[1] The bacterium encodes for enzymes such as glycoside hydrolases and polysaccharide lyases, allowing it to break down dietary fibers, such as cellulose and hemicellulose, into fermentable substrates.

This metabolic activity generates short-chain fatty acids (SCFAs) like acetate and propionate, which are absorbed by the host and provide critical energy sources for colonic cells.

B. thetaiotaomicron has been associated with other commensal bacteria and the induction of regulatory T cells, which are essential for maintaining immune tolerance and preventing excessive inflammatory response in the gut mucosa.

[5][6] The Bacteroidota bacterial phylum, distinguished by its unique motility, is present in a wide range of ecosystems, habitats, lifestyles, and physiological conditions.

Over time, this bacterium developed the ability to break down complex carbohydrates into simple sugars, which helps the host species get more energy from the food it eats.

[1] The evolution of B. thetaiotaomicron seems to have been shaped by the changing diet and immune systems of its human hosts, which influenced the bacterium’s genetic and functional traits.

[16][17][18] B. thetaiotaomicron has a starch utilizaiton system (Sus), which allows the bacteria to bind complex polysaccharides to the cell surface and the outer membrane enzymes break them down into simple sugars.

[16] The genome also contains many genes that encode proteins involved in sensing and responding to the extracellular environment, such as sigma factors and two-component systems.

[16] The B. thetaiotaomicron genome encodes a large number of small non-coding RNAs, which also play a key role in regulatory processes, though few have been characterized to date.

As the major organism of the human gut flora to break down plant polysaccharides, it can use dietary carbohydrates, as well as those sourced from the host, depending on nutrient availability.

[23] Complex plant polysaccharides, unlike simple monosaccharides and disaccharides that are digested and absorbed in the small intestines, are left to be used as a food source in the colon.

These SCFAs serve as energy sources for colonocytes and have anti-inflammatory properties[2] B. thetaiotaomicron also relies on glycolysis, the Embden-Meyerhof-Parnas (EMP) pathway, and fermentation to metabolize sugars.

[19] This is possible due to the combined effects of an increased amount of glycosyl hydrolases that degrade enzymes, membrane binding proteins, and sugar-specific transporters.

Generation of reactive oxygen species (ROS) such as hydrogen peroxide may occur, threatening the flora by attacking iron cofactors enzymes widely used in metabolism.

[26] To drive the oxygen concentration to lower levels, B. thetaiotaomicron expresses a number of proteins that scavenge ROS such as hydrogen peroxide when exposed to air.

[16][17] B. thetaiotaomicron has far more glycosyl hydrolases, in which 61% are located in the outer membrane or extracellular matrix, suggesting that the digestive capabilities serve the bacteria's host more than anything.

[20] The glycosyl hydrolases express 23 specific enzymatic functions that supply the host or even other microbes in the gut flora with the breakdown products of hydrolysis.

[27][28] The mucosal barrier, located between the intestinal epithelium and microbiota, is semipermeable, allowing the uptake of essential nutrients while restricting the passage of pathogenic molecules.

The anti-inflammatory and immunomodulatory characteristics of extracellular vesicles generated by the prevalent human gut bacteria B. thetaiotaomicron are evident, along with the identification of the molecular mechanisms governing their interaction with innate immune cells.

[30] B. thetaiotaomicron has been associated with other commensal bacteria and the induction of regulatory T cells which are essential for maintaining immune tolerance and preventing excessive inflammatory response.

[3][31] The outer membrane vesicles (OMVs) not only aid in protecting B. thetaiotaomicron from degradation, but also play a major role in promoting regulatory dendritic cell responses.

B. thetaiotaomicron OMVs in individuals with ulcerative colitis (UC) and Crohn's disease (CD) are unable to stimulate IL-10 expression, resulting in a loss of regulatory DC.

These bile induced adaptations include enhanced stress tolerance mechanisms and increased production of efflux pumps which ultimately provide cross-protection against harmful agents such as antibiotics.

[45] The accuracy of the test combined with faster analysis times of identifying B. thetaiotaomicron in samples makes these bacteria – or the bacteriophages that infect them[46] – a qualifying contender for future fecal pollution identification.