New strains of sulfate-reducing bacteria were isolated from two alkaline brackish lakes located in the Siberian region of Russia, namely in the Southern Transbaikalia, Buriatia. The article presents data describing morphology, physiology, and biochemical characteristics of the isolated strains. These strains Ki4, Ki5, and Su2 were mesophilic and alkaliphilic with optimal growth at pH 8.9, 9.4, and 10.0, respectively. All isolated strains utilized lactate, formate, and ethanol in the presence of sulfate for growth and sulfidogenesis accompanied with formation of acetate and CO2. Strains Ki5 and Su2 were able to reduce Fe(III). The DNA G + C content in strains Ki4, Ki5 and Su2 was 56.3, 48.8 and 59.6 mol%, respectively. According to phylogenetic analysis of 16S rRNA sequences, the new strains were clustered within the genus Desulfonatronum, and the closest relative D. lacustre Z-7951(T) (=DSM 10312(T)) showed 99.3-99.6 % similarity. DNA-DNA relatedness values of the strains Ki4, Ki5, and Su2 with D. lacustre Z-7951(T) were 89, 53, and 79 %, respectively. Polyphasic taxonomy data suggest that strain Ki5(T) is representative of the proposed novel species Desulfonatronum buryatense sp. nov.