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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 H 2 /CO 2 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 ).