How our bodies maintain a beneficial relationship with our gut microbes

Our gut hosts a community of trillions of microbes, called the gut microbiota, and we are becoming increasingly aware that this has significant effects on many aspects of our health. However, the molecular mechanisms underpinning this interaction remain elusive.

New research led by Dr Nathalie Juge at the Quadram Institute has identified some of the molecules used to ensure bacteria in the gut microbiota maintain healthy populations, in the correct locations in the body. This helps to ensure a continuing mutually beneficial relationship with our gut microbiota.

To achieve a friendly relationship with these microbes, our gut is lined with mucus. In the colon, the mucus layer is divided into a loose outer layer that provides a suitable habitat for bacteria, allowing us to benefit from them, and an inner layer that acts as a protective barrier. This inner layer prevents these bacteria crossing the gut lining where they could cause us harm.

Mucus is made up of large protein molecules, which are decorated and extended by different sugar molecules, called oligosaccharides that together with water make up mucus. These mucin glycan chains provide a source of nutrients as well as an attachment site for bacteria that have evolved to colonise the outer mucus layer. Over 100 different oligosaccharides have been identified in the human colon, and recent research has shown that variations in the oligosaccharides within the mucus are associated with variations in the composition of the gut microbiota. This may be one way in which the body tries to tailor the composition of the microbiota in different parts of the gastrointestinal tract.

See:

C. David Owen, Louise E. Tailford, Serena Monaco, Tanja Šuligoj, Laura Vaux, Romane Lallement, Zahra Khedri, Hai Yu, Karine Lecointe, John Walshaw, Sandra Tribolo, Marc Horrex, Andrew Bell, Xi Chen, Gary L. Taylor, Ajit Varki, Jesus Angulo, Nathalie Juge. Unravelling the specificity and mechanism of sialic acid recognition by the gut symbiont Ruminococcus gnavus. Nature Communications, 2017; 8 (1) DOI: 10.1038/s41467-017-02109-8

Posted by Dr. Tim Sandle