Methylacidiphilum kamchatkense gen. nov., sp. nov., an extremely acidophilic and moderately thermophilic methanotroph belonging to the phylum Verrucomicrobiota .

The thermo-acidophilic aerobic methanotrophic Verrucomicrobia bacterium, designated strain Kam1 ^T was isolated from an acidic geothermal mud spring in Kamchatka, Russia. Kam1 ^T is Gram-stain-negative, with non-motile cells and non-spore-forming rods, and a diameter of 0.45-0.65 µm and length of 0.8-1.0 µm. Its growth is optimal at the temperature of 55 °C (range, 37-60 °C) and pH of 2.5 (range, pH 1-6), and its maximal growth rate is ~0.11 h ^-1 (doubling time ~6.3 h). Its cell wall contains peptidoglycan with meso -diaminopimelic acid. In addition to growing on methane and methanol, strain Kam1 ^T grows on acetone and 2-propanol. Phylogenetically, it forms a distinct group together with other Methylacidiphilum strains and with the candidate genus Methylacidimicrobium as a sister group. These findings support the classification of the strain Kam1 ^T as a representative of a novel species and genus of the phylum Verrucomicrobiota . For this strain, we propose the name Methylacidiphilum kamchatkense sp. nov. as the type species within Methylacidiphilum gen. nov. Strain Kam1 ^T (JCM 30608 ^T =KCTC 4682 ^T ) is the type strain.