Yeast-eating bacteria aid human health

BACTERIA that have evolved over 7,000 years to eat their way through yeast in the human gut could support the development of new treatments to help people fight off yeast infections and autoimmune diseases such as Crohn’s disease.

 

Led by Newcastle University in the United Kingdom, and the University of Michigan Medical School, the study shows how these microbes in our digestive tract, Bacteroides thetaiotomicron, have learned to break down complex carbohydrates that make up the yeast cell wall. Their ability to degrade yeasts has been perfected over the seven millennia that we have been eating fermented food and drink -- including bread and beer.

 

Publishing their findings* on January 8 in Nature, the international team of scientists from the United Kingdom, Australia, Canada, United States and Belgium says the discovery of this process could accelerate the development of prebiotic medicines to help people suffering from bowel problems and autoimmune diseases.

 

The study, led by Harry Gilbert, Ph.D., professor of biochemistry at Newcastle University; Eric Martens, Ph.D., of University of Michigan, and Wade Abbott, Ph.D., research scientist at Agriculture and Agri-Food Canada, has unraveled the mechanism by which B. thetaiotaomicron has learned to feast upon difficult-to-break-down mannans. Derived from the yeast cell wall, mannans are a component in our diet from fermented foods including bread, beer, wine and soy sauce, as well as yeasts that call the microbiome home and are in some cases thought to be harmful.

 

“One of the big surprises in this study was that B. thetaiotaomicron is so specifically tuned to recognize the complex carbohydrates present in yeasts, such as those present in beer, wine and bread,” said Dr. Martens, an assistant professor in the University of Michigan Department of Microbiology and Immunology.

 

Researchers believed this mechanism emanated from the ability of common gut bacteria to recycle chemically similar carbohydrates present on intestinal cells, which are constantly being shed and renewed to keep the intestinal lining healthy.

 

Even the relatively small amounts of yeast that we commonly consume in foods are enough to impact the physiology of our friendly gut bacteria.

 

“People are very interested in developing dietary regimes where good bacteria are of benefit,” said Dr. Gilbert, senior study author. “When you have certain bacteria dominant in the gut these microorganisms can produce molecules which have health-promoting effects.”

 

The researchers hope their work leads to a better understanding of how to provide nutrients to specific organisms in the microbiome, and lead to the development of sophisticated prebiotics that target the growth of specific beneficial bacteria.

 

* “Human gut Bacteroidetes can utilize yeast mannan by a selfish mechanism,” Nature 517, 165–169 (08 January 2015) doi:10.1038/nature13995