News for Sushi Lovers Everywhere

During the First World War, Dr. Frederick Griffith, a young British medical officer, made an important discovery: the phenomenon known as "transformation." The transfer of DNA from one organism to another -- in Griffith's case, strains of Streptococcus -- could "transform" the original organism into a slightly different version of itself. (For more on this, see Visionlearning's DNA I module.) Now, scientists have discovered that something like this may have happened over time in the intestines of the Japanese population.

The human gut contains enzymes that break down polysaccharides -- one of the principle sources of energy for the brain. But these enzymes are not created by us, they're generated by the intestinal flora that live within us. Without a wide variety of intestinal flora, we simply wouldn't be able to acquire the energy needed to survive. Scientists all over the world study these different flora, and the enzymes they produce, in order to better understand how they function.

Two teams of researchers working at the Station Biologique de Roscoff, in France, have been studying the enzyme porphyranase, found in marine bacteria, in hopes of learning more about what, specifically, it does. It turns out that the enzyme digests the polysaccharide Porphyran,which is present in the cell walls of the red algae popularly used in sushi.

Further research showed that, while this enzyme is present in the gut of the Japanese test subjects, it is not present in those of the American subjects. They have presumed that the presence of this enzyme in the gut microbiota of the Japanese subjects is a direct result of diet. Further, they have 'explained this discovery by a transfer of genes between the bacteria, that allows the gut microbiota of the Japanese to acquire all the 'machinery' it needs to consume the algae that surround sushi." It's the first time to be shown that food bacteria can transfer genes to our own gut bacteria.

This doesn't mean that Americans' microbiota don't digest sushi well enough. Most of the seaweeds found in US supermarkets have been roasted in order to sterilize them, and in so doing have destroyed these microbiota. This project could lead to further research to see if there are added benefits to having specialized organisms living in our tummys.