Methanospirillum psychrodurum sp nova, isolated from wetland soil

A psychrotolerant nnethanogenic strain, X-18(T), was isolated from the soil of the Madoi wetland at Qinghai, Tibetan plateau, China. Cells were wavy rods (11-62 mu m long) with blunt tapered ends and Gram-stain-negative. Strain X-18(T) grew strictly anaerobically and produced methane exclusively from H-2/CO2. Growth occurred in the temperature range of 4-32 degrees C and optimally at 25 degrees 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-18(T) was 44.4 mol%. Phylogenetic analysis based on 165 rRNA gene sequences and the alpha subunit of methyl-coenzyme M reductase indicated that strain X-18(T) 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-18(T) 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-18(T) represents a novel species of the genus Methanospirillum, for which the name Methanospirillum psychrodurum sp. nov. is proposed and strain X-18(T) is assigned as the type strain (=CGMCC 1.5186(T)=JCM 19216(T)).