. control spore release (Weinberger et al., 2007). Subsequent research showed that 12% of Acrochaetium sp. ...
... The selection of colonization sites and associated behaviors are QS-mediated (Joint et al., 2007). In some marine species, signal substances affect multiple life cycle functions, such as contributing toward the initiation of Hydroides elegans larval colonization with C6-, C12-, and 3-oxo-C8-HSL (Huang et al., 2007), promoting spore release with C4-HSL (Weinberger et al., 2007), and providing protection to algal surfaces with polybrominated 2-heptanone (Nylund et al., 2008). Certain examples of QS-mediated behaviors in microalgae are also implied. ...
Algae are ubiquitous in the marine environment, and the ways in which they interact with bacteria are of particular interest in the field of marine ecology. The interactions between primary producers and bacteria impact the physiology of both partners, alter the chemistry of their environment, and shape microbial diversity. Although algal-bacterial interactions are well known and studied, information regarding the chemical-ecological role of this relationship remains limited, particularly with respect to quorum sensing (QS), which is a system of stimuli and response correlated to population density. In the microbial biosphere, QS is pivotal in driving community structure and regulating behavioral ecology, including biofilm formation, virulence, antibiotic resistance, swarming motility, and secondary metabolite production. Many marine habitats, such as the phycosphere, harbor diverse populations of microorganisms and various signal languages (such as QS-based autoinducers). QS-mediated interactions widely influence algal-bacterial symbiotic relationships, which in turn determine community organization, population structure, and ecosystem functioning. Understanding infochemicals-mediated ecological processes may shed light on the symbiotic interactions between algae host and associated microbes. In this review, we summarize current achievements about how QS modulates microbial behavior, affects symbiotic relationships, and regulates phytoplankton chemical-ecological processes. Additionally, we present an overview of QS-modulated co-evolutionary relationships between algae and bacterioplankton, and consider the potential applications and future perspectives of QS.
... For the red epiphytic alga Acrochaetium sp., life cycle completion strongly depends on AHL-producing bacteria. Spore release was stimulated by AHLs in a dose-dependent manner and blocked when using AHL-receptor-blocking halofuranones 82 . The molecular mechanisms underlying the reported ecological functions of cross-domain signaling between bacteria and seaweeds requires further investigation to fully understand the algal receptors and pathways involved in QS molecule reception. ...
Quorum sensing, first described in marine systems five decades ago, is a well-characterized chemical communication system used to coordinate bacterial gene expression and behavior; however, the impact of quorum sensing on interkingdom interactions has been vastly understudied. In this review, we examine how these molecules mediate communication between bacteria and marine eukaryotes; influencing processes such as development, disease pathogenesis, and microbiome regulation within marine ecosystems. We describe the varied mechanisms eukaryotes have evolved to interfere with bacterial quorum sensing signaling, the crucial role these signals play in host-virus interactions, and how their exchange may be governed by outer membrane vesicles, prevalent in marine systems. Here, we present a dynamic portrayal of the impact of quorum sensing signals beyond bacterial communication, laying the groundwork for future investigations on their roles in shaping marine ecosystem structure and function.
... In both red and brown algae, endogenous elicitors act as signals that stimulate defense responses. These elicitors are often cell wall degradation products due to the activity of lytic enzymes secreted by harmful organisms (Weinberger 2007). Weinberger et al. (2011) demonstrated that an extract from infected alga could trigger a defense response in a noninfected one. ...
Ulva sp. infection in seaweed is considered one of the most harmful infections, since it penetrates deep into the host cell wall and disorganizes the cortical tissue. In Gracilaria chilensis farms, epiphytism is one of the major biological problems and strong fluctuations in landings of this rhodophyte have been documented in the past decades. The present study evaluated the damage of Ulva sp. infection through histological assessment, germination of the epiphytic algal spores on G. chilensis, the photosynthetic response, and gene expression associated with stress after exposure to epiphyte infection. The histological results showed significant and a characteristic damage according to the type of infection described by this species. In addition, a higher infection in farmed than in natural individuals was observed, along with increased photoinhibition of the maximum fluorescence quantum yield (Fv/Fm). Two genes, one related to photosynthesis (PSBO) and the other responsible for neutralizing free superoxide radicals (SOD-C), followed the same pattern, although due to the high variance no significant differences were detected. VBPO, a gene related to the halo-organic compounds synthesis, showed a higher expression in infected thalli, independent of the population type, suggesting a higher protection of the alga from oxidative damage. This study confirms the sensibility of farmed populations of G. chilensis to infection by Ulva sp. and the existence of an active response to early infection.
... Agarophytes are agar-producing red seaweeds, which are cultivated worldwide. Quorum sensing signals like N-acyl homoserine lactones (AHLs) and N-butyl-homoserine-lactone (BHL) secreted by bacterial symbionts are known to be participating in the spore release in Gracilariaceae (agarophytes) family [10,14]. Additionally, the role of Bacillus and Exiguobacterium in bud induction of Gracilaria dura is reported [15]. ...
The present study explores the microbial community associated with the industrially important red seaweed Gracilaria dura to determine the diversity and biotechnological potential through culture and metagenomics approaches. In the first part of the investigation, we isolated and characterized 75 bacterial morphotypes, with varied colony characteristics and metabolic diversity from the wild seaweed. Phylogenetic analysis identified isolates in Proteobacteria, Firmicutes, and Actinobacteria, with Bacillus sp. being prevalent. B. licheniformis and Streptomyces sp. were notable in producing important enzymes like L-asparaginase, and polysaccharide lyases. Antimicrobial activity was significant in 21% of isolates, effective against seaweed pathogens such as Vibrio and Xanthomonas. Rhodococcus pyridinivorans showed strong pyridine degradation, suggesting bioremediation potential. Several isolates exhibited phosphate solubilization and nitrate indicating the roles of bacteria as algal growth promoters and biocontrol agents. Subsequent metagenome analysis of wild and cultured samples provides insights into bacterial communities associated with G. dura, revealing their distribution and functional roles. Proteobacteria (~ 95%) dominated the communities, further bacterial groups involved in algal growth, carpospore liberation, stress resistance, biogeochemical cycles, and biomedical applications were identified. A notable difference in bacteriomes was observed between the samples, with 25% remaining stable. The samples are cultured in the lab to generate seedlings for farming and serve as germplasm storage during the monsoon season. Microbiome surveys are crucial for understanding the association of pathogens and the overall health of the seedlings, supporting successful seaweed farming. Our findings provide valuable insights into G. dura-associated microbial communities and their role in algal growth, which has aquacultural implications.
... These elicitors are often cell wall degradation products due to the activity of lytic enzymes secreted by harmful organisms (Weinberger 2007). In a study developed by Weinberger et al. (2011), it was demonstrated that an extract from infected algae could trigger a defense response in a non-infected one. ...
Ulva sp. infection in seaweed is considered one of the most harmful infections, since it penetrates deep into the host cell wall and disorganizes the cortical tissue. In Gracilaria chilensis farms, epiphytism is one of the major biological problems and strong fluctuations in this rhodophyta landings have been documented in the past decades. The present study evaluated the damage of Ulva sp. infection through histological assessment, germination of the epiphytic algal spores on G. chilensis , the photosynthetic response and gene expression associated with stress after exposure to epiphyte infection. The histological results showed a significant and a characteristic damage according to the type of infection described by this species. In addition, a higher infection in farmed than in natural individuals was observed, along with increased photoinhibition of the maximum fluorescence quantum yield ( F v / F m ). Two genes, one related to photosynthesis (PSBO) and the other responsible for neutralizing free superoxide radicals (SOD-C), followed the same pattern. VBPO, a gene related to the halo-organic compounds synthesis, showed a higher expression in infected thalli, independent of the population type, suggesting a higher protection of the alga from oxidative damage. This study confirms the sensibility of farmed populations of G. chilensis to infection by Ulva sp. and the existence of an active response to early infection.
... The endophytes of the seaweed Bacillus pumilus and Bacillus licheniform of the seaweed Gracilaria dura produce mediators like Indole-3-acetic acid (IAA) which helps in the bud regeneration of the seaweed (Singh et al. 2011). Bacterial communities promote spore liberation in Acrochaetium and the formation of Ulva species zoospores on appropriate surfaces (Joint et al. 2000;Weinberger et al. 2007). Quorum sensing (QS) is a type of chemical signaling that has gained popularity among marine ecologists. ...
Seaweed endophytes are a rich source of microbial diversity and bioactive compounds. This review provides a comprehensive analysis of the microbial diversity associated with seaweeds and their interaction between them. These diverse bacteria and fungi have distinct metabolic pathways, which result in the synthesis of bioactive compounds with potential applications in a variety of health fields. We examine many types of seaweed-associated microorganisms, their bioactive metabolites, and their potential role in cancer treatment using a comprehensive literature review. By incorporating recent findings, we hope to highlight the importance of seaweed endophytes as a prospective source of novel anticancer drugs and promote additional studies in this area. We also investigate the pharmacokinetic and pharmacodynamic profiles of these bioactive compounds because understanding their absorption, distribution, metabolism, excretion (ADMET), and toxicity profiles is critical for developing bioactive compounds with anticancer potential into effective cancer drugs. This knowledge ensures the safety and efficacy of proposed medications prior to clinical trials. This study not only provides promise for novel and more effective treatments for cancer with fewer side effects, but it also emphasizes the necessity of sustainable harvesting procedures and ethical considerations for protecting the delicate marine ecology during bioprospecting activities.
... The relationship between seaweed and their associated bacteria is a rising research field with immense interest in ecology, biotechnology, and aquaculture 22 . The bacterial interactions with their seaweed hosts may alter the functionality of the seaweeds, for example, the release of carpospores in red seaweeds or the attachment of zoospores in green seaweeds 23,24 . Epiphytic microbes play a role in preserving the well-being and shaping the morphology of green and brown macroalgae, including genera like Ulva, Monostroma, and Ectocarpus 25-30 . ...
The complex interactions between epiphytic bacteria and marine macroalgae are still poorly understood, with limited knowledge about their community structure, interactions, and functions. This study focuses on comparing epiphytic prokaryotes community structure between three seaweed phyla; Chlorophyta, Rhodophyta, and Heterokontophyta in an easternmost rocky intertidal site of the Mediterranean Sea. By taking a snapshot approach and simultaneously collecting seaweed samples from the same habitat, we minimize environmental variations that could affect epiphytic bacterial assembly, thereby emphasizing host specificity. Through 16S rRNA gene amplicon sequencing, we identified that the microbial community composition was more similar within the same seaweed phylum host compared to seaweed host from other phyla. Furthermore, exclusive Amplicon Sequence Variants (ASVs) were identified for each algal phyla despite sharing higher taxonomic classifications across the other phyla. Analysis of niche breadth indices uncovers distinctive affinities and potential specialization among seaweed host phyla, with 39% of all ASVs identified as phylum specialists and 13% as generalists. Using taxonomy function prediction, we observed that the taxonomic variability does not significantly impact functional redundancy, suggesting resilience to disturbance. The study concludes that epiphytic bacteria composition is connected to host taxonomy, possibly influenced by shared morphological and chemical traits among genetically related hosts, implying a potential coevolutionary relationship between specific bacteria and their host seaweeds.
... A recent review on Ulva demonstrated that two bacteria derived from U. mutabilis could induce morphogenesis and establish a tripartite community [24]. Additionally, it has been shown that algal-associated bacteria stimulate algal spore release and settlement, positively influence algal growth, provide essential nutrients, and promote the settlement of sea urchins and other larvae [25][26][27][28]. ...
The bacterial communities related to seaweed can vary considerably across different locations, and these variations influence the seaweed’s nutrition, growth, and development. To study this further, we evaluated the bacteria found on the green marine seaweed Ulva prolifera from Garorim Bay and Muan Bay, two key locations on Republic of Korea’s west coast. Our analysis found notable differences in the bacterial communities between the two locations. Garorim Bay hosted a more diverse bacterial population, with the highest number of ASVs (871) compared to Muan Bay’s 156 ASVs. In Muan Bay, more than 50% of the bacterial community was dominated by Pseudomonadota. On the other hand, Garorim Bay had a more balanced distribution between Bacteroidota and Pseudomonadota (37% and 35.5%, respectively). Additionally, Cyanobacteria, particularly Cyanothece aeruginosa, were found in significant numbers in Garorim Bay, making up 8% of the community. Mineral analysis indicated that Garorim Bay had higher levels of S, Na, Mg, Ca, and Fe. Function-wise, both locations exhibited bacterial enrichment in amino acid production, nucleosides, and nucleotide pathways. In conclusion, this study broadens our understanding of the bacterial communities associated with Ulva prolifera in Korean waters and provides a foundation for future research on the relationships between U. prolifera and its bacteria.
... Some of these fouling microbes may be harmless, or protective (e.g., Li et al., 2021;Saha & Weinberger, 2019), involved in the regulation of host morphogenesis (Spoerner et al., 2012) or spore release (Weinberger et al., 2007), or facilitate the acquisition of nitrogen and/or vitamins (Croft et al., 2006;Gerard et al., 1990;Kazamia et al., 2012). Other taxa may represent a threat as opportunistic or specialized pathogens (Egan et al., 2014;Egan & Gardiner, 2016;Saha & Weinberger, 2019;Weinberger et al., 1994Weinberger et al., , 1997. ...
