Image courtesy Rob Dunn Lab

North Carolina researchers are exploring the far reaches of … our belly buttons. And armpits.

By Laura Pellicer

They linger on your skin, burrow in your stomach and occupy every nook and cranny in your body: microorganisms – the bacteria, parasites and even viruses that make up your microbiome. It may sound unpleasant, but scientists are eagerly working to identify which microorganisms are in – and on – your body, as new connections emerge between these microscopic critters and your overall health.

North Carolinians are doing their part to contribute to this research. Dozens of residents, many recruited through the N.C. Museum of Natural Sciences, have stepped up to have their own bodies swabbed for science.

Julie Horvath, the head of the Genomics & Microbiology Research Lab at the N.C. Museum of Natural Sciences, is exploring microbes that make up the human body. Photo by Laura Pellicer
Julie Horvath, head of the Genomics & Microbiology Research Lab at the N.C. Museum of Natural Sciences, is exploring microbes that make up the human body. Photo credit: Laura Pellicer

Julie Horvath, a comparative evolutionary genomicist with North Carolina Central University, is just one of the researchers across North Carolina who are working to answer the question of the relationship between microbial diversity and human health. But first she wants to find out just which microorganisms are making a home in your body.

Blank plates

For Horvath, this quest started with the armpit, and a collaboration with Rob Dunn, a biologist in the Department of Biological Sciences at North Carolina State University who heads a project called Your Wild Life that explores the ecology of everyday life, including the biodiversity of your backyard, home and body.

“I said, ‘Let’s do the armpit! That sounds really gross and nasty but it’ll be engaging,’” Horvath recalled of the initial conversation with Dunn that sparked her latest microbiome research.

The researchers kicked off their armpit and belly button study by swabbing their own bodies and growing microbes from the swabs in the lab. Horvath’s belly button turned out to be an enigma.

“The other people in the lab all had things growing on their plates,” she said. “My plates were blank. And I got a little freaked out because I’m a scientist. You’re supposed to have microbes on your skin, and nothing’s growing on my plates?”

After a round of discussions with her fellow researchers, Horvath determined the antiperspirant she was using might be to blame.

Photo of three petri dishes with bacteria. Publicity image from the Rob Dunn's Belly Button Biodiversity project.
Publicity image from the Rob Dunn’s Belly Button Biodiversity project. Image courtesy Rob Dunn Lab, NC State University

“I had just gotten this job and didn’t like public speaking very much; it made me nervous. So I was wearing clinical strength antiperspirant. And so, potentially, when I would take a shower, it would wash down over my body, and so maybe it was getting in my belly button and that’s why nothing was growing in my belly button.”

From the colorful Genomics & Microbiology Research Lab that she heads, enclosed in the glass walls of North Carolina’s Museum of Natural Sciences, Horvath got museum employees and a horde of volunteers to offer up their pits for science. The microbial denizens of those armpits are on display in an online gallery.

Researchers split the participants into three groups. One group wore antiperspirant, another deodorant and the third group was asked to forgo conventional pit protocol and ditch the products.

The results, published in the journal PeerJ, show the use of deodorant or antiperspirant has a strong effect on types of bacteria living on the surface of the skin. Participants who used product had significantly more staph (Staphylococcaceae) than Corynebacterium. Those who didn’t wear product had more Corynebacterium than staph. By wearing antiperspirant, these citizen scientists were also killing off microbes and lowering the bacterial density on the skin.

“The main point is the products you put on your skin can significantly change the abundance and composition of the microbes on your skin,” Horvath said. “If you look at some of the other primates, you see that they don’t have as much of the staph and Corynebacterium that we do. Potentially, humans have evolved for some reason to have a lot more staph and Corynebacterium, and maybe that’s partly due to the product use that we have.”

Armpit sweat to earwax

Horvath has now set her sights on the generally underappreciated realm of earwax, and is actively swabbing, recording and analyzing the white (or yellow) stuff with the hopes of determining whether certain earwax types harbor different microbes.

“We know microbes feed on your sweat. If you either produce a lot of sweat or wet earwax, versus if you don’t, do you have different microbes growing on you?” Horvath asks. “We know that a lot of these play a role in your health. Any microbes that live on your skin are going to play a role in your immune system.”

Despite her enthusiasm to probe the dark depths of ears and armpits for the sake of microbiome research, Horvath warns against throwing caution to the wind for the sake of microbiome diversity.

“You don’t want to just go advocate, ‘Hey, go roll in the dirt and don’t wash your hands!’ Because that’s what some people are getting at,“ she said.

“But I would say, think about what you’re putting on your body. We know antiperspirant and deodorant have an effect. We know antibacterial products have an effect. Try to limit your use of things you know are going to kill off good microbes. Because killing off your good microbes is potentially going to have negative consequences.”

Following the gut

Scientists who are plugging away at human microbiome research are eager to compare petri dishes of blossoming bacteria with samples from our closest living ancestors: primates.

Using behavioral data from chimpanzees in Gombe, Tanzania – the same group of chimps Jane Goodall and her team have been monitoring since 1960 – researchers at Duke University have discovered a key connection between socialization and the gut microbiome.

Cutline: Anne Pusey, the chair of evolutionary anthropology at Duke University in her office at Duke University. Photo by Laura Pellicer
Anne Pusey, chair of evolutionary anthropology at Duke University, in her office. Photo credit: Laura Pellicer

Anne Pusey, chair of Duke’s evolutionary anthropology department, is the keeper of this behavioral data. She heads a project to digitize all the information gathered on these chimpanzees in the field and is a contributing author on a recent study published in Science Magazine.

This new research highlights socialization as a factor for the diversity of gut microbes and complements a long-term study from Jenny Tung, an assistant professor of biology at Duke who found connections between the intermingling of wild baboons and the gut microbiome.

“In humans, [researchers] know about the microbiome being transferred from mother to baby during a normal birth but not during cesarean,” Pusey said.

Based on this principle, Pusey says a reasonable assumption is that related chimps would have a more similar gut microbiome than non-related chimps. But instead, she found chimpanzees who spent time interacting had similar gut microorganisms, independent of whether they were related.

“That suggests that there’s transfer going on between individuals in ways other than just by birth,” Pusey said.

Steffen Foerster, a senior research scientist in Duke’s department of evolutionary anthropology, developed models to study the complex social relationships between these chimpanzees.

“It’s very dynamic, much like in humans. As we move around our daily lives, we meet people, spend some time with them and then leave when we want to,” Foerster said.

By following a different chimpanzee each day, recording social interactions and collecting fecal samples, researchers determined that the level of gregariousness of the chimps correlated with the richness or diversity of their gut microbes.

So what implications does this have for humans? A key difference in human versus chimpanzee interaction is that people don’t swap fecal matter quite as readily as chimpanzees.

Two adult male chimpanzees at Gombe during a grooming session. This type of social interaction provides opportunities for the transmission of gut microbes. Photo by Steffen Foerster
Two adult male chimpanzees at Gombe during a grooming session. This type of social interaction provides opportunities for the transmission of gut microbes. Photo credit: Steffen Foerster

“When they’re together, they groom each other, they play, they mate and also they – because they’re near each other – they’re defecating and they’re walking around in the same areas where each other have defecated,” Pusey said.

But our modern battle against dirt, germs, bacteria, parasites and general foul smells may be a setback for a diverse human microbiome.

“What people are starting to realize is, not having anything to fight against is making our immune system fight against itself,” Foerster said. “This increased prevalence of autoimmune disease might have to do with not having to fight off these parasites.”

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