Brachybacterium endophyticum sp. nov., a novel endophytic actinobacterium isolated from bark of Scutellaria baicalensis Georgi.

Abstract

A Gram-positive, aerobic, coccus-shaped, non-spore-forming actinobacterium, designated strain M1HQ-2T, was isolated from a surface-sterilized bark of Scutellaria baicalensis Georgi collected from Guizhou, China and tested using a polyphasic approach to determine its taxonomic position. Strain M1HQ-2T grew at 4-37 °C (optimum, 30 °C), pH 5.0-11.0 (pH 8.0) and in the presence of 0-15 % (w/v) NaCl (1-3 %). Substrate mycelia and aerial mycelia were not formed, and diffusible pigments were not observed on any media tested. Phylogenetic analysis based on 16S rRNA gene sequence indicated that strain M1HQ-2T belonged to the genus Brachybacterium and had the highest 16S rRNA gene sequence similarity of 97.6 % to Brachybacteriumsquillarum M-6-3T. Strain M1HQ-2T contained MK-7 as the dominant menaquinone. The cell-wall peptidoglycan contained meso-diaminopimelic acid. The polar lipids profile of strain M1HQ-2T contained diphosphatidylglycerol, phosphatidylglycerol, an unidentified phospholipid and an unidentified lipid. The predominant fatty acids were anteiso-C15 : 0 and anteiso-C17 : 0. The DNA G+C content of strain M1HQ-2T was 71.0 mol%. The average nucleotide identity value between strain M1HQ-2T and type strain of Brachybacterium sacelli was 76.7 %. The estimated DNA-DNA hybridization value between strain M1HQ-2T and type strain of B. sacelli was 20.6 %. On the basis of phylogenetic analysis, chemotaxonomic characteristics and phenotypic data, strain M1HQ-2T represents a novel species of the genus Brachybacterium, for which the name Brachybacteriumendophyticum sp. nov. is proposed. The type strain is M1HQ-2T (=KCTC 49087T=CGMCC 1.16391T).