Seaweeds are colonized by a microbial community, which can be directly linked to their performance. This community is shaped by an interplay of stochastic and deterministic processes, including mechanisms which the holobiont host deploys to manipulate its associated microbiota. The Anna Karenina principle predicts that when a holobiont is exposed to suboptimal or stressful conditions, these host mechanisms may be compromised. This leads to a relative increase of stochastic processes that may potentially result in the succession of a microbial community harmful to the host. Based on this principle, we used the variability in microbial communities (i.e., beta diversity) as a proxy for stability within the invasive holobiont Gracilaria vermiculophylla during a simulated invasion in a common garden experiment. Independent of host range, host performance declined at elevated temperature (22°C) and disease incidence and beta diversity increased. Under thermally stressful conditions, beta diversity increased more in epibiota from native populations, suggesting that epibiota from non-native holobionts are thermally more stable. This pattern reflects an increase in deterministic processes acting on epibiota associated with non-native hosts, which in the setting of a common garden can be assumed to originate from the host itself. Therefore, these experimental data suggest that the invasion process may have selected for hosts better able to maintain stable microbiota during stress. Future studies are needed to identify the underlying host mechanisms.
... As holobionts (see definition in Bordenstein & Theis, 2015), macroalgae are continuously interacting with microbial organisms from the water column, which colonize and penetrate their surfaces and tissues (Wahl, Goecke, Labes, Dobretsov, & Weinberger, 2012). Some of these fouling microbes may be harmless, or protective (e.g., Li et al., 2021;Saha & Weinberger, 2019), involved in the regulation of host morphogenesis (Spoerner, Wichard, Bachhuber, Stratmann, & Oertel, 2012) or spore release (Weinberger et al., 2007), or facilitating the acquisition of nitrogen and/or vitamins (Croft, Warren, & Smith, 2006;Gerard, Dunham, & Rosenberg, 1990;Kazamia et al., 2012). Other taxa may represent a threat as opportunistic or specialized pathogens (Egan, Fernandes, Kumar, Gardiner, & Thomas, 2014;Egan & Gardiner, 2016;Saha & Weinberger, 2019;Weinberger, Friedlander, & Gunkel, 1994;Weinberger, Hoppe, & Friedlander, 1997). ...
Seaweeds are colonized by a microbial community which can be directly linked to their performance. This community is shaped by an interplay of stochastic and deterministic processes, including mechanisms which the holobiont host deploys to manipulate its associated microbiota. The Anna Karenina Principle predicts that when a holobiont is exposed to suboptimal or stressful conditions, these host mechanisms may be compromised. This leads to a relative increase of stochastic processes that may potentially result in the succession of a microbial community harmful to the host. Based on this principle, we used the variability in microbial communities (i.e., beta diversity) as a proxy for stability within the invasive holobiont Gracilaria vermiculophylla during a simulated invasion in a common garden experiment. At elevated temperature (22 °C), host performance declined and disease incidence and beta diversity increased. At optimal temperature (15 °C), beta diversity did not differ between native and non-native populations. However, under thermally stressful conditions beta diversity increased more in epibiota from native populations. This suggests that epibiota associated with holobionts from non-native populations are under thermal stress more stable than holobionts from native populations. This pattern reflects an increase of deterministic processes acting on epibiota associated with non-native hosts, which in the setting of a common garden can be assumed to originate from the host itself. Therefore, these experimental data suggest that the invasion process may have selected for hosts better able to maintain stable microbiota during stress. Future studies are needed to identify the underlying host mechanisms.
... Microorganisms have also been shown to play a critical role in seaweed reproduction by regulating or promoting spore release [37], spore germination [29], and zoospore settlement [38]. Given ...
Eukaryotic hosts are associated with microbial communities that are critical to their function. Microbiota manipulation using beneficial microorganisms, for example, in the form of animal probiotics or plant growth-promoting microorganisms (PGPMs), can enhance host performance and health. Recently, seaweed beneficial microorganisms (SBMs) have been identified that promote the growth and development and/or improve disease resistance of seaweeds. This knowledge coincides with global initiatives seeking to expand and intensify seaweed aquaculture. Here, we provide a pathway with the potential to improve commercial cultivation of seaweeds through microbiota manipulation, highlighting that seaweed restoration practices can also benefit from further understanding SBMs and their modes of action. The challenges and opportunities of different approaches to identify and apply SBMs to seaweed aquaculture are discussed.
... Chez l'algue rouge Gracilaria aussi, la production d'AHLs par ses bactéries épiphytes augmente significativement la libération de carpospores (Weinberger et al., 2007;Singh et al., 2015), jouant ainsi un rôle important dans sa reproduction. L'algue rouge Delisea pulchra interagit et contrôle son microbiote au moyen de composés de défenses, des furanones halogénées, qui ciblent les mêmes récepteurs que les AHLs, limitant ainsi la formation de biofilms (Manefield et al., 1999;Rasmussen et al., 2000) et par extension, modulent la composition du microbiote (Harder et al., 2012). ...
Saccharina latissima est une des espèces de macroalgues brunes dites ingénieures qui participent à la formation des forêts de laminaires. Plusieurs populations naturelles sont exploitées autour du monde et elle fait également l'objet de développements croissants en aquaculture. Le but de ma thèse est de caractériser le microbiote bactérien et d’étudier les interactions hôte-microbiote au sein de l’holobionte S. latissima, pour comprendre dans quelles mesures la composition du microbiote influence la croissance de l’algue. L’étude du microbiote de S. latissima issues de populations naturelles de Roscoff (France), Helgoland (Allemagne) et Norvège sud (Skagerrak) par métabarcoding 16S a montré une différence de composition en fonction de la zone de la lame, de la zone géographique et de l’état physiologique de l’algue. Des isolements bactériens ont été fait pour avoir accès à la part cultivable du microbiote. La combinaison de ces résultats avec les données de métabarcoding a permis de sélectionner des souches bactériennes d’intérêt. Des cocultures algues-bactéries ont montré leur impact sur la croissance algale et des résultats inattendus ont mené à prendre en compte d’autres paramètres : l’état général de la plantule de départ, la composition de son microbiote initial et le phénomène de quorum sensing (QS). Les résultats montrent une corrélation entre l’augmentation du QS et une baisse de la croissance. Ensemble, ces résultats apportent de nouvelles données sur la composition du microbiote de S. latissima, de son impact sur l’hôte, et participent à la meilleure compréhension de l’holobionte algue, venant à l’appui de l’idée d’interdépendance entre l’hôte et son microbiote.
... Exogenous bacteria linked to G. chilensis or other possible substrates may therefore cause the prompt release of spores in Acrochaetium sp. if the required concentration of AHL is attained. This discovery of AHL sensing in a red alga demonstrates that AHL signaling is more widespread among eukaryotes than previously thought [59]. ...
Humans have used algae for hundreds of years to make various products viz. agar, fertilizer, food, and pigments. Algae are also used in bioremediation to clean up polluted water and as essential laboratory tools in genomics, proteomics, and other research applications such as environmental warnings. Several special features of algae, including the oxygenic photosynthesis, higher yield in biomass, growth on the non-arable lands, their survival in a wide range of water supplies (contaminated or filtered waters), the production of necessary byproducts and biofuels, the enhancement of soil productivity, and the greenhouse gas emissions, etc. altogether rendered them as vital bio-resources in the sustainable development. Algae and bacteria have been assumed to coexist from the early stages of the development of the earth, and a wide variety of interactions were observed between them which have influenced the ecosystems ranging from the oceans to the lichens. Research has shown that bacteria and algae interact synergistically, especially roseobacter-algae interactions being the most common. These interactions are common to all ecosystems and characterize their primary efficiency. The commercialization of algae for industrial purposes, an important field, is also influenced by this interaction which frequently results in bacterial infections among the consumers. However, the recent findings have revealed that the bacteria improve algal growth and support flocculation which are very crucial in algal biotechnology. Some of the most exciting advancements in the area of algal biotic interactions and potential difficulties were reviewed in this article. Information gleaned in this study would provide a firm foundation for launching more contemporaneous research efforts in understanding and utilizing the algal species in biotechnology industries and medical sectors.
... Macroalgae (seaweeds) associated bacteria are critical for the normal development and health of their host (Barott et al., 2011;Egan et al., 2013;Singh and Reddy, 2014;Saha and Weinberger, 2019). For example, they are thought to provide vital nutrients for the healthy growth of the host (Croft et al., 2006) and produce antimicrobial compounds for fouling defence (Penesyan et al., 2009;Egan et al., 2013) as well as produce chemical signals that can induce the release and settlement of algal spores (Joint et al., 2007;Weinberger et al., 2007). However, seaweed associated microbes are not always beneficial and as in other systems [e.g. ...
Recent bacterial induced bleaching disease events of the commercially farmed brown seaweed Saccharina japonica has resulted in significant reduction in healthy sporeling supply. However, to date the host associated epimicrobial community shifts with the disease progression have not been characterized. We investigated the dynamic shifts in the composition of the epibacterial communities of S. japonica with disease progression using 16S rRNA gene amplicon sequencing. We found that the alpha diversity was significantly higher in the control group than in the infected group over disease progression (P < 0.01). There was a significant shift in the composition and predicted functions of the epibacterial communities in both control and infected groups. Indicator species, belonging to Stenotrophomonas, Pseudomonas and Sphingomona were significantly higher in the control group than infected group, suggesting that these taxa are associated with healthy S. japonica. In contrast, Vibrio, Pseudoalteromonas and Colwellia were keystone taxa in the infected group at 24 h, and thus maybe considered to be the secondary opportunistic pathogens. Our study describes the changes of epibacterial communities associated with the progression of bleaching disease in S. japonica. This new information not only extends our baseline knowledge of the S. japonica epimicrobiome, but also paves the way for developing measures to mitigate disease outbreaks for the sustainable aquaculture of S. japonica.
... Both the microorganisms (including archaea, bacteria, fungi, microalgae, protists and viruses) and their interactions are extremely diverse, ranging from mutualistic to parasitic. Many of the microbes play a crucial role during the host's various life cycle stages, affecting nutrient exchange, defence mechanisms, morphology, reproduction and settlement [2][3][4][5][6][7]. ...
Microbes are vitally important for seaweed growth, functioning and reproduction, and are likely to have a big impact on aquaculture. Algae-associated bacteria, however, remain mostly unmonitored in aquaculture. Here, we studied the microbiomes of Ulva australis and Ulva lacinulata, three natural populations and an aquaculture set-up, based on full-length 16S rRNA gene sequences. The microbiome of cultivated Ulva was pronouncedly different from natural populations, and was specifically associated with higher relative abundances of known growth-promoting bacteria Sulfitobacter and Roseobacter. On a smaller scale, there were species-specific differences as well. In general, Ulva-associated communities were highly distinct from environmental seawater and sediment reference samples. We demonstrated a workflow generating full-length 16S rRNA sequences in real-time using Oxford Nanopore sequencing. We compared 3 different reference databases to assign taxonomy with Kraken2 (SILVA, Greengenes and NCBI). In addition, we used Nanopore's cloud-based EPI2ME workflow for comparison. All four methods yielded comparable results in terms of relative abundances on phylum and order level, but differed widely in alpha diversity indices at genus level. Using the NCBI 16S database, especially in combination with the EPI2ME workflow, resulted in a high proportion of false identifications of cyanobacteria due to chloroplast contamination. Based on our results, we recommend assigning taxonomy of Nanopore-derived long-reads with Kraken2 and the SILVA database in seaweed-microbiome studies. The protocols used in this study provide results within 24 h and may be applicable for rapid microbial surveys in aquaculture.
... Some macroalgae species develop a wild-type phenotype only when their microbial epibionts are present (Provasoli and Pintner 1980;Nakanishi et al. 1996;Matsuo et al. 2003;Marshall et al. 2006). It has further been shown that microbial epibiont communities on the seaweed surface may induce the release and settlement of algal spores (Joint, Tait and Wheeler 2007;Weinberger et al. 2007), affect growth (Keshtacher-Liebson, Hadar and Chen 1995;Croft, Warren and Smith 2006) and induce rhizoid formation (Ghaderiardakani, Coates and Wichard 2017). The nature of the association between the macroalgae and their epibionts is still unclear. ...
The marine macroalgae Ulva sp. is considered an ecosystem engineer in rocky shores of temperate waters worldwide. Ulva sp. harbors a rich diversity of associated microbial epibionts, which are known to affect the algae's typical morphological development and 'health'. We examined the interaction between airborne microbes derived from atmospheric aerosols and Ulva ohnoi growth and physiological state. Specifically, we measured U. ohnoi growth rates and photosynthetic efficiency (Fv/Fm), alongside its microbial epibionts abundance, activity and diversity following dust (containing nutrients and airborne microorganisms) or UV-treated dust (only nutrients) amendments to filtered seawater. Parallel incubations with epibionts-free U. ohnoi (treated with antibiotics that removed the algae epibionts) were also tested to specifically examine if dust-borne microbes can replenish the epibiont community of U. ohnoi. We show that viable airborne microbes can restore U. ohnoi natural microbial epibionts communities, thereby keeping the seaweed alive and 'healthy'. These results suggest that microbes delivered through atmospheric aerosols can affect epiphyte biodiversity in marine flora, especially in areas subjected to high annual atmospheric dust deposition such as the Mediterranean Sea.
