Stable Symbiosis Research Articles

Distinctive characters of Nostoc genomes in cyanolichens

BackgroundCyanobacteria of the genus Nostoc are capable of forming symbioses with a wide range of organism, including a diverse assemblage of cyanolichens. Only certain lineages of Nostoc appear to be able to form a close, stable symbiosis, raising the question whether symbiotic competence is determined by specific sets of genes and functionalities.ResultsWe present the complete genome sequencing, annotation and analysis of two lichen Nostoc strains. Comparison with other Nostoc genomes allowed identification of genes potentially involved in symbioses with a broad range of partners including lichen mycobionts. The presence of additional genes necessary for symbiotic competence is likely reflected in larger genome sizes of symbiotic Nostoc strains. Some of the identified genes are presumably involved in the initial recognition and establishment of the symbiotic association, while others may confer advantage to cyanobionts during cohabitation with a mycobiont in the lichen symbiosis.ConclusionsOur study presents the first genome sequencing and genome-scale analysis of lichen-associated Nostoc strains. These data provide insight into the molecular nature of the cyanolichen symbiosis and pinpoint candidate genes for further studies aimed at deciphering the genetic mechanisms behind the symbiotic competence of Nostoc. Since many phylogenetic studies have shown that Nostoc is a polyphyletic group that includes several lineages, this work also provides an improved molecular basis for demarcation of a Nostoc clade with symbiotic competence.

Population diversity of bacterial endophytes from jute (Corchorus olitorius) and evaluation of their potential role as bioinoculants

Endophytes are bacterial or fungal organisms associated with plants in an obligate or facultative manner. In order to maintain a stable symbiosis, many of the endophytes produce compounds that promote plant growth and help them adapt better to the environment. This study was conducted to explore the potential of jute bacterial endophytes for their growth promotion ability in direct and indirect ways. A total of 27 different bacterial species were identified from different varieties of a jute plant (Corchorus olitorius) and different parts of the plant (leaf, root, seed, and seedling) based on 16S rRNA gene sequence. Two of the isolates showed ACC deaminase activity with Staphylococcus pasteuri strain MBL_B3 and Ralstonia solanacearum strain MBL_B6 producing 18.1 and 8.08 μM mg−1 h−1 α-ketobutyrate respectively while eighteen had the ACC deaminase gene (acdS). Fourteen were positive for siderophore activity while Kocuria sp. strain MBL_B19 (133.36 μg/ml) and Bacillus sp. strain MBL_B17 (124.72 μg/ml) showed high IAA production ability. Seven bacterial strains were able to fix nitrogen with only one testing positive for nifH gene. Five isolates exhibited phosphorus utilization ability with Bacillus sp. strain MBL_B17 producing 218.47 μg P/ml. Three bacteria were able to inhibit the growth of a phytopathogen, Macrophomina phaseolina and among them Bacillus subtilis strain MBL_B4 was found to be the most effective, having 82% and 53% of relative inhibition ratio (RIR) and percent growth inhibition (PGI) values respectively. Nine bacteria were tested for their in vivo growth promotion ability and most of these isolates increased seed germination potential and vigour index significantly. Bacillus subtilis strain MBL_B13 showed 26.8% more vigour index than the control in which no bacterial inoculum was used. All inoculants were found to increase the dry weight of jute seedlings in comparison to the control plants and the most increase in fresh weight was found for Staphylococcus saprophyticus strain MBL_B9. Staphylococcus pasteuri strain MBL_B3 exhibited diverse in vitro growth promotion activity and significant growth promoting effect in in vivo pot experiments. These bacterial strains with plant growth enhancing abilities have the potential to be used as bioinoculants.

