"They almost certainly help us defend against nastier bacteria, such as pathogens, that might invade," explained Blaser, who added they also might help to keep the skin "well oiled and toned."
Some bacteria stay put for a long time while others are more transient, coming and going.
Blaser thinks most species are acquired from other people — usually one's mother — but also from other family members, friends, partners and even pets.
"These types of surveys, whether conducted in the gut, mouth, or skin, are revealing a heretofore unappreciated level of biodiversity associated with our bodies," said Jeffrey Gordon, director of the Center for Genome Sciences at Washington University's School of Medicine.
He added, "An inspiring or sobering thought: As adults we have 10 times more microbial cells than human cells, and perhaps 100 times more genes embedded in the genomes of our microbial partners than in our own human genome."
Blaser and his team next plan to study people who suffer from skin diseases, such as psoriasis or eczema, to see if they possess different microbes than those found on people with healthy skin.
