Project description:Coral reefs are declining globally. Temperature anomalies disrupt coral-algal symbioses at the molecular level, causing bleaching and mortality events. In terrestrial mutualisms, diversity in pairings of host and symbiont individuals (genotypes) results in ecologically and evolutionarily relevant stress response differences. The extent to which such intraspecific diversity provides functional variation in coral-algal systems is unknown. Here we assessed functional diversity among unique pairings of coral and algal individuals (holobionts). We targeted six genetically distinct Acropora palmata coral colonies that all associated with a single, clonal Symbiodinium ‘fitti’ strain in a natural common garden. No other species of algae or other strains of S. ‘fitti’ could be detected in host tissues. When colony branches were experimentally exposed to cold stress, host genotype influenced the photochemical efficiency of the symbiont strain, buffering the stress response to varying degrees. Gene expression differences among host individuals with buffered vs. non-buffered symbiont responses included biochemical pathways that mediate iron availability and oxygen stress signaling—critical components of molecular interactions with photosynthetic symbionts. Spawning patterns among hosts reflected symbiont performance differences under stress. These data are some of the first to indicate that genetic interactions below the species level affect coral holobiont performance. Intraspecific diversity serves as an important but overlooked source of physiological variation in this system, contributing raw material available to natural selection. Note: in the final publication, only ambient and cold treatments are discussed, but there was an additional hot treatment for each genotype at 34C. Most colonies expired after 6 hours, so PAM data could not be collected. The microarray data from 3.5 hours are included here.
Project description:This SuperSeries is composed of the following subset Series: GSE11944: Mucosal Glycan Foraging Enhances the Fitness and Transmission of a Saccharolytic Human Distal Gut Symbiont GSE11953: Mucosal Glycan Foraging Enhances the Fitness and Transmission of a Saccharolytic Human Distal Gut Symbiont: ECF mutant GSE11962: Growth of B. thetaiotaomicron on purified host mucosal glycans and glycan fragments Refer to individual Series
Project description:Given the overwhelming evidence that symbiont genotypes differentially affect host processes such as growth, bleaching susceptibility, and nutrient acquisition, we set out to measure gene expression differences in fragments of Montastraea faveolata harboring two different clades of Symbiodinium. On the reefs near Puerto Morelos, México, colonies of M. faveolata are known to shift algal symbiont clade with depth, often associating with clade A at the top, clade B in the middle, and clade C near the bottom of the colony. By measuring photosynthetic efficiency and gene expression in control and heat-stressed fragments containing either clade B, clade C, or a mix of both, we found that: 1) the algal response to thermal stress is due to both host and algal factors; 2) fragments of M. faveolata express different genes in response to sub-bleaching thermal stress depending on algal genotype; 3) the overall effect of heat stress on coral gene expression is less significant than the effect of housing different zooxanthellae types. Overall, we present convincing evidence that different Symbiodinium clades may be functionally distinct, which in turn, greatly influences host gene expression.
Project description:A mutualistic relationship between reef-building corals and endosymbiotic algae (Symbiodinium spp.) forms the basis for the existence of coral reefs. Genotyping tools for Symbiodinium spp. have added a new level of complexity to studies concerning cnidarian growth, nutrient acquisition, and stress. For example, the response of the coral holobiont to thermal stress is connected to the host-Symbiodinium genotypic combination, as different partnerships can have different bleaching susceptibilities. If, and to what extent, differences in algal symbiont clade contents can exert effects on the coral host transcriptome is currently unknown. In this study, we monitored algal physiological parameters and profiled the coral host transcriptional responses in acclimated, thermally stressed, and recovered coral fragments using a custom cDNA gene expression microarray. Combining these analyses with results from algal and host genotyping revealed a striking symbiont effect on both the acclimated coral host transcriptome and the magnitude of the thermal stress response. This is the first study that links coral host transcriptomic patterns to the clade content of their algal symbiont community. Our data provide a critical step to elucidating the molecular basis of the apparent variability seen among different coral-algal partnerships.
Project description:The deep-sea tubeworm Riftia pachyptila is a model system for a mutualistic association: The adult worm has no digestive system, but completely relies on one phylotype of endosymbiotic chemosynthetic bacteria for nutrition. The bacteria, in turn, are provisioned by the host. Metabolism and physiology of this symbiosis, particularly of the uncultured symbiont, have been subject to various studies. Yet, how both partners interact on the molecular level remains largely unknown. To study these host-symbiont interactions in detail, we sequenced the R. pachyptila host transcriptome de novo, and conducted comprehensive metaproteomic comparisons of symbiont-containing and symbiont-free R. pachyptila tissues under energy-rich and energy-limiting conditions. Our results demonstrate that R. pachyptila invests a considerable part of its proteome to provision the symbionts with inorganic compounds. It acquires symbiont-derived biomass primarily by digesting parts of the symbiont population. The R. pachyptila immune system apparently not only protects the holobiont from pathogens, but is also involved in symbiont population control. The symbiont expresses a repertoire of proteins dedicated to communication with the host, including eukaryote-like proteins that may counteract phagocytosis. During energy limitation, i.e., when reduced sulfur compounds are lacking, the host apparently increases symbiont digestion. We show here an intricate network of interaction pathways that shapes the R. pachyptila holobiont. Together with the metabolic flexibility of the association under varying energy conditions, this probably forms the basis for the success of this tight association under the highly challenging deep-sea conditions.
