Diversity of dissimilatory bisulfite reductase genes of bacteria associated with the deep-sea hydrothermal vent polychaete annelid Alvinella pompejana

A unique community of bacteria colonizes the dorsal integument of the polyc haete annelid Alvinella pompejana, which inhabits the high-temperature envi ronments of active deep-sea hydrothermal vents along the East Pacific Rise. The composition of this bacterial community was characterized in previous studies by using a 16S rRNA gene clone library and in situ hybridization wi th oligonucleotide probes. In the present study, a pair of PCR primers (P94 -F and P93-R) were used to amplify a segment of the dissimilatory bisulfite reductase gene from DNA isolated from the community of bacteria associated with A. pompejana, The goal was to assess the presence and diversity of ba cteria with the capacity to use sulfate as a terminal electron acceptor. A clone library of bisulfite reductase gene PCR products was constructed and characterized by restriction fragment and sequence analysis. Eleven clone f amilies were identified. Two of the 11 clone families, SR1 and SR6, contain ed 82% of the clones. DNA sequence analysis of a clone from each family ind icated that they are dissimilatory bisulfite reductase genes most similar t o the dissimilatory bisulfite reductase genes of Desulfovibrio vulgaris, De sulfovibrio gigas, Desulfobacterium autotrophicum, and Desulfobacter latus, Similarities to the dissimilatory bisulfite reductases of Thermodesulfovib rio yellowstonii, the sulfide oxidizer Chromatium vinosum, the sulfur reduc er Pyrobaculum islandicum, and the archaeal sulfate reducer Archaeoglobus f ulgidus were lower. Phylogenetic analysis separated the clone families into groups that probably represent two genera of previously uncharacterized su lfate-reducing bacteria. The presence of dissimilatory bisulfite reductase genes is consistent with recent temperature and chemical measurements that documented a lack of dissolved oxygen in dwelling tubes of the worm. The di versity of dissimilatory bisulfite reductase genes in the bacterial communi ty on the back of the worm suggests a prominent role for anaerobic sulfate- reducing bacteria in the ecology of A. pompejana.