Magenta points represent data from experiments with strains 1 and 2. Cyan points represent data from experiments with strains 3 and 4, where strain 3 expresses constitutively mKate2Hyb and the IPTG-inducible Venus yellow fluorescent protein (YFP) and strain 4 expresses mVenus constitutively (see Materials and Methods and Fig. S.1). Error bars represent two standard deviations. Note that the normalized protein production rates are not directly comparable across magenta and cyan points (see Materials and Methods). a The experimental selection coefficient S (y axis) decreases linearly with the normalized production rate of the inducible protein, measured as the temporal variation of the mean cell fluorescence signal at different concentrations of the inducer IPTG, accounting for dilution of such protein via cell division (see Materials and Methods). The gray band represents the 68% confidence interval of the linear fit. The time series of ln[f/(1 − f)] for the two experiments are reported in Figs. S.19 and S.20. b Induced protein production rates as functions of IPTG concentration (see Materials and Methods). c Inferred values of the ratios Φ1/Φ2 and Φ3/Φ4 (minus one) as functions of the induced protein production rate (normalized). Also shown are the linear fits of the data with their 68% confidence interval. d Mean (induced) red fluorescence of strain 1 at 4 h and 8 h after inoculation in the conditions used for our experiment (see Materials and Methods). e Mean (induced) yellow fluorescence of strain 3 at 4 h and 8 h after inoculation in the conditions used for our experiment (see Materials and Methods).