Project description:Legionella pneumophila are important opportunistic pathogens for which environmental reservoirs such as protists are crucial for the infection of humans. Free-living amoebae are considered key hosts providing nutrients and shelter for highly efficient intracellular proliferation of L. pneumophila, which eventually leads to lysis of the amoeba host cell. Yet, the significance of other bacterial players for L. pneumophila ecology is poorly understood. In this study we used a ubiquitous amoeba and their bacterial endosymbiont to investigate the impact of this common association on L. pneumophila infection. We demonstrate that Acanthamoeba castellanii harboring the chlamydial symbiont Protochlamydia amoebophila were able to erase L. pneumophila and, in contrast to symbiont-free amoebae, survived the infection and were able to resume growth. Environmental amoeba isolates harboring P. amoebophila were equally well-protected, and fresh environmental isolates of L. pneumophila were equally well-erased, suggesting ecological relevance of this symbiont-mediated protection. We further show that protection was not mediated by impaired L. pneumophila uptake. Instead, we observed reduced virulence of L. pneumophila released from symbiont-containing amoebae that is strongly supported by transcriptome data. Interference with transition to the transmissive phase is thus likely the basis for this protection. Finally, our data indicate that the defensive response of amoebae harboring P. amoebophila leaves the amoebae with superior fitness reminiscent of immunological memory. Given that mutualistic associations between bacteria and amoebae are widely distributed, P. amoebophila and potentially other amoeba endosymbionts could be key elements in shaping environmental survival, abundance and virulence of this important pathogen thereby affecting frequency of human infection.
Project description:Bathymodiolus mussels inhabiting deep-sea hydrothermal vents harbor bacterial symbionts in their gills, which support the animals’ diet. While the basic mechanisms of energy generation and CO2 fixation that drive these symbioses are largely established, details of molecular interactions between the symbiotic partners and adaptations to their respective habitats remain unknown. In this study, we therefore comparatively examined the genomes and proteomes of two Bathymodiolus hosts and their respective symbionts from different geographical locations. Two mussel species were proteomically compared: i) B. thermophilus mussel containing sulfur-oxidizing symbiont from the east pacific rise. thermophilus and ii) B. azoricus containing thiotrophic and methanotrophic symbionts from the mid-atlantic ridge. Symbionts (for both species) and host components (for B. azoricus) were selectively enriched using a multi-step centrifugation procedure. Enriched host and symbiont fractions along with unenriched gill foot tissue were subject to in-depth semi-quantitative proteomic analyses using the orbitrap and velos mass spectrometers. Proteins were quantified based on their spectral counts using the normalized spectral abundance factor (NSAF) method. We identified common strategies of metabolic interactions that provide mutual nutritional support between host and symbionts, such as the detoxification of ambient sulfide by the Bathymodiolus host, which provides a stable thiosulfate reservoir for the thiotrophic symbionts, and a putative amino acid cycling mechanism that could supply the host with symbiont-derived amino acids. A suite of genes and proteins putatively related to virulence or defense functions was particularly abundant in the B. thermophilus symbiont, compared to its symbiont relatives, and may pose a host species-specific adaptation. Our results reveal both, a high degree of integration between the symbiotic partners, and great potential to adapt to the prevailing environment, which facilitate the holobiont’s survival in its hydrothermal vent habitat.
Project description:Bathymodiolus azoricus is a deep-sea mussel found in the hydrothermal vent fields of the Mid-Atlantic Ridge. It lives in symbiosis with sulfur- and methane-oxidizing γ-proteobacteria within its gills. In our study, we aimed to understand the metabolic and physiological interconnections between the symbiotic partners. For this purpose, symbionts and host were physically separated using density gradient centrifugation. This procedure yielded a symbiont-enriched gradient pellet fraction and a supernatant fraction enriched in host components. The cytosolic and membrane-associated proteome of both these fractions along with whole gill and foot tissue of the mussel were then investigated through 1D-PAGE LC-MS/MS. Proteins were quantified based on their spectral counts using the NSAF method. For efficient identification, sequences from evolutionarily related endosymbiotic and free-living bacteria and from bivalve host relatives were compiled into a comprehensive protein database. A total of 3178 host and symbiont proteins were identified from all samples.