Researchers have completed the first "census" of the bacteria, viruses, and other microscopic organisms that "live, eat, excrete, reproduce and die in or on us," the Los Angeles Times reports.
The $170 million Human Microbiome Project, which ran for five years and involved hundreds of researchers, found there are about 100 trillion microscropic life forms living on or in the human body, with as many as 10,000 different strains or types. For example, a human vagina may be dominated by a single bacteria, whereas the mouth is "rain-forest like" in its diversity.
Adding to the variation, different microbes appear to be performing the same tasks in different people, researchers found. According to Curtis Huttenhower of the Harvard School of Public Health, "you can think about it like jobs in a city... If you go to two different cities, both will have banks and transportation and lawyers, but the specific people performing those tasks might be very different."
The research is described in Nature and several other papers released on Wednesday. Scientists hope that a better understanding of human bacteria will help improve health care delivery, perhaps by linking bacteria changes to medical disorders.
Altogether, the bacteria may weigh as much as six pounds in a fully grown adult male (Mestel, Los Angeles Times, 6/13).