Methylomonas stagni sp. nov., a methanotroph of the genus Methylomonas, from a reservoir pond in Korea

A Gram-stain-negative, aerobic, motile, short rod-shaped methanotrophic bacterium, designated CM2^T, was isolated from a reservoir pond in Korea. Cells of strain CM2^T possessed a single polar flagellum, intracytoplasmic membrane stacks characteristic of type I methanotrophs, and contained electron-dense granules. The strain grew only on methane and methanol as carbon and energy sources. Growth occurred at 20-35 °C (optimum, 30 °C), pH 5.5-8.5 (optimum, 6.5) and with 0-0.5% (w/w) NaCl. Phylogenetic analysis based on the 16S rRNA gene sequence placed strain CM2^T within the genus <i>Methylomonas</i>, with sequence similarities to known species ranging from 94.5 to 98.3%. The major cellular fatty acids were C_16:1 and C_14:0, and the predominant respiratory quinone was ubiquinone-8. The genome of strain CM2^T is 5.06 Mb in size with a G+C content of 56.8 mol%. The digital DNA-DNA hybridization, average nucleotide identity and average amino acid identity values between the genome of strain CM2^T and those of <i>Methylomonas</i> species were 19.2-21.3 %, 73.5-77.5 % and 72.3-76.7 %, respectively. Genome analysis identified genes encoding two distinct particulate forms and one soluble form of methane monooxygenase. Based on a polyphasic characterization, strain CM2^T is considered to represent a novel species of <i>Methylomonas</i>, for which the name <i>Methylomonas stagni</i> sp. nov. is proposed. The type strain is CM2^T (KCTC 8468^T=JCM 36702^T).