Not to gross you out, but your belly button is crawling with bacteria in all shapes, sizes and appetites.
That's a good thing, a group of North Carolina researchers says after studying more than 500 belly-button swabs, some from their own navels.
Most of the tiny critters in that "jungle of microbial diversity" are harmless, the researchers say, and lots of them kill off their disease-causing cousins.
Not just numerous, they also are diverse: 2,368 types identified so far, with everybody's belly button carrying a different cast of characters.
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Those are among findings of the Belly Button Biodiversity Project, an effort by researchers at North Carolina State University and the North Carolina Museum of Natural Sciences, both in Raleigh.
Magnified mug shots of the bacteria are posted on the project's website, Wildlifeofyourbody.org — along with an article detailing the likely critters crawling on pop superstar Lady Gaga.
"Your belly button is a great place to grow up if you're a bacterium," said Dr. Tom Kottke, a cardiologist at Regions Hospital in St. Paul, Minn. "It's warm, dark and moist — a perfect home."
Too many people think all bacteria are bad, said lead researcher Jiri Hulcr. The Belly Button Project is out to "educate the public about the role bacteria play in our world. Bacteria are always present on our skin and in our bodies."
They live in and on every square inch of you, and for the most part it's a win-win relationship — just you and 100 trillion very close friends, about 10 times the number of cells that make up your body.
The one-celled creatures — so tiny you'd have to stack up 25,000 or so to equal an inch — help out in many ways. Some help us make use of the nutrients in food and make waste from what's leftover. Some consume leftover detritus on our skin that otherwise might feed harmful pathogens. Still others are harnessed by scientists to produce medicines and vaccines.
But sometimes they can cause sore throats, ear infections, pneumonia or more deadly diseases such as cholera and leprosy. They also can cause belly-button infections.
"Infections usually are treated with antibiotics," Kottke said, "but we've gotten more cautious about prescribing them. Sometimes antibiotics do more harm than good, like when they wipe out all the beneficial bacteria in your gut and the bad ones take over."
Gently washing your navel with soap and water regularly will lower the likelihood of bacterial problems, but you'll still have lots of microbial visitors in there.
About 90 percent of belly buttons are "innies," navel depressions that fold inward, created when the umbilical cord connecting a mom with a newborn baby is cut after birth and heals. Not surprising, innies carry more bacteria than protruding "outies," Hulcr said.
"Each person's microbial jungle is so rich, colorful and dynamic that in all likelihood your body hosts species that no scientist has ever studied," he said. "Your navel may well be one of the last biological frontiers."
The researchers continue to gaze at navels, but they've also cast their eyes on wildlife that flourish on other body parts.
So stay tuned: The new targets are armpit microbes and forehead mites.