Source of pictures: Pixabay.com
After dinner, Daniel left the table right away and searched for something in the cupboard. Finally, he found a medicine box. He took out the instructions, read it and learned that it was penicillin. Daniel asked Mom, who was cleaning the table, "what is penicillin, Mom?"
Mom didn't stop working, but said mysteriously, "It's our weapon against disease. It's designed to kill the bacteria that infect us. Without penicillin, many people around the world would have died of wound infections."
Daniel couldn't help but exclaimed, "what a powerful medicine!"
"There's a well-known story about penicillin. In 1928, a microbiologist named Alexander Fleming had just come back from vacation, and he noticed that there was a kind of bacteria on the culture medium without other bacteria around. He wondered, could it be that the bacteria secreted a substance that killed other bacteria, so that they didn't grow near it? With this in mind, he examined the secretions of the bacteria in the culture medium, and was surprised to find that the substance did kill other bacteria. This's very important for human beings. It is the first substance that killed bacteria, the first antibiotic, penicillin. Do you know how penicillin kills those bacteria?"
Daniel shook his head in confusion, and Mom went on, "Bacteria and human cells are different. Our cells are generally made up of cell membranes, cytoplasm and nuclei. Bacteria also have a layer of cell wall consisting of peptidoglycan outside of the cell membrane, which acts as a kind of armor, allowing the bacteria to survive in harsh environments. But penicillin breaks the connection of peptidoglycans, drilling holes in cell walls, so that material inside the cell membrane leaks out and water from the outside flows in, making the bacteria rupture and die."
Daniel was curious about penicillin's ability of "drilling holes" in cell walls and asked, "but doesn't penicillin drill holes in our cells?"
Mom turned around and said, "Penicillin only works on cell walls consisting of peptidoglycan, which human beings don't have, so the medicine selectively kills the bacteria without harming the human body. That's not always true though. For example, some people are allergic to penicillin, so the doctor will ask and check carefully before giving the medicine. You know, compared with its side effects, penicillin has much more positive effects. Some people believe that modern medicine began with Fleming's discovery of penicillin in 1928, and that was the first shot in our war against bacteria."
Author: Huang Jing
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