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

A halotolerant, psychrotolerant and methylotrophic methanogen, strain SY-01(T), was isolated from the saline Lake Tus in Siberia. Cells of strain SY-01(T) were non-motile, cocci and 0.8-1.0 mu m in diameter. The only methanogenic substrate utilized by strain SY-01(T) was methanol. The temperature range of growth for strain SY-01(T) was from 4 to 40 degrees C and the optimal temperature for growth was 30 degrees 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(T) was 43.6 mol% as determined by genome sequencing. Phylogenetic analysis revealed that strain SY-01(T) was most closely related to Methanolobus zinderi SD1(T) (97.3% 16S rRNA gene sequence similarity), and had 95.5-97.2 % similarities to other Methanolobus species with valid names. Genome relatedness between strain SY-01(T) and DSM 21339(T) was computed using average nucleotide identity and digital DNA-DNA-hybridization, 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(T) represents a novel species of the genus Methanolobus, and the name Methanolobus halotolerans sp. nov. is proposed. The type strain is SY-01(T) (=BCRC AR10051(T)=NBRC 113166(T)=DSM 107642(T)).