(665f) Engineered Synbiotic Production and Sensing of Butyrate

Short-chain fatty acids (SCFAs), especially butyric acid, have many roles in the human gut, affecting immunomodulation, cell differentiation and apoptosis. In addition, butyrate is the preferred carbon source for colon cells. Butyrate is normally produced in the colon by butyrogenic anaerobic bacteria that respond to dietary fiber or other prebiotics. However, diets rich in low-fiber, highly processed foods can result in low gut butyrate levels, which can lead to inflammation and other bowel diseases. In these disease states, populations of butyrogenic bacteria are also decreased.

Using a CRISPR-Cas based genome engineering method, we have engineered a model probiotic organism, E. coli Nissle 1917, to produce butyrate in both aerobic and anaerobic culture conditions. Additionally, to optimize butyrate concentration, we have developed a synthetic circuit that responds to and regulates intracellular butyrate concentrations, allowing for feedback control of butyrate production. We also demonstrate synbiotic (synergistic pairing of prebiotics with probiotics) production of butyrate from complex carbohydrates in cells engineered to uniquely consume these substrates. Finally, we tested our strains in an animal model by feeding of butyrate-producing probiotics to C. elegans. Nematodes receiving engineered probiotics behaved similarly to controls and had slightly improved brood size. Taken in total, this work provides a method of controlled butyrate delivery to the gut and is an important step towards engineered SCFA production in situ in the complex microbial milieu of the gut.