A novel haloalkaliphilic sulfate-reducing bacterium, designated Al915-01(T), was isolated from benthic sediments of the Lake Alginskoe, a soda lake located in the Trans-Baikal Region, Russia. Cells of the strain were Gram-stain negative, motile, non-spore-forming vibrion (0.4-0.5 × 1.2-2.3 µm). Strain Al915-01(T) grew in the pH range from 8.0 to 10.5 (optimum pH 9.0) and required NaCl for growth (5-100 g l(-1) NaCl, optimum 40 g l(-1)). The bacterium grew at 10-40 °C (optimally at 36 °C) and used lactate, formate and pyruvate as electron donors in the presence of sulfate. It was able to reduce sulfate, sulfite, thiosulfate and nitrate with lactate as an electron donor. The isolate was able to grow lithoheterotrophically with sulfate and molecular hydrogen if acetate was added as a carbon source. The predominant fatty acids were anteisoC15:0, isoC17:1, C18:1ω7 and C16:1ω7. The G+C content in the DNA was 58.3 ± 1 mol %. Analysis of the 16S rRNA gene sequence showed that the new bacterium belongs to the genus Desulfonatronum. The closest relatives were Desulfonatronum buryatense Ki5(T) (99.9 % similarity) and Desulfonatronum lacustre Z-7951(T) (99.2 % similarity). On the basis of the genotypic, phenotypic and phylogenetic characteristics, the isolate is proposed as a representative of a novel species Desulfonatronum zhilinae with the type strain Al915-01(T) (=VKM B-2744(T) = DSM 26338(T)).