The coevolved relationship between <italic>Helicobacter pylori</italic> and human

Helicobacter pylori ( H. pylori ) is a known pathogen of human stomach which is linked to gastric adenocarcinoma, and antibiotic therapy is commonly used for H. pylori eradication. However, accumilating data have formed enough testimony to convey that H. pylori may have coevolved with human host as symbiotic flora rather than pathogenic bacteria. Firstly, a majority of infected individuals are asymptomatic; only a small fraction of infected individuals develop H. pylori -associated diseases, such as peptic ulcers and, more rarely, gastric adenocarcinomas. Secondly, H. pylori has colonization in human stomach for a long time. Genetic evidences have suggested that H. pylori is one of the oldest and most common occupants of the human gastric microbiome, arriving before the migration out of Eastern Africa over 60000 years ago. Thirdly, H. pylori can confer a benefit to human health. Since mutual benefits obliged both partners to adapt themselves in order to establish stable symbiosis, it is therefore possible that the bacterium confers a benefit to its host under some circumstances and is therefore maintained in the human population. It has been suggested that H. pylori can be beneficial for host health in several aspects, including regression in child asthma and other allergic disorders, confering protection against tuberculosis (TB) through induction of antagonistic interferons for the causative agent, Mycobacterium tuberculosis , and playing a role in reducing the risk of esophageal adenocarcinoma (EAC), gastroesophageal reflux disease, stroke, lung cancer, asthma, allergies, and inflammatory bowel disease. We need rethinking the complexity relationship between H. pylori and human, and the impact of this bacterium on human health. Elimination of H. pylori as permanent resident of human microbiome would not be the first option to deal with gastroduodenal diseases, and the long cohabitation in our stomach calls for more deep studies to elucidate microbiota and human health. In this review, we aim to elucidate the secret of H. pylori infection inducing gastric adenocarcinomas. The coevolved relationship between H. pylori and human may help us understanding why a majority of infected individuals are asymptomatic, while a small fraction of infected individuals develop gastric adenocarcinomas. Thus, we elucidate the detail about the long period of H. pylori gastric colonization for 60000 years, and the highly adaptable strategies used by H. pylori to make a lifelong colonization, which has been obtained in the longtime coevolved with human. On basis of these, we discuss the impact of H. pylori on human health, and explore future therapeutic strategies for disease management in light of the longstanding evolutionary history between H. pylori and its human host. We suggest that disrupted coevolution between a pathogen and its human host can induce diseases like gastric adenocarcinoma, and maintaining symbiosis is key for effective detection, management, and disease prevention.

Symbiosis process between Acropora larvae and Symbiodinium differs even among closely related Symbiodinium types

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 592:119-128 (2018) - DOI: https://doi.org/10.3354/meps12474 Symbiosis process between Acropora larvae and Symbiodinium differs even among closely related Symbiodinium types Hiroshi Yamashita1,*, Go Suzuki1, Chuya Shinzato2,3, Mitsuru Jimbo4, Kazuhiko Koike5 1Research Center for Subtropical Fisheries, Seikai National Fisheries Research Institute, Japan Fisheries Research and Education Agency, Ishigaki, Okinawa 907-0451, Japan 2Marine Genomics Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa 904-0495, Japan 3Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Chiba 277-8564, Japan 4School of Marine Biosciences, Kitasato University, Sagamihara, Kanagawa 252-0373, Japan 5Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8528, Japan *Corresponding author: hyamashita@fra.affrc.go.jp ABSTRACT: The symbiosis between corals and the dinoflagellate genus Symbiodinium is a fundamental pillar of coral reef ecosystems. Many of the coral species, including Acropora, acquire Symbiodinium from the environment during early ontogeny for symbiosis. Genetically diverse members of Symbiodinium have been identified from the environment, but naturally settled Acropora recruits (i.e. settlers or spats) usually harbor specific members of Symbiodinium. Thus, symbiosis between Acropora and Symbiodinium is not established haphazardly in the wild. Conversely, under laboratory conditions, Acropora larvae can acquire other Symbiodinium varieties. However, it remains unclear whether a stable symbiosis between these Symbiodinium that are never detected in natural Acropora recruits and corals is successfully established. Here, we artificially supplied A. tenuis larvae with 3 closely related Symbiodinium culture strains, namely, type A1 (common within natural Acropora recruits), type A2-relative (never detected within corals), and type A3 (often found within natural Acropora recruits). We then determined the percentage of Symbiodinium-infected larvae and the density of Symbiodinium cells infecting the larvae. For types A1 and A3, the percentage of Symbiodinium-infected larvae and the density of Symbiodinium cells did not decrease even after stopping the Symbiodinium supply. This result indicated that stable symbiosis was successfully established, even in the laboratory. However, the percentage of Symbiodinium-infected larvae and Symbiodinium cell density of type A2-relative declined after stopping the Symbiodinium supply. Thus, under laboratory conditions, A. tenuis larvae can acquire Symbiodinium that is never detected within natural corals; however, stable symbiosis between these Symbiodinium and corals was not successfully established. KEY WORDS: Early symbiosis · Symbiodinium · Zooxanthellae · Acropora · Coral larvae Full text in pdf format PreviousNextCite this article as: Yamashita H, Suzuki G, Shinzato C, Jimbo M, Koike K (2018) Symbiosis process between Acropora larvae and Symbiodinium differs even among closely related Symbiodinium types. Mar Ecol Prog Ser 592:119-128. https://doi.org/10.3354/meps12474 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 592. Online publication date: March 29, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.

