WASHINGTON — There’s a zoo full of critters living on your skin — a bacterial zoo, that is. Consider your underarm a rain forest.
Healthy skin is home to a much wider variety of bacteria than scientists ever knew, according to the first big census of our co-inhabitants.
That’s not a bad thing, said genetics specialist Julia Segre of the National Institutes of Health, who led the research.
Sure they make your sneakers stinky, “but they also keep your skin moist and make sure if you get a wound that (dangerous) bacteria don’t enter your bloodstream,” she said. “We take a lot for granted in terms of how much they contribute to our health.”
The NIH’s “Human Microbiome Project” aims to find out which microbes live where on our bodies. Healthy volunteers were recruited to learn what microbes they harbor so scientists can compare the healthy with diseases of microbes gone awry.
The skin research, published today in the journal Science, is part of that project. Scientists decoded the genes of 112,000 bacteria in samples taken from a mere 20 spots on the skin of 10 people.
Those numbers, Segre said, translated into roughly 1,000 strains, or species, of bacteria, hundreds more than ever have been found on skin largely because the project used newer genetic techniques to find them.
Topography matters a lot, the researchers reported. If a moist, hairy underarm is like a rain forest, the dry inside of the forearm is a desert. They harbor distinctly different bacteria suited to those distinctly different environments.
How many are supposed to live there? That’s not clear yet. Some could be tourists, picked up as we go about our day. When researchers rechecked five of these volunteers a few months later, the bacteria in some spots — the moist nostril and groin, for example — proved pretty stable, while other spots, including the forearm, had changed quite a bit.
