Sulfidogenesis in hypersaline chloride–sulfate lakes of K ulunda S teppe ( A ltai, R ussia)

The activity and culturable diversity of sulfidogens were investigated in anoxic sediments of four hypersaline lakes with p H 7.6–8.2 in the K ulunda S teppe ( A ltai, R ussia). Sulfate reduction rates were low, varying from 0.1 to 6.0 nmol HS − /(cm 3  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 H 2 as e ‐donors), several closely related alkalitolerant strains belonging to the genus D esulfonatronovibrio were isolated. Enrichments at heterotrophic conditions with lactate, propionate, acetate, or butyrate using sulfate or thiosulfate as e ‐acceptors yielded isolates related to D esulfosalsimonas propionicica , D esulfohalobium utahense, and D esulfocella halophila . Sulfur‐reducing enrichments at 2 M NaCl with ethanol produced a member of the genus H alanaerobium , while enrichments at 4 M NaCl with acetate were dominated by archaea, demonstrating for the first time such type of catabolism in haloarchaea.