BIOTECHNOLOGICAL POTENTIAL OF BIFIDOBACTERIA

Bifidobacteria commonly known as classic probiotics and today they gain huge popularity among supporters of wealth nutrition. These microorganisms colonize the intestines of a newborn baby through the mother's milk and joining him in a stable symbiosis, accompany the person throughout his life, exerting a beneficial effect on his health. These amazing microorganisms have great biotechnological potential and are widely used in medicine, veterinary medicine, food and pharmaceutical industries, agriculture and other fields of national economy.The beneficial effects of bifidobacteria on the host organism are vast and diverse. They are involved in enzymatic processes, perform vital minerals function (synthesis of vitamins B, K, folic and nicotinic acids), improve indices of protein, lipid, and mineral metabolism/ They also reinforce the hydrolysis of proteins, carbohydrates ferment, hydrolyzed fats, dissolve fiber, stimulate peristalsis, promote normal evacuation of the intestinal contents, promote the synthesis of essential aminoacids, better assimilation of calcium salts and vitamin D. Moreover, they have anti-anemic, anti-allergic action, and stimulate the lymphoid apparatus.The article presents a review of important technological and biological properties of bifidobacteria, which determine their biotechnological potential: culture-morphological, physiological, biochemical properties; habitat, taxonomy, nutrient medium, and conditions of incubation, antagonistic, antioxidant properties, acid resistance, probiotic properties, the practical application of bifidobacteria.

Transmission of a heterologous clade C Symbiodinium in a model anemone infection system via asexual reproduction.

Anemones of genus Exaiptasia are used as model organisms for the study of cnidarian-dinoflagellate (genus Symbiodinium) endosymbiosis. However, while most reef-building corals harbor Symbiodinium of clade C, Exaiptasia spp. anemones mainly harbor clade B Symbiodinium (ITS2 type B1) populations. In this study, we reveal for the first time that bleached Exaiptasia pallida anemones can establish a symbiotic relationship with a clade C Symbiodinium (ITS2 type C1). We further found that anemones can transmit the exogenously supplied clade C Symbiodinium cells to their offspring by asexual reproduction (pedal laceration). In order to corroborate the establishment of stable symbiosis, we used microscopic techniques and genetic analyses to examine several generations of anemones, and the results of these endeavors confirmed the sustainability of the system. These findings provide a framework for understanding the differences in infection dynamics between homologous and heterologous dinoflagellate types using a model anemone infection system.

Role of bacterial adhesin RAPA1 in formation of efficient symbiosis of Rhizobium leguminosarum with bean plants

Bacterial adhesins, the proteins responsible for attachment of plant growth-promoting rhizobacteria to plant roots, are involved in formation of stable associative symbioses. In the present work enhanced expression of the rapA1 adhesin gene in Rhizobium leguminosarum PVu5 was shown to improve the efficiency of nodulation on bean roots inoculated with the modified strain. The rapA1 gene was cloned into the pJN105Turbo plasmid, this construct was used for transformation of R. leguminosarum PVu5, bean plants were inoculated by this transgenic strain, and efficiency of root nodule formation was determined. In the plants treated with rapA1-transgenic rhizobia, the number of root nodules was on average two times higher than in the plants inoculated with the original strain. Aggregation of R. leguminosarum was achieved when the rapA1 gene expression was enhanced either in rhizobia or in the co-cultured modified strain E. coli pJN105TurboRapA1.

