Phenotypic and Genomic Characterization of Streptomyces sp. HR58 Reveals Its Potential Against Fungal Phytopathogens

Streptomyces sp. HR58, isolated from the hop rhizosphere, exhibits antifungal activity against a variety of fungal phytopathogens affecting many crops. HR58 was characterized using phenotypic and genomic approaches. Growth tolerance and enzymatic activities were assessed, and whole-genome sequencing enabled the prediction of biosynthetic gene clusters. The strain HR58 displayed morphological and biochemical traits characteristic of the genus Streptomyces, growing from pH 5 to pH 12 and salt tolerance up to 5% NaCl. Genome analysis revealed a size of 8,270,372 bp with a GC content of 71.76% and the presence of gene clusters associated with antifungal activity. Although ANI analysis showed 96.6% identity with Streptomyces anulatus ATCC 11523, the dDDH value of 66.5% fell below the species delineation threshold of 70%, indicating that HR58 cannot be confidently assigned to any currently described Streptomyces species. A biosynthetic gene cluster encoding the antifungal compound cycloheximide was identified in its genome, and cycloheximide production was assessed in liquid cultures. Silver nanoparticle (AgNP) biosynthesis by strain HR58 was also confirmed, and its antimicrobial activity was evaluated. The ability of strain HR58 to biosynthesize antifungal nanoparticles further enhances its potential applications in sustainable agriculture, offering a promising alternative for the development of eco-friendly plant disease control strategies.