Methanomethylophilus alvi gen. nov., sp. nov., a Novel Hydrogenotrophic Methyl-Reducing Methanogenic Archaea of the Order Methanomassiliicoccales Isolated from the Human Gut and Proposal of the Novel Family Methanomethylophilaceae fam. nov.

The methanogenic strain Mx-05 T was isolated from the human fecal microbiome. A phylogenetic analysis based on the 16S rRNA gene and protein marker genes indicated that the strain is affiliated with the order Methanomassiliicoccales . It shares 86.9% 16S rRNA gene sequence identity with Methanomassiliicoccus luminyensis , the only member of this order previously isolated. The cells of Mx-05 T were non-motile cocci, with a diameter range of 0.4-0.7 μm. They grew anaerobically and reduced methanol, monomethylamine, dimethylamine, and trimethylamine into methane, using H 2 as an electron donor. H 2 /CO 2 , formate, ethanol, and acetate were not used as energy sources. The growth of Mx-05 T required an unknown medium factor(s) provided by Eggerthella lenta and present in rumen fluid. Mx-05 T grew between 30 °C and 40 °C (optimum 37 °C), over a pH range of 6.9-8.3 (optimum pH 7.5), and between 0.02 and 0.34 mol.L -1 NaCl (optimum 0.12 mol.L -1 NaCl). The genome is 1.67 Mbp with a G+C content of 55.5 mol%. Genome sequence annotation confirmed the absence of the methyl branch of the H 4 MPT Wood-Ljungdahl pathway, as described for other Methanomassiliicoccales members. Based on an average nucleotide identity analysis, we propose strain Mx-05 T as being a novel representative of the order Methanomassiliicoccales , within the novel family Methanomethylophilaceae , for which the name Methanomethylophilus alvi gen. nov, sp. nov. is proposed. The type strain is Mx-05 T (JCM 31474T).