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 research from Newcastle University in the UK and the University of Michigan.

The study, published 7 January 2015 in the journal Nature, showed that microbes in the human 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.

Mannans found in fermented foods

The research involving scientists from Newcastle, Australia, Canada, USA and Belgium identified 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 the diet from fermented foods including bread, beer, wine and soy sauce.

Discovery could ‘accelerate development’ of prebiotic medicines

The international research team said 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, identified the complex machinery that targets yeast carbohydrates.

The researchers said this discovery has provided a better understanding of how human beings’ “unique intestinal soup of bacteria” – called the microbiome – has the capacity to obtain nutrients from the highly varied diet human beings consume.

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

“There’s a lot of interest in developing prebiotics,” Professor Gilbert said. “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,” he said.

Importance of microbiota for human immune responses

The researchers said they 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 (ThetanixTM), the researchers said yeast mannan “may have health promoting effects” on the microbiome by stimulating the growth of Bt.

“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,” said Professor Gideon Davies, of York Structural Biology Laboratory at the University of York, and researcher on the study.

Professor Spencer Williams, of the University of Melbourne, who also contributed to the research said that Bacteroides thetaiotaomicron was “an important part of our microbiota”.

“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,” Professor Williams said.

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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