Methanofollis fontis sp. nov., a methanogen isolated from marine sediment near a cold seep at Four-Way Closure Ridge offshore southwestern Taiwan

A mesophilic, hydrogenotrophic methanogen, strain FWC-SCC2^T, was isolated from deep-sea sediments collected by a real-time video multiple-corer at the C5-6 station near a cold seep at Four-Way Closure Ridge region during R/V Ocean Researcher III ORIII-1900 cruise in 2015. The cells were irregular cocci, non-motile and 0.8-1.2 µm in diameter. The methanogenic substrates utilized by strain FWC-SCC2^T were formate or H₂+CO₂, but not acetate, methanol, ethanol or methylamines. Strain FWC-SCC2^T was lysed in SDS (0.01 %, w/v). The M _r of surface-layer protein was 116 400. The optimum growth conditions of strain FWC-SCC2^T were 37 °C, 0.17 M NaCl and pH 6.7-7.0. The genomic DNA G+C content calculated from the genome sequence of strain FWC-SCC2^T was 59.5 mol %. Phylogenetic analysis revealed that strain FWC-SCC2^T was a member of the genus Methanofollis, and was most closely related to Methanofollis tationis Chile 9^T (97.6 % similarity of 16S rRNA gene sequence) and shared 97.4, 95.9, 95.9 and 95.4 % with Methanofollis liminatans GKZPZ^T, Methanofollis formosanus ML15^T, Methanofollis aquaemaris N2F9704^T and Methanofollis ethanolicus HASU^T, respectively. The genome relatedness values between strain FWC-SCC2^T and M. tationis DSM 2702^T were estimated by average nucleotide identity and digital DNA-DNA hybridization analyses and the results were 79.4 and 21.2 %, respectively. Based on the differences in physiological and biochemical properties, 16S rRNA gene phylogeny and genome relatedness presented here, it is suggested that strain FWC-SCC2^T represents a novel species of the genus Methanofollis, and the name Methanofollis fontis sp. nov. is proposed. The type strain is FWC-SCC2^T (=BCRC AR10052^T=DSM 107935^T= NBRC 113164^T).