Analysis on the symbiosis stability of agricultural equipment manufacturing value network based on Lotka–Volterra

The agricultural equipment manufacturing value network is a symbiotic organization with stability serving as its important sustaining mechanism. Higher stability corresponds with stronger self-sustainability. In light of this, in accordance with the theory of biologic population symbiosis and the internal relationship of agricultural equipment manufacturing value network, the Lotka–Volterra ecosystem dynamic model is established and the enterprise income under the state of stable equilibrium analyzed and compared so as to study the conditions and reasons for their stable symbiosis. The analysis results clearly explain the operational risk of the symbiosis of value network, which could provide a reference for the policy formulation in the agricultural equipment manufacturing enterprises and the positive role of value network organization in advancing the development of agricultural equipment manufacturing.

ASSOCIATIVE SYMBIOSIS BETWEEN RHIZOBIA AND TRANSGENIC TOMATOES INCREASES PLANT RESISTANCE TO Fusarium oxysporum f. sp. lycopersici

It has been shown that a tomato cultivar Gruntovy Gribovsky 1180 transformed with pea lectin gene (psl ) has been shown to form a stable associative symbiosis with a Rhizobium leguminosarum bacteria that have fungistatic activity. This provides the protection of the plant root system from the phytopathogen Fusarinm oxysporum f. sp. lycopersici. The survival of the plants transgenic for the psl gene and incubated with rhizobia made up 81.5% after the fungal contamination. The analogous value for the nontransgenic plants was equal to 47.6%.

Menthol-induced bleaching rapidly and effectively provides experimental aposymbiotic sea anemones (Aiptasia sp.) for symbiosis investigations.

Experimental manipulation of the symbiosis between cnidarians and photosynthetic dinoflagellates (Symbiodinium spp.) is crucial to advancing the understanding of the cellular mechanisms involved in host-symbiont interactions, and overall coral reef ecology. The anemone Aiptasia sp. is a model for cnidarian-dinoflagellate symbiosis, and notably it can be rendered aposymbiotic (i.e. dinoflagellate-free) and re-infected with a range of Symbiodinium types. Various methods exist for generating aposymbiotic hosts; however, they can be hugely time consuming and not wholly effective. Here, we optimise a method using menthol for production of aposymbiotic Aiptasia. The menthol treatment produced aposymbiotic hosts within just 4weeks (97-100% symbiont loss), and the condition was maintained long after treatment when anemones were held under a standard light:dark cycle. The ability of Aiptasia to form a stable symbiosis appeared to be unaffected by menthol exposure, as demonstrated by successful re-establishment of the symbiosis when anemones were experimentally re-infected. Furthermore, there was no significant impact on photosynthetic or respiratory performance of re-infected anemones.

Potential for Industrial Application of Microbes in Symbioses that Influence Plant Productivity and Sustainability in Agricultural, Natural, or Restored Ecosystems

Abstract Microbes in three widespread and evolutionarily stable mutualistic symbioses with plants offer a range of nutritional and other benefits that may be modified or enhanced through selection or genetic manipulation for biotechnological applications. In this review, the biology, ecology, and genetics of arbuscular mycorrhizal fungi partnering with more than 80% of all land plant species; rhizobia bacteria that nodulate legumes and fix atmospheric nitrogen; and Epichloe fungi endophytic on cool-season grasses, are discussed. Research on these symbioses indicates considerable potential to utilize modified or natural microbial strains to stimulate production selectively of desirable compounds in plants or to introduce or over-express genes that can stimulate beneficial effects of the mutualisms on desirable traits in plant hosts, whether in agricultural or more natural ecosystems.

Helicobacter pylori: A Beneficial Gastric Pathogen?

