Today is the birthday of Alexander Fleming, a Scottish bacteriologist born in 1881 who accidentally discovered the antibiotic penicillin, one of the most important medicines of the 20th century. A strange and rare mold, Penicillium notatum, happened to be floating around in Fleming's lab because another researcher was studying it. Luckily, Fleming had the untidy habit of keeping his bacterial plates longer than usual, and when he returned from a weeklong vacation in 1928, he discovered the mold growth. He determined that a compound produced by the mold, which he called penicillin, could kill pathogenic bacteria, but not white blood cells or human tissue. The finding lay dormant until 1940, when chemists Ernst Chain and Howard Florey isolated, purified, and tested the antibiotic in clinical trials. Fleming, Chain, and Florey were subsequently awarded the 1945 Nobel Prize in medicine.
[Source: Emily McMurray, Ed. Notable Twentieth Century Scientists (Gale Research Inc., ITP, 1995).]