Microbispora clausenae sp. nov., an endophytic actinobacterium isolated from the surface-sterilized stem of a Thai medicinal plant, Clausena excavala Burm. f.

Abstract

An endophytic actinobacterium, strain CLES2T, was discovered from the surface-sterilized stem of a Thai medicinal plant, Clausena excavala Burm. f., collected from the Phujong-Nayoa National Park, Ubon Ratchathani Province, Thailand. The results of a polyphasic taxonomic study identified this strain as a member of the genus Microbispora and a Gram-stain-positive, aerobic actinobacterium. It had well-developed substrate mycelia, which were non-motile and possessed paired spores. A phylogenetic evaluation based on 16S rRNA gene sequence analysis placed this strain in the family Streptosporangiaceae , being most closely related to Microbispora bryophytorum NEAU-TX2-2T (99.4 %), Microbispora camponoti 2C-HV3T (99.2 %), Microbispora catharanthi CR1-09T (99.2 %) and Microbispora amethystogenes JCM 3021T and Microbispora fusca NEAU-HEGS1-5T (both at 99.1 %). The major cellular fatty acid of this strain was iso-C16 : 0 and major menaquinone was MK-9(H4). The polar lipid profile of strain CLES2T contained diphosphatidylglycerol, phosphatidylmethylethanolamine, phosphatidylinositol and phosphatidylinositol dimannosides. These chemotaxonomic data confirmed the affiliation of strain CLES2T to the genus Microbispora . The DNA G+C content of this strain was 70 mol%. Digital DNA–DNA hybridization and average nucleotide identity blast values between strain CLES2T and M. catharanthi CR1-09T were 62.4 and 94.0 %, respectively. The results of the polyphasic study allowed the genotypic and phenotypic differentiation of strain CLES2T from its closest species with valid names. The name proposed for the new species is Microbispora clausenae sp. nov. The type strain is CLES2T (=DSM 101759T=NRRL B-65340T).