Where can you find your skin's most diverse community of bacteria? Not in a sweaty armpit or linty belly button. According to a new survey of the bacterial ecosystem that covers us, the diversity hot spot of the body's exterior is the forearm. And the surprises don't end there.
Microbes that live in and on our bodies outnumber our own cells 10 to one, but researchers have only recently begun to catalog the residents on our skin. Traditionally, scientists identified human skin bacteria by swabbing volunteers and culturing the samples, but those results skewed toward microbes that grow well in the lab. Thanks to ever-evolving gene-sequencing technology, scientists can now use microbial RNA to identify organisms. With these techniques, researchers have found an unexpectedly wide variety of bacteria on human skin (Science, 23 May 2008, p. 1001). But no one had ever systematically compared bacterial colonies from different areas on the human body.