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Today in History: Alexander Fleming discovers penicillin in his lab

9/28/2025

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Story summary

On September 28, 1928, Scottish biologist Alexander Fleming discovered penicillin after observing a mould, Penicillium rubens, that killed bacteria in his lab. This breakthrough led to the development of antibiotics, revolutionizing medicine and earning Fleming the Nobel Prize in Physiology or Medicine in 1945, shared with Howard Florey and Ernst Chain.

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Story summary

On September 28, 1928, Scottish biologist Alexander Fleming discovered penicillin after observing a mould, Penicillium rubens, that killed bacteria in his lab. This breakthrough led to the development of antibiotics, revolutionizing medicine and earning Fleming the Nobel Prize in Physiology or Medicine in 1945, shared with Howard Florey and Ernst Chain.