Skin is our first line of defense against disease and injury. It's anessential barrier against the germs of the outside world. And when youlook at your skin, it's hard to imagine that it's completely covered inbacteria. Now some new research finds your skin is even more colonizedby micro-organisms than previously thought.
Despite bacteria'sbad reputation, not all micro-organisms are bad, says Elizabeth Grice,a geneticist working at the U.S. National Human Genome ResearchInstitute.
Grice says many bacteria play some kind ofbeneficial role in maintaining health. Others exacerbate skin diseasessuch as eczema or acne. But our knowledge about these microscopichitchhikers is incomplete.
Grice and her colleagues decided touse some new technology to examine skin bacteria. They recruited 10volunteers to donate samples of their skin bacteria, and the volunteershad skin scrapings taken from 20 different locations on their bodies.
"Theseareas were chosen based on the diversity in terms of the types ofenvironments they are," Grice says. "For example, we chose a very hairyarea of the body, the back of the scalp, but we also chose hairlessareas such as the palm of the hand."
Grice used a genetictechnique called PCR, or polymerase chain reaction testing, to examinethe bacteria's DNA. This helped her identify the differentmicro-organisms more precisely. Previously, scientists were only ableto identify bacteria that tolerated the growth media well. But withPCR testing, Grices says they were able to find bacterial speciesheretofore unknown on skin. And she says they found many more typesthan expected.
"The dominant bacteria in the oily areas is apropioni bacterium which we know is present in oily areas for the mostpart because this type of bacteria is able to break down the oils inour skin," Grice says. "In the moist areas, we commonly seeStaphylococcus species, and in the drier areas, we generally see agreater mix and variety of bacteria. There didn't seem to be onedominant type."
Grice says surprisingly, dry areas of the skin, such as the forearm, had the greatest number and variety of bacterial species.
"Someof the drier areas are more exposed to the environment, and what we mayhave sampled from the drier areas may actually be transient bacteriaand not actually bacteria that set up permanent residence there," shesays.
Grice says there's much more to be learned about the manydifferent kinds of bacteria on the skin and what role they play inhealth. And she posits that the bacterial environment on your skin maydetermine what types of pathogens you are susceptible to.
Grice's paper is published in the journal .