ON THIS DAY: 14 February 1929

Sir Alexander Fleming, a Scottish physician and microbiologist, discovered benzylpenicillin (penicillin G), an antibiotic originating from the mould Penicillium rubens, a species of fungus. Penicillium rubens was first discovered in 1923 by French microbiologist Philibert Melchior Joseph Ehi Biourge. However, in 1928, Fleming stumbled upon that one of his bacterial cultures, which he was experimenting with, was contaminated with this mould. P. rubens is an extremely common and resilient mould found in indoor environments, which quickly spreads when humidity is high. After many experiments using this mould, Fleming made one of the most important advances in the history of medicine.