"We found the bacteria in my underarm are more similar to the bacteria in your underarm, than my underarm bacteria are to my forearm bacteria," Segre said.
That offers a clue to disease, because different skin diseases tend to appear in specific places on the body.
"We are using these findings to start to explore how the microbiome contributes to disease such as eczema or MRSA [methicillin-resistant staph] infection. We know there is a contribution, but we think there may be even a greater bacterial contribution than we had previously appreciated," Segre said.
That contribution is not one-sided. We tend to think of bacteria as germs that cause disease -- but the new findings suggest that a healthy crop of normal bacteria prevents disease.
"For example, 1.5% of Americans have MRSA in their nose -- but they don't show any signs of infection," Segre said. "Maybe it is that the other bacteria are keeping the MRSA in check and not letting it grow and create an infection. Or maybe it is because the MRSA is changing between when it's up in someone's nose and when it causes an infection."
In future studies, the researchers will compare the microorganisms living on healthy people to those living on people with diseases.
"We want to see if there is a shift between what we find in normal individuals and what we find in someone with a skin disease," Segre said.
"Our results underscore that skin is home to vibrant communities of microbial life, which may significantly influence our health," Grice says in a news release.