Sulfidogenesis in hypersaline chloride-sulfate lakes of Kulunda Steppe (Altai, Russia)

The activity and culturable diversity of sulfidogens were investigated in anoxic sediments of four hypersaline lakes with pH 7.6-8.2 in the Kulunda Steppe (Altai, Russia). Sulfate reduction rates were low, varying from 0.1 to 6.0 nmol HS−/(cm3 h) with a maximum in the top 10 cm layer. Potential sulfidogenic rates with thiosulfate and sulfur as the e-acceptors were higher than with sulfate and were stimulated by formate, lactate, and acetate. Sulfidogenesis was optimal at salt concentrations below 2 M NaCl. Cultivation at 2 M NaCl resulted in the isolation of several strains of moderately halophilic SRB, but no growth of SRB was observed at 4 M NaCl. At lithotrophic conditions (i.e., with formate or H2 as e-donors), several closely related alkalitolerant strains belonging to the genus Desulfonatronovibrio were isolated. Enrichments at heterotrophic conditions with lactate, propionate, acetate, or butyrate using sulfate or thiosulfate as e-acceptors yielded isolates related to Desulfosalsimonas propionicica, Desulfohalobium utahense, and Desulfocella halophila. Sulfur-reducing enrichments at 2 M NaCl with ethanol produced a member of the genus Halanaerobium, while enrichments at 4 M NaCl with acetate were dominated by archaea, demonstrating for the first time such type of catabolism in haloarchaea.