
Wellcome Images supplied the picture that marks the discovery of the antibiotic penicillin made by pharmacologist Sir Alexander Fleming (1881-1955). It is a photograph of a petri dish containing the mould Penicillium notatum, a mould that began its fame as a contaminant in Fleming’s laboratory at St Mary’s Hospital, London. Fleming was a brilliant, if untidy, scientist who left the lab for a summer holiday in 1928 without washing his petri dishes. Upon returning in September, he discovered an invasion of blue-green mould in a dish containing the bacteria Staphylococcus. Where the mould grew, the bacteria didn’t.
Fleming’s subsequent experiments revealed that the mould exuded a substance that destroyed many disease-causing bacteria. Fleming named this substance penicillin. In 1945 he was jointly awarded the Nobel Prize in Physiology or Medicine with Ernst B. Chain and Howard Florey, who enabled the commercial production of the antibiotic during World War II.

The Wellcome Library holds some fascinating insights into Fleming, including Robert Fleming's story of his brother's life, held in the Archives and Manuscripts collection. Wellcome Film has digitised a short film featuring footage of Fleming called The discovery of penicillin. There are many portraits of him in Wellcome Images, including this pose with a petri dish similar to the one featured on the stamp that recognises his remarkable work – and his untidiness.
Author: Louise Crane, Picture Researcher, Wellcome Images
Images, from top:
Penicillium notatum CMSP/Wellcome Images
Sir Alexander Fleming Wellcome Library, London