Since Helicobacter pylori (H. pylori) is the first successful culture three decades ago, ongoing perspectives regarding the relationship between the bacterium and human health have changed radically (1, 2). Apart from tremendous studies performed during the last years, there are still many debates regarding the unclear rationale for existence of such bacteria in human stomach (3, 4). Basically, due to the beneficiary effects of H. pylori colonization (regression in child asthma and other allergic disorders), it has been concluded that H. pylori is a common flora or at least harmless bacterium (5–10), Conversely, because of the causative role of H. pylori in certain digestive diseases such as duodenal ulcer and gastric cancer, other reports are quite contradictory (11–13). A large number of discussions led to a consensus regarding presence of H. pylori in the human stomach (5, 11, 14, 15). Our knowledge about biology of H. pylori suggests that the bacterium is highly adapted to stay in gastric mucosa for long time (1, 16). Indeed, living in lower surface of gastric mucosa, with no bacterial competition, provided a novel place to survive. Moreover, H. pylori is able to multiply freely due to the protective effects by mucosal layer. Thus, H. pylori had an opportunity to thrive in stomach over the course of tens of thousands of years of co-evolution with humans (17). Additionally, the high frequency of mutation in the genome also led to higher chances of survival, and natural selection helped them to remain and cause chronic infection (18). Determining whether H. pylori is beneficial or detrimental in human stomach has been a challenging area of research in gastroenterology (5, 11, 19, 20). In this article, we aim to elucidate various aspects of this persistent colonization of this beneficial infection. H. pylori: Carried by human over the history It seems that H. pylori is an old recognized bacterium, which is not clinically comparable with new discovered infectious agents such as human immunodeficiency virus (HIV). In other words, HIV was introduced to human hosts <50 years ago. Given a long period of H. pylori colonization in the human stomach, mutual benefits obliged both partners to adapt themselves in order to establish stable symbiosis. It has been firmly established that H. pylori first subverts innate immunity and then modulates the adaptive immune system (blocking the activation of both B and T cells) (21–23). As a result, cagA and vacA, the main bacterial products, will inhibit B cell and T cell proliferation, respectively. Accordingly, immune response in the stomach is silenced against digested microbes (24, 25). Undeniably, the stomach, with its harsh acidic condition, is a container for many digested microbes every day. Possibly, regulation and modulation of immune response arose after microbial exposure to H. pylori colonizing the stomach (24, 25). Our current understanding of the strategies used by this pathogen to make a lifelong colonization, disclosed that maybe for our old ancestors having this bacteria in the stomach happened initially by accident, but due to natural selection, H. pylori made a set of adaptations, enabling the bacterium to survive and also thrive in the surface of human gastric epithelial cells. To everyone’s surprise, after millions years of living in human stomach, H. pylori became a strategic member of our microbiome (26). Undoubtedly, it is no exaggeration to say that both host and the bacterium are following a constant beneficial relationship, which is quite unique in biological world. After long period of H. pylori gastric colonization, it has evolved into a highly adaptable persistent bacterium, obtaining all necessary features of the most successful human pathogen.

Population genetic data of a model symbiotic cnidarian system reveal remarkable symbiotic specificity and vectored introductions across ocean basins

The Aiptasia-Symbiodinium symbiosis is a promising model for experimental studies of cnidarian-dinoflagellate associations, yet relatively little is known regarding the genetic diversity of either symbiotic partner. To address this, we collected Aiptasia from 16 localities throughout the world and examined the genetic diversity of both anemones and their endosymbionts. Based on newly developed SCAR markers, Aiptasia consisted of two genetically distinct populations: one Aiptasia lineage from Florida and a second network of Aiptasia genotypes found at other localities. These populations did not conform to the distributions of described Aiptasia species, suggesting that taxonomic re-evaluation is needed in the light of molecular genetics. Associations with Symbiodinium further demonstrated the distinctions among Aiptasia populations. According to 18S RFLP, ITS2-DGGE and microsatellite flanker region sequencing, Florida anemones engaged in diverse symbioses predominantly with members of Symbiodinium Clades A and B, but also C, whereas anemones from elsewhere harboured only S.minutum within Clade B. Symbiodinium minutum apparently does not form a stable symbiosis with other hosts, which implies a highly specific symbiosis. Fine-scale differences among S.minutum populations were quantified using six microsatellite loci. Populations of S.minutum had low genotypic diversity and high clonality (R=0.14). Furthermore, minimal population structure was observed among regions and ocean basins, due to allele and genotype sharing. The lack of genetic structure and low genotypic diversity suggest recent vectoring of Aiptasia and S.minutum across localities. This first ever molecular-genetic study of a globally distributed cnidarian and its Symbiodinium assemblages reveals host-symbiont specificity and widely distributed populations in an important model system.

