Great Britons – Sir Alexander Fleming

Sir Alexander Fleming was one of the most influential scientists of the 20th century.

Fleming’s discovery of penicillin has had a tremendous impact on the world because penicillin became the basis for medication to treat bacterial infections.

Penicillin has saved millions of lives by stopping the growth of the bacteria that are responsible for poisoning the blood and causing many other once fatal diseases.

Alexander Fleming was born on 6th August 1881 at Lochfield farm near Darvel, in Ayrshire, Scotland.

Fleming, a private in the London Scottish Regiment of the Volunteer Force from 1900 to 1914, had been a member of the rifle club at the medical school. The captain of the club, wishing to retain Fleming in the team, suggested that he join the research department at St Mary’s Hospital Medical School in Paddington, where he became assistant bacteriologist to Sir Almroth Wright, a pioneer in vaccine therapy and immunology. In 1908, he gained a BSc degree with a gold medal in Bacteriology and became a lecturer at St Mary’s until 1914.

World War 1

During World War 1, Fleming served as a captain in the Royal Medical Corps, working in the battlefield hospitals in France. During this time, Fleming saw large numbers of soldiers dying from infected wounds. He realised that the antiseptics being used destroyed the patient’s immune system and didn’t effectively stop the invading bacteria.

Fleming set about trying to find anti-bacterial agents.

Alexander Fleming’s Road to Discovery

One day in 1928, he discovered that a mould (which was accidentally growing nearby) killed bacteria he had grown on a culture plate. So, he isolated the mould and showed that it released a substance that inhibited bacterial growth. He named the substance penicillin after the name of the mould.

Fleming reported his ground-breaking results in a scientific paper published in the British Journal of Experimental Pathology (1929).

World War 2

The scientists Howard Florey and Ernst Boris Chain built on Fleming’s findings and used them to mass-produce penicillin to treat the wounded soldiers of World War 2. Consequently, the antibiotic revolutionised battlefield medicine and, on a broader scale, the field of infection control.

In 2009, Alexander Fleming was commemorated on a new series of banknotes issued by the Clydesdale Bank; his image appeared on the £5 note.

His discovery in 1928 of what was later named benzylpenicillin (or penicillin G) from the mould Penicillium rubens is described as the “single greatest victory ever achieved over disease.”

He also discovered the enzyme lysozyme from his nasal discharge in 1922, and along with it, a bacterium he named Micrococcus Lysodeikticus, later renamed Micrococcus luteus.

Fleming was a man of integrity with strong moral and ethical principles, so when he learned of Robert D. Coghill and Andrew J. Moyer patenting the method of penicillin production in the US in 1944, he was furious and commented:

“I found penicillin and have given it free for the benefit of humanity. Why should it become a profit-making monopoly of manufacturers in another country?”


1944 – Knighted by King George VI.

1945 – Fleming received the Nobel Prize (along with Florey and Chain).

1999 – Time Magazine named Sir Alexander Fleming one of the 100 Most Important People of the 20th century.

2002 – Fleming named in the BBC’s list of the 100 Greatest Britons following a nationwide vote.

The laboratory at St Mary’s Hospital where Fleming discovered penicillin is home to the Fleming Museum, a popular London attraction. His alma mater, St Mary’s Hospital Medical School, merged with Imperial College London in 1988. The Sir Alexander Fleming Building on the South Kensington campus was opened in 1998, where his son Robert and his great-granddaughter Claire were presented to the Queen; it is now one of the main preclinical teaching sites of the Imperial College School of Medicine.

His other alma mater, the Royal Polytechnic Institution (now the University of Westminster), has named one of its student halls of residence Alexander Fleming House, which is near Old Street in central London.

He died on 11th March 1955 in London.

The grave of Sir Alexander Fleming in the crypt of St Paul’s Cathedral, London.

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