WEDNESDAY, June 13 (HealthDay News) -- For the first time, researchers have been able to identify what is "normal" when it comes to the microorganisms living in and on the human body.
According to 14 new studies being published in the June 14 issue of Nature and several Public Library of Science journals, the human "microbiome" consists of more than 10,000 microbial species and 8 million microbial genes, most of which co-exist happily with humans to their mutual benefit.
"This is giving us a picture of what a healthy individual looks like," said Jeffrey Cirillo, a professor of microbial and molecular pathogenesis at Texas A&M Health Science Center College of Medicine in Bryan, who was not involved with the study.
Scientists hope that knowing what "normal" looks like will one day help scientists prevent and treat diseases.
Little has been known about the inhabitants of the various parts of the human body because it's difficult if not impossible to grow most of the bacteria found there, Dr. Eric Green, director of the National Human Genome Research Institute, said during a Wednesday news conference.
But the advent of new and cost-effective DNA sequencing techniques now allows researchers to sample and identify microorganisms directly from the human body.
This massive five-year project involved 240 healthy adult volunteers in St. Louis and Houston.
Researchers took samples from 15 sites in men and 18 sites in women, including the mouth, skin, nose, vagina and lower intestine.
The researchers counted more than 10,000 species of microbes in the body and as many as 10 bacterial cells for every human cell.
In a 200-pound adult, that amounts to between two and six pounds of bacteria, Green said.
The 8 million or so genes from these microbes (compare that to only 22,000 in the normal human genome) "play a critical role i
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