(A) Schematic illustration.
(B) Genome integration. Integration into the genome avoids circuit loss due to plasmid segregation error. It can also reduce the advantage of a mutant if it appears (see Strategy 2).
(C) Reducing the host mutation rate. This can be achieved by (Top) removing transposable elements and IS elements and by (Bottom) optimizing the host for a specific circuit by directed evolution.
(D) Reducing the local population size. Enclosing the cells into smaller culture compartments, such as microfluidics, microwells, or microcapsules, reduces the probability by which a mutant can emerge in a local population.
(E) External ecological intervention. Before a mutant emerges, one can eliminate the current population with another carrying the same circuit function. Cycling through different populations allows prevention of mutants while maintaining a common circuit function.