Characterization of Streptomyces sporangiiformans sp. nov., a Novel Soil Actinomycete with Antibacterial Activity against Ralstonia solanacearum

Ralstonia solanacearum is a major phytopathogenic bacterium that attacks many crops and other plants around the world. In this study, a novel actinomycete, designated strain NEAU-SSA 1(T), which exhibited antibacterial activity against Ralstonia solanacearum, was isolated from soil collected from Mount Song and characterized using a polyphasic approach. Morphological and chemotaxonomic characteristics of the strain coincided with those of the genus Streptomyces. The 16S rRNA gene sequence analysis showed that the isolate was most closely related to Streptomyces aureoverticillatus JCM 4347(T) (97.9%). Phylogenetic analysis based on 16S rRNA gene sequences indicated that the strain formed a cluster with Streptomyces vastus JCM4524(T) (97.4%), S. cinereus DSM43033(T) (97.2%), S. xiangluensis NEAU-LA29(T) (97.1%) and S. flaveus JCM3035(T) (97.1%). The cell wall contained LL-diaminopimelic acid and the whole-cell hydrolysates were ribose, mannose and galactose. The polar lipids were diphosphatidylglycerol (DPG), phosphatidylethanolamine (PE), hydroxy-phosphatidylethanolamine (OH-PE), phosphatidylinositol (PI), two phosphatidylinositol mannosides (PIMs) and an unidentified phospholipid (PL). The menaquinones were MK-9(H(4)), MK-9(H(6)), and MK-9(H(8)). The major fatty acids were iso-C(17:0), C(16:0) and C(17:1) ω9c. The DNA G+C content was 69.9 mol %. However, multilocus sequence analysis (MLSA) based on five other house-keeping genes (atpD, gyrB, recA, rpoB, and trpB), DNA–DNA relatedness, and physiological and biochemical data showed that the strain could be distinguished from its closest relatives. Therefore, it is proposed that strain NEAU-SSA 1(T) should be classified as representatives of a novel species of the genus Streptomyces, for which the name Streptomyces sporangiiformans sp. nov. is proposed. The type strain is NEAU-SSA 1(T) (=CCTCC AA 2017028(T) = DSM 105692(T)).