Engineering non-exponential proliferation in Escherichia coli using functionalized protein aggregates.

Microbes naturally grow exponentially, but this trait might not always be desirable for applications with genetically modified microorganisms. Especially in microorganisms engineered for therapeutic applications, uncurbed exponential proliferation might cause unpredictable liabilities in their behavior that in turn compromise their dosing and biocontainment. In an effort to fundamentally reprogram population growth dynamics, we constructed a bacterial chassis that adheres to linear proliferation for a finite number of generations. More specifically, growth of the chassis is directed by an intracellular protein aggregate that is engineered to reconstitute a split enzyme producing cAMP as a conditionally essential metabolite. Due to the asymmetric segregation and gradual disaggregation of this aggregate, it autonomously keeps growth restricted to the aggregate inheriting cell and to a limited number of divisions. By imposing such a transient and linear growth potential without the need for external intervention, this chassis offers a unique venue for the controlled application of engineered microorganisms.