Abstract
An anaerobic, thermophilic methanogen, designated strain LWZ-6(T), was isolated from the Shengli oil field, China. The cells of strain LWZ-6(T) were non-motile cocci, with a diameter of 0.5-1.0 µm, and formed aggregates. They reduced methanol and monomethylamine into methane, using H(2) as an electron donor. Dimethylamine, trimethylamine and methanethiol, H(2)/CO(2), formate, acetate, pyruvate, lactate and glucose were not used as energy sources. Strain LWZ-6(T) required yeast extract, acetate or CO(2) as carbon sources. Strain LWZ-6(T) grew at 35-65 °C (optimum 55 °C), pH 5.0-8.0 (optimum 6.0-6.5) and 0-60 g l(-1) NaCl (optimum 9 g l(-1)). The genome was 1.54 Mbp with a G+C content of 54.42 mol%. Strain LWZ-6(T) shared 83.54% 16S rRNA gene sequence identity with Infirmifilum lucidum strain 3507LT(T) in the class Thermoprotei. Phylogenetic analysis based on the 16S rRNA gene, along with phylogenomic analysis, indicated that strain LWZ-6(T) belonged to the candidate class 'Candidatus Methanomethylicia', which lacks cultivated representatives. Based on these findings, a new species within a new genus, Methanosuratincola petrocarbonis gen. nov., sp. nov., is proposed for LWZ-6(T) (=CCAM 1872(T)=JCM 39528(T)). In addition, we propose the Methanosuratincolia class. nov. for candidate class 'Ca. Methanomethylicia' represented by Methanosuratincolaceae fam. nov. and Methanosuratincolales ord. nov. within the phylum Thermoproteota.