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

Abstract

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-H2^T, was isolated from the rhizosphere soil of wheat (<i>Triticum aestivum</i> L.). 16S rRNA gene sequence similarity studies showed that strain NEAU-H2^T belonged to the genus <i>Streptomyces</i>, with high sequence similarities to <i>Streptomyces rhizosphaerihabitans</i> NBRC 109807^T (98.8%), <i>Streptomyces populi</i> A249^T (98.6%), and <i>Streptomyces siamensis</i> NBRC 108799^T (98.6%). Phylogenetic analysis based on 16S rRNA, <i>atpD</i>, <i>gyrB</i>, <i>recA</i>, <i>rpoB</i>, and <i>trpB</i> gene sequences showed that the strain formed a stable clade with <i>S. populi</i> A249^T. Morphological and chemotaxonomic characteristics of the strain coincided with members of the genus <i>Streptomyces</i>. A combination of DNA-DNA hybridization results and phenotypic properties indicated that the strain could be distinguished from the abovementioned strains. Thus, strain NEAU-H2^T belongs to a novel species in the genus <i>Streptomyces</i>, for which the name <i>Streptomyces triticiradicis</i> sp. nov. is proposed. In addition, the metabolites isolated from cultures of strain NEAU-H2^T 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-H2^T (= CCTCC AA 2018031^T = DSM 109825^T).