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 notatum in 1928, for which he shared the Nobel Prize in Physiology and Medicine in 1945 with Howard W. Florey and Ernst B. Chain.