Genetic identity of free‐living Symbiodinium obtained over a broad latitudinal range in the Japanese coast

SummaryThe dinoflagellate Symbiodinium is well known to engage symbiosis with various marine animals, including corals. Recent records of environmental Symbiodinium (occurring in the environment and separately from host animals; usually referred to as ‘free‐living’ Symbiodinium) are of special interest, since these environmental populations are essential as symbiont sources for many host animals. In the present study, we carried out a phylogenetic analysis of environmental Symbiodinium isolates (culture strains) from sand, tide pools, or macroalgal surfaces, and environmental DNA clones extracted from the water‐column, at numerous sites around Japan. Our phylogenetic analysis based on the nuclear rRNA gene (internal transcribed spacers ‐1, ‐2, and 5.8S), indicated that most of the environmental isolates form monophyletic subclades within the Clade‐A lineage, and separate from a host‐associated Clade‐A population with high bootstrap values. Results of the partial nuclear 28S rDNA phylogeny and thecal‐plate observations revealed that these environmental isolates were closely related to a previously‐described ‘planktonic species’, Symbiodinium natans Gert Hansen et Daugbjerg, which was isolated from a plankton‐net sample from the Northeast‐Atlantic Ocean. On the other hand, the environmental DNA clones were also noted to be mostly nested within host‐associated Symbiodinium groups scattered in various clades. These results led to the assumption that the environmental Symbiodinium can be divided into two groups. One group, as typified by environmental isolates in the present study and previous reports, may be exclusively free‐living; the other group exists transiently in free‐living forms, possibly having been expelled from animal hosts. The populations within the latter group probably represent environmental sources of viable symbionts, because these are normally host‐associated. However, the Symbiodinium in the former group are not expected to engage in stable symbioses with host cnidarians.

The larval sponge holobiont exhibits high thermal tolerance

Marine sponges are critical components of benthic environments; however, their sessile habit, requirement to filter large volumes of water and complex symbiotic partnerships make them particularly vulnerable to the effects of global climate change. We assessed the effect of elevated seawater temperature on bacterial communities in larvae of the Great Barrier Reef sponge, Rhopaloeides odorabile. In contrast to the strict thermal threshold of 32°C previously identified in adult R. odorabile, larvae exhibit a markedly higher thermal tolerance, with no adverse health effects detected at temperatures below 36°C. Similarly, larval microbial communities were conserved at temperatures up to 34°C with a highly significant shift occurring after 24 h at 36°C. This shift involved the loss of previously described symbionts (in particular the Nitrospira, Chloroflexi and a Roseobacter lineage) and the appearance of new Gammaproteobacteria not detected at lower temperatures. Here, we demonstrated that sponge larvae maintain highly stable symbioses at seawater temperatures exceeding those that are predicted under current climate change scenarios. In addition, by revealing that the shift in microbial composition occurs in conjunction with necrosis and mortality of larvae at 36°C we have provided additional evidence of the strong link between host health and the stability of symbiont communities.

Endophytes: a potential resource for biosynthesis, biotransformation, and biodegradation

In natural ecosystems, endophytes, which live in the inner tissues of healthy plants, exhibit complex interactions with their hosts. During a long coevolutionary process with their hosts, endophytes have developed many significant and novel characteristics. In order to maintain a stable symbiosis, endophytes secrete varieties of extracellular enzymes that contribute to colonization and growth. All these specific enzymes, under certain conditions, could be exploited. Nowadays, more and more complex chemical reactions are being replaced by moderate and pollution-free enzymatic reactions. Bacteria have been widely used in bioengineering, but endophytes, as a kind of organism, have not been fully developed. Therefore, great efforts to develop endophyte resources could bring us a variety of benefits, such as novel and effective bioactive compounds that cannot be synthesized by chemical reactions. It is noteworthy that, after long-term coexistence with hosts, endophytes can synthesize biologically active substances similar to the secondary metabolites produced by host plants. This could help us to accumulate many valuable drug compounds such as paclitaxel and camptothecin in a short time period. In addition, endophytes are widespread in plant roots; they can deeply affect soil chemical composition, micro-ecosystems, and physical structure over their life cycle. Besides that, endophytes play an important role in the degradation of plant litter and organic pollutants, which have an active effect on the improvement of soil fertility. Endophytes are a most promising microbial resource, waiting to be exploited.

