Engineering dual-glycan responsive expression systems for tunable production of heterologous proteins in Bacteroides thetaiotaomicron

Genetically engineering symbiotic bacteria remains an underexploited opportunity to improve host-health and create new classes of biological devices, such as diagnostics or intestinal delivery systems for therapeutics. Bacteroides thetaiotamicron (B. theta) is a Gram-negative intestinal anaerobe with potential for the capability to produce functional heterologous proteins within a host intestine. To improve the strength and regulatory fidelity of transgene expression in B. theta, I have developed platform expression strains with engineered regulatory proteins under control of promoter elements that respond to dextran and arabinogalactan, two chemically distinct glycans. In addition to single glycan induction, I have also developed a novel “dual-glycan” expression system that requires the addition of both dextran and arabinogalactan for induction. Additionally my engineered strains are compatible with a series of chromosomal integration and episomal vectors that improve the throughput of gene cloning, integration, and expression. Together this expression system provides a new collection of glycan-responsive tools to improve transgene expression in B. theta and provides the proof-of-concept for engineering more complex dual-glycan expression systems.