During an investigation exploring potential sources of novel thermophilic species and natural products, a novel thermophilic and alkaliphilic actinomycete with alkaline cellulase producing ability, designated strain 4-2-13T, was isolated from soil of a tropical rainforest in Xishuangbanna, Yunnan province, China. The morphological and chemotaxonomic characteristics of strain 4-2-13T are consistent with those of the members of the genus Streptomyces. The strain forms extensively branched aerial mycelia and substrate mycelia. Spiral spore chains were observed on aerial mycelia; spores were oval to cylindrical, with smooth surfaces. The organism was found to contain LL-diaminopimelic acid as the diagnostic diamino acid in the cell wall peptidoglycan. The whole cell hydrolysates were found to contain glucose and ribose. The cellular fatty acid profile mainly consists of anteiso-C17:0 and iso-C16:0. The menaquinones were identified as MK-9(H8), MK-10(H6) and MK-9(H6). The polar lipids profile were found to consist of diphosphatidylglycerol, phosphatidylmethylethanolamine, a ninhydrin-positive glycophospholipid, phosphatidylinositol, phosphatidylglycerol and unidentified glycolipids. The 16S rRNA gene sequence analysis showed that the organism belongs to the genus Streptomyces and in the 16S rRNA gene tree it formed a distinct phyletic line together with the closely related type strain Streptomyces burgazadensis Z1R7T (95.2% sequence similarity). However, the phenotypic characteristics of strain 4-2-13T are significantly different from those of S. burgazadensis Z1R7T. Based on the phenotypic, chemotaxonomic and phylogenetic characteristics, strain 4-2-13T represents a novel species in the genus Streptomyces, for which the name Streptomyces thermoalkaliphilus sp. nov. is proposed. The type strain is 4-2-13T (= DSM 42159T = CGMCC 4. 7205T).
Keywords: 16S rRNA gene; Alkaline cellulase; Polyphasic taxonomy; Streptomyces thermoalkaliphilus sp. nov..