Bacteria are like opossums – they live stupid and have a lot of offspring


Bacteria are essentially DNA wrapped in a coat. No brain, no spinal cord, no ability to think. So why, then, do we say they “outsmart” us? Is it really, as we so often read, an “arms race” between us and “clever” bacteria who have begun to “outsmart” us and our drugs? Or is there something else going on that better explains things?

Mike Apley, a veterinarian, and professor of medicine and clinical pharmacology at Kansas State University’s College of Veterinary Medicine, offers us an alternative view of bacteria:

Bacteria are like opossums; they live stupid and have a lot of offspring. It’s not that the bacteria outsmart us, but it’s that there are so many offspring with so many different mutations that the ones that can survive multiply, and we have a new, adapted population.


Apley is nobody’s fool. Aside from the above credentials, he was also a member of President Obama’s prestigious Advisory Council on Combating Antibiotic-Resistant Bacteria.

To understand his seemingly silly statement, take a look at the standard diagram used to teach antibiotic resistance. The trick is in going from step 2 to step 3. Question: What did the two (antibiotic resistant) bacteria do in step 2 that was so “clever” that resulted in so many of them in step 3?


Answer: Not a thing. They survived – that’s all they did. And then they did what bacteria do all day – they had “a lot of offspring.” So now we have a ton of bacteria all of whom are resistant to our drugs – Apley’s “new, adapted population.”

So if it’s not a case of us being outsmarted by the bacteria, then what’s going on here? In Apley’s view, it’s just your basic case of evolution and natural selection – which isn’t what most people think it is.

Carefully thought through, the antibiotic resistance diagram – going from step 2 to 3 – corrects this common yet crucial misunderstanding: Bacteria under threat from antibiotics don’t change by acquiring the trait of antibiotic resistance, thereby “outsmarting” us. Instead, what happens is that those few bacteria that already possess the trait of resistance to antibiotics, survive the onslaught of the drug and go on to reproduce.

This Khan video smartly explains what evolution is and isn’t. To get the most out of it, keep in mind that the example they use of an advantageous trait selected to be passed on to future generations – longer legs – is analogous to the advantageous trait of antibiotic resistance in bacteria that they, too, pass on to future generations.


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