Microbes and Human Skin

Human skin is the largest organ in the body, and it's our first line of defence against disease, injury, and the pathogens that would do us harm. Part of its success is due to the delicate balance between the cells of our body and the microbes crawling all over us.

You may have a scrupulous hygiene regime, and the cleanest skin on the planet, but you will still have millions of microbes all over you, and it's no bad thing. Most are probably doing us the power of good. We have evolved with them over the centuries and some probably provide benefits that we aren't even aware of at the present time. There will be some that are neutral, such as Staphylococcus epidermis that by its presence prevents dangerous pathogens such as Staphylococcus aureus from taking up residence. There are also microbes that turn the oily substance produced by the sebaceous glands into a kind of natural skin moisturizer.

Human skin is an oasis for microbes, an ecosystem that supports bacteria, fungi, and other microbes. The sheer diversity of bugs that keep us company is much greater than previously thought. That was the conclusion of a survey published in the journal Science in May 2009. Scientists decoded the genes of 112,000 bacteria in samples taken from 20 spots on the skin of 10 healthy research volunteers. Powerful gene sequencing technology allowed researchers to locate more types of bacteria than had ever been found before on the human skin. The study found bacteria belonging to 19 different phyla and 205 different genera.

And it turns out that these microbes have their favourite spots. For example, those that reside on the moist hairy skin under the armpit are very different from those that reside on the relatively hairless forearm. The forearm had the most diverse range of species with 44, and the area behind the ear had the least with 19.

The survey forms part of a much larger study - the Human Microbiome Project (HMP) - which aims to understand the relationship between humans and the microbial communities that exist with us.

The skin survey was much more than a counting exercise. The research will feed into work aimed at studying why some pathogens become resistant to antibiotics, and scientists will also use the findings to try and understand what is different about the skin of people with psoriasis and eczema.

National Human Genome Research Institute