The Reluctant Hero: The Life and Discovery of Sir Alexander Fleming

Julian Beckett
Aug 2
5 min read

An older man in a lab coat studies a petri dish, surrounded by lab equipment. Another image shows him examining a dish. Serious expressions. — *Synthetic Production of Penicillin* Professor Alexander Fleming, holder of the Chair of Bacteriology at London University, who first discovered the mould Penicillin Notatum. Here in his laboratory at St Mary's, Paddington, London (1943).

In the summer of 1928, after a long holiday with his wife and son, Alexander Fleming returned to his lab at St Mary’s Hospital in London. Waiting for him was a pile of Petri dishes he’d left out before the break—dishes that had since been exposed to the open air. In most labs, this kind of contamination would be an annoyance, a ruined experiment. But in one dish, Fleming noticed something peculiar. A patch of mould had grown—and around it, the usually stubborn Staphylococcus bacteria had vanished.

What he’d stumbled upon was penicillin, the world’s first true antibiotic. But like so many discoveries in science, its impact was neither immediate nor solitary. This is the story of a Scottish farm boy who changed medicine forever—and did it with humility, stubbornness, and a bit of lucky timing.

Early Life in Rural Ayrshire

Alexander Fleming was born on 6 August 1881 on a remote farm just outside the village of Darvel in Ayrshire, Scotland. His parents, Hugh Fleming and Grace Stirling Morton, came from farming stock. Alexander was the seventh of eight children, and the rhythms of rural life shaped his early years. His father was 59 when Alexander was born and already in poor health. He died when Alexander was just seven.

Fleming’s first school was a tiny one-room moorland setup where a dozen pupils of all ages were taught by a single teacher. Between the ages of five and eight, this was his whole world.

Next came Darvel School, a slightly more conventional institution—but one that involved an eight-mile round-trip walk each day. By 11, his academic talents had become apparent. He was awarded a scholarship to Kilmarnock Academy, a boarding school that broadened his horizons considerably. He stayed there for two years before heading south to London, aged 13.

Young man in a black suit and tie poses formally against a dark background, exuding a serious and composed mood. — Fleming as a young man. Date: 1881 - 1955.

A Move to London, and an Unexpected Path

In early 1895, Alexander arrived in London to live with his older brother Tom, a doctor. By then, most of the Fleming family had moved into Tom’s household, leaving the eldest sibling, Hugh, to manage the family farm in Scotland.

Alexander enrolled at the Royal Polytechnic School, where he studied business and commerce. Though he entered a class based on his age, he quickly proved more capable than his peers and was bumped up to study alongside boys two years older. He finished school at 16.

He landed a job in a shipping office, thanks to his business training—but found the work dull and uninspiring. Fortunately, in 1901, a small inheritance from his uncle, John Fleming, offered an escape route. He decided to follow Tom into medicine.

First, he needed the right qualifications. As it turned out, that wasn’t much of a hurdle: Fleming passed the entrance exams with the highest scores in the UK.

Becoming a Doctor

In 1903, aged 22, Fleming enrolled at St Mary’s Hospital Medical School in London. He graduated with distinction three years later, earning degrees in both Medicine and Surgery. His teachers saw something special in him. Among them was Sir Almroth Wright, a pioneer in immunology and early vaccines. Wright persuaded the young doctor to stay on at St Mary’s as a researcher in bacteriology.

By 1908, Fleming had earned a further degree in bacteriology and was awarded the Gold Medal for top student. He was promoted to lecturer at the medical school and worked closely with Wright, whose research interests focused on the body’s natural ability to fight infection. This curiosity would fuel some of Fleming’s most significant discoveries.

The Accidental Breakthrough

That brings us back to 1928, and those Petri dishes in his lab. One of them contained a bluish-green mould, which appeared to have killed the Staphylococcus bacteria around it. The further from the mould, the more normal the bacteria appeared.

It was classic Fleming to be curious about what others might discard. He isolated the mould and identified it as belonging to the Penicillium genus. The liquid it secreted was capable of destroying a wide range of bacteria—yet it was harmless to white blood cells. On 7 March 1929, he named this substance “penicillin”.

The medical applications seemed endless. Penicillin proved effective against scarlet fever, pneumonia, meningitis, and diphtheria. Even more remarkable, it was non-toxic.

Fleming published his findings—but to his dismay, the scientific community largely ignored them.

Mold sample labeled "The mould which makes Penicillin" with Sir Alexander Fleming's card. Dark background, historic scientific context. — Samples of penicillin mould, signed and inscribed by Sir Alexander Fleming,

The Setbacks

There were several reasons Fleming struggled to turn his discovery into a working medicine:

The penicillin compound was difficult to isolate and purify.
It was not very concentrated in its natural form.
It acted slowly.
Early attempts to use it as a surface antiseptic weren’t promising.

To make matters worse, Almroth Wright’s lab had a strong anti-chemist bias—he wouldn’t allow chemists into his team. This meant that the people who might have helped refine penicillin simply weren’t there.

Fleming continued to tinker with penicillin throughout the 1930s but could never quite crack the problem of mass production. Fortunately, others would.

Old newspaper featuring Nobel Prize winners for Medicine. Includes black-and-white photos of three men. Headline highlights penicillin discovery. — Fleming and pathologist Howard Florey and biochemist Ernst Boris Chain featured in *New York Times* headlines, Oct. 26, 1945

The Oxford Team and Penicillin’s Rise

In the early 1940s, a group of scientists at the University of Oxford, led by pathologist Howard Florey and biochemist Ernst Boris Chain, took Fleming’s work and ran with it.

Using advanced chemical techniques, they managed to purify and concentrate penicillin into a usable drug. Their team’s wartime efforts to scale up production helped make penicillin widely available just in time to save countless lives on the battlefield.

In 1945, the Nobel Prize in Physiology or Medicine was jointly awarded to Fleming, Florey, and Chain. The citation read:

“For the discovery of penicillin and its curative effect in various infectious diseases.”

In his Nobel lecture, Fleming offered a prescient warning:

“It is not difficult to make microbes resistant to penicillin in the laboratory… The time may come when penicillin can be bought by anyone in the shops. Then there is the danger that the ignorant man may easily underdose himself… and make them resistant.”

That day has arguably come—and his warning remains at the heart of global conversations about antibiotic resistance.

An elderly man in formal attire presents an award to another older man in a suit. Others in tuxedos watch. The mood is dignified. — Alexander Fleming receives the Nobel Prize from King Gustaf V of Sweden, 1945

Fame, Fortune, and Modesty

Despite his Nobel status, Fleming remained modest. He often credited Florey, Chain, and their team more than himself. Still, he became an international celebrity. On a tour of the United States in 1945, chemical companies offered him $100,000 as a personal gift of gratitude. True to form, he donated it to the research labs at St Mary’s.

He was knighted in 1944, becoming Sir Alexander Fleming. In 1953, following the death of his first wife Sarah in 1949, he married Dr Amalia Koutsouri-Voureka, a Greek colleague who had been working in his lab.

Fleming died of a heart attack in London on 11 March 1955, aged 73. His ashes were interred in St Paul’s Cathedral, a fitting resting place for a man whose discovery had helped change the course of human health.

Plaque honoring Sir Alexander Fleming, discoverer of penicillin. Text notes his birth and death dates, with decorative border. — Grave of Sir Alexander Fleming in the crypt of St Paul's Cathedral, London

Legacy

Fleming’s story is often told as one of luck—a mouldy dish left out by accident. But that’s only part of the picture. The real genius was in recognising the importance of what he saw, and following it up with curiosity, patience, and persistence.

He once said: