How Penicillin Was Discovered In 1928, Sir Alexander Fleming was studying Staphylococcus bacteria growing in culture dishes. He
noticed that a mold called Penicillium was also growing in some of the dishes. A clear area existed
around the mold because all the bacteria that had grown in this area had died. In the culture dishes
without the mold, no clear areas were present.
Fleming hypothesized that the mold must be producing a chemical that killed the bacteria. He decided
to isolate this substance and test it to see if it would kill bacteria. Fleming transferred the mold to a
nutrient broth solution. This solution contained all the materials the mold needed to grow. After the
mold grew, he removed it from the nutrient broth. Fleming then added the nutrient broth in which the
mold had grown to a culture of bacteria. He observed that the bacteria died which was later used to
develop antibiotics used to treat a variety of diseases.
6. Identify the problem.
7. What was Fleming's hypothesis?
8. How was the hypothesis tested?
9. Should the hypothesis be supported or rejected based on the experiment?
10. This experiment lead to the development of what major medical advancement?