A primer on antibiotic resistance, part I: what are antibiotics?

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Sandra Porter

Antibiotics are molecules of biological warfare. Produced by bacteria and some fungi, in response to extracellular signals, antibiotics represent a diverse group of compounds that inhibit bacterial growth at different points and different stages of the life cycle. We will get around to antibiotic resistance, but in these few words, I think I already wrote quite a bit. Admittedly, some of these ideas need a bit of chewing, if they are to be properly digested. Already, I can imagine hands raised and questions waiting to be asked.

What are antibiotics made of? I'm confused about this idea of biological warfare. Why would bacteria make substances that can kill other bacteria? You said bacteria make antibiotics! Don't we use antibiotics to kill bacteria?

Bacteria (and a few fungi) make antibiotics. In other words, they are natural products; just as natural as ginseng, digitalis, and golden seal.

But who makes them?

Bacteria make them - more later, and they bear a strong physical resemblance to the fungi that make antibiotics.

Do they exchange DNA? Do they represent some odd branch of the phylogenetic tree? What do these compounds do that inhibits bacterial growth? What do they kill and how do they do it? How can bacteria make antibiotics if antibiotics inhibit bacterial growth? Isn't this some kind of microbial suicide?

Come back soon and I'll do my best to answer some of the questions.


Other articles in this series:
1. A primer on antibiotic resistance: an introduction to the question of antibiotic resistance.
2. Natural vs. synthetic drugs: what is the difference between an antibiotics and synthetic drugs?
3. How do antibiotics kill bacteria? a general discussion of the pathways where antibiotics can act and one characteristic that helps some bacteria survive.
4. Are antibiotics really only made by bacteria and fungi? It depends on what you'd like to call them.
5. The Five paths to antibiotic resistance: a quick summary

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