Thesis Defense: Rory WIlliams

Title: Development and scaling of differentiation circuit architectures for improving the evolutionary stability of burdensome functions in E. coli

With advances in the sequencing and synthesis of DNA, automation, and computation, we are increasingly able to rapidly and reliably program functions into cells. However, because the functions we engineer cells to perform are often both unnecessary for the cell's survival and burdensome to cell growth, mutation and natural selection can rapidly lead to loss of function. Though numerous strategies have made headway, improving the evolutionary stability of engineered functions remains a goal of the synthetic biology community. To address this problem generally, we developed a strategy of integrase mediated differentiation which allows non-producing progenitor cells to continuously replenish differentiated producer cells expressing the orthogonal T7 RNAP. We further explore how restricting the division of differentiated cells prevents the selection for mutations which inactivate the function of interest, and how strategic redundancy can improve the evolutionary stability of the differentiation architecture.