在线英语听力室_免费在线英语听力学习网站

This is Scientific American's 60-Second Science. I'm Karen Hopkin. This'll just take a minute.

If you want to shell a walnut¹, it helps to have a nutcracker. And if you want to digest seaweed, it helps to have the right enzymes³. Now, a study in the journal Nature shows that Japanese people—but not North Americans—have what it takes to eat their sushi, and digest it, too.

The scientists were studying a particular marine⁴ bacterium⁵, which makes enzymes that break down the kind of seaweed used to wrap sushi. In searching the public databases, they discovered, to their surprise, that the enzymes were not just confined to ocean organisms. They also turned up in bacteria that live in the human gut⁶.

Our intestines⁷ are teeming⁸ with trillions of bacteria from hundreds of different species. By sequencing the genomes of the microbial tenants⁹ from 30 volunteers, the scientists found that the Japanese harbor bugs¹⁰ with seaweed-eating enzymes. Not so the North Americans.

The enzymes were most likely gifts from a marine microbe, eaten along with some seaweed a long time ago. The marine microbe happened to transfer some of its enzyme² genes¹¹ to gut microbes. And with seaweed a staple¹² in the Japanese diet, the genes stuck around. So it was a good bargain between man and microbe. Not a raw deal.

Thanks for the minute for Scientific American's 60-Second Science. I'm Karen Hopkin.