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

A novel methane-oxidizing bacterium, strain Fw12E-Y-T, was isolated from floodwater of a rice paddy field in Japan. Cells of strain Fw12E-Y-T 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 degrees C (optimum 30 degrees 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-Y-T 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 S1(T), respectively). The DNA G+C content of strain Fw12E-Y-T was 57.1 mol%. Chemotaxonomic data regarding the major quinone (MQ-8) and major fatty acids (C-16:1 and C-14:0) also supported its affiliation to the genus Methylomonas. Based on phenotypic, genomic and phylogenetic data, strain Fw12E-Y-T 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-Y-T (=JCM 16701(T)= NBRC 105905(T)= NCIMB 14606(T)).