sp. nov., isolated from the saline Lake Tus in Siberia.

A halotolerant, psychrotolerant and methylotrophic methanogen, strain SY-01, was isolated from the saline Lake Tus in Siberia. Cells of strain SY-01 were non-motile, cocci and 0.8-1.0 µm in diameter. The only methanogenic substrate utilized by strain SY-01 was methanol. The temperature range of growth for strain SY-01 was from 4 to 40 °C and the optimal temperature for growth was 30 °C. The pH range of growth was from pH 7.2 to 9.0, with optimal growth at pH 8.0. The NaCl range of growth was 0-1.55 M with optimal growth at 0.51 M NaCl. The G+C content of the genome of strain SY-01 was 43.6 mol % as determined by genome sequencing. Phylogenetic analysis revealed that strain SY-01 was most closely related to SD1 (97.3 % 16S rRNA gene sequence similarity), and had 95.5-97.2 % similarities to other species with valid names. Genome relatedness between strain SY-01 and DSM 21339 was computed using average nucleotide identity and digital DNA-DNAhybridization, which yielded values of 79.7 and 21.7 %, respectively. Based on morphological, phenotypic, phylogenetic and genomic relatedness data presented here, it is evident that strain SY-01 represents a novel species of the genus , and the name sp. nov. is proposed. The type strain is SY-01 (=BCRC AR10051=NBRC 113166 =DSM 107642).