Engineering Logical Inflammation Sensing and Secreting Circuit for Gut Modulation

Citation

Merk, Liana Noor (2021) Engineering Logical Inflammation Sensing and Secreting Circuit for Gut Modulation. Senior thesis (Major), California Institute of Technology. doi:10.7907/wr7s-6436. https://resolver.caltech.edu/CaltechTHESIS:06042021-234419803

Abstract

The mammalian gut contains trillions of microbes that interact with host cells and monitor changes in the environment. Opportunistic pathogens exploit environmental conditions to stimulate their growth and virulence, leading to a resurgence of chronic disorders such as inflammatory bowel disease (IBD). Current therapies are effective in less than 30% of patients due to the lack of adherence to prescription schedules and overall, off-target effects. Microbial therapeutics can be engineered to colonize the gut, providing in situ surveillance and conditional disease modulation. However, many current engineered microbes can only respond to single gut environmental factors, limiting their effectiveness. In this work, we implement a previously characterized split activator AND logic gate in the probiotic E. coli strain Nissle 1917. Our system can respond to two input signals: the inflammatory biomarker tetrathionate and a second input signal, IPTG or aTC. We report 4-6 fold induction with minimal leak when both signals are present. We model the dynamics of the AND gate using chemical reaction networks, and by tuning parameters in silico, we identified perturbations that affect our circuit’s selectivity. We then engineer our optimized AND gate to secrete an anti-inflammatory therapeutic cytokine, IL-22, using the hemolysin secretion pathway. We anticipate that our results will prove useful for designing living therapeutics for spatial targeting and signal processing in complex environments.

Thesis Files