What are the sources of many antibiotics are in chemicals produced by?

Many antibiotics are derived from natural compounds produced by microorganisms, particularly bacteria and fungi. For example, penicillin, one of the first discovered antibiotics, is produced by the mold Penicillium. Other antibiotics, such as streptomycin and tetracycline, are derived from soil-dwelling bacteria like Streptomyces. These microorganisms synthesize these chemicals as part of their survival mechanisms, often to inhibit the growth of competing bacteria.