An Unusual Galactofuranose Lipopolysaccharide That Ensures the Intracellular Survival of Toxin‐Producing Bacteria in Their Fungal Host

Dress code for living in a fungus: Analysis of the carbohydrate coating of the toxin-producing endobacterium of the phytopathogenic fungus Rhizopus microsporus revealed an unprecedented lipopolysaccharide (LPS) structure, which is important for infection and colonization of the fungal host. A mutant lacking the unusual [→2)-β-D-galactofuranose-(1→]n O antigen (red in the schematic illustration) was incapable of forming a stable symbiosis with the fungus. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Symbiosis between Symbiodinium (Dinophyceae) and various taxa of Nudibranchia (Mollusca: Gastropoda), with analyses of long-term retention

Long-term retention of zooxanthellae in five different species belonging to two different nudibranch groups (Aeolidoidea and Dendronotoidea) was investigated. Specimens belonging to the species Phyllodesmium briareum, Phyllodesmium colemani, Phyllodesmium longicirrum, Pteraeolidia ianthina and Melibe engeli were cultivated for 70–270 days under various feeding conditions, and photosynthetic activity was analysed by taking pulse amplitude modulated (PAM) fluorometer measurements. All five species showed stable symbiosis and long-term retention of zooxanthellae. Interspecific differences are discussed. Morphological adaptations for housing zooxanthellae in the digestive glandular system were investigated and documented by histological means.

Genetic diversity in cyanobacterial symbionts of thalloid bryophytes

Two species of thalloid liverworts, Blasia pusilla and Cavicularia densa, form stable symbioses with nitrogen-fixing cyanobacteria. Both bryophytes promote the persistence of their cyanobacterial associations by producing specialized gemmae, which facilitate the simultaneous dispersal of the host and its nitrogen-fixing symbionts. Here the genetic diversity of cyanobacterial symbionts of Blasia and Cavicularia is examined. The results indicate that the primary symbionts of both bryophytes are closely related and belong to a specific group of symbiotic Nostoc strains. Related strains have previously been reported from hornworts and cycads, and from many terricolous cyanolichens. The evolutionary origins of all these symbioses may trace back to pre-Permian times. While the laboratory strain Nostoc punctiforme PCC 73102 has been widely used in experimental studies of bryophyte-Nostoc associations, sequence-identical cyanobionts have not yet been identified from thalloid liverworts in the field.

Genetics of the relationship between the ciliate Paramecium bursaria and its symbiotic algae

Abstract. Paramecium bursaria, a freshwater protozoan, typically harbors hundreds of symbiotic algae (Chlorella sp.) in its cytoplasm. The relationship between host paramecia and symbiotic algae is stable and mutually beneficial in natural environments. We recently collected an aposymbiotic strain of P. bursaria. Infection experiments revealed that the natural aposymbiotic strain (Ysa2) showed unstable symbiosis with Chlorella sp. The algae aggregated at the posterior region of the host, resulting in aposymbiotic cell production after cell division. Cross‐breeding analyses were performed to determine the heritability of the aposymbiotic condition. In crosses of Ysa2 with symbiotic strains of P. bursaria, F1 progeny were able to form stable symbioses with Chlorella sp. However, unstable symbiosis, resembling Ysa2 infection, occurred in some F2 progeny of sibling crosses between symbiotic F1 clones. Infection experiments using aposymbiotic F2 cells showed that these F2 subclones have limited ability to reestablish the symbiosis. These results indicate that the maintenance of stable symbiosis is genetically controlled and heritable, and that Ysa2 is a mutant lacking the mechanisms to establish stable symbiosis with Chlorella sp.