Methanococcoides mangrovi sp. nov. and Methanococcus mangrovi sp. nov., two novel methanogens isolated from mangrove sediments

Two novel methanogens, designated strains FTZ1 T and CF T , were isolated from mangrove sediment and from a magnetite-amended enrichment derived from the same sediment, respectively, collected from the Futian Mangrove Nature Reserve, Shenzhen, China. Strain FTZ1 T utilized methanol, trimethylamine, dimethylamine, monomethylamine and glycine betaine as substrates for growth and methane production, while strain CF T grew on H 2 /CO 2 and formate. Cells of both strains were irregular cocci, with diameters of 0.5–1.3 µm for strain FTZ1 T and 0.5–1.2 µm for strain CF T . Using methanol as the substrate, strain FTZ1 T grew at 20–42 °C (optimum 37 °C), pH 5.5–8.0 (optimum 7.5) and 0–0.85 M NaCl (optimum 0.34 M NaCl). Strain CF T grew at 20–45 °C (optimum 33–37 °C), pH 6.0–8.5 (optimum 7.3) and 0–0.62 M NaCl (optimum 0.10–0.21 M NaCl) when growing on H 2 /CO 2 . The genomic G+C contents are 44.4 mol% for strain FTZ1 T and 33.4 mol% for strain CF T . Phylogenetic analyses showed that strain FTZ1 T belongs to the genus Methanococcoides , sharing 85.20% average nucleotide identity (ANI) and 29.4% digital DNA–DNA hybridization (dDDH) with its closest relative Methanococcoides cohabitans LMO-2 T . Strain CF T is assigned to the genus Methanococcus , exhibiting 88.52% ANI and 35.3% dDDH with its closest relative Methanococcus maripaludis JJ T . Based on phenotypic and phylogenetic evidence, two novel species are proposed: Methanococcoides mangrovi sp. nov. (type strain FTZ1 T =CCAM 1318 T =JCM 39395 T ) and Methanococcus mangrovi sp. nov. (type strain CF T =CCAM 2191 T =JCM 39555 T ).