Host Evolution Improves Genetic Circuit Function in Complex Growth Environments

The systematic design of genetic circuits with predictable behaviors in complex environments remains a significant challenge. Here, we engineered a population control circuit and used a combination of evolutionary and rational engineering approaches to enhance Escherichia coli for robust genetic circuit behavior in nontraditional growth environments. We utilized adaptive laboratory evolution (ALE) on E. coli MG1655 in minimal media with a sole carbon source and saw improved dynamics of the circuit after host evolution. Additionally, we applied ALE to E. coli Nissle, a probiotic strain, in a more complex medium environment with added reactive oxygen species (ROS) stress. In combination with directed mutagenesis and high-throughput microfluidic screening, we observed restored circuit function and improved tolerance of the circuit components. These findings serve as a framework for the optimization of relevant bacterial host strains for improved growth and gene circuit performance in complex environments.