Pathways of XXXX and energy metabolism of the epibiotic community associated with the deep-sea hydrothermal vent shrimp Rimicaris exoculata.

@entity505 @entity599 @entity3884 @entity6626
BACKGROUND: The shrimp Rimicaris exoculata dominates the faunal biomass at many deep-sea hydrothermal vent sites at the Mid-Atlantic Ridge. In its enlarged gill chamber it harbors a specialized epibiotic bacterial community for which a nutritional role has been proposed. METHODOLOGY/PRINCIPAL FINDINGS: We analyzed specimens from the Snake Pit hydrothermal vent field on the Mid-Atlantic Ridge by complementing a 16S rRNA gene survey with the analysis of genes involved in @entity505 , @entity599 and @entity3884 metabolism. In addition to Epsilon- and Gammaproteobacteria, the epibiotic community unexpectedly also consists of Deltaproteobacteria of a single phylotype, closely related to the genus Desulfocapsa. The association of these phylogenetic groups with the shrimp was confirmed by fluorescence in situ hybridization. Based on functional gene analyses, we hypothesize that the Gamma- and Epsilonproteobacteria are capable of autotrophic growth by oxidizing reduced @entity599 compounds, and that the Deltaproteobacteria are also involved in @entity599 metabolism. In addition, the detection of proteobacterial hydrogenases indicates the potential for @entity3884 oxidation in these communities. Interestingly, the frequency of these phylotypes in 16S rRNA gene clone libraries from the mouthparts differ from that of the inner lining of the gill chamber, indicating potential functional compartmentalization. CONCLUSIONS: Our data show the specific association of autotrophic bacteria with Rimicaris exoculata from the Snake Pit hydrothermal vent field, and suggest that autotrophic @entity505 fixation is contributing to the productivity of the epibiotic community with the reductive @entity6626 cycle as one important @entity505 fixation pathway. This has not been considered in previous studies of @entity505 fixation and stable @entity505 isotope composition of the shrimp and its epibionts. Furthermore, the co-occurrence of @entity599 -oxidizing and @entity599 -reducing epibionts raises the possibility that both may be involved in the syntrophic exchange of @entity599 compounds, which could increase the overall efficiency of this epibiotic community.
