(643a) Selecting for Small Molecule Production in Competitive Microfluidic Droplets

Evolutionary selections can be powerful tools for metabolic pathway optimization. However, finding an appropriate selective pressure for the production of a desired compound can be difficult. To extend these methods to new classes of compounds, we have developed in vitro selections in which the production of a small molecule mediates competition between two microbial strains. We construct systems in which a resistant producer can inhibit the growth of a sensitive competitor by producing the target small molecule. When the two strains are mixed and co-cultured in microfluidic droplets, producers that make more of the target compound have a fitness advantage. We have developed strategies for manipulating the sensitivity of the producer and competitor strains to the target compounds and have characterized the dynamics and selective pressures in the competitive co-cultures. We are applying this selection strategy to the production of fuels and chemicals from sugars and aromatics.