The document discusses the history of antibiotics, including early contributors like Alexander Fleming who discovered penicillin in 1928 after unintentionally contaminating Staphylococcus aureus culture plates with Penicillium mold. It also discusses the rediscovery of penicillin by Florey, Abraham, Chain and Heatley in the 1940s and their work to mass produce it, allowing its effective use in World War II to prevent amputations and deaths. The majority of modern antibiotics are derived from the soil-dwelling bacteria Streptomyces, which produces them as secondary metabolites to compete with other species.