1945 Nobel Prize in Physiology or Medicine — Fleming, Florey, and Chain for Penicillin

What You Will Learn in This Article

This article explores why Fleming’s “accidental” discovery of penicillin in 1928 took 11 years to translate into clinical application, how the Oxford team of Florey and Chain, along with the Peoria fermentation team, transformed this discovery into a life-saving drug, and how this narrative mirrors the maturation cycle of modern open-source libraries. Finally, it addresses the seeds of antibiotic resistance, a concern that Fleming already cautioned against in his Nobel lecture.

A Story Different from Common Knowledge — The True Face of “Accidental Discovery Saving Humanity”

The story of penicillin is often summarized as “a Scottish doctor, forgetting a Petri dish, returned from summer vacation and saved humanity.” This summary is a myth that compresses history by a factor of 30, omitting several crucial details.

First, Fleming was neither the first nor the last to observe a mold-contaminated Petri dish. Laboratory contamination was commonplace for microbiologists of that era, and Penicillium contamination had been reported in several laboratories previously. What distinguished Fleming was that he was the first to interpret this contamination in a medically significant way.

Second, and this is the key point of this article, Fleming’s initial discovery alone could not save lives. The 11-year gap between his 1928 observation and the 1941 Alexander case represents the time in which penicillin was not yet established as a purified chemical substance. Fleming was not a chemist, and the resources and manpower at St. Mary’s Hospital were insufficient to accomplish this. The realization of a discovery often requires as much effort as the discovery itself.

Third, the final development of penicillin was the result of a three-team relay, not the work of a single genius. Fleming (discovery) → Oxford Florey and Chain team (purification and clinical trials) → Peoria fermentation team (mass production). Without this relay, penicillin would have remained a footnote in an academic paper. The Nobel Committee’s decision to award the prize jointly to these three individuals recognized this relay structure.

If we reframe this narrative using the language of computer science, it perfectly aligns with the maturation cycle of an open-source library. Someone uploads an incomplete code to GitHub (Fleming). Another team forks it and refines it into a functional version (Oxford). A third team creates the infrastructure for production-scale deployment (Peoria). And then, various organizations begin building their applications on top of it (the post-war antibiotic industry). Understanding why each step of this relay was necessary is crucial to fully understanding the story of penicillin.

The Historical Context — On the Cusp of a New Era After the War

1945 was the year humanity emerged from its greatest era of death and stood on the threshold of a new era.

In May, Nazi Germany surrendered, ending six years of war in Europe. The reality of the Holocaust began to be revealed to the world. In July, the Potsdam Conference brought together the United States, the United Kingdom, and the Soviet Union to discuss the post-war world order. On August 6 and 9, atomic bombs were dropped on Hiroshima and Nagasaki, and on August 15, Japan surrendered, marking the end of the largest war in human history.

August 15 also marks the day of liberation for Korea. The 35 years of colonial rule ended, and the leaders of the provisional government began preparing for their return. Scholars who had been imprisoned during the Korean Language Society Incident were released. In Europe, penicillin was emerging as a symbol of the end of the war, while on the Korean peninsula, intellectuals who had regained their language and identity began to work towards building the foundations of a new nation.

By the latter part of the war, penicillin was already dramatically reducing mortality rates from infections among Allied soldiers. In 1944, the fermentation facilities in Peoria were fully operational, and soldiers received penicillin injections in field hospitals. Soldiers who would have died from infections in previous wars were now surviving. This fact cemented penicillin’s place as a symbol of 20th-century medicine in the minds of the medical community, the military, and the public, and the Nobel Committee was not immune to this trend.

The Nobel Prize ceremony was held in Stockholm in December, and all three laureates attended. It was the first large-scale ceremony after the war, a symbolic moment marking the complete restoration of the Nobel Prize system after six years.

Relay 1: Fleming — What the Mold Dish Tried to Say

Alexander Fleming was the son of a Scottish farmer. He trained at the medical school of St. Mary’s Hospital in London and worked as a bacteriologist in the hospital’s vaccine department. During World War I, he witnessed the severity of wound infections, which shaped his subsequent research focus: finding new anti-infective agents.

In the summer of 1928, he was studying Staphylococcus. He returned from a vacation without tidying his laboratory and discovered that one of the Petri dishes had been contaminated with blue mold. This dish was remarkable because the bacterial colonies around the mold were transparent, forming a circular zone. The mold appeared to be secreting something that killed the surrounding bacteria.

