A novel actinomycete isolate, designated strain MK-45T, was isolated from soil sampled at a manganese-contaminated area in Xiangtan, China. The isolate formed extensively branched substrate mycelia and aerial mycelia that differentiated into tightly coiled or spiral spore chains with smooth-surfaced spores. The cell-wall hydrolysates contained ll-diaminopimelic acid and traces of meso-diaminopimelic acid. The major menaquinones consisted of MK-9(H4), MK-9(H6) and MK-9(H8). The major polar lipids contained diphosphatidylgycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphotidylinositol and phosphotidylinositol mannosides. The predominant cellular fatty acids were iso-C16 : 0, C16 : 0 and summed feature 3. Phylogenetic analysis based on the 16S rRNA gene sequences and concatenated partial sequences of the five protein-coding genes indicated that strain MK-45T was a member of the genus Streptomyces and most closely related to Streptomyces caeruleatus GIMN4.002T (99.5 % similarity), Streptomyces curacoi CGMCC 4.1680T (99.5 %), Streptomyces shaanxiensis CCNWHQ 0031T (99.4 %) and Streptomyces cinnabarinus NRRL B12382T (98.9 %), respectively. However, the digital DNA-DNA hybridization values, the average nucleotide identity values and MLSA evolutionary distances between strain MK-45T and them showed that it belonged to a distinct species. Furthermore, the results of morphological, physiological and biochemical tests allowed further phenotypic differentiation of strain MK-45T from the four closely related type strains mentioned above and other species of the genus Streptomyces with which this strain has 98.0-99.2 % 16S rRNA gene sequence similarity. Therefore, it is concluded that strain MK-45T represents a novel species of the genus Streptomyces, for which the name Streptomycescyaneochromogenes sp. nov. is proposed, with MK-45T (=CICC 11045T=KCTC 49099T) as the type strain.
Keywords: Streptomyces cyaneochromogenes sp. nov.; manganese-contaminated soil; polyphasic taxonomy.