Microbial Genome Sequencing: Comparative Genomics of Chemosynthetic Symbionts

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A grant has been awarded to Dr. Colleen Cavanaugh of Harvard University, in collaboration with Dr. Jonathan Eisen of The Institute for Genome Research (TIGR), to sequence the genomes of two representative chemosynthetic bacteria which live in symbiotic associations with marine invertebrates. Like chloroplasts in plants (the sugar-producing organelles), chemosynthetic symbionts provide their host an internal source of nutrition, using sulfide instead of sunlight as an energy source. Chemosynthetic bacteria are widespread as symbionts of marine invertebrates, as-yet-uncultured, and substantial components of sulfur and carbon cycling in marine environments, including deep-sea hydrothermal vents. Obtaining these symbiont genome sequences will allow comparison with the genomes of related free-living bacteria and other endosymbionts, providing rapid insights into the genetics, metabolic potential, and evolution of chemosynthetic symbioses. These animal-bacteria symbioses are significant evolutionarily, effectively creating "sulfur-eating animals" and as models for understanding the bacterial origin and evolution of animal cellular organelles, and, ecologically, as primary producers in sulfide-rich environments. Genome analyses will answer questions regarding microbial symbiosis, physiology, genetics, ecology, and evolution. Further, comparison of these genomes will advance our understanding of how the bacteria are passed between host generations and the similarities and differences between infection mechanisms of mutualistic symbionts vs. pathogens. Outreach efforts associated with the project will include the availability of the genome sequences via the TIGR website. The project website, www.endosymbiont.org, contains relevant links to publications, other genomes, researchers, news in the field, and educational materials. Undergraduates, graduate students, and postdoctoral fellows will have ample opportunity to participate in analyses of the symbiont genomes. Information on endosymbiont genomics will be disseminated to scientific and general audiences by lectures at venues ranging from elementary school classes through international research meetings.