Methanosarcina subterranea sp nov., a methanogenic archaeon isolated from a deep subsurface diatomaceous shale formation

A methanogenic archaeon, strain HC-2(T), was isolated from a deep diatomaceous shale formation. The strain grew on methanol, monomethylamine, dimethylamine, trimethylamine and dimethylsulphide, but not on acetate, H-2/CO2, formate, 2-propanol, 2-butanol or cyclopentanol. Cells were Gram-stain-negative, non-motile, and coccus-like, 0.9-1.4 mu m in diameter, and occurred singly, in pairs, or as aggregates. The strain grew at 10-40 degrees C (optimum 35 degrees C), pH 5.9-7.4 (optimum pH 6.6-6.8) and in 0-0.6 M NaCl (optimum 0.1-0.2 M). The genomic DNA G 1-C content was 41.5 mol% and the 16S rRNA gene sequence was closely related to those of Methanosarcina lacustris DSM 13486(T) (99.1%) and Methanosarcina siciliae DSM 3028(T) (98.3 %). Values for DNA DNA hybridization with these strains were less than 30%. The phenotypic and phylogenetic features of HC-2(T) indicate that it represents a novel species of the genus Methanosarcina, for which the name Methanosarcina subterranea sp. nov. is proposed. The type strain is HC-2(T) (=DSM 22503(T)=JCM 15540(T)=NBRC 102578(T)).