Methylovulum miyakonense gen. nov., sp. nov., a type I methanotroph isolated from forest soil

Abstract

A novel methanotroph, designated strain HT12T, was isolated from forest soil in Japan. Cells of strain HT12T were Gram-reaction-negative, aerobic, non-motile, coccoid and formed pale-brown colonies. The strain grew only with methane and methanol as sole carbon and energy sources. Cells grew at 5–34 °C (optimum 24–32 °C). The strain possessed both particulate and soluble methane monooxygenases and assimilated formaldehyde using the ribulose monophosphate pathway. The major cellular fatty acids were C16 : 0 (46.9 %) and C14 : 0 (34.2 %), whereas unsaturated C16 fatty acids, typical of type I methanotrophs, were absent. Comparative 16S rRNA gene sequence analysis showed that the most closely related strains were Methylosoma difficile LC 2T (93.1 % sequence similarity) and Methylobacter tundripaludum SV96T (92.6 % similarity). Phylogenetic analysis based on the pmoA gene indicated that strain HT12T formed a distinct lineage within the type I methanotrophs and analysis of the deduced pmoA amino acid sequence of strain HT12T showed that it had a 7 % divergence from that of its most closely related species. The DNA G+C content was 49.3 mol%. Based on this evidence, strain HT12T represents a novel species and genus of the family Methylococcaceae, for which the name Methylovulum miyakonense gen. nov., sp. nov. is proposed. The type strain of the type species is HT12T ( = NBRC 106162T  = DSM 23269T  = ATCC BAA-2070T).