Healthy human bodies are inhabited by 10,000 germ species

We've known for a long time that the average human body is home to trillions of germs. It is believed that bacterial cells outnumber human cells 10 to 1, making up between 1 and 3 percent of our body mass. But scientists have only recently begun to learn which types of microbes live in healthy people, where they live, and what they do:

AP photo

They live on your skin, up your nose, in your gut - enough bacteria, fungi and other microbes that collected together could weigh, amazingly, a few pounds.

Now scientists have mapped just which critters normally live in or on us and where, calculating that healthy people can share their bodies with more than 10,000 species of microbes.

Don't say "eeew" just yet. Many of these organisms work to keep humans healthy, and results reported Wednesday from the government's Human Microbiome Project define what's normal in this mysterious netherworld.

One surprise: It turns out that nearly everybody harbors low levels of some harmful types of bacteria, pathogens that are known for causing specific infections. But when a person is healthy - like the 242 U.S. adults who volunteered to be tested for the project - those bugs simply quietly coexist with benign or helpful microbes, perhaps kept in check by them.

Full article here.