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

An endophytic actinobacterium, strain CLES2^T, was discovered from the surface-sterilized stem of a Thai medicinal plant, Clau-sena 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-TX2-2^T (99.4%), Microbispora camponoti 2C-HV3^T (99.2%), Microbispora catharanthi CR1-09^T (99.2%) and Microbispora amethystogenes JCM 3021^T and Microbispora fusca NEAU-HEGS1-5^T (both at 99.1%). The major cellular fatty acid of this strain was iso-C_16:0 and major menaquinone was MK-9(H₄). The polar lipid profile of strain CLES2^T contained diphosphatidylglycerol, phosphatidylmethylethanolamine, phosphatidylinositol and phosphatidylinositol dimannosides. These chemotaxonomic data confirmed the affiliation of strain CLES2^T 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 CLES2^T and M. catharanthi CR1-09^T were 62.4 and 94.0%, respectively. The results of the polyphasic study allowed the genotypic and phenotypic differentiation of strain CLES2^T from its closest species with valid names. The name proposed for the new species is Microbispora clausenae sp. nov. The type strain is CLES2^T (=DSM 101759^T=NRRL B-65340^T).