Study Finds Unexpected Bacterial Diversity on Human Skin
The health of our skin—one of the body's first lines of defense against illness and injury—depends upon the delicate balance between our own cells and the millions of bacteria and other one-celled microbes that live on its surface. To better understand this balance, National Institutes of Health researchers have set out to explore the skin's microbiome, which is all of the DNA, or genomes, of all of the microbes that inhabit human skin. Their initial analysis, published recently in the journal Science, reveals that our skin is home to a much wider array of bacteria than previously thought.
Levi Salley: In order to maintain healthy skin, it is essential to have just the right balance of the body's own cells and microbes—tiny organisms that include bacteria.
Segre: We need to think about that there are bacteria that are promoting our health and move away from thinking of them as our adversaries but rather as our allies.
Levi Salley: Dr. Julia Segre, Senior Investigator at the National Human Genome Institute explains that researchers are taking a closer look at microbes by using the power of modern DNA sequencing technology. Compared to traditional research methods that involved growing microbial samples—or cultures—in the laboratory, these new findings show unexpected bacterial diversity on the skin.
Segre: We've always suspected that there was probably 100 bacteria that we couldn't find for every one, but now we have names for them and we know what they are so that we can change the culture conditions and try to grow them and use this as a baseline for then seeing how the microbioda, the small microorganisms, how their communities change in disease states.
Levi Salley: Understanding the complex genetic and environmental factors involved in skin conditions like eczema, psoriasis, acne, antibiotic-resistant infections and many other skin disorders may lead to new and better strategies for treating and preventing skin diseases. Dr. Segre explains that microbe samples were taken from 20 different sites on the bodies of 10 healthy volunteers. These sites represent three distinct microenvironments: oily, moist, and dry.
Segre: We're analyzing what bacteria live at all different depths of your skin, and with these methods, the diversity that we found is about 100 times greater than what was previously known.
Levi Salley: In the study, the greatest bacterial diversity of about 44 specie types was found on the forearm. The least amount of diversity was found behind the ear with only 19 specie types. Bacterial samples were taken from body locations pre-disposed to skin disease. Some locations were sampled twice over a 4-6 month period to closely examine how bacterial communities change with time. While Dr. Segre says the study reinforces the benefit of some bacteria, she also points out the importance of continuing basic public health practices such as hand washing.
Segre: This study underscores what we've known all along. We have to focus on the sanitation. We have to focus on washing our hands and not bringing bacteria from the environment onto our bodies or bringing bacteria from one place in our bodies to another.
Levi Salley: Dr. Segre explains that the study, published in the journal Science, is part of a bigger initiative.
Segre: This year the NIH Roadmap for Medical Research, launched the Human Microbiome Project, whose aim is to study the diversity of bacteria that live in and on the human body, assessing then the bacterial diversity on the skin, the vagina, the nose, the gut, and the oral cavity and are also funding projects that begin to examine the correlation between disease states and the microbiome.
Levi Salley: For more information on this study and the Human Microbiome Project, visit www.nihroadmap.nih.gov/hmp. This is Alaya Levi Salley, National Institutes of Health, Bethesda, Maryland.