Methanoculleus bovis sp. nov., a New Methanogenic Hydrogen-Utilizing Archaeon from the Cow Rumen

A new methanogenic archaeon (strain 7T T ) was isolated from the content of the bovine rumen (Moscow region, Russia). Morphologically, the strain has nonmotile coccoid irregularly shaped cells, 1.3–4.3 μm cells, single or in small aggregates. The strain exclusively utilizes the hydrogen—carbon dioxide mixture as the energy substrate for methanogenesis and requires the presence of acetate in the cultivation medium. The cells grow at a temperature of 20–53°С (optimally at 45°С) and a рН value of 6.5–7.8 (the optimal рН 7.2–7.4); they are tolerant to NaCl at concentrations up to 0.34 М. Based on the 16S rRNA sequencing data, the new methanogen belongs to the genus Methanoculleus and reveals 98.16% similarity with the closest species of this genus, M. bourgensis MS2 Т . The average nucleotide identity (ANI) between the genomes of strains 7T Т and M. bourgensis MS2 Т was 88.24%, and the virtual estimate of hybridization of the genomes of these two strains was 31.40%. The G+C content of the genomic DNA was 65.27 mol %. Based on the data of phylogenetic analysis and the physiological and biochemical properties of the isolate, it is suggested that the isolated strain 7T T (=VKM B-3409 T = JCM 39547 T ) belongs to the new species Methanoculleus bovis sp. nov.