A novel strain of methanogenic archaea, designated MC-20T, was isolated from the anoxic sediment of a subsurface lake in Movile Cave, Mangalia, Romania. Cells were non-motile, Gram-stain-negative rods 3.5–4.0 µm in length and 0.6–0.7 µm in width, and occurred either singly or in short chains. Strain MC-20T was able to utilize H2/CO2, formate, 2-propanol and 2-butanol as substrate, but not acetate, methanol, ethanol, dimethyl sulfide, monomethylamine, dimethylamine or trimethylamine. Neither trypticase peptone nor yeast extract was required for growth. The major membrane lipids of strain MC-20T were archaeol phosphatidylethanolamine and diglycosyl archaeol, while archaeol phosphatidylinositol and glycosyl archaeol were present only in minor amounts. Optimal growth was observed at 33 °C, pH 7.4 and 0.08 M NaCl. Based on phylogenetic analysis of 16S rRNA gene sequences, strain MC-20T was closely affiliated with Methanobacterium oryzae FPiT (similarity 97.1 %) and Methanobacterium lacus 17A1T (97.0 %). The G+C content of the genomic DNA was 33.0 mol%. Based on phenotypic and genotypic differences, strain MC-20T was assigned to a novel species of the genus Methanobacterium for which the name Methanobacterium movilense sp. nov. is proposed. The type strain is MC-20T ( = DSM 26032T = JCM 18470T).
A psychrotolerant methanogenic strain, X-18T, was isolated from the soil of the Madoi wetland at Qinghai, Tibetan plateau, China. Cells were wavy rods (11–62 µm long) with blunt tapered ends and Gram-stain-negative. Strain X-18T grew strictly anaerobically and produced methane exclusively from H2/CO2. Growth occurred in the temperature range of 4–32 °C and optimally at 25 °C. Growth pH ranged from 6.5 to 8.0 and the optimum was 7.0. The G+C content of the genomic DNA of strain X-18T was 44.4 mol%. Phylogenetic analysis based on 16S rRNA gene sequences and the alpha subunit of methyl-coenzyme M reductase indicated that strain X-18T was affiliated to the genus Methanospirillum and was most closely related to Methanospirillum lacunae Ki8-1T, with 96.3 % 16S rRNA gene sequence similarity. However, strain X-18T could be distinguished from the existing species of the genus Methanospirillum by its lower growth temperature and obligate hydrogenotrophic methanogenesis. On the basis of phenotypic characteristics and phylogenetic analysis, strain X-18T represents a novel species of the genus Methanospirillum , for which the name Methanospirillum psychrodurum sp. nov. is proposed and strain X-18T is assigned as the type strain ( = CGMCC 1.5186T = JCM 19216T).