Engineered E. Coli That Detect and Respond to Gut Inflammation Through Nitric Oxide Sensing
Archer, Eric Jeffry
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Within the last several years, advances in synthetic biology have allowed for the development of re-programmed microorganisms that perform useful tasks in areas like fuel production, bioremediation, and medicine. Several engineered microorganisms are in pre-clinical development for the treatment of human diseases, but may face critical limitations that decrease their utility in medicine due to adverse events like sepsis, caused by the introduction of bacteria within patients. Here I describe the design, construction, and characterization of a synthetic genetic network that is intended for use by E. coli within lumen of the intestine, which is presumed to be a safer location than other tissues, such as blood, for the introduction of engineered microbes. The synthetic gene regulatory circuit described here regulates gene expression through the activation of a permanent DNA switch in response to nitric oxide produced by inducible nitric oxide synthase. The detection of nitric oxide initiates the expression of a DNA recombinase, causing the permanent genetic rearrangement of a short DNA segment containing a gene promoter, allowing for the regulation of output gene expression upon nitric oxide sensing. Here I demonstrate that E. coli containing this synthetic genetic circuit respond to nitric oxide as designed from both chemical nitric oxide donors and from injured mouse intestinal explants. This synthetic genetic circuit could be optimized for clinical use by allowing E. coli to reliably detect and treat inflammation in patients with inflammatory bowel disease, but the circuit described herein now serves as the proof-of-concept for both bacterial sensing of mammalian inflammation and for the use of DNA recombinases to translate transient environmental signals into permanent responses in engineered bacteria.