Methylogaea oryzae gen. nov., sp nov., a mesophilic methanotroph isolated from a rice paddy field

A novel methanotroph, designated strain E10(T), was isolated from a rice paddy field in Uruguay. Strain E10(T) grew on methane and methanol as sole carbon and energy sources. Cells were Gram-negative, non-motile, non-pigmented, slightly curved rods showing type I intracytoplasmic membranes arranged in stacks. The strain was neutrophilic and mesophilic; optimum growth occurred at 30-35 degrees C with no growth above 37 degrees C. The strain possessed only a particulate methane monooxygenase (pmoA). Phylogenetic analysis based on 16S rRNA gene sequences indicated that the strain was most closely related to the moderately thermophilic strains Methylocaldum szegediense OR2(T) (91.6% sequence similarity) and Methylococcus capsulatus Bath (91.5%). Comparative sequence analysis of pmoA genes also confirmed that strain E10(T) formed a new lineage among the genera Methylocaldum and Methylococcus with 89 and 84% derived amino acid sequence identity to Methylococcus capsulatus Bath and Methylocaldum gracile VKM-14L(T), respectively. The DNA G+C content was 63.1 mol% and the major cellular fatty acid was C-16:0 (62.05 %). Thus, strain E10(T) (=JCM 16910(T) =DSM 23452(T)) represents the type strain of a novel species within a new genus, for which the name Methylogaea oryzae gen. nov., sp. nov. is proposed.