Bacterial community of sediments from the Australian-Antarctic ridge

Benthic bacterial communities in the ocean comprise the vast majority of prokaryotes on Earth and play crucial roles in the biogeochemical cycles and remineralization of organic matter. Despite the importance of the benthic bacterial communities in the ecosystem, no previous investigations of the bacterial community of sediments from the Australian-Antarctic ridge (AAR) have been conducted to date. In this study, the composition of the bacterial community in the surface sediments from AAR was revealed by the 454 pyrosequencing method. Bacterial communities inhabiting the sediments of AAR were highly diverse, covering 39 distinct major lineages of bacteria. Among them, Gammaproteobacteria, Planctomycetes, Actinobacteria, Deltaproteobacteria, Acidobacteria, Alphaproteobacteria, Chloroflexi, Bacteroidetes, Chlorobi, and Gemmatimonadetes were dominant, accounting for 85–88 % of the bacterial community. The 16S rDNA sequences of major OTUs with 1 % or higher relative abundance showed high similarity (96.6–100 %) with uncultured environmental sequences that were primarily recovered from the sediments of various areas of the Arctic, Southern, Atlantic, Indian, and Pacific Oceans. As the first report of the bacterial community of marine sediments in the AAR region, the results presented herein suggest that members of the predominant phyla are well adapted to the environment of marine sediment and that the low variability in the bacterial communities of deep-sea sediments might reflect the similar environmental conditions among various regions of the deep sea.