Methanobacterium aridiramus sp. nov., a methanogen isolated from potential methane hydrate bearing area offshore southwestern Taiwan

A novel mesophilic, hydrogenotrophic methanogen, strain CWC-01^T, was isolated from the sediment sample of the piston core collected at station 3 at Good Weather Ridge area offshore southwestern Taiwan from ORI-902A cruise in 2009. Cells of strain CWC-01^T are rod-shaped, measuring 0.4–0.5 µm in width and 1.0–2.0 µm in length. Strain CWC-01^T utilizes formate and H₂/CO₂ to produce methane, but not secondary alcohol, methanol, ethanol, methylamines or acetate as catabolic substrates. The optimal growth conditions are 37 °C, 0.043 M NaCl and pH 6.3. Growth effectors tests indicate tryptone, but not acetate and yeast extract, could stimulate the growth of strain CWC-01. Phylogenetic analysis of 16S rRNA gene reveals that strain CWC-01^T is most closely related to Methanobacterium petrolearium Mic5c12^T, with 96.63% identity. Genome size of strain CWC-01^T is 1.98 Mb and it is the smallest genome size of genus. The genomic DNA G+C content obtained from the genome sequence of strain CWC-01^T is 44.15 mol%. Based on these phenotypic, phylogenetic and genomic analyses, we propose that strain CWC-01^T represents a novel species in genus Methanobacterium, for which the name Methanobacterium aridiramus sp. nov. is proposed. The type strain is CWC-01^T (=BCRC AR10053^T=NBRC 113991^T).