Alexander Fleming and His Accidental Discovery

Contributor: Jay Gregorio. Lesson ID: 13378

What if you forgot to clean up your lab, only to discover something that would change the face of medicine forever? That is exactly what happened when Alexander Fleming discovered penicillin!


Chemistry, Life Science

learning style
Auditory, Visual
personality style
Grade Level
Middle School (6-8), High School (9-12)
Lesson Type
Dig Deeper

Lesson Plan - Get It!

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In 1826, British pharmacist John Walker noticed a lump at the end of a stick that he used to mix chemicals. When he tried to scrape it off, it sparked and created fire!

Walker accidentally created a match from a dirty stick! He jumped right into his discovery and began selling his new friction lights in his pharmacy.

match igniting

This is just one of the many accidental discoveries and inventions throughout history. In fact, 30 to 50 percent of scientific discoveries are in some way accidental, according to experts.

These discoveries have changed the world in one way or another, sometimes for the better and sometimes not.

Learn about one of the most significant serendipities in medical history - the discovery of penicillin! Unravel a breakthrough in human history, as you explore the journey of Sir Alexander Fleming and other scientists who received less recognition despite their efforts.

Take a look at this close-up picture of a mold colony:


Mold is a type of fungi that grows on fruits, bread, or surfaces where conditions are favorable.

Not all molds are the same. Some of them are poisonous, but others can be purified and made into something helpful.

  • How did Alexander Fleming discover penicillin out of a special type of mold?

Let's find out!

Who Was Alexander Fleming?

Alexander Fleming was a Scottish scientist who studied medicine and served as a physician during World War I.

While conducting research and experimentation in 1928, Fleming noticed a mold that was able to kill bacteria. He called it penicillin and was awarded the Nobel Prize in 1945 alongside other scientists.

This bacteria-destroying breakthrough paved the way for the use of antibiotics in modern medicine.

Early Life

Alexander Fleming was born on a large farm in Ayrshire, Scotland on August 6, 1881. His interest in medicine and the world around him developed during his childhood there.

At the age of 13, he moved to London to study at Regent Street Polytechnic (now University of Westminster), where he reaffirmed his love for medicine and did very well. He eventually received a scholarship to St. Mary's Hospital Medical School, a branch of the University of London, at the age of 25.

In 1908, he was awarded a gold medal as a top medical student at the university.

Career During World War I

During the first World War, Alexander worked as a bacteriologist at the Royal Army Medical Corps. Through his works, he discovered that antiseptics used to treat wounds were ineffective and caused more harm than good. His recommendation on how to keep wounds dry and clean was unheeded.

After the war, he returned to St. Mary's as assistant director of the Inoculation Department. In 1921, he discovered a mild antiseptic called lysozyme when he tried to mix mucus on a bacteria and discovered that the bacteria dissolved.

This is his first contribution to human immune system research.

Alexander Fleming in his laboratory

The Journey to Penicillin Discovery

Returning to his laboratory from a family vacation in September 1928, he noticed that a bacterial culture of Staphylococcus aureus he had left out had become contaminated with a mold he would later identify as Penicillin notatum.

Fleming also discovered that the colonies of staphylococci surrounding this mold had been destroyed, which made him suspect that something in it was resistant to the bacteria. He originally called this substance mould juice before dubbing it penicillin.

Fleming initially thought he discovered a more powerful lysozyme; however, he later determined that its characteristics were not of enzymes but of an antibiotic.

The journey toward this accidental discovery was long because the preparation and isolation of the chemical penicillin from within the Penicillin notatum mold is a difficult process.

He later asked for help from a team of scientists from the University of Oxford. Led by Howard Florey and his co-worker, Ernst Chain, they isolated and purified penicillin.

The antibiotic came into use during World War II, revolutionizing battlefield medicine and, on a much broader scale, the field of infection control.

Honor and Recognition

Howard Florey, Ernst Chain, and Alexander Fleming shared the 1945 Nobel Prize in Physiology and Medicine for their work on antibiotics. Their relationship is believed to have been tainted over disagreements about who deserved the most credit for their work.

Alfred Nobel Prize medals

In 1946, Fleming returned to St. Mary's and succeeded Almroth Edward Wright as the head of the Inoculation Department. This department was later called the Wright-Fleming Institute in honor of their contributions to the field.

Alexander Fleming served as president of the Society for General Microbiology, as a member of the Pontifical Academy of Science, and as an honorary member of numerous medical and scientific societies.

He was also awarded many honorary doctorate degrees from around the world before dying of a heart attack in 1955 at the age of 74.

Watch The accident that changed the world - Allison Ramsey and Mary Staicu from TED-Ed:

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Life is full of surprises. No one expects to wake up one day and change their life forever.

In Fleming's own words:

"When I woke up just after dawn on September 28, 1928, I certainly didn't plan to revolutionize all medicine by discovering the world's first antibiotic, or bacteria killer. But I suppose that was exactly what I did."

He certainly did change the world.

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