Study Finds Multitude of Bacteria on Human Skin

May 29 -- THURSDAY, May 28 (HealthDay News) --Should it worry you that there are 19 different species of bacteria living behind your ears?

Not especially, when you consider that there are 44 species thriving right out in the open on your forearm.

This information comes to you from scientists at the U.S. National Human Genome Research Institute, who have used the same techniques that enabled them to map the human genetic makeup to identify all the bacteria living on human skin.

There are lots of them, of all sorts. In scientific terms, 19 separate phyla and 205 different genera to be found on the 20 sites sampled by the researchers. The diversity of microbial life on human skin was much greater than expected, according to a report in the May 29 issue of Science.

This might strike some people as an odd way to be spending tax dollars, but that's the wrong view to take, said Julia A. Segre, a senior investigator at the institute who took part in the study.

For one thing, there are many potential medical applications of the work, Segre said. "We are using these results already to initiate clinical research," she said. "We want to know what is the contribution of the human microbiota to common and rare skin disorders."

Segre herself is studying the skin disorder eczema. "We are hoping with this project that we can understand the pathogenic processes in these conditions," she said. "And perhaps we can learn how to help healthy bacteria keep pathogens in check."

But there is also the sheer scientific beauty of what is called the Human Microbiome Project, an offspring of the Human Genome Project, which mapped all the genes in the body. The same techniques used to go through the human genetic sequence now can be applied to bacteria, Segre said.

The diversity found as the investigators sequenced bacteria found in moist sites (inside the nose, the armpits, the navel), dry areas (such as the forearm) and oily sites (inside the ear, between the eyebrows, the back of the scalp) was a surprise, she said.