Microbispora siamensis sp. nov., a thermotolerant actinomycete isolated from soil.

An actinomycete, strain DMKUA 245(T), isolated from soil, was investigated using a polyphasic approach. The isolate formed longitudinally paired spores on the tips of short sporophores that branched alternately from aerial hyphae. The morphological and chemotaxonomic properties clearly demonstrated that the new isolate belonged to the genus Microbispora. 16S rRNA gene sequence analysis supported the assignment of the novel strain to the genus Microbispora. The gene sequence similarity values between the novel strain and the closely related species Microbispora corallina, Microbispora rosea subsp. rosea, Microbispora rosea subsp. aerata and Microbispora amethystogenes were 98.4 %, 97.4 %, 97.0 % and 96.9 %, respectively. The DNA-DNA hybridization values and some physiological and biochemical properties indicated that strain DMKUA 245(T) could be distinguished from its phylogenetically closest relatives. Based on these genotypic and phenotypic data, strain DMKUA 245(T) represents a novel species in the genus Microbispora for which the name Microbispora siamensis sp. nov. is proposed. The type strain is strain DMKUA 245(T) (=BCC 14407(T)=NBRC 104113(T)). In addition, DNA-DNA relatedness values in reciprocal hybridization experiments showed that M. amethystogenes was a separate genomic species from M. rosea subsp. rosea. A combination of genotypic and phenotypic data supported the classification of M. amethystogenes as a separate species.