<i>Methanosarcina baikalica</i> sp. nov., a new methanogenic archaea isolated from surface bottom sediments of Lake Baikal

A new methane-forming archaeon strain Z-7115T was isolated from the bottom sediments of the freshwater Lake Baikal (Eastern Siberia, Russia). Morphologically, the strain is represented by non-motile coccoid cells 0.5–3 µm in size, collected in packets of 2–4 and their small aggregates. The strain uses methanol, mono-, di-, trimethylamine and acetate as energy substrates for methanogenesis. The cells grow at a temperature of 15–35°C (optimum 25°C), pH 6.3–7.5 (optimum pH 7.3) and are tolerant to NaCl concentrations 0.1 M. The G + C content of genomic DNA is 40.76 mol. %. According to the 16S rRNA gene analysis, the new isolate belongs to the genus Methanosarcina, having a similarity level of 98.51% with the closest species of this genus M. siciliae T4/MT . The average nucleotide similarity (ANI) between the genomes of strains Z-7115T and M. siciliae T4/MT was 83.8%. The virtual assessment of the hybridization of the genomes of these two strains was 23.3%. Based on the data of phylogenetic analysis and morpho-physiological properties, it is proposed to classify the isolated strain Z-7115T (=JCM 39438, =VKM B-3565) as a new species Methanosarcina baikalica sp. nov.