... AHLs produced by epibiotic bacteria associated with Gracilaria dura and Acrochaetium sp. induce algal spore liberation [98] (Table 1). Interestingly, unsaturated long chain hydrocarbons and dibutylphthalates also induce settlement in U. linza [99]. ...
Marine biofilms are composed of many species of bacteria, unicellular algae, and protozoa. Biofilms can induce, inhibit, or have no effect on settlement of larvae and spores of algae. In this review, we focus on induction of larval settlement by marine bacteria and unicellular eukaryotes and review publications from 2010 to September 2019. This review provides insights from meta-analysis on what is known about the effect of marine biofilms on larval settlement. Of great interest is the impact of different components of marine biofilms, such as bacteria and diatoms, extracellular polymeric substances, quorum sensing signals, unique inductive compounds, exoenzymes, and structural protein degradation products on larval settlement and metamorphosis. Molecular aspects of larval settlement and impact of climate change are reviewed and, finally, potential areas of future investigations are provided.
... The AHLs produced by Acrochaetium sp. control spore release in the red alga, G. chilensis whereas its production was inhibited in the brown alga, C. sinuosa (Kanagasabhapathy, Yamazaki, Ishida, Sasaki, & Nagata, 2009;Weinberger et al., 2007). The motile zoospores of Enteromorpha exploit the diffusible signal molecules produced by bacterial biofilms for temporary settlement on the surface (Joint et al., 2002). ...
Macroalgae surfaces are considered as a potentially suitable substratum present underwater for the dynamic epibiotic microbiome. They secrete various organic substances as nutrients for the multiplication of bacteria and the formation of microbial biofilms. The microbial biofilm itself acts as a biological defence mechanism to prevent the establishment of pathogenic microbes as well as to protect the surface of the seaweed from the macrofoulers. In most cases, the presence and diversity of these organisms are host-specific. The macroalgal host and their associated microbiont are often referred to as a ‘Holobiont’.
The surface-associated microbiome of macroalgae plays a crucial role in the growth, morphogenesis and defence in the normal favourable environmental conditions of the macroalgae (Symbiotism). Whereas, when there is a change i.e. reversed, unfavourable conditions, the microbiome reverses its symbiotic nature and affects growth and degrades the macroalgae by causing different diseases in different species (Pathogenism). In parallel, marine macroalgae employ different defence mechanisms, a physical defence such as continuous shedding of the outer layer of cells, and the mucilaginous covering and chemical defence such as the production of secondary metabolites.
The following chapter focuses on the macroalgal surface-associated microbiome and its defence system with a certain number of relevant examples from related literature on this subject.
Keywords: Surface-associated microbiome; microbionts; holobionts; symbiotism; secondary metabolites; microbial colonization; biofilm.
... For example, when cultured in an axenic environment, some seaweed species will develop abnormal morphologies which become normal again when bacteria are added, suggesting the synthesis by the bacteria of compounds necessary for the macroalgal morphology (Egan et al., 2013). Weinberger et al. (2007) have also observed that secondary compounds produce by the bacteria are important in the algal spore release and settlement. Moreover, cyanobacteria are often abundant on benthic macroalgae probably due to their nitrogen fixing function that will help the macroalga in relatively poor nitrogen environment (de Oliveira et al., 2012). ...
Most marine macroalgae live attached to a substrate in coastal areas characterized by a very variable environment mainly due to the tide cycle which is more or less important depending on the geographical situation. Macroalgae spread over coastal zones according to their resistance to several abiotic and biotic factors. Some species are thus present on intertidal zones and are outside the water for a more or less long time each day; on the other hand, others are always underwater if they are living in the subtidal zone or in pools in which abiotic parameters can be strongly modified during a tide cycle. During these alternating immersion/emersion phases, macroalgae deal then with important modifications of many abiotic parameters, such as light, temperature, salinity, and biotic parameters, such as grazing, fouling, pathogens. To counteract these important variations, intertidal macroalgae develop resistance mechanisms such as the synthesis of special compounds, like photoprotectors, osmolytes, antifouling molecules as examples. In this chapter, after a presentation of the main environmental parameters facing intertidal seaweeds in temperate environment, some adaptation/protection mechanisms of these algae are presented, with an emphasis on brown (structural species whose biomass is very high on intertidal zones) and red seaweeds (whose diversity is very high).
... Algal spore release is often controlled by abiotic factors, such as light and temperature conditions (Amsler and Neushul, 1989;Ganesan et al., 1999) or desiccation (Suto, 1952). It may, however, also involve more complex mechanisms such as cross-talk, i.e. bidirectional biochemical interaction, with hosts or the presence of bacteria (Weinberger et al., 2007). ...
The sugar kelp Saccharina latissima is cultivated in Europe for food, feed and ultimately the production of chemical commodities and bioenergy. Being cultivated in the open sea, S. latissima is exposed to potentially harmful organisms, such as Laminarionema elsbetiae, a filamentous brown algal endophyte with a very high prevalence in wild populations of European S. latissima. As it was shown previously that S. latissima sporophytes get infected by L. elsbetiae very early in their life, seeding the spores on collectors and keeping them under controlled conditions during the critical time of a possible infection with filamentous endophytes could be advantageous over direct seeding techniques, where the ropes are deployed within days after seeding. We used a qPCR-assay to assess the prevalence of the endophyte L. elsbetiae in S. latissima cultivated during winter in Northern Brittany, comparing individuals from direct-seeded ropes and collector-seeded lines that were kept in laboratory conditions for different time spans. No DNA of the endophyte was detected in the samples, suggesting that either the kelps were not infected or the amount of endophytic filaments were below the detection rate of the qPCR assay. Furthermore, L. elsbetiae could not be detected in the seawater surrounding the kelp farm, indicating that L. elsbetiae is not fertile or disperses at a very small scale in Northern Brittany during the deployment time of young kelps. Our results suggest that infections of cultivated S. latissima with the endophyte L. elsbetiae might be a minor problem in kelp farms in Northern Brittany if the seeding production is kept under controlled conditions without external contamination.
... Kelps, and seaweeds more generally, are covered in microorganisms, and the importance of surface-associated microbes on the functioning of seaweeds is increasingly recognised (Egan et al. 2013). Changes in surface-associated microbial communities can have significant effects on host seaweeds, ranging from development and recruitment (Marshall et al. 2006, Morris et al. 2016, photosynthetic capacity (Marzinelli et al. 2015a), fecundity (Weinberger et al. 2007, Campbell et al. 2011) and survival (Egan et al. 2013, Peters 2015. Recently, there has been an increasing focus on understanding the interactions between microbiomes and large habitat-forming kelps because of their ecological importance (e.g. ...
Ecklonia radiata is one of the most widespread kelps globally, dominating temperate reefs throughout much of Australasia and southeastern Africa. Throughout much of its range, it is the only laminarian kelp and hence plays a key role in facilitating biodiversity and driving food webs, and it underpins immense ecological and socioeconomic values. This review synthesises the growing literature on E. radiata from its phylogeny and distribution through to its biology, ecology and recent changes. It provides an assessment of the state of knowledge and identifies gaps in our understanding of this important species. Despite being tolerant of a wide range of abiotic conditions, recent environmental change has caused direct and indirect loss of E. radiata forests, with extensive areas transitioning to turf and urchin barrens. Ongoing climate change may require application of multifaceted and novel strategies to increase its resistance and resilience to future conditions. By integrating variation across space, time and environmental change, this review provides a description of the current status and possible future trajectories of E. radiata forests. © S. J. Hawkins, A. L. Allcock, A. E. Bates, L. B. Firth, I. P. Smith, S. E. Swearer, and P. A. Todd, Editors Taylor & Francis.
... These studies have demonstrated that the specific bacteria presence is necessary for morphological development and growth in green (Singh et al. 2011a;Spoerner et al. 2012;Wichard 2015;Grueneberg et al. 2016;Ghaderiardakani et al. 2017), red (Singh et al. 2011b;Fukui et al. 2014), and brown algae (Tapia et al. 2016). Bacteria are also known to induce zoospore colonization (Singh et al. 2013;Vesty et al. 2015) and spore release (Weinberger et al. 2007;Singh et al. 2015;Tapia et al. 2016). Furthermore, bacteria associated with benthic algae have ecological roles such as establishment of planktonic propagules (larvae, spores, bacteria) Othmani et al. 2016;Satheesh et al. 2016) and host defense against deleterious microorganisms (Goecke et al. 2010;Singh and Reddy 2014;Campbell et al. 2015). ...
Macroalgae play a crucial role in marine ecosystems when they contribute to the global primary production in the habitats formation, providing food and shelter to a range of aquatic organisms. They have a number of interactions with bacteria and other organisms such as fouling and disease. To inhibit the settling, growing, and biofilm formation by bacteria, it has been suggested that the macroalgae influence bacterial metabolism and quorum sensing through the production of secondary metabolites with antibiotic effect. Macroalgae-bacteria interactions have been investigated for many years. These interactions can be beneficial when the bacteria assist with the normal development of macroalgae as well as reducing secondary fouling on the algal surface. On the other hand, the interactions may have a deleterious effect when the biofilm impairs the photosynthetic ability or promotes disease development. This review reports the recent advances in the understanding of bacteria-brown algae interactions, highlighting the diversity and functional role of epiphytic bacteria, including the maintenance of the health of the algae and the biological activities described from this association. Through combined bacterial culture, microscopy, and molecular biology, it has been possible to identify and establish the phylogenetic origin of different bacterial communities associated with brown algae, being predominantly the phyla Proteobacteria, Bacteroidetes, and Firmicutes. Further investigation of the bacterial communities that live on different macroalgae using new technologies are still required, mainly to evaluate the production and secretions of metabolites with biotechnological potential.
... Algae, as the primary producer in freshwater and marine environments, provide dissolved organic nutrients to phycosphere heterotrophic bacteria (Field et al., 1998;Kouzuma and Watanabe, 2015). Complementarily, associated bacteria contribute to growth, morphogenesis, spore germination and colonization of algae by fixing nitrogen, as well as releasing minerals, vitamins, auxins, and quorum sensing signaling molecules (Joint et al., 2002;Croft et al., 2005;Marshall et al., 2006;Weinberger et al., 2007;Goecke et al., 2010;Foster et al., 2011;Reddy, 2014, 2015). Algae-associated bacteria have the potential to stimulate the growth of algae, similar to plant growth-promoting rhizobacteria. ...
Algae-bacteria associations occurred widely in marine habitats, however, contributions of bacteria to macroalgal blooming were almost unknown. In this study, a potential endophytic strain SI-3 was isolated from Ulva prolifera, the causative species for the world's largest green tide in the Yellow Sea, following a strict bleaching treatment to eliminate epiphytes. The genomic sequence of SI-3 was determined in size of 4.8 Mb and SI-3 was found to be mostly closed to Pseudomonas stutzeri. To evaluate the characteristics of SI-3 as a potential endophyte, the genomes of SI-3 and other 20 P. stutzeri strains were compared. We found that SI-3 had more strain-specific genes than most of the 20 P. stutzeri strains. Clusters of Orthologous Groups (COGs) analysis revealed that SI-3 had a higher proportion of genes assigned to transcriptional regulation and signal transduction compared with the 20 P. stutzeri strains, including four rhizosphere bacteria, indicating a complicated interaction network between SI-3 and its host. P. stutzeri is renowned for its metabolic versatility in aromatic compounds degradation. However, significant gene loss was observed in several aromatic compounds degradation pathways in SI-3, which may be an evolutional adaptation that developed upon association with its host. KEGG analysis revealed that dissimilatory nitrate reduction to ammonium (DNRA) and denitrification, two competing dissimilatory nitrate reduction pathways, co-occurred in the genome of SI-3, like most of the other 20 P. stutzeri strains. We speculated that DNRA of SI-3 may contribute a competitive advantage in nitrogen acquisition of U. prolifera by conserving nitrogen in NH4+ form, as in the case of microalgae bloom. Collectively, these data suggest that Pseudomonas sp. strain SI-3 was a suitable candidate for investigation of the algae-bacteria interaction with U. prolifera and the ecological impacts on algal blooming.
... Only a few studies demonstrated exogenous control of spore release such as wave motion in Alaria esculenta and Ulva lactuca (Gordon and Brawley, 2004) or bacteria in Acrochaetium sp. (Weinberger et al., 2007) (Appendix 1 in Supplementary Material). Many papers mentioned periodicity of spore release linked with tidal movement, specific day time (light intensity) and wave action to both facilitate the mechanical scouring of reproductive tissue and spore dispersal, and synchronize spore release once matured (Hoffmann, 1987;Amsler and Neushul, 1989;de Bettignies et al., 2013). ...
As plants on land, seaweeds are likely to be susceptible to temperature-mediated changes in phenology such as shifts in their reproductive timing. With this review, we aimed to investigate the importance of temperature on reproductive phenophase transitions (i.e., maturation and release of propagules) of temperate seaweeds while discussing how global warming might affect their reproductive phenology. A systematic literature search returned a total of 81 relevant papers, which were reviewed for evidence of environmental, factors (including temperature) driving reproductive phenology. Only a few of studies reported effects of temperature on propagule release (spores and gametes). In contrast, reproductive maturation (both sporogenesis and gametogenesis) was found predominantly to be controlled by temperature. Our findings highlight the potential for phenological shifts in seaweeds in response to ocean warming. In contrast to the consistent advancement of spring events observed for terrestrial plants, there was evidence that warming can both advance and delay the timing of reproductive events for temperate seaweeds, especially the maturation of propagules. Because temperature was often found to act in combination with either day length or spectral composition, ocean warming might result in a mismatch between light and temperature requirements that could lead to reduced reproductive performance.
