An electron microscope view shows a clump of Staphylococcus epidermidis bacteria (green), one of the 10,000 species of microbes found in healthy humans, the Human Microbiome Project has found.
For the first time, scientists have cataloged human germs, determining that more than 10,000 species of microbes can be found in and on a healthy person.
These bugs -- mostly benign but occasionally causing illness -- occupy just about every part of the body, living on the skin, in the stomach and intestines, up the nose (and every other other orifice), according to the Human Microbiome Project.
The germ gene map is the culmination of the five-year, $173 million effort involving hundreds of scientists and dozens of universities.
Here's the news release from the National Institutes of Health.
The Washington Post summarizes the findings:
Researchers found that both the number and variety of microbes differed among an individual's body habitats. They also observed that conditions such as temperature and acidity, as well as the work being done by the human cells in the various body habitats, appear to influence which microbes live there.
For example, there are roughly 4,000 species of microbe in the intestine, where they help digest nutrients and produce vitamins and anti-inflammatory compounds. On the other hand, the vagina has only about 300 - and the diversity decreases during pregnancy to provide a healthy passage for the infant.
Live Science points out that there are trillions of microbes, which outnumber human cells 10 to 1. Most are bacteria. Other creature features include protozoa, archaea, bacteriophages, wormlike helminth parasites and yeasts.
"This is a whole new way of looking at human biology and human disease, and it's awe-inspiring," Dr. Phillip Tarr of Washington University at St. Louis, one of the lead researchers, told the Associated Press. "These bacteria are not passengers. They are metabolically active. As a community, we now have to reckon with them like we have to reckon with the ecosystem in a forest or a body of water."
The findings appear in 16 scientific articles to be published Thursday in Nature and in several journals in the Public Library of Science (PLoS).