Discovering Penicillin
In 1928, bacteriologist Alexander Fleming was studying Staphylococcus, a type of bacteria that can cause serious infections. He grew the bacteria in small containers called petri dishes. One day he noticed that mold had accidentally been introduced into one of the petri dishes and was startled to see that there were no bacteria around the moldy area. Fleming correctly deduced that the mold had had an antibacterial effect; somehow it had prevented the bacteria from growing. Fleming identified the mold as the strain Penicillium notatum and called its antibacterial ingredient—which he was unable to successfully extract—penicillin. Fleming's discovery of penicillin's unique effect led to the eventual finding that it could be used to treat infections. Several years after his initial observation, scientists built on his work by extracting penicillin from mold and demonstrating its effectiveness as a treatment.
One day he noticed that mold had accidentally been introduced into one of the petri dishes and was startled to see that there were no bacteria around the moldy area. What was the observation made by him?
1) The mold killed all the bacteria in the petri dish.
2) The mold attracted all the bacteria in the petri dish.
3) The mold had no effect on the bacteria in the petri dish.
4) The mold grew on the bacteria in the petri dish.