In September 1928, British bacteriologist Alexander Fleming returned from vacation and discovered in his laboratory what any conscientious researcher would have immediately thrown in the trash — a moldy Petri dish. But around the colony of Penicillium notatum fungus, a clear zone of dead staphylococci had formed, and this accidental contamination triggered a chain of events that by 1945 led three scientists to a Nobel Prize and saved millions of lives in World War II.
Fleming was working with staphylococcus — a bacterium that turns any scratch into potential sepsis. Before his vacation, he left several Petri dishes on a table by an open window, and mold spores from the air did what they always do — began to grow. But Penicillium notatum (later refined to P. chrysogenum) turned out to be no ordinary tenant: it secreted a substance that dissolved bacterial colonies within a radius of several centimeters.
Fleming named this substance penicillin and in 1929 published his results. He understood that he had found a natural antibiotic — a chemical weapon that the fungus uses in competitive struggle for resources. The problem was that penicillin proved capricious: it broke down quickly, dissolved poorly, and Fleming couldn't obtain a sufficiently pure preparation for clinical trials. The substance worked in vitro — in a test tube, but the path from test tube to operating room turned out to be twelve years long.
In 1938, a team at Oxford University led by pathologist Howard Florey took up penicillin. He was joined by biochemist Ernst Chain, who developed a purification method, and microbiologist Norman Heatley, who invented a design for growing fungus in large volumes. Heatley used ceramic bedpans for acidifying urine — literally hospital bedpans — because there wasn't enough glassware, and ceramic didn't react with the nutrient medium.
In May 1940, they infected eight mice with a lethal dose of streptococcus. Four were treated with penicillin, four were left as a control group. After 24 hours, the control mice were dead, and the treated ones were running around their cages. This was the first convincing test on a living organism: penicillin worked not just in a dish, but in blood, in tissues, in the real battle of the immune system against infection.
In February 1941, Florey's team got a chance to test penicillin on a human. The patient was a 43-year-old policeman with a severe infection: he had scratched his face on a rose bush, the wound became infected, streptococcus entered his bloodstream, sepsis began. Doctors were already preparing for the worst — abscesses had spread to his lungs and eyes.
Florey administered the first dose of penicillin, and within 24 hours the temperature dropped, pus began to resolve. But the supply of the drug was negligible: just a few grams, obtained after weeks of work. Lab technicians even filtered the patient's urine to extract unmetabolized penicillin and inject it again — the drug was more expensive than gold. After five days, improvement was obvious, but after ten days the supplies ran out. The policeman died from the infection's return.
This case proved two things: penicillin could save hopeless patients, and its production on laboratory scales was useless. Tons were needed, not grams, and British industry in the midst of war couldn't provide that.
In July 1941, Florey and Heatley flew to the USA, to the Northern Regional Research Laboratory of the Department of Agriculture in Peoria, Illinois (NRRL). The Americans were working on fermentation for the food industry and proposed a radical solution: instead of growing fungus in a thin layer on the surface of the medium, use deep fermentation — submerge the mycelium in huge vats with nutrient solution and blow air through them.
The key breakthrough was corn steep liquor — a byproduct of starch production. It contained an ideal cocktail of carbohydrates and nitrogen, on which Penicillium chrysogenum grew tens of times faster. By the end of 1942, supplies were enough for fewer than one hundred patients, but by September 1943, volumes covered the needs of the Allied armies. American pharmaceutical companies — Pfizer, Merck, Squibb — built factories with vats holding up to 40 thousand liters. This was the industrialization of biology: not simply scaling up a laboratory process, but creating a new type of production.
Simultaneously, production was underway in occupied Netherlands. The company NG&SF in Delft grew penicillin under the code name Bacinol, hiding it from German authorities. Researchers worked in basements, risks were enormous — discovery meant a concentration camp, but by war's end the Dutch line was also supplying the drug for Resistance underground hospitals. This was a parallel race where the stakes were measured not in patents, but in the lives of the wounded.
Mass production by 1944 changed the statistics of war. Wound infections that in World War I killed one in five wounded now healed within a week. Gangrene retreated, amputations decreased, survival after abdominal wounds doubled. Penicillin didn't stop the war, but it changed the arithmetic of survival.
In 1945, the Nobel Committee awarded the prize in physiology and medicine to Alexander Fleming, Ernst Chain, and Howard Florey. This was a rare recognition of collective work: Fleming discovered the phenomenon, Chain developed the purification chemistry, Florey organized clinical trials and scaling. But Norman Heatley, who designed the fermentation apparatus, remained offstage — the engineer's contribution proved less visible than the theorist's.
The prize drew a line under the era of empirical medicine. Before penicillin, doctors could only support the organism in its fight against infection: cut abscesses, lower temperature, hope for immunity. Now a direct-action tool appeared — a molecule that kills bacteria without touching human cells. Antibiotics opened the era of targeted therapy, where treatment is not a ritual, but a precise chemical attack on the pathogen.
The history of penicillin is a story of how chance met the readiness to notice it, and observation turned into technology through the persistence of a dozen teams on three continents. Fleming saw dead bacteria, Florey organized a conveyor of evidence, American engineers built bioreactors, the Dutch risked their lives for underground synthesis. Each stage required different talents, and no single person could traverse the entire path alone — from a moldy dish to millions of saved lives.