Vol. 7, Issue 5, Part A (2025)

Antibiotics are bioactive compounds that inhibit or eliminate bacterial growth and are widely applied in clinical, agricultural, and industrial settings. The first antibiotic, penicillin, was discovered in 1928 by Alexander Fleming, who observed that a mold (Penicillium notatum) inhibited the growth of Staphylococcus aureus. Since then, antibiotics have been extensively studied and employed to treat bacterial infections. Various environments—including soil, water, plants, animals, and fermented foods—serve as reservoirs for antibiotic-producing microorganisms. Among them, actinomycetes, particularly Streptomyces species, are prolific producers of structurally diverse antibiotics and have contributed thousands of secondary metabolites to the natural product repertoire. Marine ecosystems also represent an emerging and rich source of novel antibiotic-producing bacteria. Beyond their therapeutic applications, antibiotics play important ecological roles in microbial communities. They function as chemical weapons to inhibit competitors or deter predators and act as protective shields, enhancing microbial survival in competitive environments. Furthermore, antibiotics exhibit concentration-dependent behavior: at high concentrations, they act as growth inhibitors, while at subinhibitory levels, they may serve as signaling molecules involved in microbial communication and regulation. In soil and plant-associated environments, bacterial genera such as Bacillus, Pseudomonas, and Streptomyces have been shown to produce a variety of bioactive peptides with antimicrobial properties. These natural compounds play crucial roles in microbial fitness and environmental adaptability, making the study of antibiotic production central to both drug discovery and microbial ecology.