... The role of bacteriamediated morphogenisis has been especially well characterized for macroalgae in the class Ulvophyceae, which do not develop normally in the absence of surface bacteria; instead, axenically cultured Ulvophyceae are slow growing with atypical morphologies (Wichard, 2015). Similarly, both the release (Weinberger et al., 2007) and settlement (Joint et al., 2007) of marine algal spores depend on the presence of bacteria-derived signalling molecules, suggesting that microbial symbionts are necessary for even the most basic aspects of algal life history. Beyond the direct benefits to algal hosts, heterotrophic marine bacteria metabolize algae-derived polysaccharides (Michel et al., 2006;Bengtsson et al., 2011;Hehemann et al., 2014), providing a major pathway for the flow of carbon from algal primary production to higher trophic levels (Norderhaug et al., 2003;Azam and Malfatti, 2007). ...
... La N-butanoyl-L-homosérine lactone (C4-HSL) a été montrée comme régulant la sporulation de l'algue rouge Acrochaetium sp. : pour des concentrations de 10 à 100 µM, la sporulation est induite (Weinberger et al., 2007). Le remplacement d'HSL naturelles par des HSL de synthèse ne favorise pas autant l'adhésion des larves (Huang et al., 2007). ...
Le développement de salissures marines (ou biofouling) est à l’origine de nombreux problèmes économiques et écologiques. Ces salissures marines sont constituées de microorganismes (bactéries, microalgues…) formant le microfouling sur lequel va se développer le macrofouling constitué de macroorganismes tels que les algues, coquillages et éponges. La formation de ces salissures va induire un ralentissement des navires provoquant une surconsommation de carburant. De plus, l’utilisation de revêtements antisalissures ou peintures antifouling à base de métaux lourds et de biocides dans le passé a conduit à des problèmes environnementaux. L’objectif de la thèse est de rechercher une alternative aux composés actuellement utilisés (cuivre) en respectant le milieu marin. L’environnement est une source d’inspiration, une approche biomimétique pourrait être une stratégie de lutte efficace contre le biofouling. Dans une première partie, un criblage d’une centaine de composés est réalisé contre des souches bactériennes. Huit composés issus des deux familles : les batatasins et les hemibastadins sont étudiées en vue de comprendre leurs modes d’action. Parmi les composés sélectionnés, la famille des hemibastadins comprenant le DiBromoHemiBastadin-1 (DBHB) a montré des propriétés antifouling prometteuses. En effet, cette molécule est capable d’inhiber 50 % la formation du biofilm avec une IC50= 6,44 µg/mL pour la bactérie Pseudomonas aeruginosa PAO1 et une IC50 = 12,8 µg/mL pour la bactérie marine Paracoccus sp. 4M6. Afin de comprendre le mode d’action de cette molécule, son impact sur la communication bactérienne, le quorum sensing est étudié et le composé DBHB est capable de l’inhiber. Dans une seconde partie, un autre groupe d’organismes participant au microfouling est étudié : les microalgues. Afin d’évaluer l’impact de composés de la famille des hemibastadins et notamment du DBHB, l’adhésion et la formation de biofilm de microalgues sont étudiées. Le DBHB montre des inhibitions de l’adhésion et de la formation du biofilm uniquement envers la diatomée Cylindrotheca closterium. Une dernière partie, s’est intéressée à l’évaluation de revêtements contenant six composés de la famille des batatasins et des hemibastadins sur le microfouling naturel. Une méthode d’immersion de revêtements en conditions contrôlées (photobioréacteur) est mise au point afin de pallier aux contraintes environnementales. L’ensemble de cette étude a permis de mettre en évidence les propriétés antifouling du DBHB et de caractériser son mode d’action. Ce composé offre d’intéressantes voies d’étude dans la lutte contre le biofouling. De plus, l’approfondissement des connaissances sur les procédés d’adhésion et de formation de biofilm de microalgues permet de définir de nouvelles stratégies de lutte.
... Macroalgae control bacterial epibionts by growth inhibition via antibiotics or destabilisation of quorum sensing (QS) systems [23]. Algal morphogenesis in turn is affected by QS molecules of Gram-negative bacteria [29,69]. Recently, we investigated 25 Rhodobacteraceae strains isolated from macroalgae, including nine strains of the present study, for production of QS autoinducers (N-acylhomoserine lactones; AHLs) [73]. ...
Macroalgae harbour specific microbial communities on their surface that have functions related to host health and defence. In this study, the bacterial biofilm of the marine brown alga Fucus spiralis was investigated using 16S rRNA gene amplicon-based analysis and isolation of bacteria. Rhodobacteraceae (Alphaproteobacteria) were the predominant family constituting 23% of the epibacterial community. At the genus level, Sulfitobacter, Loktanella, Octadecabacter and a previously undescribed cluster were most abundant, and together they comprised 89% of the Rhodobacteraceae. Supported by a specific PCR approach, 23 different Rhodobacteraceae-affiliated strains were isolated from the surface of F. spiralis, which belonged to 12 established and three new genera. For seven strains, closely related sequences were detected in the 16S rRNA gene dataset. Growth experiments with substrates known to be produced by Fucus spp. showed that all of them were consumed by at least three strains, and vitamin B12 was produced by 70% of the isolates. Since growth of F. spiralis depends on B12 supplementation, bacteria may provide the alga with this vitamin. Most strains produced siderophores, which can enhance algal growth under iron-deficient conditions. Inhibiting properties against other bacteria were only observed when F. spiralis material was present in the medium. Thus, the physiological properties of the isolates indicated adaption to an epiphytic lifestyle.
... functions include, but are not limited to, the organization of light-emitting reactions (bioluminescence) 18 , the formation of biofilms 19 , the production of antibiotics 20 , spore formation 21 or the expression of virulence factors 22,23 . These pathways, under the control of QS, provide alternative targets for second-generation antibiotics. ...
An ethyl acetate (EtOAc) extract isolated from the marine bacterium, Rheinheimera aquimaris QSI02, was found to exhibit anti-quorum sensing (anti-QS) activity. A subsequent bioassay-guided isolation protocol led to the detection of an active diketopiperazine factor, cyclo(Trp-Ser). Biosensor assay data showed that the minimum inhibitory concentration (MIC) of cyclo(Trp-Ser) ranged from 3.2 mg/ml to 6.4 mg/m for several microorganisms, including Escherichia coli, Chromobacterium violaceum CV026, Pseudomonas aeruginosa PA01, Staphylococcus aureus, and Candida albicans. Additionally, sub-MICs of cyclo(Trp-Ser) decreased the QS-regulated violacein production in C. violaceum CV026 by 67%. Furthermore, cyclo(Trp-Ser) can decrease QS-regulated pyocyanin production, elastase activity and biofilm formation in P. aeruginosa PA01 by 65%, 40% and 59.9%, respectively. Molecular docking results revealed that cyclo(Trp-Ser) binds to CviR receptor more rigidly than C6HSL with lower docking energy −8.68 kcal/mol, while with higher binding energy of −8.40 kcal/mol than 3-oxo-C12HSL in LasR receptor. Molecular dynamics simulation suggested that cyclo(Trp-Ser) is more easy to bind to CviR receptor than natural signaling molecule, but opposite in LasR receptor. These results suggest that cyclo(Trp-Ser) can be used as a potential inhibitor to control QS systems of C. violaceum and P. aeruginosa and provide increased the understanding of molecular mechanism that influences QS-regulated behaviors.
... Although QS typically mediates interbacterial interactions, it is becoming apparent that marine eukaryotes can respond directly to AHLs, and therefore that AHLs can also play a role in interactions between bacteria and eukaryotes in the ocean (Huang et al. 2007, Joint et al. 2002, Tait & Havenhand 2013, Tait et al. 2005, Weinberger et al. 2007). In the marine environment, one particularly well-studied example of an AHL-mediated interdomain interaction is between the biofouling macroalga Ulva and the resident bacteria within biofilms onto which they settle. ...
Quorum sensing (QS) is a form of chemical communication used by certain bacteria that regulates a wide range of biogeochemically important bacterial behaviors. Although QS was first observed in a marine bacterium nearly four decades ago, only in the past decade has there been a rise in interest in the role that QS plays in the ocean. It has become clear that QS, regulated by signals such as acylated homoserine lactones (AHLs) or furanosyl-borate diesters [autoinducer-2 (AI-2) molecules], is involved in important processes within the marine carbon cycle, in the health of coral reef ecosystems, and in trophic interactions between a range of eukaryotes and their bacterial associates. The most well-studied QS systems in the ocean occur in surfaceattached (biofilm) communities and rely on AHL signaling. AHL-QS is highly sensitive to the chemical and biological makeup of the environment and may respond to anthropogenic change, including ocean acidification and rising sea surface temperatures. Expected final online publication date for the Annual Review of Marine Science Volume 9 is January 03, 2017. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.
... Moreover, associated bacteria are known to induce settlement of zoospores of Ulva species and release of spores from Acrochaetium sp. (Joint et al., 2007;Weinberger et al., 2007). ...
Associated microbiota play crucial roles in health and disease of higher organisms. For macroalgae, some associated bacteria exert beneficial effects on nutrition, morphogenesis and growth. However, current knowledge on macroalgae–microbiota interactions is mostly based on studies on green and red seaweeds. In this study, we report that when cultured under axenic conditions, the filamentous brown algal model Ectocarpus sp. loses its branched morphology and grows with a small ball-like appearance. Nine strains of periphytic bacteria isolated from Ectocarpus sp. unialgal cultures were identified by 16S rRNA sequencing, and assessed for their effect on morphology, reproduction and the metabolites secreted by axenic Ectocarpus sp. Six of these isolates restored morphology and reproduction features of axenic Ectocarpus sp. Bacteria-algae co-culture supernatants, but not the supernatant of the corresponding bacterium growing alone, also recovered morphology and reproduction of the alga. Furthermore, colonization of axenic Ectocarpus sp. with a single bacterial isolate impacted significantly the metabolites released by the alga. These results show that the branched typical morphology and the individuals produced by Ectocarpus sp. are strongly dependent on the presence of bacteria, while the bacterial effect on the algal exometabolome profile reflects the impact of bacteria on the whole physiology of this alga.
Ocean warming is driving profound changes in the ecology of marine habitat formers such as kelps, with negative implications for the biodiversity and ecosystem services they support. Thermal stress can disturb associated microbiota that are essential to the healthy functioning of kelp, but little is known about how this process influences early‐life stages. Because kelps have a biphasic life cycle, thermal stress dynamics of adult sporophyte microbiota may not reflect those of the free‐living haploid gametophyte. We investigated the role of microbial disruption under thermal stress on gametophytes of the kelp Ecklonia radiata and compared sporophyte and gametophyte microbiota. The microbiota of gametophytes changed significantly when the microbiome was disrupted and under increased temperature (26°C), in which putative generalist bacterial taxa proliferated and bacterial families associated with nitrogen fixation decreased. Concurrently, the survival of gametophytes decreased to <10%, and surviving gametophytes did not become fertile when the microbiome was disrupted. The length of gametophytes decreased under both microbial disruption and thermal stress. Taken together, this suggests that the associated microbiota of Ecklonia gametophytes is important for their survival, fertility, and response to warming. Gametophyte and parental sporophyte microbiota were also distinct from the water column but not each other, suggesting vertical transmission of microbiota from one life stage to the next. This study furthers our understanding of the role of microbiota in gametophyte stress tolerance as well as the acquisition of microbiota, which may prove vital in protecting and increasing the stress resilience of these foundation species.
Different marine seaweed species have been shown to harbour specific bacterial communities, however, the extent to which vertical symbiont transmission from parents to offspring contributes to host‐specificity is unclear. Here we use fluorescence and electron microscopy as well as 16S rRNA gene‐based community analysis to investigate symbiont transmission in members of the three major seaweed groups (green Chlorophyta , red Rhodophyta and brown Phaeophyceae ). We found seaweeds employ diverse strategies to transfer symbionts to their progeny. For instance, the green Ulva australis does not appear to have the capacity for vertical transmission. In contrast, the brown Phyllospora comosa adopts a non‐selective vertical transmission. The red Delisea pulchra demonstrates weak selectivity in symbiont transmission, while the brown Hormosira banksii exhibits a strongly selective symbiont transfer. Mucilage on the gametes appears to facilitate vertical transmission and transferred bacteria have predicted properties that could support early development of the seaweeds. Previous meta‐analysis has indicated that vertical transmission is rare in aquatic compared to terrestrial environments, however, our results contribute to the growing evidence that this might not be the case and that instead vertical transmission with various degrees of symbiont selection occurs in the ecologically important group of seaweeds.
Phototrophic and heterotrophic microorganisms coexist in complex and dynamic structures called periphyton. These structures shape the biogeochemistry and biodiversity of aquatic ecosystems. In particular, microalgae-bacteria interactions are a prominent focus of study by microbial ecologists and can provide biotechnological opportunities for numerous applications (i.e. microalgal bloom control, aquaculture, biorefinery and wastewater bioremediation). In this review, we analyze the species dynamics (i.e. periphyton formation and factors determining the prevalence of one species over another), coexisting communities, exchange of resources and communication mechanisms of periphytic microalgae and bacteria. We extend periphyton mathematical modelling as a tool to comprehend complex interactions. This review is expected to boost the applicability of microalgae-bacteria consortia, by drawing out knowledge from natural periphyton.
