A novel methylotrophic methanogen Methanococcoides orientis sp. nov. was isolated from East China Sea sediment. Type strain LMO-1^T of Methanococcoides orientis sp. nov. was irregular 1-2 µm cocci without flagella. Strain LMO-1^T could utilize a variety of methylated compounds including methanol, methylamine, dimethylamine and trimethylamine for growth and methanogenesis, while H₂/CO₂ or acetate could not be used for growth or methanogenesis. Optimum growth temperature was 30-35 °C, optimum pH range for growth was 7.0-7.5, while the optimum salinity spectrum for growth was 1.0%-5.0% NaCl. Based on 16S rRNA gene similarity, strain LMO-1^T belongs to Methanococcoides, with the highest sequence similarity to Methanococcoides methylutens DSM 2657^T (99.8 %), Methanococcoides vulcani SLH33^T(99.4 %), followed by Methanococcoides alaskense AK-5^T(98.1 %), Methanococcoides burtonii DSM 6242^T (98.0 %). Digital DNA-DNA hybridization also showed highest similarity with Methanococcoides methylutens DSM 2657^T, with the value of 58.4 %. The average nucleotide identity between strain LMO-1^T and Methanococcoides methylutens DSM 2657^T was 94.06 %. In summary, LMO-1^T represents a novel species of the genus Methaococcoides, for which the name Methanococcoides orientis sp. nov. is proposed. The type strain is LMO-1^T (=MCCC 4K00106^T=JCM 39195^T).

Yijing Dong

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