Taxonomic Characterization, and Secondary Metabolite Analysis of Streptomyces triticiradicis sp. nov.: A Novel Actinomycete with Antifungal Activity

The rhizosphere, an important battleground between beneficial microbes and pathogens, is usually considered to be a good source for isolation of antagonistic microorganisms. In this study, a novel actinobacteria with broad-spectrum antifungal activity, designated strain NEAU-H2T, was isolated from the rhizosphere soil of wheat (Triticum aestivum L.). 16S rRNA gene sequence similarity studies showed that strain NEAU-H2T belonged to the genus Streptomyces, with high sequence similarities to Streptomyces rhizosphaerihabitans NBRC 109807T (98.8%), Streptomyces populi A249T (98.6%), and Streptomyces siamensis NBRC 108799T (98.6%). Phylogenetic analysis based on 16S rRNA, atpD, gyrB, recA, rpoB, and trpB gene sequences showed that the strain formed a stable clade with S. populi A249T. Morphological and chemotaxonomic characteristics of the strain coincided with members of the genus Streptomyces. A combination of DNA&ndash
DNA hybridization results and phenotypic properties indicated that the strain could be distinguished from the abovementioned strains. Thus, strain NEAU-H2T belongs to a novel species in the genus Streptomyces, for which the name Streptomyces triticiradicis sp. nov. is proposed. In addition, the metabolites isolated from cultures of strain NEAU-H2T were characterized by nuclear magnetic resonance (NMR) and mass spectrometry (MS) analyses. One new compound and three known congeners were isolated. Further, genome analysis revealed that the strain harbored diverse biosynthetic potential, and one cluster showing 63% similarity to natamycin biosynthetic gene cluster may contribute to the antifungal activity. The type strain is NEAU-H2T (= CCTCC AA 2018031T = DSM 5775T).