A novel alkaliphilic spore-forming bacterium was isolated from the benthic sediments of the highly mineralized steppe Lake Khilganta (Transbaikal Region, Russia). Cells of the strain, designated Х-07-2T, were straight to slightly curved rods, Gram-stain-positive and motile. Strain Х-07-2T grew in the pH range from 7.0 to 10.7 (optimum pH 9.6-10.3). Growth was observed at 25-47 °C (optimum 30 °C) and at an NaCl concentration from 5 to 150 g l-1 with an optimum at 40 g l-1. Strain Х-07-2T was a chemo-organoheterotroph able to reduce amorphous ferric hydroxide, Fe(III) citrate and elemental sulfur in the presence of yeast extract as the electron donor. It used tryptone, peptone and trypticase with Fe(III) citrate as the electron acceptor. The predominant fatty acids in cell walls were C16:1ω8, iso-C15:0, C14 : 0 3-OH and C16 : 0. The DNA G+C content was 32.6 mol%. 16S rRNA gene sequence analysis revealed that strain Х-07-2T was related most closely to members of the genus Alkaliphilus within the family Clostridiaceae. The closest relative was Alkaliphilus peptidifermentans Z-7036T (96.4 % similarity). On the basis of the genotypic, chemotaxonomic and phenotypic data, strain Х-07-2T represents a novel species in the genus Alkaliphilus, for which the name Alkaliphilus namsaraevii sp. nov. is proposed. The type strain is Х-07-2T (=VKM В-2746Т=DSM 26418Т).

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)).

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A psychrotolerant facultative anaerobe, strain SKBGT, was isolated from the bottom sediments of the cold mineral spring Buxichen (Buryatia, Russia). Gram-positive non-motile cocci with a diameter of 1.75–2.5 µm were observed singly or in long chains. Cells grew in the temperature range from ̶ 5–35 °C. Growth was observed within the pH range of 7.0–9.5, with the optimum growth at pH 7.6 and at a NaCl concentration from 0–1.0 % (optimum 0.1 % (w/v)). Strain SKBGT was a chemoorganoheterotroph that used sugars and some organic acids as substrates. The predominant fatty acids in cell walls were С16:1ω9, С18:1ω9, and С16 : 0. The 16S rRNA gene sequence of strain SKBGT shared high similarity (>99 %) with those of the type strains of the genus Trichococcus . Digital DNA–DNA hybridization (dDDH) and average nucleotide identity (ANI) values between strain SKBGT and Trichococcus shcherbakoviae ArtT (=DSM 107162T=VKM B-3260T) were 70.1 and 95.4 %, respectively. The genomic DNA G+C content of strain SKBGT was 47.1 mol%. Compared with the type strain of T. shcherbakoviae , the new strain was characterized by a temperature optimum for growth (10 °C) significantly lower than that of T. shcherbakoviae DSM 107162T (20–30 °C). Based on phenotypic and genomic characteristics, the isolate SKBGT was classified as T. shcherbakoviae subsp. psychrophilus subsp. nov. The type strain is SKBGT (=VKM B-3241Т=JCM 33326T).