A Butyrate-Producing Synthetic Biotic to Treat Inflammatory Bowel Disease In Vivo

Recent studies into the interplay between the microbiome and host have extensively implicated short-chain fatty acid (SCFA) fermentation products as contributors to both intra and extra intestinal health. In the context of the gut, butyrate (a four carbon SCFA) serves as the primary energy source for epithelial colonocytes, drives regulatory T cell differentiation and is therefore essential for the maintenance of colonic mucosal health. On a systemic level, butyrate may influence insulin sensitivity, cholesterol synthesis and autoimmunity. Typically, butyrate is produced by the action of slow-growing Gram positive organisms – often Clostridial in origin – during the fermentation of cellulose and complex carbohydrates. To counteract the depletion of butyrate in the gut, we iteratively engineered Escherichia coli Nissle 1917 to produce butyrate. The new butyrate-producing Nissle was capable of millimolar level production of butyrate comparable with the levels produced by enteric Clostridial species. The circuitry was placed under anaerobic control to support induction upon entry into the gastrointestinal track. Finally, proof-of-concept in vivo experimentation showed production of butyrate in the mouse gut. This engineered strain may be useful for the treatment of a variety of gastrointestinal and systemic conditions associated with SCFA deficiency.