for National Geographic News
The ever present armies of microbes in your digestive tract are so essential to your survival, a new study says, that you might consider yourself a super-organismhuman plus microbes equals you.
These hordes of "gut bugs" perform digestive duties that the human body alone cannot, according to the first ever comprehensive study of these microbes' genes.
To reach their conclusions, scientists conducted the most intensive intestinal exit poll yet.
By sampling two people's excrement, the researchers have revealed just how the microbes help us ferment our food, produce vitamins for us, and break down toxic chemicals.
The study maps the genes of the estimated 500 or more species that live inside us. About a quarter of these genes appear to belong to unknown species.
(See our quick overview of genetics.)
A Whole New World
The bacteria primarily cling to the intestinal walls in the bowels of the bowelsthe colon. They also hitch rides on chunks of undigested food, which researchers have nicknamed "whovilles," after the tiny villages in Dr. Seuss stories.
"We are discovering parts of ourselves we were not aware of," said microbiologist and study co-author Jeffrey Gordon of the School of Medicine at Washington University in St. Louis, Missouri.
"It's a whole other planet down there."
Our bodies carry ten times more microbial cells than human cells, and these microbes collectively contain at least a hundred times the number of genes in the human genome.
"Not only are we never alone," said microbiologist David Relman of Stanford University in Palo Alto, California. "Our partners contribute essential functions to our collective."
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