Methanosarcina baikalica sp. nov. a New Methanogenic Archaeon Isolated from Surface Bottom Sediments of Lake Baikal

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