Viruses, Bacteria, Protists, and Fungi

How was it discovered that microorganisms are effective against bacterial infections?

British microbiologist Alexander Fleming (1881–1955) happened upon the discovery of penicillin’s use as an antibacterial agent. In 1928 Fleming was researching staphylococci at St. Mary’s Hospital in London. As part of his investigation, he had spread staphylococci on several Petri dishes before going on vacation. Upon his return he noticed a green-yellow mold contaminating one of the Petri dishes. The staphylococci had failed to grow near the mold. He identified the mold as being of the species of Penicillium notatum. Further investigation proved that the staphylococci and other Gram-positive organisms are killed by P. notatum. It was not until the 1940s that Howard Florey (1898–1968) and Ernst Boris Chain (1906–1979) rediscovered penicillin and were able to isolate it for medical use. In 1945 Fleming, Florey, and Chain shared the Nobel Prize in Physiology or Medicine for their work on penicillin.


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