Scientists Surprised by Diversity of Skin Bacteria

This illustration shows the 20 sites on the human body that were targeted for microbial genome sequencing analysis. (Credit: Jane Ades/NHGRI)

This illustration shows the 20 sites on the human body that were targeted for microbial genome sequencing analysis. (Credit: Jane Ades/NHGRI)

Researchers recently discovered that the diversity of bacteria on human skin is much greater than previously thought. The research, conducted by scientists from the National Human Genome Research Institute (NHGRI), National Cancer Institute (NCI), and the National Institutes of Health (NIH) Clinical Center.

In the study, skin samples were taken from twenty different locations on the bodies of ten healthy volunteers. The sites on the body were specifically chosen due to each location’s propensity to develop skin disorders. The sites were categorized into three different microenvironments: oily, moist, and dry. Oily sites included locations beside the nose and inside the ear; moist sites included the armpit and inner elbow; and dry sites included the inside surface of the mid-forearm and the palm of the hand.

After collecting the skin samples, the scientists used modern DNA sequencing techniques and computational analysis to determine the diversity of skin bacteria. After DNA was extracted from each sample, the scientists sequenced the 16S rRNA genes (a type of gene specific to bacteria).

In their analysis, the scientists identified over 112,000 different bacterial gene sequences. The sequences were then classified and compared–this led to the classification of skin bacteria into 19 different phyla and 205 different genera. The scientists found that the greatest diversity of bacteria occur on the forearm and the smallest diversity of bacteria are found behind the ear. In addition, the scientists discovered that the biggest influence on bacterial diversity is body location. That is, the skin bacteria on the back of your arm are more similar to the skin bacteria on the back of someone else’s arm than they are to the skin bacteria on the front of your arm.

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