Mobilitalea sibirica gen. nov., sp. nov., a halotolerant polysaccharide-degrading bacterium.

A novel strictly anaerobic, halotolerant, organotrophic bacterium, strain P3M-3(T), was isolated from a microbial mat formed under the flow of hot water emerging from a 2775 m-deep well in Tomsk region (western Siberia, Russia). Cells of strain P3M-3(T) were straight and curved rods, 0.2-0.4 µm in width and 1.5-20 µm in length. Strain P3M-3(T) grew optimally at 37 °C, pH 7.0-7.5 and in a NaCl concentration of 15 g l(-1). Under optimum growth conditions, the doubling time was 1 h. The isolate was able to ferment a variety of mono-, di- and polysaccharides, including microcrystalline cellulose. Acetate, ethanol, H2 and CO2 were the main products of glucose fermentation. The DNA G+C content was 33.4 mol%. 16S rRNA gene-based phylogenetic analysis showed that strain P3M-3(T) was a member of family Lachnospiraceae, whose representatives are also found in Clostridium cluster XIVa. 16S rRNA gene sequence similarity with Clostridium jejuense HY-35-12(T), the closest relative, was 93.9%. A novel genus and species, Mobilitalea sibirica gen. nov., sp. nov., are proposed based on phylogenetic analysis and physiological properties of the novel isolate. The type strain of the type species is P3M-3(T) ( = DSM 26468(T) = VKM B-2804(T)).