Streptomyces gilvus sp. nov., Actinomycete Isolated from Cassava (Manihot esculenta Crantz) Rhizosphere Soil.

A novel actinomycete designated CME 23 was isolated from cassava rhizosphere soil collected from Chon Buri province, Thailand. The strain was characterized using a polyphasic approach and classified as a member of the genus Streptomyces. Strain CME 23 formed spiral chains of non-motile cylindrical spores with a smooth surface developed on aerial mycelia. The cell wall peptidoglycan contained LL-diaminopimelic acid. Rhamnose, ribose, mannose, and glucose were found in its whole-cell hydrolysates. The predominant menaquinones were MK-9(H) and MK-9(H). The predominant fatty acids were iso-C, anteiso-C, and iso-C. The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannoside, and three unidentified phospholipids. The 16S rRNA gene sequence analysis indicated that strain CME 23 shared the highest sequence similarity with Streptomyces curacoi DSM 40107 (98.8%). The average amino acid identity (ANI) values and digital DNA-DNA hybridization (dDDH) values between the genome sequence of strain CME 23 and closest type strains of Streptomyces curacoi DSM 40107, Streptomyces cylindrosporus 7R015, and Streptomyces shaanxiensis CCNWHQ 0031, were 83.0-88.5% and 28.0-32.8%, respectively. The G + C content of the genome DNA was 71.1%. Based on comparative analyses of genotypic and phenotypic data, the actinomycete strain CME 23 (= TBRC 15810 = NBRC 115859) represents a novel Streptomyces species, for which the name Streptomyces gilvus sp. nov. is proposed. The in vitro assay showed that strain CME 23 produced IAA, siderophore, as well as solubilize phosphate and zinc.