10,000 bugs identified in humans
A major census of the trillions of bugs that inhabit the human body has identified more than 10,000 species.
Researchers sampled more than a dozen body sites in almost 250 healthy men and women to analyse their bacteria.
Bugs were collected from the mouth, skin, nose, vagina and lower intestine.
The study, published in Nature and several other journals, showed that even healthy people carry low numbers of potentially harmful bacteria.
The findings will help scientists discover how some of these microbes can suddenly turn deadly.
Lead investigator Professor George Weinstock, associate director of the Genome Institute at Washington University in the United States, said: "It's not possible to understand human health and disease without exploring the massive community of micro-organisms we carry around with us.
"Knowing which microbes live in various ecological niches in healthy people allows us to better investigate what goes awry in diseases that are thought to have a microbial link, like Crohn's and obesity, and why dangerous pathogens sometimes, but not always, cause life-threatening illnesses."
He added: "Our bodies are part of a microbial world. You can think of our ecosystems like you do rain forests and oceans, very different environments with communities of organisms that possess incredible, rich diversity."