Bacillus methylotrophicus sp. nov., a methanol-utilizing, plant-growth-promoting bacterium isolated from rice rhizosphere soil

Abstract

A Gram-positive bacterium, designated strain CBMB205T, was isolated from the rhizosphere soil of traditionally cultivated, field-grown rice. Cells were strictly aerobic, motile, rod-shaped and formed endospores. The best growth was achieved at 30 °C and pH 7.0 in ammonium mineral salts (AMS) medium containing 600 mM methanol. A comparative 16S rRNA gene sequence-based phylogenetic analysis placed strain CBMB205T in a clade with the species Bacillus amyloliquefaciens, Bacillus vallismortis, Bacillus subtilis, Bacillus atrophaeus, Bacillus mojavensis and Bacillus licheniformis and revealed pairwise similarities ranging from 98.2 to 99.2 %. DNA–DNA hybridization experiments revealed a low level (<36 %) of DNA–DNA relatedness between strain CBMB205T and its closest relatives. The major components of the fatty acid profile were C15 : 0 anteiso, C15 : 0 iso, C16 : 0 iso and C17 : 0 anteiso. The diagnostic diamino acid of the cell wall was meso-diaminopimelic acid. The G+C content of the genomic DNA was 45.0 mol%. The lipids present in strain CBMB205T were diphosphatidylglycerol, phosphatidylglycerol, a minor amount of phosphatidylcholine and two unknown phospholipids. The predominant respiratory quinone was MK-7. Studies of DNA–DNA relatedness, morphological, physiological and chemotaxonomic analyses and phylogenetic data based on 16S rRNA gene sequencing enabled strain CBMB205T to be described as representing a novel species of the genus Bacillus, for which the name Bacillus methylotrophicus sp. nov. is proposed. The type strain is CBMB205T (=KACC 13105T=NCCB 100236T).