Genomic and Metabolic Profiling of the Endophytic Streptomyces hygroscopicus OsiSh-2 for Protective Bacterial...

Beneficial endophytic bacteria play crucial roles in enhancing plant growth and are commonly utilized as probiotics. These effects are often mediated by bacterial natural products. In this study, we characterized the biosynthetic potential of Streptomyces hygroscopicus OsiSh-2, an endophytic species isolated from the rice leaf sheath. High-quality genome sequencing revealed 43 putative biosynthetic gene clusters (BGCs), suggesting substantial, yet unexploited, metabolic potential. By employing a one-strain-many-compounds (OSMAC) cultivation strategy, we identified 13 distinct structural scaffolds of natural products, with ten scaffolds directly correlated to known BGCs. These analyses led to the annotation of 82 metabolites. Functional validation further demonstrated that two ansamycin compounds exhibited significant protective and curative effects against rice bacterial leaf blight and wheat Fusarium crown rot. Our findings reveal the vast untapped potential of endophytic Streptomyces and highlight the need for a further comprehensive characterization of their chemical repertoire and associated ecological functions.