Methylomonas koyamae sp. nov., a type I methane-oxidizing bacterium from floodwater of a rice paddy field

Abstract

A novel methane-oxidizing bacterium, strain Fw12E-YT, was isolated from floodwater of a rice paddy field in Japan. Cells of strain Fw12E-YT were Gram-negative, motile rods with a single polar flagellum and type I intracytoplasmic membrane arrangement. The strain grew only on methane or methanol as sole carbon and energy source. It was able to grow at 10–40 °C (optimum 30 °C), at pH 5.5–7.0 (optimum 6.5) and with 0–0.1 % (w/w) NaCl (no growth above 0.5 % NaCl). 16S rRNA gene sequence analysis showed that strain Fw12E-YT is related most closely to members of the genus Methylomonas , but at low levels of similarity (95.0–95.4 %). Phylogenetic analysis of pmoA and mxaF genes indicated that the strain belongs to the genus Methylomonas (97 and 92 % deduced amino acid sequence identities to Methylomonas methanica S1T, respectively). The DNA G+C content of strain Fw12E-YT was 57.1 mol%. Chemotaxonomic data regarding the major quinone (MQ-8) and major fatty acids (C16 : 1 and C14 : 0) also supported its affiliation to the genus Methylomonas . Based on phenotypic, genomic and phylogenetic data, strain Fw12E-YT is considered to represent a novel species of the genus Methylomonas , for which the name Methylomonas koyamae sp. nov. is proposed. The type strain is Fw12E-YT ( = JCM 16701T = NBRC 105905T = NCIMB 14606T).