Figure 1.

The takeover of a nonfunctional mutant with a higher growth rate in a population. The predicted time (in days) to a nonfunctional mutant strain of a synthetic microbe becoming the majority of the population as a function of the log of the circuit size and the ratio of growth rate of the mutant to that of wild type. The circuit size is a proxy for the cross-section of the circuit for deleterious mutation, which is also a function of growth rate, basal mutation rate m and circuit architecture. The larger the size and larger the growth advantage of the mutant strain, the faster the population loses function. The inset shows a schematic of the underlying model which tracks competitive growth (g) of a wild-type (wt) population and mutant (mut) population on a common resource (S) in continuous culture. ks is the influx rate of resource into the bioreactor and d is the dilution rate of cell and substrate out of the reactor. The parameter m is proportional to circuit size and is the rate of production of non-functional (and growth competitive) mutants from the wild-type population.