Phylogenetic and functional prokaryotic diversity in the Hoito-Gol mesothermal mineral spring (Eastern Sayan Mountains, Buryat Republic)

High-throughput sequencing was used for comparative analysis of microbial communities of the water and mat from the Hoito-Gol mesothermal mineral sulfide spring (Eastern Sayan Mountains, Buryat Republic). Activity of microbial communities was determined. While both spring biotopes were dominated by members of three bacterial phyla— Proteobacteria, Bacteroidetes , and Firmicutes —they differed drastically in the composition of predominant phylotypes (at the genus level). In the water, the organisms widespread in aquatic environments were predominant, mostly aerobic chemoorganotrophs of the genera Acinetobacter, Pedobacter , and Flavobacterium . In the microbial mat, the organisms actively involved in the sulfur cycle predominated, including sulfur-reducing bacteria Sulfurospirillum , sulfate-reducing deltaproteobacteria, sulfuroxidizing chemoautotrophic bacteria, anoxygenic phototrophic bacteria of the phyla Chloroflexi and Chlorobi , as well as purple bacteria belonging to the α-, ß-, and γ- Proteobacteria . Microbial mats of the spring exhibited higher phylogenetic diversity compared to high-temperature mats containing photosynthetic microorganisms.