Humans Wear Diverse "Wardrobe" of Skin Microbes, Study Finds

Ben Harder
for National Geographic News
February 6, 2007
The billions of microscopic critters that cloak your skin are a bit like fashionable threads—the ones you're wearing today may be out by next season.

That's the implication of a new study, which identified more than 240 distinct microbes on the forearms of six healthy people.

Each person's "wardrobe" of germs seems to be as unique as his or her sense of style. No two volunteers had all the same microbes on their flesh, though they did have some overlap, said study leader Martin J. Blaser.

"There's a lot of variation from person to person—tremendous variation," said Blaser, a microbiologist and infectious disease doctor at the New York University School of Medicine.

At the same time, he said, "we also found this kind of scaffold—a preserved set of organisms—that's pretty consistent."

People's microbial outfits seem to be coordinated: Left and right arms matched in any given test.

But volunteers who were tested repeatedly showed little similarity among the microbes they sported from one time to another.

"The skin is an extremely complex ecosystem [that's readily] affected by our environment," Blaser said.

(Related photos: skin as art.)

"When we change our soap [or] shampoo [or] laundry detergent, when we change whether we're wearing a cotton shirt or a wool shirt, all of these are going to have an effect on our skin flora," he said. ("Flora" is microbiologists' term for microscopic life forms.)

Wardrobe Malfunction?

For their study, Blaser and three colleagues probed small skin samples from the six volunteers and found 1,221 signatures of nonhuman DNA (get an overview of human genetics).

From these they identified 182 distinct species, some of which are new to science. Eight to ten months later they retested four subjects and found 65 additional species.

The results appear this week in the online early edition of the Proceedings of the National Academy of Sciences.

Blaser notes that his research goal is not merely to census our most intimate microscopic companions.

He and other experts want to know whether certain skin microbes are connected to chronic inflammatory diseases such as psoriasis and eczema—which would make the critters our skin's version of a wardrobe malfunction.

David A. Relman is a microbiologist at Stanford University and chief of infectious diseases at the VA Hospital in Palo Alto, California.

"A lot of skin diseases look as if they ought to be caused by an infectious agent," Relman said. "But we don't have an infectious agent" to blame.

Relman suggests that "orchestrated manipulation" of the skin's ecosystem, perhaps with science-based cosmetic products, might someday suppress disease-causing skin bacteria and nurture friendly ones.

"A better understanding of the indigenous microbiota of the human body," he said, "will lead to much more prudent strategies for maintaining and restoring health."

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