Alexander Fleming was born in Ayrshire on 6 August 1881, the son of a farmer and third of four children.
He attended Kilmarnock Academy before studying at the Royal Polytechnic Institution in London. Aged twenty, Alexander, followed in the footsteps of his brother to study medicine.
He qualified with distinction in 1906 and began research at St Mary’s Hospital Medical School at the University of London under Sir Almroth Wright, a pioneer in vaccine therapy. In World War One Fleming served in the Army Medical Corps and was mentioned in dispatches. After the war, he returned to St Mary’s.
In 1928, while studying influenza, Fleming noticed that mould had developed accidentally on a set of culture dishes being used to grow the staphylococci germ. The mould had created a bacteria-free circle around itself. Fleming experimented further and named the active substance penicillin. It was two other scientists however, Australian Howard Florey and Ernst Chain, a refugee from Nazi Germany, who developed penicillin further so that it could be produced as a drug.
Fleming wrote numerous papers on bacteriology, immunology and chemotherapy. He was elected fellow of the Royal Society in 1943 and knighted in 1944. In 1945 Fleming, Florey and Chain shared the Nobel Prize in Medicine. Fleming died on 11 March 1955.