Engineered sensors and genetic regulatory networks for control of cellular metabolism

Abstract

Complex synthetic genetic programs promise unprecedented control over cellular metabolism and behavior. In this thesis, I describe the design and development of a synthetic genetic program to detect conditions underlying acetate formation in Escherichia coli. To construct this program, I first developed sensors that detected and propagated relevant information into genetic circuits. These sensors include a novel sensor for genotoxic methylation exposure in Saccharomyces cerevisiae and sensors for oxygen, acetate, and glycolytic flux in E. coli. The methylation sensor served to prototype generalizable tuning mechanisms and was tuned to a sensitivity and detection threshold useful for several applications, including the detection of Mel formation in methyl halide transferase-expressing cultures of yeast and the detection of Mel in soil. The sensors for oxygen and acetate were integrated into a program that can uniquely detect acetate formation in anaerobic conditions in E. coli. Finally, to validate their use at higher scales in production strains, the oxygen sensor and two genetic programs were characterized in 10 L fed-batch fermentations. Together, this work demonstrates the characterization of novel genetic elements, their integration into genetic programs, and the validation of those programs at industrially relevant scales.