Study On Population Diversity Of Actinomycete Isolated From Tibet Soil And Polyphasic Taxonomy Of Gordonia

156 actinomycetes were isolated from 10 Tibet soil samples using dispersion and differential centrifugation (DDC). More than 90 % were streptomycetes. The isolates were assigned to 6 different genera, Streptomyces, Norcardia, Micromonospora, Microbacterium , Pseudonocardia and Amycolatopsis by a combination of morphological and cultural features, components of cell-wall DAP, ARDRA patterns and analysis of 16S rRNA gene sequences. Antimicrobial activities of the representative strains were also tested, with the result that 38.5% isolates were positive.Strain SD29^T, isolated from farmland soil collected in Shandong Province, China, was subject to polyphasic taxonomic study. It was found to be a Gram-positive, aerobic, acid-fast actinomycete that fragmented into rod/coccus-like elements. Colonies werelight yellow, rough with irregular margin on ISP 2 agar. Hydrolysates of whole cell were composed of meso-DAP, arabinose and galactose. The principle menaquinone was MK-9 (H₂)f the polar lipids were PE, PI , DPG and PIMs. The mycolic acid possessed by the isolate was identical with that of Gordonia sihwensis DSM 44576 . A range of physiological characteristics were different between strain SD29^T and related type strains. Based on the 16S rRNA gene sequences analysis, strain SD29^T was closely related to the type strains of the genus Gordonia. It located in a monophyletic clade with G sihwensis DSM 44576^T and G hydrophobica DSM 44015^T in the neighbor-joining tree and shared the highest 16S rRNA gene sequence similarity values of 97.1 % and 97.0 %, respectively. According to the above results, strain SD29^T represents a novel taxonomic unit of the genus Gordonia and Gordonia shandongensis sp. nov. was proposed for this new taxon. The type strain is SD29^T (=AS 4.3492^T= JCM 13907^T) .