Prokaryotic Diversity in the Biotopes of the Gudzhirganskoe Saline Lake (Barguzin Valley, Russia)

The hydrochemical water composition and the mineralogical composition of microbial mats and bottom sediments were determined for the ephemeral saline soda lake Gudzhirganskoe (Barguzin Valley, Baikal Rift zone). Analysis of the 16S rRNA gene amplicons was applied to investigation of microbial diversity in several biotopes: brine (1 sample), sediments (3), and microbial mats (3). During sampling in October 2017, the lake was almost dry, with the residual brine (salinity 100 g/dm3) occurring occasionally, and microbial formations at two sampling points existing as dry crusts. A total of 38636 nucleotide sequences were analyzed and assigned to 193 OTUs. Bacteria predominated in all biotopes, while archaea constituted 0.013 to 4.5%. The biotopes exhibited differences in their taxonomic composition. Members of the Gammaproteobacteria (36.5%), Bacteroidetes (25.4%), and Alphaproteobacteria (18.3%) were predominant in the brine. The Gammaproteobacteria predominated (52%) in the dense dry crust (Gudzh 1-mat), while Cyanobacteria constituted only 3.4%. In the dry crust (Gudzh 2-mat), the Gammaproteobacteria also were the main component of the community (80%), primarily members of the genus Aliidiomarina (68%). In the bottom microbial mat below the residual brine, the community contained mainly Gammaproteobacteria (37.4%) and Cyanobacteria (27.8%). Firmicutes prevailed in the bottom sediments (30‒32%), while Actinobacteria (14.56%) and Deinococcus‒Thermus (15.4%) were subdominant at sampling point 1. These data made it possible to assess the present state of the lake and the taxonomic diversity of microbial communities in Lake Gudzhirganskoe biotopes.