Intertidal macroalgae face periodic water loss and rehydration caused by daily tidal changes. However, the effect of water loss stress on algal epiphytic bacteria has not yet been reported. In this study, the effects of water loss stress on the epiphytic bacteria community of Sargassum thunbergii were analyzed, and the different responses of epiphytic bacteria to water loss stress were compared between male and female algae. The results showed that after water loss stress, the diversity of the epiphytic bacterial community of S. thunbergii first decreased and then increased. Among the dominant taxa, the abundance of Cyanobacteria decreased significantly, whereas the abundance of Portibacter and Aquimarina first increased and then decreased. Additionally, the indicator species and the abundance of predicted functional genes related to carbon, nitrogen, and sulfur metabolism both changed significantly. More importantly, when the epiphytic bacteria were analyzed separately according to the algal sex, the changes in algal epiphytic bacterial community structure and indicator species were more significant, and there were sexual differences. Therefore, it was concluded that water loss stress has a significant effect on the community structure and function of the epiphytic bacteria on S. thunbergii. Meanwhile, the epiphytic bacteria community of two sexes of S. thunbergii differed in the response to water loss stress.
The bacterial flora associated with Gracilaria dura , the sole producer of natural agarose was obtained. Screening for the presence of various enzymes and bioactive compounds resulted in discerning different clinically and industrially important enzymes. Three isolates were identified to be producing L-asparaginase (LA), a potent anticancer drug. The strain 4T1-C26E registered highest LA activity (25.2 IU ml − 1 ) in the enzyme assay, was selected for yield improvement by optimizing process parameters through Response Surface Methodology (RSM). Various parameters like glucose concentration, L-asparagine concentration, pH of the media, and incubation period were optimized through Central Composite Design (CCD) for enhanced yield of LA by 4T1-C26E, identified as Bacillus licheniformis . The CCD table was exploited for application in artificial neural networking (ANN) for the development of optimum method of cultivation. In this study, we obtained 2.5-fold (88.4 IU ml − 1 ) increase in LA production by this strain through RSM optimization. Further, Artificial Neural Networking Particle Swarm Optimization (ANN-PSO) predicted the input combinations. The experimental validation of LA production was found to be 4-fold (126.4 IU ml − 1 ) higher with respect to the unoptimized conditions. This illustrates the effectiveness of ANN-PSO based optimization technique, the error percent between the predicted and experimental output was 4.03%. The most important benefit of LA from 4T1-C26E is that it possesses no L-glutaminase activity. Further, it is extracellularly produced which is suitable for easier downstream processing thereby reducing chances of immunogenic responses by endotoxins. However, characterization of kinetic parameters and cytotoxic studies on cell cultures are mandatory to confirm its pharmaceutical application.
In order to further obtain sustainable wastewater treatment technology, in-depth analysis based on algal-bacterial symbiosis, quorum sensing signal molecules and algal-bacterial relationship will lay the foundation for the synergistic algal-bacterial wastewater treatment process. The methods of enhancing algae and bacteria wastewater treatment technology were systematically explored, including promoting symbiosis, reducing algicidal behavior, eliminating the interference of quorum sensing inhibitor, and developing algae and bacteria granular sludge. These findings can provide guidance for sustainable economic and environmental development, and facilitate carbon emissions reduction by using algae and bacteria synergistic wastewater treatment technology in further attempts. The future work should be carried out in the following four aspects: (1) Screening of dominant microalgae and bacteria; (2) Coordination of stable (emerging) contaminants removal; (3) Utilization of algae to produce fertilizers and feed (additives), and (4) Constructing recombinant algae and bacteria for reducing carbon emissions and obtaining high value-added products.
The green seaweed Ulva is a model system to study seaweed–bacteria interactions, but the impact of environmental drivers on the dynamics of these interactions is little understood. In this study, we investigated the stability and variability of the seaweed‐associated bacteria across the Atlantic–Baltic Sea salinity gradient. We characterized the bacterial communities of 15 Ulva sensu lato species along 2,000 km of coastline in a total of 481 samples. Our results demonstrate that the Ulva‐associated bacterial composition was strongly structured by both salinity and host species (together explaining between 34% and 91% of the variation in the abundance of the different bacterial genera). The largest shift in the bacterial consortia coincided with the horohalinicum (5–8 PSU, known as the transition zone from freshwater to marine conditions). Low‐salinity communities especially contained high relative abundances of Luteolibacter, Cyanobium, Pirellula, Lacihabitans and an uncultured Spirosomaceae, whereas high‐salinity communities were predominantly enriched in Litorimonas, Leucothrix, Sulfurovum, Algibacter and Dokdonia. We identified a small taxonomic core community (consisting of Paracoccus, Sulfitobacter and an uncultured Rhodobacteraceae), which together contributed to 14% of the reads per sample, on average. Additional core taxa followed a gradient model, as more core taxa were shared between neighbouring salinity ranges than between ranges at opposite ends of the Atlantic–Baltic Sea gradient. Our results contradict earlier statements that Ulva‐associated bacterial communities are taxonomically highly variable across individuals and largely stochastically defined. Characteristic bacterial communities associated with distinct salinity regions may therefore facilitate the host's adaptation across the environmental gradient.
Developmental biology is an area of great interest to biologists, as it addresses the mechanisms underlying plant, animal, fungal, and bacterial growth and development. Modern developmental biology combines a multidisciplinary approach to understand the genetic control of cell growth, differentiation, and morphogenesis. It applies the most recent methods and techniques from disciplines such as biochemistry, molecular biology, cell biology, and molecular genetics, to fully understand the complex regulatory processes involved. It is beyond the means of this book to cover all relevant subjects in developmental biology; hence, the book scope is restricted to relevant aspects of the prokaryotic and lower eukaryotic worlds, with an occasional foray into the higher eukaryotes realm.
The surface of Halymenia floresii, a Mexican Rhodophyta, was observed to be remarkably free of epiphytes under Integrated MultiTrophic Aquaculture (IMTA) conditions. This suggests the presence of allelopathic active compounds released by this macroalgae. The aim of this work was to explore the defence mechanisms developed by H. floresii against surface epibiosis, to detect and identify the secondary metabolites produced at the surface of the algae, and to study its relation with surface associated bacteria. For the first time, we isolated the epibacterial community of H. floresii cultivated under controlled conditions (IMTA) and uncontrolled ones (beach-cast material collected in the area). The isolated epibacteria were screened in vitro to analyse Quorum Sensing (QS) signals, and others H. floresii surface extracts were assayed for any QS interference with them. We differentiated the epibacteria significant pathogens from the non- pathogens ones by their ability to induce bleaching, a well-known algal disease. Vibrio owensii was identified as an opportunistic pathogen inducing bleaching in H. floresii which was also associated to the presence of its C4-HSL QS signal. The surface and whole cell metabolites extracts from H. floresii specimens cultivated under controlled conditions were analysed by means of LC/MS. An untargeted metabolomic analysis of H. floresii was performed to provide a global metabolic profile as a first database. We identified ‘41’ active metabolites in H. floresii, among which halogenated compounds, furanones and various inhibitors were overrepresented. Interestingly, the first two classes are well known potent QS interfering compounds. The relatively higher occurrences of allelopathic metabolites at the surface of H. floresii strongly supports the hypothesis that they must be involved in the host protection. Further investigations are needed to explore the secondary metabolites of H. floresii et their role in the seaweed.
Endophytic brown algae invade stipes and fronds of kelps with potential negative effects for their hosts. The molecular diversity of kelp endophytes was investigated and a majority of the isolated endophytes belonged to the genera Laminarionema and Laminariocolax. Using a qPCR approach, a high prevalence of the endophyte Laminarionema elsbetiae was detected in natural Saccharina latissima populations, but with seasonal and geographical variations. Co-cultivation experiments showed different physiological responses of the main host, S. latissima, and an occasional host, Laminaria digitata, to L. elsbetiae. A transcriptomic approach revealed important differences between the molecular responses of the two kelps, related to the recognition of the endophyte and subsequent defence reactions. These specific differences in the molecular cross-talk during the early steps of the interaction could explain the variability of natural infection patterns in kelp species.
Microalgae have emerged as a renewable and sustainable candidate for bioenergy production coupled with pollutant removal from wastewater. However, costly biomass harvesting, insufficient biomass productivity, and energy-intensive extraction methods are major bottlenecks restricting their large-scale development. To break through such limitations, researchers have focused on the technologies towards consolidating microalgal-bacterial consortia, which exhibit numerous advantages related to economy, energy, and environment, due to the cooperative interactions between microalgae and bacteria. This paper recapitulates the most recent work on microalgal-bacterial interaction mechanisms, and describes the diverse biotechnological applications of microalgal-bacterial consortia. Based on this review, the interaction mechanisms cover substrate exchange, cell-to-cell signaling, and horizontal gene transfer. Nutrient availability, growth phase, and cultivation conditions are major factors affecting their interactions. In terms of wastewater treatment, attached microalgal-bacterial consortia are economically feasible and technically superior compared to suspended microalgal-bacterial consortia. Appropriate carrier, bioreactor type, operation mode, operational factor, and further perspectives for engineering attached microalgal-bacterial consortia are critically assessed. Bacteria play an important role in promoting microalgal growth, enhancing bio-flocculation and facilitating cell wall disruption, and thus expanding the application potential of microalgal biofuel production. The current state of other promising biotechnological applications of microalgal-bacterial consortia (particularly mitigation of CO2 emissions, microalgal bloom control, and electricity generation) and the appropriate strategies to enhance their practical applications are discussed. The major challenges to scale up microalgal-bacterial consortia and corresponding recommendations for further research are also addressed.
Purpose
Medical textile is one aspect of technical textiles and it is classified according to performance and functional properties for hygienic and healthcare products. Seaweeds have curative powers for curing most degenerative diseases. The paper aims to discuss these issues.
Design/methodology/approach
The present study focusses on the extraction of dyes from five seaweeds such as Ulva reticulata , Ulva lactuca , Sargassum wightii , Padina tetrastomatica and Acanthophora spicefera . The presence of bioactive compounds, antioxidant and antimicrobial properties of dye extracted from seaweeds was analysed. The dye extracted from green seaweed was applied on cotton fabric to obtain antimicrobial and other properties used to make non- implantable materials.
Findings
A maximum antioxidant inhibition percentage of 86.48+2.84 and a maximum antibacterial activity of 27 mm inhibition zone were obtained on the fabric treated with the dye extract from the Ulva lactuca seaweed. The physical properties such as tensile strength and tearing strength did not show much significant difference in untreated and treated fabric. The air permeability, water absorbency and wicking behaviour of treated fabric were reduced compared with untreated fabric. The washing and rubbing properties of treated fabric were very good after repeated washing.
Originality/value
This bioactive fabric has been used for non-implantable materials such as wound healing, face mask, surgical gowns and hygienic textiles in recent years.
Experiments were carried out with tetrasporophytes of Padina boergesenil to understand the effects of ultra violet radiation, light intensity, photoperiod, temperature, salinity and desiccation on the liberation of tetraspores. UV-B radiation inhibits spore liberation while UV-C radiation enhances spore release. UV-A radiation increases spore liberation initially during short time exposure and inhibits spore release during long time exposure. UV-B radiation combined with day light increases the spore liberation. Low illuminance (26 μEam-2s-1),short day (8:16 hr LD) and submerged condition of plants and seawater of 35 ppt salinity and 20°C temperature were found to be favourable for maximum liberation of tetraspores. Temperature shock (ranges from 0°C to 50°C up to 120 minutes) could not enhance the spore discharge in Padina boergesenii.
This study identified the most common epiphytes infecting the algal host Gracilaria chilensis on a farm in northern Chile. Simultaneously, the types of host–epiphyte interfaces were characterized and their relative abundance and temporal variability were monitored. Five types of anatomical relationships were detected. Infection type I included the epiphytes weakly attached to the surface of the host and not associated with damage of host tissues (i.e. Hincksia mitchelliae, H. granulosa and Ectocarpus acutus). Infection type II included those epiphytes strongly attached to the surface of the host but not associated with any host tissue damage (i.e. Acrochaetium sp., Antithamnionella sp. and Colpomenia sinuosa). Infection type III included all the epiphytes that penetrated the outer layer of the host wall without damaging its cortical cells (i.e. Xenococcus sp. and Sahlingia subintegra). Infection type IV included epiphytes penetrating deep into the host cell wall, disorganizing the cortical tissue (i.e. Ulva lactuca and Acrosorium corallinarum). Infection type V included epiphytes that penetrated deeply into the cortex, reached the medullary tissue and caused destruction of the host's cells in the area around the infection (i.e. Ceramium rubrum and Polysiphonia harveyi). Prevalence varied with time and with infection type, with types II and III reaching up to 80% and 90% of the thalli respectively. Severity of epiphyte infection was similar to the distribution of infection prevalence, with crustose epiphytes colonizing up to 80% of the host surface.
