Sir Alexander Fleming (6 August 1881 – 11 March 1955) was a Scottish biologist and pharmacologist. Fleming published many articles on bacteriology, immunology, and chemotherapy. His best-known achievements are the discovery of the enzyme lysozyme in 1923 and the antibiotic substance penicillin from the fungus penicillium natatorium in 1928, for which he shared the Nobel Prize in Physiology or Medicine in 1945 with Howard Walter Florey and Ernst Boris Chain.
In 1999, Time Magazine named Fleming one of the 100 Most Important People of the 20th Century for his discovery of penicillin, and stated, “it was a discovery that would change the course of history. The active ingredient in that mold, which Fleming named penicillin, turned out to be an infection-fighting agent of enormous potency. When it was finally recognized for what it was-the most efficacious life-saving drug in the world-penicillin would alter forever the treatment of bacterial infections.