Objective: We characterized bacterial divefity in a deep-sea hydrothermal plume seawater in the southwest Indian Ocean to increase our understanding of the impact of the microorganisms on the ocean ecosystem and to survey microbial resources in this special environment.
Methods: The deep-sea hydrothermal plume seawater in the southwest Indian Ocean was concentrated in situ by 1000 folds, enrichment cultures were established with the concentrated sample, and isolates were purified. Bacterial 16S rRNA gene libraries were constructed from both the concentrated seawater sample and from the enrichment culture and analyzed. The 16S rRNA genes from the isolated strains were also analyzed.
Results: A total of 104 16S rRNA genes were obtained, in which 50 were from the concentrated plume seawater, 40 from the enrichment culture, and 14 from the isolated strains. These sequences are affiliated with gamma-proteobacteria (74), alpha-proteobacteria (14), beta-Proteobacteria (5), Bacteroidetes (4), Firmicutes (2), Planctomycetes (2), Verrucomicrobia (2) and Actinobacteria (1), and fall into 29 different operational taxonomic units (OTUs). Twenty-six sequences share less than 97% identity with the best-matched sequences in the public database, with the lowest being 86%.
Conclusions: There is rich bacterial diversity in the deep-sea hydrothermal plume seawater in the southwest Indian Ocean, where gamma-proteobacterial groups were dominant, followed by alpha-proteobacterial groups. A number of species remain uncultured.