Recent studies indicate that a taxonomically diverse range of marine eukaryotes produce metabolites which inhibit phenotypic traits in bacteria, with no or minimal effects on growth. In this review, we present evidence for the existence of such eukaryotic interference with a conserved prokaryotic signalling system. We demonstrate that halogenated furanones, a class of secondary metabolites produced by the Australian subtidal red alga DeLisea pulchra, interfere with the acylated homoserine lactone (AHL) regulatory system in several Gram-negative bacteria. Furanones were found to interfere with the AHL mediated expression of bioluminescence, swarming (surface) motility, and exoenzyme synthesis in different bacterial species. Furthermore, adhesion and swarming in a range of marine bacteria, for which the identity of the signalling molecules is not yet determined, were inhibited by furanones at concentrations that did not affect growth. Evidence for these effects were obtained in both field and laboratory experiments. Competition experiments in the presence of different concentrations of AHLs and furanones showed that the expression of swarming and bioluminescence in laboratory strains is competitively inhibited in a fashion that suggests that both classes of compounds have affinity for the same receptor site in the AHL regulatory system. Finally, by performing structure-function experiments on the inhibition of AHL systems by a range of different furanones, we identified the structural prerequisites responsible for interference.
Studies were made on the diurnal periodicity of spore shedding in Ectocarpus mitchellae, Bangiopsis subsimplex and Porphyra vietnamensis. In all three of these marine algae, spore shedding was observed during daytime, and peak shedding of spores occurred between 1000 and 1400 h. Experimental alteration of salinity, exposure to air and light intensity did not change the period of peak spore shedding. Experiments were also conducted to determine optimal environmental conditions (e.g. salinity, desiccation, light intensity) for liberation of plurispores from E. mitchellae, monospores from B. subsimplex and monospores and carpospores from P. vietnamensis growing on the Visakhapatnam coast. In laboratory experiments, 30 to 40 ppt salinity, submergence of fronds and 27 to 44 µE m-2 s-1 light intensity were found to be favourable conditions for the maximum liberation of spores.
In laboratory culture, controlled fertilization resulted in mature carposporophytes of the Ceramiales indicated below. Carpospore discharge was observed daily. In the Ceramiaceae Spyridia filamentosa cystocarp-pairs released spores twice in succession (range: 32–537 total spores/carposporophyte). Discharge by all cystocarp-pairs occurred during the dark period of the daily light:dark cycle (12:12 LD) and was completed in 12 d. In reverse cycle (12:12 and 16:8 DL) spore release reversed in 3d. In the Rhodomelaceae Bostrychia moritziana, Pterosiphonia pennata and Murrayella periclados discharged spores from isolated cystocarps over periods up 58 d (ranges: 318–4112, 1051–2271 and 451–3162 total spores/carposporophyte respectively) without any diurnal or long-term rhythmicity. In the Delesseriaceae cystocarps of Caloglossa leprieurii and Caloglossa ogasawaraensis released spores for up to 31 d (ranges: 271–3050 and 565–1286 total spores/carposp orophyte respectively). Discharge peaks occurred at 5–7 d intervals with viable cystocarps and spore numbers gradually declining. Thus, in the plants studied, there are at least three patterns of carpospore release from individual mature carposporophytes: a relatively short- term dual release pattern, a long-term non-rhythmic release pattern and a long-term rhythmic release pattern. Results also indicated that excised cystocarps without associated vegetative branches showed a much reduced spore production.
Carpospore shedding was studied in Gracilaria cornea in order to determine maximum spore output potential for mariculture purposes. The combined effects of temperature (23, 26 and 29 C), daylength (8:16, 12:12 and 16:8 light:dark), photon irradiance (darkness, 20 and 40 mol m–2 s–1) and spore release method (spontaneous release, osmotic shock and drying) were tested. Maximum spore shedding in cystocarpic G. cornea occurred within the first three days depending on temperature. A reduction in spore release periodicity was more evident at 29 C. Carpospore shedding was mainly affected by temperature and daylength. A higher number of carpospores was released per cystocarp at 26 C than at 23 or 29 C. Short day conditions (8:16 L:D) produced a higher number of carpospores at 26 C, even at the lowest irradiances tested (darkness and 20 mol m–2 s–1). A combination of 26 C and short days (8:16) gave the highest carpospore discharge per cystocarp. There was no significant difference between the spore release methods. These results could be applied to promote the establishment of extensive cultivation of G. cornea from spores as an alternative to vegetative propagation in Yucatan coast.
Acylated homoserine lactones (AHLs) play a widespread role in intercellular communication among bacteria. The Australian macroalga Delisea pulchra produces secondary metabolites which have structural similarities to AHL molecules. We report here that these metabolites inhibited AHL-controlled processes in prokaryotes. Our results suggest that the interaction between higher organisms and their surface-associated bacteria may be mediated by interference with bacterial regulatory systems.
Acylated homoserine lactone (AHL)-mediated gene expression controls phenotypes involved in colonization, often specifically of higher organisms, in both marine and terrestrial environments. The marine red alga Delisea pulchra produces halogenated furanones which resemble AHLs structurally and show inhibitory activity at ecologically realistic concentrations in AHL bioassays. Evidence is presented that halogenated furanones displace tritiated OHHL [N-3-(oxohexanoyl)-L-homoserine lactone] from Escherichia coli cells overproducing LuxR with potencies corresponding to their respective inhibitory activities in an AHL-regulated bioluminescence assay, indicating that this is the mechanism by which furanones inhibit AHL-dependent phenotypes. Alternative mechanisms for this phenomenon are also addressed. General metabolic disruption was assessed with two-dimensional PAGE, revealing limited non-AHL-related effects. A direct chemical interaction between the algal compounds and AHLs, as monitored by 1H NMR spectroscopy, was shown not to occur in vitro. These results support the contention that furanones, at the concentrations produced by the alga, can control bacterial colonization of surfaces by specifically interfering with AHL-mediated gene expression at the level of the LuxR protein.
The phylogenetic relationships of bacterial symbionts from three gall-bearing species in the marine red algal genusPrionitis (Rhodophyta) were inferred from 16S rDNA sequence analysis and compared to host phylogeny also inferred from sequence comparisons
(nuclear ribosomal internal-transcribed-spacer region). Gall formation has been described previously on two species ofPrionitis, P. lanceolata (from central California) and P. decipiens (from Peru). This investigation reports gall formation on a third related host,Prionitis filiformis. Phylogenetic analyses based on sequence comparisons place the bacteria as a single lineage within theRoseobacter grouping of the α subclass of the divisionProteobacteria (99.4 to 98.25% sequence identity among phylotypes). Comparison of symbiont and host molecular phylogenies confirms the presence
of three gall-bearing algal lineages and is consistent with the hypothesis that these red seaweeds and their bacterial symbionts
are coevolving. The species specificity of these associations was investigated in nature by whole-cell hybridization of gall
bacteria and in the laboratory by using cross-inoculation trials. Whole-cell in situ hybridization confirmed that a single
bacterial symbiont phylotype is present in galls on each host. In laboratory trials, bacterial symbionts were incapable of
inducing galls on alternate hosts (including two non-gall-bearing species). Symbiont-host specificity in Prionitis gall formation indicates an effective ecological separation between these closely related symbiont phylotypes and provides
an example of a biological context in which to consider the organismic significance of 16S rDNA sequence variation.
Oxidized halogen antimicrobials, such as hypochlorous and hypobromous acids, have been used extensively for microbial control in industrial systems. Recent discoveries have shown that acylated homoserine lactone cell-to-cell signaling molecules are important for biofilm formation in Pseudomonas aeruginosa, suggesting that biofouling can be controlled by interfering with bacterial cell-to-cell communication. This study was conducted to investigate the potential for oxidized halogens to react with acylated homoserine lactone-based signaling molecules. Acylated homoserine lactones containing a 3-oxo group were found to rapidly react with oxidized halogens, while acylated homoserine lactones lacking the 3-oxo functionality did not react. The Chromobacterium violaceum CV026 bioassay was used to determine the effects of such reactions on acylated homoserine lactone activity. The results demonstrated that 3-oxo acyl homoserine lactone activity was rapidly lost upon exposure to oxidized halogens; however, acylated homoserine lactones lacking the 3-oxo group retained activity. Experiments with the marine alga Laminaria digitata demonstrated that natural haloperoxidase systems are capable of mediating the deactivation of acylated homoserine lactones. This may illustrate a natural defense mechanism to prevent biofouling on the surface of this marine alga. The Chromobacterium violaceum activity assay illustrates that reactions between 3-oxo acylated homoserine lactone molecules and oxidized halogens do occur despite the presence of biofilm components at much greater concentrations. This work suggests that oxidized halogens may control biofilm not only via a cidal mechanism, but also by possibly interfering with 3-oxo acylated homoserine lactone-based cell signaling.
N-acyl-L-homoserine lactones (AHLs) are co-regulatory ligands required for control of the expression of genes encoding virulence traits in many Gram-negative bacterial species. Recent studies have indicated that AHLs modulate the cellular concentrations of LuxR-type regulatory proteins by binding and fortifying these proteins against proteolytic degradation (Zhu & Winans, 2001 ). Halogenated furanones produced by the macroalga Delisea pulchra inhibit AHL-dependent gene expression. This study assayed for an in vivo interaction between a tritiated halogenated furanone and the LuxR protein of Vibrio fischeri overproduced in Escherichia coli. Whilst a stable interaction between the algal metabolite and the bacterial protein was not found, it was noted by Western analysis that the half-life of the protein is reduced up to 100-fold in the presence of halogenated furanones. This suggests that halogenated furanones modulate LuxR activity but act to destabilize, rather than protect, the AHL-dependent transcriptional activator. The furanone-dependent reduction in the cellular concentration of the LuxR protein was associated with a reduction in expression of a plasmid encoded P(luxI)-gfp(ASV) fusion suggesting that the reduction in LuxR concentration is the mechanism by which furanones control expression of AHL-dependent phenotypes. The mode of action by which halogenated furanones reduce cellular concentrations of the LuxR protein remains to be characterized.
Bacteria are capable of complex assemblage behavior through cell-to-cell communication using diffusible chemical signal molecules that accumulate to a threshold concentration that activates target genes ([1][1]). This process, termed “quorum sensing,” has not been shown to cross the prokaryote-
Traditional treatment of infectious diseases is based on compounds that kill or inhibit growth of bacteria. A major concern with this approach is the frequent development of resistance to antibiotics. The discovery of communication systems (quorum sensing systems) regulating bacterial virulence has afforded a novel opportunity to control infectious bacteria without interfering with growth. Compounds that can override communication signals have been found in the marine environment. Using Pseudomonas aeruginosa PAO1 as an example of an opportunistic human pathogen, we show that a synthetic derivate of natural furanone compounds can act as a potent antagonist of bacterial quorum sensing. We employed GeneChip microarray technology to identify furanone target genes and to map the quorum sensing regulon. The transcriptome analysis showed that the furanone drug specifically targeted quorum sensing systems and inhibited virulence factor expression. Application of the drug to P.aeruginosa biofilms increased bacterial susceptibility to tobramycin and SDS. In a mouse pulmonary infection model, the drug inhibited quorum sensing of the infecting bacteria and promoted their clearance by the mouse immune response.
The unicellular soil-freshwater alga Chlamydomonas reinhardtii was found to secrete substances that mimic the activity of the N-acyl-L-homoserine lactone (AHL) signal molecules used by many bacteria for quorum sensing regulation of gene expression. More than a dozen chemically separable but unidentified substances capable of specifically stimulating the LasR or CepR but not the LuxR, AhyR, or CviR AHL bacterial quorum sensing reporter strains were detected in ethyl acetate extracts of C. reinhardtii culture filtrates. Colonies of C. reinhardtii and Chlorella spp. stimulated quorum sensing-dependent luminescence in Vibrio harveyi, indicating that these algae may produce compounds that affect the AI-2 furanosyl borate diester-mediated quorum sensing system of Vibrio spp. Treatment of the soil bacterium Sinorhizobium meliloti with a partially purified LasR mimic from C. reinhardtii affected the accumulation of 16 of the 25 proteins that were altered in response to the bacterium's own AHL signals, providing evidence that the algal mimic affected quorum sensing-regulated functions in this wild-type bacterium. Peptide mass fingerprinting identified 32 proteins affected by the bacterium's AHLs or the purified algal mimic, including GroEL chaperonins, the nitrogen regulatory protein PII, and a GTP-binding protein. The algal mimic was able to cancel the stimulatory effects of bacterial AHLs on the accumulation of seven of these proteins, providing evidence that the secretion of AHL mimics by the alga could be effective in disruption of quorum sensing in naturally encountered bacteria.
In laboratory culture, controlled fertilization resulted in mature carposporophytes of the Ceramiales indicated below. Carpospore discharge was observed daily. In the Ceramiaceae Spyridia filamentosa cystocarp-pairs released spores twice in succession (range: 32-537 total spores/carposporophyte). Discharge by all cystocarp-pairs occurred during the dark period of the daily light:dark cycle (12:12 LD) and was completed in 12 d. In reverse cycle (12:12 and 16:8 DL) spore release reversed in 3d. In the Rhodomelaceae Bostrychia moritziana, Pterosiphonia pennata and Murrayella periclados discharged spores from isolated cystocarps over periods up 58 d (ranges: 318-4112, 1051-2271 and 451-3162 total spores/carposporophyte respectively) without any diurnal or long-term rhythmicity. In the Delesseriaceae cystocarps of Caloglossa leprieurii and Caloglossa ogasawaraensis released spores for up to 31 d (ranges: 271-3050 and 565-1286 total spores/carposporophyte respectively). Discharge peaks occurred at 5-7 d intervals with viable cystocarps and spore numbers gradually declining. Thus, in the plants studied, there are at least three patterns of carpospore release from individual mature carposporophytes: a relatively short-term dual release pattern, a long-term non-rhythmic release pattern and a long-term rhythmic release pattern. Results also indicated that excised cystocarps without associated vegetative branches showed a much reduced spore production.
