Credit: Nikki Horne and Kathryn Gotts with QIB Advanced Microscopy Facility and JIC Bioimaging

Our gut is home to a complex community of over 100 trillion microorganisms that form a mutually beneficial relationship with us. Specific species of bacteria are more abundant in our gut.

Bacteroides thetaiotaomicron, or Bt for short, is a bacterium that dominates our intestinal microbiota, with an emerging role in our gut health.

Where is Bacteroides thetaiotaomicron found?

Bacteroides thetaiotaomicron is a strict anaerobe, meaning that it requires an oxygen free environment to grow and thrive. Therefore, it is found in the large intestine where oxygen levels are low.

Crunching carbohydrates to compete with other microbes

Bacteroides thetaiotaomicron is not the only microbe found in the human colon.

Bacteroides thetaiotaomicron competes with hundreds of other bacterial species for its survival. One of the ways it can successfully compete in the colonic environment is by digesting a broad array of complex carbohydrates in our diet, such as plant fibres, that as humans we can’t digest. In doing so, it produces lots of metabolites and signalling molecules.

The molecules produced by Bacteroides thetaiotaomicron serve as an energy source and regulate key functions in human gut and beyond, including inflammatory responses and neurological functions. This friendly gut bacteria is therefore associated with health benefits such as promoting anti-inflammatory responses and protecting against certain diseases.

Therapeutic potential in intestinal inflammation

Inflammatory bowel diseases (IBDs) are a group of chronic gastrointestinal inflammatory diseases that manifests in two primary forms, Ulcerative Colitis, and Crohn’s disease.

We think disrupted immune regulation is one of the major driving forces behind the chronic and dysregulated inflammation in the intestine in Inflammatory Bowel Disease. Several studies also report microbial dysregulation in IBD patients along with reductions in the amount of Bacteroides species, including Bacteroides thetaiotaomicron.

Interestingly, Bacteroides thetaiotaomicron has shown to have effects on anti-inflammatory immune responses.

In mouse studies of IBD, giving Bacteroides thetaiotaomicron to mice has been shown to slow disease progression. This happens through the bacteria having anti-inflammatory effects and promoting intestinal barrier function. The intestinal barrier forms a physical and essential barrier against harmful substances and bad bacteria, providing a separation between the inside of the body from the outside environment.

These studies suggest that using specific gut microbes, such as Bacteroides thetaiotaomicron may be a viable approach to rebalance immune pathways to maintain intestinal balance. This can prevent inflammation and progression of chronic inflammatory diseases such as IBD.

A regulator of gut feelings?

There is plenty of evidence that supports the importance of gut-brain signalling in health and disease.

The gut-brain axis describes the bi-directional communication between the gut and brain. Growing evidence shows the importance of a “normal” gut microbiota in regulating and maintaining the gut-brain axis.

Bacteroides thetaiotaomicron regulates the structure and function of neurones in the colon.

Recent research also shows the bacteria can maintain the population of specialised hormone producing cells in the intestine. These hormone producing cells are present in the intestinal barrier and can respond to microbial signals by producing gut hormones, including serotonin and GLP-1. Serotonin is important in regulating gut functions such as motility and used as a signalling molecule in neurones. GLP-1 in an important gut hormone that regulates appetite and insulin secretion.

Gut Bacteroides species, including Bacteroides thetaiotaomicron may be a possible treatment to improve brain function.

Bacteroides thetaiotaomicron for the future

At the Quadram Institute we’re exploring the mechanisms Bacteroides thetaiotaomicron influences our gut health.

Understanding the role of this microbe within the gut microbial ecosystem may lead to the development of new therapeutic strategies for gut health and potentially gut-brain related diseases.