Methanobacterium petrolearium sp. nov. and Methanobacterium ferruginis sp. nov., mesophilic methanogens isolated from salty environments Mori, Koji and Harayama, Shigeaki,, 61, 138-143 (2011), doi = https://doi.org/10.1099/ijs.0.022723-0, publicationName = Microbiology Society, issn = 1466-5026, abstract= Two methane-producing archaea, designated Mic5c12T and Mic6c05T, were isolated from sludge deposited in a crude oil storage tank and a tubercle on the interior of a pipe transporting natural gas-containing brine, respectively. The isolates were Gram-staining-variable, non-motile rods and grew only on H2/CO2. Strain Mic6c05T produced methane from some alcohols without showing any growth; strain Mic5c12T did not utilize alcohols. The optimum growth conditions for strain Mic5c12T were 35 °C, pH 6.5 and 0–0.68 M NaCl and for strain Mic6c05T were 40 °C, pH 6.0–7.5 and 0.34 M NaCl. Strain Mic5c12T was halotolerant and strain Mic6c05T was halophilic. Comparative 16S rRNA gene sequence analysis revealed that strains Mic5c12T and Mic6c05T belonged to the genus Methanobacterium and their closest relative was Methanobacterium subterraneum A8pT (97.3 and 97.9 % 16S rRNA gene sequence similarity, respectively). The findings from the 16S rRNA gene sequence analyses were supported by analysis of McrA, the alpha subunit of methyl-coenzyme M reductase. On the basis of phylogenetic analyses and phenotypic characteristics, two novel species are proposed, Methanobacterium petrolearium sp. nov. and Methanobacterium ferruginis sp. nov., with type strains Mic5c12T (=NBRC 105198T =DSM 22353T) and Mic6c05T (=NBRC 105197T =DSM 21974T), respectively., language=, type=