Methanolobus mangrovi sp. nov. and Methanolobus sediminis sp. nov, two novel methylotrophic methanogens isolated from mangrove sediments in China

Two methylotrophic methanogens, designated strains FTZ2 T and FTZ6 T , were isolated from mangrove sediment sampled in Futian Mangrove Nature Reserve in Shenzhen, PR China. Cells of strains FTZ2 T and FTZ6 T were cocci, with diameters of 0.6–1.0 µm and 0.6–0.9 µm, respectively. Both strains grew on methanol, methylamine, dimethylamine and trimethylamine, but not on acetate, formate, H 2 /CO 2 , choline, betaine or dimethyl sulphide. Strain FTZ2 T grew at 10–37 °C (optimally at 33 °C), pH 5.5–8.0 (optimally at pH 7.0) and 0–1.03 M NaCl (optimally at 0.17 M NaCl). In contrast, strain FTZ6 T grew at 15–42 °C (optimally at 37 °C), pH 5.0–7.5 (optimally pH 6.5) and 0–1.03 M NaCl (optimally at 0.17 M NaCl). Both strains required magnesium for growth and were susceptible to sodium dodecyl sulphate. Biotin was required for the growth of strain FTZ2 T but not of strain FTZ6 T . The genomic G+C contents of strains FTZ2 T and FTZ6 T were 41.6 and 40.9 mol%, respectively. Phylogenetic analyses revealed that strain FTZ2 T was mostly related to Methanolobus psychrotolerans YSF-03 T , with 16S rRNA gene similarity of 98.6 %, an average nucleotide identity (ANI) of 82.5 %, and a digital DNA–DNA hybridization (dDDH) of 24.6 %. While strain FTZ6 T was mostly related to Methanolobus vulcani PL-12/M T , with 16S rRNA gene similarity of 99.4 %, an ANI of 88.6% and a dDDH of 34.6 %. Based on phenotypic, phylogenetic and genotypic evidence, two novel species of the genus Methanolobus , Methanolobus mangrovi sp. nov. and Methanolobus sediminis sp. nov., are proposed. The type strain of M. mangrovi sp. nov. is FTZ2 T (=CCAM 1276 T =JCM 39396 T ) and the type strain of M. sediminis sp. nov. is FTZ6 T (=CCAM 1277 T =JCM 39397 T ).