sp. nov., a novel spherical halotolerant spirochete from a Russian heavy oil reservoir, emended description of the genus , reclassification of to a new genus gen. nov. as comb. nov. and proposal of fam. nov.

Anaerobic, fermentative, halotolerant bacteria, strains 4-11 and 585, were isolated from production water of two low-temperature petroleum reservoirs (Russia) and were characterized by using a polyphasic approach. Cells of the strains were spherical, non-motile and 0.30-2.5 µm in diameter. Strain 4-11 grew optimally at 35 °C, pH 6.0 and 1.0-2.0% (w/v) NaCl. Both strains grew chemoorganotrophically with mono-, di- and trisaccharides. The major cellular fatty acids of both strains were C, C, C ω9 and C 3-OH. Major polar lipids were glycolipids and phospholipids. The 16S rRNA gene sequences of the strains 4-11 and 585 had 99.9% similarity and were most closely related to the sequence of GLS2 (96.9, and 97.0% similarity, respectively). The G+C content of the genomic DNA of strains 4-11 and 585 were 46.8 and 46.9%, respectively. The average nucleotide identity and digital DNA-DNA hybridization values between the genomes of strain 4-11 and GLS2 were 73.0 and 16.9%, respectively. Results of phylogenomic metrics analysis of the genomes and 120 core proteins of strains 4-11 and 585 and their physiological and biochemical characteristics confirmed that the strains represented a novel species of the genus , for which the name sp. nov. is proposed, with the type strain 4-11 (=VKM B-3269=KCTC 15833). Based on the results of phylogenetic analysis, was reclassified as member of a new genus gen. nov., comb. nov. The genera and form a separate clade, for which a novel family, fam. nov., is proposed.