In order to get knowledge on the shedding of Undaria, Ecklonia and Eisenia (Laminariaceae) in nature, their sporophylls were cultured in running sea water and the amount of spores, shed was successively observed.
Shedding season of Undaria is supposed to begin when the sea water temperature rises to 14°C. in spring (see Table 4).
Shedding of these algae occurs daily in mass in 1-2 hours, chiefly during from 9 a.m. to 6 p.m. The shedding amount rises to an enourmous level on some days, likely on every 4th-5th day (10⁶-10⁷ spores per gr. in Undaria, 10⁵-10⁶ in Ecklonia and Eisenia), while in other days it stays at much lower level (10⁴-1O⁵ per gr.). Besides above mentioned, shedding occurs fast in all the time in a day in a small quantity (less than 10⁴ per gr. hrs.) (see Fig. 1, Table 1-3). It is supposed that shedding of these algae will occur in the same way also in nature.
In dark cultures there seemed no difference in the manner of shedding at least for 3 days, from in day-light cultures.
??
To get spores of these algae, it is a custom to immerse sporophylls into sea water after drying for a few hours. In compared with the shedding in running sea water, this treatment seems not to be effective to enlarge the amount of shedding, but seems to have only some effect to hasten the time of shedding (see Table 3).
The microorganisms on the surface of the brown algaAscophyllum nodosum, collected from an intertidal area in Nahant, Massachusetts, were examined using scanning electron microscopy. Differences in the microbial populations on the holdfast, internodal regions of the stipe, and the apical tips were apparent. The populations ranged from a lawn of end-attached bacteria above the holdfast to microcolonies of yeast cells near the apical tips. The greatest diversity of microorganisms was noted in the internodal region representing the fourth year of growth where a dense lawn of end-attached bacteria was overlaid by filamentous bacteria, pennate diatoms, and filamentous blue-green algae. A simple procedure was developed to estimate the number of bacteria on the surface of the seaweed using the scanning electron microscope. The observed distribution of epiphytes may be explained in terms of the age of the algal surface, differences in light intensity, and the differential secretion of tannin by various parts ofAscophyllum.
The algal genus Gracilaria has become the major source of commercial agar extraction in Chile. Recently G. chilensis Bird, McLachlan and Oliveira has been extensively cultivated in Southern Chile in response to wild crop deterioration. This paper evaluates the performance of this species under suspended cultivation, using ropes at two different depths. Treatments including different algal inoculum and harvesting methods were evaluated. Moreover, monthly thallus losses and epiphyte abundance were quantified. The highest biomass production was found in treatments placed at 0.5 m from the bottom. Factors such as light and water movement seem to regulate temporal patterns of biomass variation. Epiphytes exhibited a more marked incidence in the warmer months and were seen to be abundant in stands with a small algal inoculum. Finally, estimated yields of Gracilaria reach values close to 100 t·ha−1·yr−1 fresh weight. These data, together with small losses of algal thalli, suggest good economic opportunities for this suspension culture system.
The heterotrophic bacterial communities associated with the seaweedsFucus vesiculosus andUlva rigida in an estuary were studied. Changes in these communities were monitored by monthly sampling during the year. The isolated strains were identified at the genus level and grouped into 14 clusters by their similarities. Seasonal changes in genera and clusters as well as variations in diversity were related to primary production periods and fluctuation of salinity levels. TheFlavobacterium group was the major inhabitant of algal surfaces, being dominant after the primary production peaks occurred in spring and autumn. The decrease of dissolved organic matter after these peaks yielded an increase in diversity. Important alterations in these bacterial communities were observed during a period of large decrease in the salinity of estuarine water. In general, the epiphytic communities of both seaweeds were similar in their composition and dynamics, but they were very different from the surrounding water communities.
The surfaces of macroalgal thalli are colonized by planktonic propagules (larvae, spores, cells, etc.) from a wide diversity of eukaryotes and prokaryotes. Colonization (here defined broadly to include processes such as settlement, attachment, metamorphosis, biofilm formation, and infection) of seaweed surfaces can be both induced and inhibited by metabolites produced at those surfaces. However, detailed examples of chemically mediated interactions at seaweed surfaces for which chemical cues have been characterized, quantified in situ, a biological effect determined, and the consequences to the demography of the seaweeds or colonizers demonstrated are very rare. Here we briefly review the literature on both deterrents (“natural antifoulants”) and inducers of colonization and on interactions at seaweed surfaces between the hosts and associated bacterial biofilms. One theme that emerges is the strong need to integrate ecology, cell biology, and chemistry to understand the distribution of surface-active molecules in situ and their ecological consequences. This multidisciplinary approach is further emphasized for research on biofilms on seaweeds, where recently developed molecular tools for characterizing bacterial communities are opening up an entire new area of marine chemical ecology. Finally, we emphasize an integrated approach to the topic, as we believe that many aspects of somewhat disparate fields including, for example, induction of larval settlement, algal pathogenesis, and the molecular biology of bacterial signaling can be usefully viewed within the overall framework of chemical mediation of surface colonization.
Alpha-1-antitrypsin deficiency is one of the more common metabolic disorders, and is usually associated with one common gene mutation. The deficiency results in increased susceptibility to chronic obstructive pulmonary disease and liver disease, both in childhood and adult life.
Keywords:
serine proteinase inhibitor;
serpin;
emphysema;
liver disease, PI types, lung
Susceptibility of rhodophycean macroalgae to infection by the green endophytes, Acrochaete operculata Correa & Nielsen and A. heteroclada Correct & Nielsen was studied. Cross-infection experiments showed that A. operculata is host specific and developed only in sporophytic fronds of Chondrus crispus Stackh. and Iridaea cordata (Turn.) Bory. Although A. operculata penetrated equally the multilamellar outer cell wall of sporophytic and gametophytic fronds of C. crispus, subsequent development was arrested in the gametophytic fronds. Susceptibility of the sporophytic phase of C. crispus was detected early in the development of the host, at a discoid stage that is structurally distinct from the adult fronds. The evidence strongly suggests that host specificity in A. operculata is determined by cell-wall composition of the hosts, likely the carrageenan fraction. In contrast, A. heteroclada was not host specific, infecting all offered hosts, including carrageenophytes and agarophytes. Germination occurred on the surface of the hosts and led to the development of an epiphytic stage. Subsequent penetration in many cases involved total displacement of cortical tissue in the infected frond.
Preferential consumption of algal reproductive tissues has been predicted to potentially reduce algal fitness by reduction of reproductive output. This study shows that the amphipod Hyale media (Dana) has a marked trophic preference for mature cystocarpic tissues of Iridaea laminarioides Bory. However, during the feeding process the amphipod tears the cystocarps releasing large numbers of spores into the water column. Germination and growth rate experiments indicate that grazer-mediated release does not affect further spore development. Field populations of I. laminarioides might have unopened cystocarps even in senescent, decaying fronds, while the total number of open cystocarps in mature and senescent fronds increases at higher amphipod density sites, suggesting a facilitation mechanism. Laboratory observations indicate spores can stick to the legs and body sides of the amphipods while a fraction of the ingested spores survives passage through the amphipod digestive tract. Thus, the amphipod seems ecologically important not only as a grazer but also as spore releaser and disperser.
The control of algal epiphytes is a major technical problem for the expanding Gracilaria culture activity in southern Chile. Both harvestable biomass of Gracilaria and epiphytes show marked seasonal variation. In the spring months, epiphytism by Giffordia sp. can be very high (up to 300% of the Gracilaria biomass), the epiphyte forming a dense algal turf over its host. During the summer, Ceramiales are the dominant epiphytes, but abundance is significantly lower (P < 0.01) compared with Giffordia. Epiphytism can significantly (P < 0.05) affect Gracilaria production, and harvesting during a period of high Giffordia infestation can significantly increase (P < 0.05) the negative effect of the epiphytes. The use of higher algal biomass has no significant effect on the abundance of Giffordia. A Gracilaria inoculum obtained from a subtidal culture center was more susceptible (P < 0.05) to epiphytism than an inoculum from an intertidal area. In addition, the use of sand-filled polyethylene tubes to plant Gracilaria beds can promote the fixation of Giffordia in some cases.
Propagule dispersal in seaweeds is a process influenced by a variety of biological and physical factors, the complexity of which has hindered efforts to understand colonization, persistence, post-disturbance recovery, and dynamics of algal populations in general. In view of this limitation, we employ here modifications to an existing turbulent-transport model to explore the mechanics of nearshore macroalgal spore dispersal and its relationship to coastal hydrodynamic conditions. Our modeling efforts focus on four ex-ample species of seaweed whose reproductive propagules span a wide range in sinking speed and height of release above the sea floor: the giant kelp Macrocystis pyrifera, the erect fucoid Sargassum muticum, the small filamentous brown alga Ectocarpus siliculosus, and the flaccid red alga Sarcodiotheca gaudichaudii. Results indicate that both propagule sinking speed and release height can affect dispersal distance substantially, but that the influence of these biological parameters is modulated strongly by the intensity of turbulence as dictated by waves and currents. In rapid flows with larger waves, it is primarily fluid dynamic processes, in particular current velocities, that determine dispersal distance. Ad-ditional simulations suggest that patterns of spore dispersal are highly skewed, with most propagules encountering the sea floor within a few meters to hundreds of meters of their parents, but with a sizeable fraction of spores also dispersing as far as kilometers. Such model predictions imply a much greater potential for longer range dispersal than has typ-ically been assumed, a finding with important implications for understanding the demo-graphics of algal populations and for predicting levels of connectivity among them.
Any living or non-living surface immersed in seawaterrapidly acquires a bacterial biofilm. For living marineorganisms, biofilm formation can result in the death ofthe host, and thus there is strong evolutionary pressure formarine eukaryotes to evolve mechanisms which inhibit orcontrol the development of biofilms on their surfaces.Some marine eukaryotes are indeed successful incontrolling biofilms on their surfaces, and in manyinstances this control is achieved by the production ofinhibitory chemicals which act at or near the surface ofthe organism. In some cases these natural inhibitors aresimply toxic to bacteria. However, increasingly it appearsthat at least some of these compounds act by interferingspecifically with bacterial characteristics which effect theability of bacteria to colonize their hosts, such asattachment, surface spreading, or the production ofextracellular macromolecules. As an example, theAustralian seaweed Delisea pulchra appears tocontrol bacterial colonization by interfering with abacterial regulatory system (the acylated homoserinelactone system) that regulates several colonizationrelevant bacterial traits. Understanding how marineorganisms control specific bacterial colonization traitsshould provide us with insights into new technologies forthe control of biofilms on artificial surfaces.
Of 45 bacterial isolates from healthy tips of Gracilaria conferta (Schousboe ex Montagne) J. et G. Feldmann, 29% were identified
as ‘conditional inducers’ of an apical necrosis. That is, the isolates induced necrotic tips in G. conferta within 16 h after
elimination of most of the resident microflora from the alga. Several disinfectants and antibiotics were screened for their
ability to induce algal susceptibility to the bacteria and to suppress uncontrolled appearance of tip necrosis. Treatment
with 100 mg L-1 Cefotaxim + 100 mg L-1Vancomycin over three days was the least damaging and most efficient. Tip necrosis was related to isolates of the Corynebacterium-Arthrobacter-group
and to the Flavobacterium-Cytophaga-group. The damaging effect occurred due to the bacterial excretion of active agents and
was not correlated with acapability to degrade agar. The damaging influence of four Cytophaga-likestrains was inhibited by
20 of 40 isolates. This protective effect was caused by very different organisms. In five of six cases examined further, the
effect was not cellbound, but due to the excretion of agents. These were not antimicrobially active, but inactivated necrosis-inducing
excretions. These results indicate that epiphytic bacterial degradation or inactivation of damaging agents is a protecting
factor in Gracilaria, which prevents the alga from being harmed by epiphytes.
The cultivation of the agarophytic red alga Gracilaria has become an activity of major importance in several parts of the world. However, Gracilaria cultivation in Chile still faces problems such as epiphytism. We report ceramialean epiphytism abundance, recruitment patterns and the microscopic stages fixed on the Gracilaria thalli in an intertidal bed (Metri bay) of southern Chile. Using a factorial field experiment, we analyze the effect of intertidal elevation and the use of epiphyte free inoculum on the abundance of ceramialean epiphytic algae. This evidence is used to provide management and control recommendations for ceramialean epiphytes.
The results show a summer recruitment and increase in abundance of ceramialean epiphytes. A seasonal and spatial pattern of abundance of microscopic stages of this epiphytic algae was also found, showing a significant increase from the apical (new tissues) to the central parts of the thalli (older tissues). Apical tissues are free of epiphytic propagules. The epiphyte-free tissue zone decreases significantly from winter to summer. Also, a significantly higher density of microscopic stages of ceramialean epiphytes was found on the thalli collected in the farming are a during the summer at low tidal levels. The experimental results indicated that the abundance of epiphytes was greater at the lower tidal levels than at the higher distribution limits of Gracilaria and it was not possible to control epiphytism by manual cleaning.
