So does this mean sushi-loving Americans will soon acquire B. plebeius, too?
Probably not, the researchers said.
Today's food supply is far more sterile than the diets people were eating when this "lateral" gene transfer occurred, the experts said. Back then, people were probably eating seaweed that came directly from the ocean, with a higher microbe load than the nori sheets people eat today.
Overall, cleaner food and better hygiene is a good thing, responsible for dramatically reducing food-borne illness. But there might be some unintended consequences, including altering the microbiota in the intestines.
"The microbial load on the seaweed we currently eat is probably incredibly low," Sonnenburg said. "Gene transfer is probably less likely to occur in present day than it was 100 or 1,000 years ago. It's probably a very rare event."
Still, modern man isn't lacking for microbes. The human body is host to tens of trillions and possible hundreds of trillions of microbial cells -- more, in fact, than human cells. "Just by cell number, we are more microbial than we are human," Sonnenburg said.
The vast majority of the microbes are bacteria, although there are also smaller amounts of fungi and archaea, another type of single-celled organism. And most bacteria live inside the large bowel.
For the most part, it's a win-win relationship. The microbes have a safe habitat in which to grow and divide, and humans derive nutrients from the microbes and get help digesting food and fending off pathogens that can make them sick, Sonnenburg said.
"We have co-evolved with them, and they have become an integral part of our biology," he said."
Altering the microbiota can cause problems, Sonnenburg said. For instance, taking antibiotics, which knock down intestinal microbes in addition to killing harmful bugs, makes people more su
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