Gut microbiome; meet Ruminococcus gnavus

15th September 2023

Professor Nathalie Juge explains the role of Ruminoccocus gnavus in the gut microbiome and its impact on our health and disease.

Our gut is populated with trillions of microbes living, for most of the time, in harmony with our body. Ruminococcus gnavus is one of the many bacterial species present in the gut of infants and adults.

A microscopy image of cylindrical shaped bacteria.

Scanning electron microscopy image of Ruminococcus gnavus (courtesy of Catherine Booth Quadram Institute Advanced Microscopy Facility)

A common gut bacteria that can be linked with disease

Ruminococcus gnavus (R.gnavus) is a normal inhabitant of the gut. But many sequencing studies looking at the composition of the gut microbiota in humans have reported an increase of R.gnavus in people with intestinal diseases such as inflammatory bowel disease (IBD), irritable bowel syndrome (IBS) or colon cancer.

These studies have also found associations with diseases affecting other parts of the body such as skin allergies, cardiovascular or liver diseases, brain disorders.

Association with diseases does not necessarily mean that R.gnavus is a cause of these diseases, it may just indicate that these conditions may be more favourable to R.gnavus expansion in the gut compared to other bacteria.

Researchers are actively working towards understanding how R.gnavus influences health or disease outcomes.

Diversity in strains and sugars

Not all Ruminococcus gnavus are equal. As with other bacteria, the name covers a multitude of strains with different characteristics.

Some R. gnavus strains live close to our body, in the lining of our gut, and are well positioned to sense changes in the gut environment and communicate with the rest of the body. Complex carbohydrates are the main source of food for the bacteria inhabiting the gut. Not all sugars in the gut come from the food we eat; our body can also produce its own type of sugars. In addition, sugars can be found covering the surface of the bacteria themselves.

At the Quadram Institute, we have shown that while R. gnavus can use sugars found in plant foods, some R. gnavus strains have developed a sweet tooth for the sugars present in the lining of the gut and evolved selfish strategies to unsure they will always get a piece of the pie. This will allows these strains of R. gnavus to persist throughout different stages of life or health conditions, and make them more independent from our diet.

Ruminococcus gnavus’s impact beyond the gut

Ruminococcus gnavus has an impact beyond the gut too. R. gnavus produces some small molecules called metabolites. These metabolites can travel to different sites of the body and influence the response of different organs. Some of these metabolites are also produced by other gut bacteria but some are unique to R. gnavus and can exacerbate gut mobility which when over-represented may contribute to IBS symptoms associated with abnormal gut contractions such as abdominal pain and discomfort or stimulate activity of the brain. Finally, sugars coating R. gnavus can differ depending on the strain, and on some occasions may generate an inflammatory response as seen in the case of IBD.

R. gnavus strains have been shown to have a protective effect against induced colitis or atopic eczema in mice, or to ameliorate growth and metabolic abnormalities seen when the gut of mice is colonised with the gut microbiota from undernourished infants.

The more we study R. gnavus, the more we understand the complex relationship the gut bacteria has with our body.

Learning more about R. gnavus will help us to find new solutions to diagnose and treat diseases to promote human health across the life span.

Banner image: Image of Ruminococcus gnavus in the mucus layer overlying the epithelium surface of the gut (courtesy of Laura Vaux)

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Nathalie Juge

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A green background with an illustration of a gut full of microbes.

Food, Microbiome and Health