Skin is our first line of defense against disease and injury. It's an
essential barrier against the germs of the outside world. And when you
look at your skin, it's hard to imagine that it's completely covered in
bacteria. Now some new research finds your skin is even more colonized
by micro-organisms than previously thought.
Despite bacteria's
bad reputation, not all micro-organisms are bad, says Elizabeth Grice,
a geneticist working at the U.S. National Human Genome Research
Institute.
Grice says many bacteria play some kind of
beneficial role in maintaining health. Others exacerbate skin diseases
such as eczema or acne. But our knowledge about these microscopic
hitchhikers is incomplete.
Grice and her colleagues decided to
use some new technology to examine skin bacteria. They recruited 10
volunteers to donate samples of their skin bacteria, and the volunteers
had skin scrapings taken from 20 different locations on their bodies.
"These
areas were chosen based on the diversity in terms of the types of
environments they are," Grice says. "For example, we chose a very hairy
area of the body, the back of the scalp, but we also chose hairless
areas such as the palm of the hand."
Grice used a genetic
technique called PCR, or polymerase chain reaction testing, to examine
the bacteria's DNA. This helped her identify the different
micro-organisms more precisely. Previously, scientists were only able
to identify bacteria that tolerated the growth media well. But with
PCR testing, Grices says they were able to find bacterial species
heretofore unknown on skin. And she says they found many more types
than expected.
"The dominant bacteria in the oily areas is a
propioni bacterium which we know is present in oily areas for the most
part because this type of bacteria is able to break down the oils in
our skin," Grice says. "In the moist areas, we commonly see
Staphylococcus species, and in the drier areas, we generally see a
greater mix and variety of bacteria. There didn't seem to be one
dominant type."
Grice says surprisingly, dry areas of the skin, such as the forearm, had the greatest number and variety of bacterial species.
"Some
of the drier areas are more exposed to the environment, and what we may
have sampled from the drier areas may actually be transient bacteria
and not actually bacteria that set up permanent residence there," she
says.
Grice says there's much more to be learned about the many
different kinds of bacteria on the skin and what role they play in
health. And she posits that the bacterial environment on your skin may
determine what types of pathogens you are susceptible to.
Grice's paper is published in the journal Science.
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