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(In)Formation
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What the Japanese have that Americans don't: a special gut bacteria with a gene that allows them to digest a specific kind of carbohydrate found only in seaweed. That's what a group of marine glycobiology researchers in France discovered when they went looking at a marine bacteria called Zobellia galactanivorans. The researchers, at the National Center for Scientific Research in Roscoff, France, found that the bacteria carries a gene for making a very specialized carbohydrate-digesting enzyme. It can break down a polysaccharide (a class of complex carbohydrates) called porphyran found in the purple algae of the genus Porphyra. We call it laver in English, but in Japan it's made into sheets of nori, which wrap sushi. The scientists report their findings in this week's edition of the journal Nature. When they looked at gene-sequence databases, they found that genes for making that enzyme occurred not just in other marine bacteria, but also in a bacteria called bacteroides plebeius found in the human gut. Why would humans have a gene to make an enzyme that breaks down a polysaccharide found only in algae? When the researchers looked at who those humans were, they found that all were Japanese living in Japan. They then tested 13 Japanese volunteers and 18 North Americans and found that only the Japanese carried the bacteria that could digest seaweed. At some point in history, they surmise, the bacteria in the guts of seaweed-eating Japanese picked up genetic material from the marine bacterium. This kind of swapping of DNA resources, called lateral gene transfer, is common among bacteria. By Elizabeth Weise
