By ED YONG - NOT EXACTLY ROCKET SCIENCE
Added: Wed, 07 Apr 2010 23:00:00 UTC

Thanks to Michael Meadon for the link.
Original link



Japanese people have special tools that let them get more out of eating sushi than Americans can. They are probably raised with these utensils from an early age and each person wields millions of them. By now, you’ve probably worked out that I’m not talking about chopsticks.

The tools in question are genes that can break down some of the complex carbohydrate molecules in seaweed, one of the main ingredients in sushi. They are wielded by the hordes of bacteria lurking in the guts of every Japanese person, but not by those in American intestines. And most amazingly of all, this genetic cutlery set is a loan. Some gut bacteria have borrowed the seaweed-digesting genes from other microbes living in the coastal oceans. This is the story of how these genes emigrated from the sea into the bowels of Japanese people.

Within each of our bowels live around a hundred trillion microbes, whose cells outnumber our own by ten to one. This ‘gut microbiome’ act like an extra organ, helping us to digest molecules in our food that we couldn’t break down ourselves. These include the large carbohydrate molecules found in the plants we eat. But marine algae – seaweeds – contain special sulphur-rich carbohydrates that aren’t found on land. Breaking these down is a tough challenge for our partners-in-digestion. The genes and enzymes that they normally use aren’t up to the task.

Fortunately, bacteria aren’t just limited to the genes that they inherit from their ancestors. They can swap genes between individuals as easily as we humans trade money or gifts. This ‘horizontal gene transfer’ means that bacteria have an entire kingdom of genes, ripe for the borrowing. All they need to do is sidle up to the right donor. And in the world’s oceans, one such donor exists – a seagoing bacterium called Zobellia galactanivorans.
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TAGGED: EVOLUTION, GENETICS