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

Abstract

A Gram-positive bacterium, designated strain CBMB205(T), 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 CBMB205(T) 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 CBMB205(T) 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 CBMB205(T) 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 CBMB205(T) 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 CBMB205(T) (=KACC 13105(T)=NCCB 100236(T)).