A genetic gift for sushi-eaters
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A genetic gift for sushi-eatersA genetic gift for sushi-eatersGenes picked up from a microbial hitch-hiker may enable some Japanese individuals to extract otherwise intractable nutrients from seaweed.A study published this week in Nature1 suggests that a marine microbe — perhaps ingested on a sliver of seaweed — probably transferred genes that encode algae-munching enzymes to bacteria that live in the human gut. #xThe enzymes break down algal carbohydrates including one found in red algae of the genus Porphyra,Concrete Machinebest known to sushi lovers as 'nori'.Although gene transfer to gut microbes is suspected in other cases, this is the first clear-cut example in which a gut microbe has gained a new biological niche by snatching genes from an ingested bacterium, says Mirjam Czjzek,Compact fluorescent lamp, a chemist at the Pierre and Marie Curie University in Paris, one of the two researchers who led the study. "Probably there are many more examples," she says. "It's only because of this exotic niche and the very rare specificity of this enzyme that we were able to pinpoint where it came from."You are what you eatMany of the microbes residing in the human gut are likely to be beneficial to their host. Some may give their host a calorific boost by breaking down ingested plant carbohydrates that human enzymes cannot touch. In Japan, where about 14 grams of seaweed are consumed per person each day,Concrete Machinesome of these indigestible carbohydrates come from the algae that wrap sushi rolls and form. the basis for a variety of soups and salads.#xCzjzek together with Gurvan Michel, a structural biologist also at the Pierre and Marie Curie University, and their colleagues found a new class of algae-degrading enzymes called β-porphyranases while hunting for proteins that break down algal biomass.In the genome of the marine bacterium Zobellia galactanivorans they found enzymes that were similar to those that degrade the algal compounds agarose and carrageenan. But the enzymes lacked a crucial region needed to recognize these polysaccharides.Instead,Concrete Machinethe enzymes broke down a Porphyra polysaccharide called porphyran.#x The team searched databases for related enzymes and found that they are all also made by marine microbes — except one found in the genome of a human gut bacterium called Bacteroides plebeius.相关的主题文章：
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