期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2008
卷号：105
期号：45
页码：17516-17521
DOI：10.1073/pnas.0802782105
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Hydrothermal vent ecosystems support diverse life forms, many of which rely on symbiotic associations to perform functions integral to survival in these extreme physicochemical environments. Epsilonproteobacteria, found free-living and in intimate associations with vent invertebrates, are the predominant vent-associated microorganisms. The vent-associated polychaete worm, Alvinella pompejana, is host to a visibly dense fleece of episymbionts on its dorsal surface. The episymbionts are a multispecies consortium of Epsilonproteobacteria present as a biofilm. We unraveled details of these enigmatic, uncultivated episymbionts using environmental genome sequencing. They harbor wide-ranging adaptive traits that include high levels of strain variability analogous to Epsilonproteobacteria pathogens such as Helicobacter pylori, metabolic diversity of free-living bacteria, and numerous orthologs of proteins that we hypothesize are each optimally adapted to specific temperature ranges within the 10-65 {degrees}C fluctuations characteristic of the A. pompejana habitat. This strategic combination enables the consortium to thrive under diverse thermal and chemical regimes. The episymbionts are metabolically tuned for growth in hydrothermal vent ecosystems with genes encoding the complete rTCA cycle, sulfur oxidation, and denitrification; in addition, the episymbiont metagenome also encodes capacity for heterotrophic and aerobic metabolisms. Analysis of the environmental genome suggests that A. pompejana may benefit from the episymbionts serving as a stable source of food and vitamins. The success of Epsilonproteobacteria as episymbionts in hydrothermal vent ecosystems is a product of adaptive capabilities, broad metabolic capacity, strain variance, and virulent traits in common with pathogens.
