Alexander Fleming 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 1922 and the discovery of the antibiotic substance penicillin from the fungus Penicillium notatum in 1928, for which he shared the Nobel Prize in Physiology or Medicine in 1945 with Florey and Chain.