Epiphytes can have a considerable effect on Gracilaria production, and Ulva is one of the commonest algal species identified as an epiphyte, reaching loads of 60% (g of epiphytes per g of Gracilaria) in the intertidal cultures of southern Chile. This study evaluates the relative importance of light reduction, addition of weight to the host thalli and nutrient depletion, as mechanisms determining the interaction effects of Ulva epiphytes on Gracilaria cultivation. Using field experiments undertaken during the main Gracilaria growth season (spring), we evaluate the mechanisms of epiphyte-host algae interaction by manipulating artificial epiphytes. The results indicate that Ulva can significantly depress Gracilaria biomass production and that the addition of weight to the host algae and the consequent dislodgement increase, appear to be the main mechanisms involved in the Ulva-Gracilaria interaction. However, the light reduction caused by the epiphytes can also partially explain the reduction in Gracilaria production. Nutrients depletion would not appear to fully account for the detrimental effects of Ulva over Gracilaria in intertidal farming areas of southern Chile.
Populations of bacterial cells often coordinate their responses to changes in their local environmental conditions through quorum sensing, a cell-to-cell communication system employing small diffusible signal molecules. While there is considerable diversity in the chemistry of such signal molecules, in different Gram-positive and Gram-negative bacteria they control pathogenicity, secondary metabolite production, biofilm differentiation, DNA transfer and bioluminescence. The development of biosensors for the detection of these signal molecules has greatly facilitated their subsequent chemical analysis which in turn has resulted in significant progress in understanding the molecular basis of quorum sensing-dependent gene expression. Consequently, the discovery and characterisation of natural molecules which antagonize quorum sensing-mediated responses has created new opportunities for the design of novel anti-infective agents which control infection through the attenuation of bacterial virulence.
Pollution has a considerable effect on biological communities, in terms of size and diversity of the populations. Yet, the
precise consequences of human activity on microbial communities in the marine environment are poorly understood. Therefore,
in an ongoing collaborative research programme between Heriot-Watt University and the Ocean University of Qingdao, bacteria
were isolated in 1999 and 2000 from marine sediment, seawater, seaweed, fish and shellfish, taken from locations in Shandong
Province adjacent to Qingdao. Sampling locations were comprised of industrial and aquacultural sites and a clean, control
site. In order to analyse microbial diversity, a polyphasic approach was adopted for characterisation of these isolates, specifically
through examination of key phenotypic traits, i.e. using Biolog GN MicroPlate™ profiles, bacterial whole cell protein profiles and 16S and 23S rRNA gene sequences. These techniques yielded complex taxonomic
data, which were subjected to statistical and cluster analyses. The application of these methods to studies of microbial communities
is discussed.
The cosmopolitan presence of Ulva spp. is partly due to its great reproductive ability, but relatively little information is available for the radiation conditions triggering reproduction. In the present study, we investigated the effect of photon irradiance, photoperiod, and spectral qualities of light on growth and reproduction of Ulva pertusa.During 8-day culture of discs cut from marginal parts of the thallus of U. pertusa, the size of the thallus discs was greatest at 10 μmol m−2 s−1, while saturation of reproduction occurred at 30 μmol m−2 s−1. The minimum photon irradiance allowing growth and reproduction was 5 and 10 μmol m−2 s−1, respectively. Rapid increases in the size and subsequent initiation of sporulation were observed in samples transferred to saturating irradiance from 5 μmol m−2 s−1 or darkness for 9 days. When exposed to different photoperiods (8:16-, 12:12-, 16:8-h LD and continuous light regimes) combined with different photon irradiances (10 and 100 μmol m−2 s−1), U. pertusa thallus showed that the thallus size attained at the low irradiance was similar in daylengths longer than 12 h per day, while the surface area increased in parallel with increasing light duration at the high irradiance. The degree of sporulation at 10 μmol m−2 s−1 varied, ranging from no sporulation in 8:16-h LD to 80% in 16:8-h LD and continuous light. On the other hand, there was no remarkable difference in the degree of sporulation between the photoperiods except for slightly smaller percentage sporulation in 8:16-h LD at 100 μmol m−2 s−1.At 5 μmol m−2 s−1, the growth of U. pertusa was markedly lower in green than in blue or red light, but there was no sporulation in any spectral quality. The degree of sporulation at 20 μmol m−2 s−1 was almost twice as much in blue or red as in green light.The size of plants irradiated with 1.0 W m−2 of UV-B for 20–40 min increased by 18–21% relative to control, whereas higher UV irradiance caused inhibition of growth. There was a significantly lower incidence of sporulation in UV-B-irradiated plants with the degree of reduction being greater in those exposed to higher UV doses. The total biologically effective UV-B dose for 50% inhibition of sporulation was 0.085 Doseeff kJ m−2. The time required to achieve 50% inhibition would be longer than 13 h at depths below 1 m in Ahnin coastal waters. The vertical attenuation coefficient of PAR (λ=400–700 nm) and UV-B (λ=300–320 nm) in April 1998 at Ahnin on the eastern coast of Korea was 0.21 m−1 for KPAR and 0.54 m−1 for KUV-B. A large reduction of light quantity and rapid disappearance of blue wavelength occurred by shading from overlying thalli.Percentage inhibition of sporulation was only 14–18% at 150–200 μmol m−2 s−1 compared with 70% at 10 μmol m−2 s−1, when plants were incubated under different irradiances of PAR immediately after UV-B exposures.These different photoadaptive strategies for sporulation may in part account for the great ecological success of U. pertusa.
The diversity of microorganisms associated with the leaves of the seagrass Halophila stipulacea in the northern Gulf of Elat was examined by culture-independent analysis. Microorganisms were harvested by a sonication treatment for total-community genomic DNA isolation. Oligonucleotides complementary to conserved regions in the 16S rRNA-encoding DNA (rDNA) of bacteria were used for PCR amplification. The 16S rDNA PCR products were subcloned and further characterized by a restriction fragment length analysis termed ARDRA (amplified rDNA restriction analysis). These analyses were carried out after reamplifying the cloned fragments with two primers binding symmetrically to the plasmid immediately on both sides of the cloned insert. Computer-aided clustering was performed after separate restriction analysis with enzymes HinfI and HpaII. By this method, 103 cloned 16S rDNA fragments were clustered into a total of 58 different groups. Sequence analysis of clones with an identical ARDRA pattern confirmed that members of an ARDRA group were closely related to each other. The sequenced clones were found to be affiliated with a marine snow-associated plastid-like rRNA clone and with a marine Hyphomonas strain, respectively. The method applied in this study could be useful for the routine study of other microbial communities of interest.
Bacterial cell-to-cell communication (quorum sensing) relies upon the interaction of a small diffusible signal molecule with a sensor or transcriptional activator to couple gene expression with cell population density. In Gram-negative bacteria, it is now clear that N-acylhomoserine lactones bind directly to LuxR homologues and can be synthesized via one of three unrelated bacterial protein families and by transgenic plants. New chemical classes of signal molecules have been identified, some of which exhibit crosstalk with N-acylhomoserine-lactone-mediated quorum sensing. As the determinant of cell population density, quorum sensing is emerging as an integral component of bacterial global gene regulatory networks responsible for facilitating bacterial adaptation to environmental stress. N-acylhomoserine lactones are produced during experimental animal and human infections, and a function beyond quorum sensing has been suggested by their intrinsic immunomodulatory and pharmacological activities.
The accidental introduction of Caulerpa taxifolia into the Mediterranean is no longer under dispute. What has eluded researchers until now, is definitive evidence for the original, biogeographical source population. Here we present two independent lines of evidence that support an Australian origin for the Mediterranean populations of C. taxifolia. First, we reanalysed algal rDNA-internal transcribed spacer (rDNA-ITS) sequences, combining previously published sequences from different studies with 22 new sequences. The ITS sequence comparison showed that the Australian sample is the sister group of the Mediterranean-aquarium clade. Second, cloned bacterial 16S rDNA gene sequences were analysed from the associated microflora of C. taxifolia collected from Australia, Tahiti, the Philippines and the Mediterranean. Five bacterial lineages were identified, of which three were dominant. Alpha Proteobacteria were the most abundant and were found in all samples. In contrast, members of the beta Proteobacterial line and Cytophaga-Flexibacter-Bacteroides line (CFB) were mainly associated with Mediterranean and Australian samples. Frequency distributions of the five bacterial lineages were significantly different among biogeographical locations. Phylogenetic analyses of the 54 bacterial sequences derived from the four C. taxifolia individuals resulted in a well-resolved tree with high bootstrap support. The topologies of the beta Proteobacteria and CFB mirror the geographical sources of their algal hosts. Bacterial-algal associations provide an identification tool that may have wide application for the detection of marine invasions.
The discovery that bacterial cells can communicate with each other has led to the realization that bacteria are capable of exhibiting much more complex patterns of co-operative behaviour than would be expected for simple unicellular microorganisms. Now generically termed 'quorum sensing', bacterial cell-to-cell communication enables a bacterial population to mount a unified response that is advantageous to its survival by improving access to complex nutrients or environmental niches, collective defence against other competitive microorganisms or eukaryotic host defence mechanisms and optimization of population survival by differentiation into morphological forms better adapted to combating environmental threats. The principle of quorum sensing encompasses the production and release of signal molecules by bacterial cells within a population. Such molecules are released into the environment and, as cell numbers increase, so does the extracellular level of signal molecule, until the bacteria sense that a threshold has been reached and gene activation, or in some cases depression or repression, occurs via the activity of sensor-regulator systems. In this review, we will describe the biochemistry and molecular biology of a number of well-characterized N-acylhomoserine lactone quorum sensing systems to illustrate how bacteria employ cell-to-cell signalling to adjust their physiology in accordance with the prevailing high-population-density environment.
Zoospores of the eukaryotic green seaweed Ulva respond to bacterial N-acylhomoserine lactone (AHL) quorum sensing signal molecules for the selection of surface sites for permanent attachment. In this study we have investigated the production and destruction of AHLs in biofilms of the AHL-producing marine bacterium, Vibrio anguillarum and their stability in seawater. While wild type V. anguillarum NB10 was a strong attractor of zoospores, inactivation of AHL production in this strain by either expressing the recombinant Bacillus lactonase coding gene aiiA, or by mutating the AHL biosynthetic genes, resulted in the abolition of zoospore attraction. In seawater, with a pH of 8.2, the degradation of AHL molecules was temperature-dependent, indicating that the AHLs produced by marine bacterial biofilms have short half-lives. The Ulva zoospores sensed a range of different AHL molecules and in particular more zoospores settled on surfaces releasing AHLs with longer (>six carbons) N-linked acyl chains. However, this finding is likely to be influenced by the differential diffusion rates of AHLs from the experimental surface matrix. Molecules with longer N-acyl chains, such as N-(3-oxodecanoyl)- L-homoserine lactone, diffused more slowly than those with shorter N-acyl chains such as N-(3-hydroxy-hexanoyl)- L-homoserine lactone. Image analysis using GFP-tagged V. anguillarum biofilms revealed that spores settle directly on bacterial cells and in particular on microcolonies which we show are sites of concentrated AHL production.
Sporulation and spore germination in Westiellopsis prolifica Janet in various culture conditions
- Agrawal S. C.
Agrawal, S. C. & Sharma, U. K. 1994. Sporulation and spore ger-mination in Westiellopsis prolifica Janet in various culture con-ditions. Phykos 33:1–2.
Hydrodynamics and algal reproduction
- Gordon R. J.
Gordon, R. J. & Brawley, S. H. 2001. Hydrodynamics and algal reproduction. J. Phycol. 37:19–20.
Cultivation of Gracilaria verrucosa (Hudson) Papenfuss and Iridaea ciliata Kützing (Rhodophyta, Gigartinaceae), “in vitro”: induced shedding and carpospore settlement on different substrates
- E R Infante
- P A Candia
Infante, E. R. & Candia, P. A. 1988. Cultivation of Gracilaria verrucosa (Hudson) Papenfuss and Iridaea ciliata Kü (Rhodophyta, Gigartinaceae), ''in vitro'': induced shedding and carpospore settlement on different substrates. Gayana Bot. 45:1–4.
Sporulation in Gracilaria crassa Harvey ex
- S Sukumaran
- N Kaliaperumal
Sukumaran, S. & Kaliaperumal, N. 2001. Sporulation in Gracilaria crassa Harvey ex. J. Agardh at different environmental factors. Seaweed Res. Utilisat. 23:1–2.
Influence of low and high temperature on diurnal periodicity of tetraspore shedding in some red algae
- Kaliaperumal N.
Kaliaperumal, N. 1990. Influence of low and high temperature on diurnal periodicity of tetraspore shedding in some red algae. J. Mar. Biol. Ass. India 32:1–2.
Observations of red algal spore settlement
- Carrier J. E.
Carrier, J. E. 1984. Observations of red algal spore settlement. J. Phycol. 20 (Suppl.): 13.
Effects of nutrients present in Bold's basal medium on sporulation of the green alga Pithophora oedogonia
- S C Agrawal
Effects of nutrients present in Bold's basal medium on sporulation of the green alga Pithophora oedogonia (Mont.) Wittrock
- Agrawal S. C.
Sporulation in Gracilaria crassa Harvey ex. J. Agardh at different environmental factors
- Sukumaran S.
Cultivation of Gracilaria verrucosa (Hudson) Papenfuss and Iridaea ciliata Kützing (Rhodophyta, Gigartinaceae), “in vitro”
- Infante E. R.