Fleming identified the mold as ** Penicillium notatum ** and named the antibacterial substance it secreted ** “penicillin.” ** In 1929, he published his findings in the ** British Journal of Experimental Pathology. **

This is where the story essentially stalls. Fleming was interested in the clinical application of the substance, but he faced two critical limitations. First, the amount of penicillin obtained from the culture medium was extremely small and highly unstable. Even slight fluctuations in temperature or pH would cause it to lose its activity. Second, he lacked the chemical expertise to purify the substance. Fleming was not a chemist, and neither was his team at St. Mary’s. He tried for several years with a few chemical colleagues, but they failed, and he eventually turned his attention to other research.

This 11-year standstill began. Penicillin was not forgotten by the academic community, but it could not be developed into a practical drug. Some researchers cited the paper, and some chemists attempted purification, but all failed.

Relay 2: Oxford — Purification and First Clinical Trials

Howard Florey was a pathologist from Adelaide, Australia. As a professor of pathology at the Dunn School at Oxford, he began a new project in 1938: a systematic search for natural compounds that inhibit bacterial growth. Penicillin was one of the first candidates he chose.

A crucial figure in Florey’s team was Ernst Boris Chain, a German-born Jewish biochemist. He emigrated to England in 1933 to escape Nazi persecution of Jews, trained at Cambridge, and then moved to Oxford. Chain possessed the meticulousness characteristic of Jewish chemists and had the precise skills needed to tackle the extremely challenging problem of penicillin purification.

Chain and Norman Heatley developed a purification method in 1939-1940 that combined freeze-drying and column chromatography. Using this method, they obtained a penicillin solution that was used in a mouse experiment in May 1940. Eight mice were injected with a lethal dose of Streptococcus, and half of them were given penicillin. All four mice in the penicillin group survived, while all four in the control group died. This was a dramatic result.

The events following this experiment were detailed in a previous article. The first successful human clinical trial was conducted on Alexander in February 1941, but the patient died due to a lack of supply, which pushed the Oxford team to solve the problem of mass production.

Florey and Heatley made a crucial trip at this point. In July 1941, the two traveled to the United States to approach the National Research Institute in Peoria. Their goal was to leverage American industrial capacity to produce penicillin on a large scale. This trip marked the beginning of the Peoria fermentation process, which was detailed in a previous article.

Chain’s role remained crucial during this period. He focused on elucidating the chemical structure of penicillin (the discovery of the β-lactam ring), which provided the theoretical basis for the development of synthetic antibiotics (semi-synthetic penicillins, cephalosporins, etc.) in the future. However, subtle conflicts began to emerge between Chain and Florey during this period. Chain wanted to secure patents and commercialize penicillin, while Florey and Oxford University wanted to keep penicillin as a public good. This conflict ultimately led to the acquisition of penicillin-related patents by American pharmaceutical companies. Chain was disappointed by this outcome and later moved to the Weizmann Institute in Israel.

Relay 3: Peoria — Production at Scale

The Peoria team’s story has already been covered in a previous article, so I will summarize it briefly: the development of deep-tank fermentation, Mary Hunt’s discovery of the super strain, and the participation of American pharmaceutical companies (Merck, Pfizer, Squibb, etc.) in mass production. The final stage of this relay was completed between 1943 and 1944, and by 1944, the Peoria fermentation facility was fully operational, allowing penicillin to be supplied to Allied soldiers.

The key to understanding why this final stage was so crucial is that Fleming’s discovery was academically significant, but it would have been meaningless to humanity without mass production by Peoria. Once mass production was achieved, penicillin became the standard of care for civilian medicine after the war, and in the following decades, mortality rates from numerous infectious diseases, such as syphilis, pneumonia, endocarditis, and puerperal fever, were dramatically reduced. It is now a common assertion in demography that a significant portion of 20th-century population growth is a direct result of the antibiotic era.

The CS Framework for the Open-Source Relay

Let’s take this analogy one step further.

Fleming’s discovery was like an incomplete prototype library uploaded to GitHub. The idea was clear, and there was a proof of concept, but it was not usable in a production environment. It lacked documentation, the build was unstable, and there was no dependency management. Most developers ignored this repository.

