Wednesday, November 11, 2009

In a world overrun by antibiotics, what are we selecting for?

As a graduate student, I read a lot of self-help books. One of my favorite concepts is from Marcus Buckingham’s “Find Your Strongest Life”:

What does working look like?

It’s a very goal-oriented approach to life. Envision what you want your life to look like, and work backwards from there.

The concept of selection is very similar to the “what does working look like” approach. In my college microbiology class, I was tasked with isolating a microbe—from the environment—that could eat milk (casein proteolysis). So I left an open container of milk out in my dorm room for a week and waited to see what grew. To select for a milk-eating microbe, provide an environment where a milk-eating microbe would do well.

But what does this have to do with the zombie apocalypse that I was rambling on about in an earlier blog entry?

Well, if you want to get humans who are good at surviving zombie attacks, one way to do it would be to flood the world with zombies and see who’s left. If you did that, you’d be selecting for zombie survivors.

But while you would nearly guarantee the remaining humans were zombie-resistant, you would have little control over HOW they were zombie-resistant, or any number of other traits they would possess. You might end up with an excellent marksman, a swift runner, or a violent sociopath. You might find the survivor was just very good at hiding.

So what do antibiotics select for?
When you take antibiotics, you’re basically flooding your microbial world with something deadly. Unless you kill every single microbe, you will select for microbes that survived the antibiotics onslaught. They will survive and multiply in a land empty of competing microbes that used to keep them in check.

I could go on for several more paragraphs about antibiotics, but I’ll try to wrap this up: when you use antibiotics, anything that survives is antibiotic-resistant, but both “good” and “bad” microbes can have that ability. High dosages of antibiotics will kill off more microbes, leaving less to prosper. Using a combination of antibiotics would be like unleashing zombies on the world and then following it up with vampires: while there are citizens uniquely skilled at surviving either monster, there are far fewer individuals who can survive both.

So what happens if the world is full of violent criminals and suddenly zombies kill off a huge portion of civilized society, including law enforcement? Do you think a bad guy or two would survive? Would anyone left standing be able to keep them in check?


  1. Discussion of the zombie apocalypse started some lively conversation on RadioScienceNews this past saturday, from the same caller who wondered about arthritis and nanobacteria... RJ Pollack

  2. checking the posting, with profile

  3. So, Amber, to recap - Don't use antibiotics if you can help it - your body has good, helpful microbes and antibiotics don't discriminate, and in fact kill off the weakest ones leaving the resistant bugs (hence yeast infections following antibiotic use). Would you say that sometimes they're still appropriate though? Like a sinus infection that doesn't go away?

  4. @musicwench: That's pretty much what I'm saying. There are definitely cases where antibiotics are necessary and appropriate--sometimes even a healthy immune system can't clear an infection. I just want folks to understand that antibiotics still somewhat indiscriminate in the microbes they kill, and a lot of microbial collateral damage is going to happen when you take your antibiotics!

  5. Just remember, Amber, that many/most antibiotics don't actually kill bacteria, but inhibit their growth (by killing growing bacteria). But I LOVE this post and have shared it with my students.

  6. That is an excellent point Mark! Perhaps antibiotics are even more like zombies than I previously thought (targeting the living and growing).

  7. J. Preston Van BurenNovember 19, 2009 at 10:30 PM

    Now you are just making me picture a bunch of zombies getting their panty hose (peptidoglycan as it relates to microbes) ripped off by these so called zombie killers. What a strange image!

  8. A strange image is a memorable image! If you're moved by zombie metaphors, another fun microbiology topic is the E. coli GASP (growth advantage in stationary phase) phenotype. Although in that situation it is the living feeding off the dead!