According to their U.S. study, which was published on May 29, 2009, in the journal Science, they say that the, “Human skin is a large, heterogeneous organ that protects the body from pathogens while sustaining microorganisms that influence human health and disease.”
Their Science article is titled “Topographical and Temporal Diversity of the Human Skin Microbiome” and it was written by: Elizabeth A. Grice, Heidi H. Kong, Sean Conlan, Clayton B. Deming, Joie Davis, Alice C. Young, Gerard G. Bouffard, Robert W. Blakesley, Patrick R. Murray, Eric D. Green, Maria L. Turner, and Julia A. Segre.
Julia Segre, a senior investigator with The National Human Genome Research Institute's (NHGRI) and the head it its Epithelial Biology section, was the lead researcher in the study.
Dr. Segre studies the human skin and how it interacts with the outside world.
She states, “The skin is a major organ system that has to interact with and adapt to the environment. It's the interface between our complex physiology and an often hostile environment that dries us out and exposes us to chemicals and infectious agents. You don't want kitchen cleanser in your bloodstream and your skin is the way you keep it out." [NHGRI: “Unlocking The Skin's Many Secrets”]
Dr. Segre and her colleagues used cotton swabs to collect bacterial samples from ten healthy but “diverse” volunteers. Half of them were men, and the other half women. In all, the researchers found 112,283 organisms in the bodies of these participants.
Page two continues.
The NIH researchers analyzed 16S ribosomal ribonucleic acid (16S rRNA) gene sequences from twenty different skin (epidermal) locations on healthy humans.
Some were better adapted on the forearm, where it is relatively dry. Others prefer the armpit, toes, or eyebrows, where it is relatively moist.
The researchers stated, “The complexity and stability of the microbial community are dependent on the specific characteristics of the skin site.” [Abstract to Paper]
According to The Los Angeles Times article “1,000 species of bacteria found on healthy humans,” the study, “… reflects a growing realization that bacteria have colonized us inside and out -- and that their presence is not only harmless but also probably essential to the proper functioning of the body.”
In fact, the study found that “Mice bred to be entirely germ-free have smaller hearts and are unable to digest food properly.” [Los Angeles Times]
They concluded, “This topographical and temporal survey provides a baseline for studies that examine the role of bacterial communities in disease states and the microbial interdependencies required to maintain healthy skin.” [Abstract]
That baseline includes the Human Microbiome Project, whose mission is to catalog bacteria and other microorganisms that live in and around the human skin, nose, mouth, vagina, and gut.
Page three concludes with specific conclusions from the NIH study.
According to The Los Angeles Times article, the following list is a summary of some of the important findings of the NIH study.
• “More than half [of the species of bacteria] belonged to one of three big groups that made them a cousin either of the bacterium that causes acne; one that causes diphtheria; or Staphylococcus aureus, the culprit behind many dangerous antibiotic-resistant infections.”
• Moist areas -- such as the belly button and the inner bend of the elbow -- have up to 10 times as many bacteria per square inch compared with dry areas, like the inside of the mid-forearm….”
• “… the forearm turned out to have the greatest diversity of bacterial species, with a median of 44 among the 10 human volunteers.”
• “The least diverse site sampled was the oily area behind the ear, with a median of 15….”
• “… the locations of bacterial species is relatively consistent from person to person, perhaps implying some function that confers a benefit to the host.”
One of the purposes of the study was to learn more about how bacteria is involved with diseases of the skin. Dr. Segre states, "We don't really know what causes skin diseases.”
This study is helping to learn more, especially with such diseases as eczema and psoriasis.
According to the study, about 100 billion individual bacteria live on the average body of a human. Yes, that would be you and I.
People often say that bacteria on the body are bad. This is generally not true.
In fact, Dr. Segre, an investigator at the National Human Genome Research Institute. states, "We have to lose this language of warfare. Our goal is to keep the bacterial ecosystem in balance and move away from the concept that all bacteria are bad."
Learn more about the skin and problems associated with the skin at the WebMD website "Skin Problems and Treatments Health Center."