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Beer and bread yeast-eating bacteria aid human health

Posted on 7 January 2015

Bacteria that have evolved to eat their way through yeast in the human gut could inform the development of new treatments for people suffering from bowel diseases, according to new research involving scientists at the University of York.

The study, led by Newcastle University and the University of Michigan, shows how microbes in our digestive tract have learned to unravel the difficult to break down complex carbohydrates that make up the yeast cell wall.

Evolving over the 7,000 years humans have consumed fermented food and drink, the ability of strains of Bacteroides thetaiotomicron (Bt) ­­­to degrade yeasts is almost exclusively found in the human gut.

Published today in Nature, the international research team, which also included scientists from Australia, Canada, USA and Belgium, say 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 Professor Harry Gilbert at Newcastle University, Professor Eric Martens, of the University of Michigan, and Dr Wade Abbott of Agriculture and Agri-Food Canada, has identified the complex machinery that targets yeast carbohydrates.

This has provided a better understanding of how our unique intestinal soup of bacteria - termed the microbiome - has the capacity to obtain nutrients from our highly varied diet.

Professor Gideon Davies, of York Structural Biology Laboratory in the Department of Chemistry at York, who contributed to the work, said: “The ability of Bacteroides thetaiotaomicron to degrade yeast cell wall components may be of importance in fighting off yeast infections and in autoimmune diseases such as Crohn’s disease."

“People are very interested in developing dietary regimes where good bacteria are of benefit,” explained Professor Gilbert.

“When you have certain bacteria dominant in the gut these microorganisms can produce molecules which have health promoting effects.

“There’s a lot of interest in developing prebiotics. The more you understand about how complex glycans are degraded the more you can think about developing sophisticated prebiotics that target the growth of specific beneficial bacteria.”

The research has unraveled the mechanism by which Bt, a dominant member of the human microbiome, has learned to feast upon difficult to break down complex carbohydrates called yeast mannans. 

Mannans, derived from the yeast cell wall, are a component in our diet from fermented foods including bread, beer, wine and soy sauce.

It is hoped the research could aid a better understanding of how to provide nutrients to specific organisms in the microbiome. Indeed, given that Bt has been granted Orphan Designation by the FDA for Paediatric Crohn’s Disease (Thetanix^TM), yeast mannan may have health promoting effects on the microbiome by stimulating the growth of Bt.

Professor Spencer Williams, of the University of Melbourne, who also contributed to the research added: “Bacteroides thetaiotaomicron is an important part of our microbiota, the community of bacteria that live within us.

“By consuming carbohydrates that we can’t, which they convert to short-chain fatty acids that they secrete into our distal gut, these bacteria establish a symbiosis that nourishes the cells that line our gut wall and provide important immune signals that establish a healthy immune response.”

The research team consisted of: The Institute for Cell and Molecular Biosciences at Newcastle University, the Complex Carbohydrate Research Centre at the University of Georgia, the Department of Microbiology and Immunology at the University of Michigan Medical School, the Department of Chemistry at the University of York, the School of Chemistry and Bio21 Molecular Science and Biotechnology Institute at the University of Melbourne, the Department of Pharmaceutical Chemistry at the University of Kansas School of Pharmacy, Oxyrane, Ghent, Agriculture and Agri-Food Canada, Biochemistry and Microbiology, University of Victoria, Canada and the USDA, Agricultural Research Service, National Laboratory for Agriculture and the Environment, Iowa.

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