The Oxford team was like the team that forked this initial prototype and refactored it into a proper library. Chain was responsible for stabilizing the core API (chemical purification), Heatley improved the build process (culture method), Florey led the clinical trials (validation of real-world use cases), and the team conducted mouse experiments and the Alexander case to demonstrate practical use. At this stage, the library had test coverage and its first real-world use case.

The Peoria team was like the team that deployed this refactored library to a production infrastructure. They created the fermentation tank infrastructure (server architecture), optimized the strain (performance tuning), and created a stable process (orchestration) to enable large-scale deployment. Only after this stage could the library be used at an enterprise scale.

Each stage of this relay required different types of skills and different types of organizations. Fleming needed an eye for observation, Oxford needed integration of chemistry and clinical medicine, and Peoria needed industrial engineering. No single person could possess all of these skills. Innovation often occurs not through the insights of individuals but through the successful relay between organizations.

This analogy breaks down in some ways. The open-source relay typically involves explicit forks and pull requests, while the penicillin relay involved more serendipitous encounters and ad-hoc requests. Today, we are trying to design these relays more explicitly—translational research programs are one such attempt. The success rate is still low, but the story of penicillin shows that the problem itself is not new.

The Shadow — Fleming’s Final Warning

Fleming’s Nobel lecture contained a chilling prediction that is worth revisiting today. I quote from his lecture on December 11, 1945, in Stockholm:

"When penicillin is available in sufficient quantities to be used in the shops, there is a danger that people will use it indiscriminately, and the bacteria which cause infection will develop resistance. For instance, if a person takes penicillin for a mild cold, the bacteria in his throat may develop resistance, and if he later develops a serious infection, the penicillin may not be effective."

Fleming’s warning during the Nobel Prize ceremony was not accidental. He had already observed penicillin-resistant bacteria in his laboratory, and he knew that the spread of this resistance was only a matter of time. His prediction has come true. Today, we live with MRSA (methicillin-resistant Staphylococcus aureus), VRE (vancomycin-resistant Enterococcus), and CRE (carbapenem-resistant Enterobacteriaceae). The WHO estimates that by 2050, 10 million people will die each year from antibiotic resistance.

The implications of this warning are profound. Whatever tools humanity creates, the way we use them determines their future lifespan. Fleming’s penicillin saved humanity, but humanity’s carelessness is gradually dulling this tool.

Why It Matters

It is difficult to summarize the legacy of Fleming, Florey, and Chain’s penicillin in a single sentence. There are multiple layers.

Medically, the fact that this drug dramatically reduced mortality from infectious diseases in the 20th century is well known. The fact that we no longer perceive minor wounds, pneumonia, syphilis, scarlet fever, and puerperal fever as diseases of death is entirely a result of the penicillin era.

Historically, this story offers a fundamental insight into the separation of discovery and realization. Even with a great idea, creating it into a form that can be used in practice requires separate efforts, and often involves different people and different organizations than the original discoverer. This insight continues to influence our understanding of the interface between academia and industry today.

Ethically, the conflict over the penicillin patent raised the question of ownership of medical discoveries, a question that remains unresolved today. The Oxford team wanted to keep penicillin as a public good, but the American pharmaceutical companies ultimately acquired the related patents, and developing countries still face challenges in accessing antibiotics. The question of who should manage humanity’s knowledge assets emerged clearly in this case.

But above all, Fleming’s warning remains. How carefully will we use this tool? With the development of new antibiotics stalled, this question is even more pressing today. Every day, in every clinic and hospital, we either practice or betray the warning that he delivered on the stage in Stockholm in December 1945.

The Nobel Committee’s award to these three individuals was a celebration of one of humanity’s greatest medical triumphs, but everyone in that auditorium knew that the duration of that triumph depended on our actions.

1945 Penicillin Summary: The three-stage relay, from Fleming’s accidental discovery (1928) to the Oxford team of Florey and Chain’s purification and clinical trials (1940-1941) to the mass production in Peoria (1942-1944), ushered in a new era of human anti-infective medicine. At the same time, the seeds of antibiotic resistance, which Fleming warned about in his Nobel lecture, remain a serious challenge today.

→ Experience it with code: DevBench — Open-Source Relay Simulation → Learn about CS concepts: DryBench — Maturation Cycle and Production Deployment → Previous: 1944 — Erlanger and Gasher for Nerve Fiber → Next: 1946 — Muller for X-ray Mutations