Biocomplexity: A Meta-Genome Level Analysis of an Extreme Microbial Symbiosis

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PI: Cary Proposal: 0102648 The project by S. Craig Cary, University of Delaware is supported by the program Biocomplexity in the Environment, subprogram Genomic-Enabled Environmental Science and Engineering (BE GEN-EN). The project focuses on symbiotic associations in deep-sea thermal vent communities. Closely integrated symbiotic associations between bacteria and eukaryotic hosts abound in nature. This is particularly the case in marine systems where novel associations are being routinely discovered. Whether the bacteria reside externally to the host or endosymbiotically the functional role of these associations often remain poorly understood. This lack of understanding, in part, stems from our inability to cultivate the majority of these symbionts free from their host. Even in instances where cultivation is possible, it is unlikely that the physiological capacities of bacteria measured in the laboratory truly represent those in the natural ecosystem. The majority of episymbiont associations exist as a phenotypically and phylogenetically mixed population making it extremely difficult to decipher the role of independent members. This project will employ a community level genomic approach to understand the metabolic potential and phenotypes of the members of a diverse episymbiotic bacterial community found associated with the tube-dwelling polychaete, Alvinella pompejana. This association exists in an extreme deep-sea hydrothermal vent biotope characterized by high concentrations of heavy metals and the steepest thermal gradient experienced by any organism yet described. It is likely that such an environment imposes strong selective pressures on the symbiont/host association. In depth rRNA analysis of the episymbiotic communities associated with A. Pompejana demonstrated the dominance of a diverse assemblage of a single bacterial subdivision (epsilon Proteobacteria). This constraint, found in the episymbiotic communities throughout A. pompejana geographic and physiochemical range, has not been described in any other symbiotic association. Because of the complex nature of this association, no specific roles have been defined for this unique symbiosis by habitat characterizations, in situ enzyme assays, classical cultivation techniques or molecular analysis. This project will address a central hypothesis that by understanding the collective genetic complexity of the episymbiont community one can resolve a core metabolic strategy that defines thecommunity in the context of its environment. Our approach assumes that by placing the genome biocomplexity of this community directly into an environmental context we will be able to resolve the ecological role and interrelationships of this microbial/invertebrate association. To achieve this goal, we will conduct a meta-genome scale analysis of the complex microbial community found intimately associated with A. pompejana. By coupling tightly integrated bioinformatic and modeling components with both environmental characterizations and microarray expression analyses we will then have the ability to genetically dissect the episymbiont community and query their functionality under various physiochemical conditions. The research will involve an interdisciplinary, international team of investigators that bring to the program expertise in microbial ecology, geochemistry, genomic sciences, proteomics and bioinformatics. The productive partnerships between academia and industry that were developed during previous work will allow access to essential technical resources and expertise otherwise unavailable for this type of investigation.