Harnessing Streptomyces sp. for Novel Antibiotics: Optimization, SEM Characterization, and Broad-Spectrum Activity

Document Type : Original Article

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Botany and Microbiology Department, Faculty of Science, Menoufia University, Menoufia, Egypt.

Abstract

The growing threat of antimicrobial resistance necessitates the discovery of novel bioactive compounds, and Streptomyces species remain a promising source of antimicrobial metabolites. This study investigated the antimicrobial potential of Streptomyces sp. against six pathogenic microorganisms (Escherichia coli, Salmonella typhi, Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans, and Penicillium marneffei). Optimal culture conditions were systematically determined by evaluating growth media, carbon/nitrogen sources, pH, temperature, and incubation periods. The modified nutrient medium exhibited superior performance, yielding the largest inhibition zones against all tested pathogens (27.3 mm for S. aureus, 27.0 mm for C. albicans, and 25.3 mm for S. typhi). Starch and NaNO₃ were identified as the most effective carbon and nitrogen sources, respectively, while neutral pH (7.0) and 25°C incubation temperature maximized antimicrobial production. Time-course experiments revealed peak activity after 8 days of cultivation. Cell-free supernatant (CFS) demonstrated dose-dependent efficacy, with 80% concentration achieving 94.7% inhibition against S. aureus and 91.48% against P. marneffei. Scanning electron microscopy (SEM) revealed severe ultrastructural damage in treated pathogens, including cell wall degradation and hyphal collapse, suggesting membrane-targeted mechanisms. These findings highlight the strain's broad-spectrum antimicrobial activity and its potential as a source of novel bioactive compounds, underscoring the vital role of actinomycetes in addressing contemporary health challenges. 

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