Figure 4

Distribution of fitness estimates within evolving E. coli populations. All competitions for fitness assay were performed against reference strain BW3454 containing metC::Tn10 as described in Materials and methods. The reported fitness, S/generation, where S is the selection coefficient (estimated according to [73]). All data presented are mean ± standard deviation from at least three independent experiments. (a) Selection coefficients of evolved isolates derived from 0.1 h^-1 populations were measured at the same dilution rate after mixing 50/50 with the reference strain. (b) Evolved isolates from 0.6 h^-1 populations were measured at the same dilution rate after mixing 50/50 with the reference strain. (c) Negative frequency-dependent fitness of isolates with negative fitness in Figure 1a were measure after mixing 1/99 with the reference strain. (d) Normal distribution of fitness in evolving isolates were estimated from standard deviations and mean fitness (Sg). Standard deviation = 0.57 for slow- and 0.207 for fast-growing populations and Sg = 0.295 for slow- and 0.283 for fast-growing populations.