Methylophilus rhizosphaerae sp. nov., a restricted facultative methylotroph isolated from rice rhizosphere soil.

Three facultative methylotrophic bacterial strains, designated CBMB127(T), CBMB145 and CBMB147, were isolated from the rhizosphere soil of rice and characterized. The strains produced indole-3-acetic acid and siderophores, had 1-aminocyclopropane-1-carboxylate deaminase activity and sulfur oxidation property and also methanol dehydrogenase. Phylogenetic analysis based on the 16S rRNA and methanol dehydrogenase (mxaF) gene sequences showed that Methylophilus methylotrophus was their close relative. The results of the phenotypic, phylogenetic and genotypic analyses showed that strains CBMB127(T) and CBMB145, with 99.4 % 16S rRNA gene sequence similarity and 99 % DNA-DNA hybridization, could be distinguished from recognized species of Methylophilus. Therefore strain CBMB127(T) and CBMB145 are considered to represent a novel species of Methylophilus, for which the name Methylophilus rhizosphaerae sp. nov. is proposed, with CBMB127(T) (=KACC 13099(T)=NCCB 100233(T)) as the type strain. Strain CBMB147 represents a novel strain of the species Methylophilus methylotrophus.