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.
6. Identify the problem. What are you trying to find out?
We are trying to find out why the dishes without mold had no clear areas
8. How was the hypothesis tested?