A thermophilic, methylotrophic methanogen, strain ZC-1T, was isolated from the Shengli oilfield, China. Cells of strain ZC-1Twere motile cocci, 0.7–1.0 μm in diameter and always occurred in clusters of two to four cells. Lysis-susceptibility experiments and analysis of transmission electron micrographs of strain ZC-1Tsuggested the presence of a proteinaceous cell wall. Strain ZC-1Tused methanol, methylamine and trimethylamine as substrates for methanogenesis. Optimal growth, with a doubling time of around 5 h, occurred at pH 6.0–6.5, 65 °C, 0.3–0.5 M NaCl and 0.05–0.20 M MgCl2. The DNA G+C content of this organism was 56 mol%. Analysis of 16S rRNA gene sequence and the inferred amino acid sequence of themcrAgene of strain ZC-1Tindicated that it is related specifically to members of the familyMethanosaetaceae(90.6 and 76.6 % sequence similarity, respectively). However, strain ZC-1Tfailed to grow with acetate as substrate for methanogenesis, which is a special characteristic of the familyMethanosaetaceae. Based on these phenotypic and phylogenic characteristics, strain ZC-1Tis proposed to represent a novel genus and species, for which the nameMethermicoccus shengliensisgen. nov., sp. nov. is proposed. The type strain is ZC-1T(=CGMCC 1.5056T=DSM 18856T).Methermicoccaceaefam. nov. is also proposed.
