A mesophilic, methylotrophic methanogen, strain MobMT, was isolated from a natural gas field in Japan. Strain MobMT grew on methanol and methylamines, but not on H2/CO2, formate, acetate or dimethyl sulfide. The cells were motile, irregular cocci (diameter, 0.9–1.2 μm) and occurred singly, in pairs, as tetracocci or (occasionally) as aggregates. Strain MobMT grew at 9–37 °C (optimally at 30 °C) and at pH 6.1–7.8 (optimally at pH 6.5). Sodium and magnesium were required for growth, at 0.1–1.0 M Na+ (optimally at 0.35 M) and 10–400 mM Mg2+ (optimally at 15–25 mM). The G+C content of the genomic DNA was 42.4 mol%. 16S rRNA gene sequencing revealed that the isolate is a member of the genus Methanolobus, but distinct from its closest neighbours, Methanolobus tindarius DSM 2278T (sequence similarity, 98.0 %) and Methanolobus vulcani DSM 3029T (98.1 %). On the basis of phenotypic and phylogenetic features of MobMT, it is clear that this strain represents a novel species of the genus Methanolobus, for which the name Methanolobus profundi sp. nov. is proposed. The type strain is MobMT (=DSM 21213T=NBRC 104158T).
A novel methane-producing archaeon, designated strain HASUT, was isolated from a lotus field. Cells were Gram-negative, non-motile, irregular cocci, 2–3 μm in diameter, and occurred singly. Growth was observed at 15–40 °C (optimum, 37 °C) and pH 6.5–7.5 (optimum, pH 7.0). The G+C content of the genomic DNA was 60.9 mol%. Strain HASUT utilized ethanol, 1-propanol, 1-butanol, hydrogen and formate for growth and methane production. It converted ethanol to methane and acetate. Based on comparative 16S rRNA gene sequence analysis, strain HASUT was shown to be affiliated with the genus Methanofollis. It was related most closely to the type strain of Methanofollis liminatans (96.1 % 16S rRNA gene sequence similarity). Based on phylogenetic analysis and phenotypic characteristics, strain HASUT is considered to represent a novel species of the genus Methanofollis, for which the name Methanofollis ethanolicus sp. nov. is proposed. The type strain is HASUT (=NBRC 104120T=JCM 15103T=DSM 21041T).