Venus Has A Crowded Belly Button

Adam: I believe you know this lady ...

Me: Yes, I think we met in a museum once, or maybe it was a textbook. She's very nice to look at ...

Adam: Yep — but let me tell you a little secret about her and about you, about all of us. One of the most intriguing parts of our anatomy turns out to be ...

Me: Be careful, Adam ...

Adam: ... right ... here.

A close-up of Venus' torso.
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Me: What do you mean? The tummy?

Adam: No, closer in. Here. The belly button.

A close-up of Venus' navel.
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Me: What's so special about a belly button?

Adam: Well, we're discovering this right now. I think you'll be astonished.

Me: I think I'll be disgusted.

Adam: No, no, come on ... If you take a really close look at a belly button, if you peer in, you might see something rather unusual ...

A close-up artist's rendering of a belly button bacteria.
Adam Cole/NPR

... you will find a discrete, stable community of bacteria living on your skin. What's more, the crowd in your belly button is not likely to resemble the crowd in my belly button.

Me: Really?

Adam: That's what the folks at the Belly Button Biodiversity project have found. For months now, they've been contemplating navels as part of a wider effort to discover what sorts of bacteria live in and on the human body. Jiri Hulcr, who leads the project, says they collected samples from hundreds of belly buttons.

Me: Why, may I ask, belly buttons?

Adam: Well, for one thing, Hulcr says they didn't want to look in our arm pits.

Me: I knew I didn't want to have this conversation.

Adam: But the long answer is: Belly buttons are "safe havens" for bacteria — they're protected from sun and water and unpleasant excretions. Because no matter what people claim, belly buttons don't get washed too often.

Me: So did they find something important?

Adam: Oh, yeah. They found around 1,400 types of bacteria, more than 600 of which were unknown to science — they were completely new, unclassified organisms!

Me: On us?

Adam: Yes. Take a look. Here are three petri dishes with bacteria from three different belly buttons.

Me: All from belly buttons? Why do they look so different?

Adam: Because they are different. As I said, belly button bacteria are personal. My guys, from babyhood on, have been different from your guys. Hulcr calls these "microbial signatures." We might share a couple of common types, but the combination of bacteria belongs particularly to us.

Me: Why?

Adam: Well, I think that's the coolest part. We are born without any bacteria on our skin, but as soon as we are exposed to the world we start to accumulate microbes. The places we go, the things we eat, the people we interact with — they all affect our "microbial signature." Our belly buttons — or really, the bacteria they contain — are reflections of our lives.

Me: But what would happen if I go in there with soap and a washcloth and get rid of mine?

Adam: You'll have trouble cleaning them all off — they're too much a part of your skin. When Hulcr resampled some belly buttons after a couple months and dozens of showers, their bacteria — the same bacteria from before — were still growing happily. You can't get rid of them. And you shouldn't want to.

Me: Why not?

Adam: Well, they clean up after you, gobbling up sweat and dead skin. They even compete with each other to keep you clean.

Me: What do you mean "compete"?

Adam: Take a look at this dish, grown from Belly Button #1263.

A petri dish shows a bacterial colony excreting antibiotics.
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Adam: This plate has a whole herd of bacteria, with one frosty-looking colony in the middle.

Me: It looks like the herd is a little thinner around that colony.

Adam: That's because the bacteria in that colony are excreting antibiotics to kill their neighbors. Bacteria can eliminate other bacteria. Especially invaders. They help protect you. Kill 'em all, and foreign microorganisms can infect you much more easily.

Me: Hmm. That's good. But I still don't like the idea of all those bacteria crawling all over me.

Adam: Well, try thinking of yourself as a planet — a beautiful home to hundreds of happy, healthy organisms.

For our native bacteria, our bodies are the whole world.
Adam Cole/NPR

Me: Hmm ... not sure if that helps.


The Belly Button Biodiversity project is a collaboration of the Rob Dunn lab at North Carolina State University and the Nature Research Center at the NC Museum of Natural Sciences. Noah Fierer's lab at the University of Colorado Boulder helped process the samples. One of the project's recent subjects, reporter (and Radiolab regular) Carl Zimmer, was told his belly button is home to rather exotic bacteria. He proudly tells about it here. In a recent post I wrote that gut bacteria don't seem to reflect human lifestyles. Jiri Hulcr thinks belly button bacteria are influenced by our experiences. This is new science.


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