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 H 2 +CO 2 , 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 ).