Fig. 2.

Cationic dyes induce EilR-regulated promoters. a Response of P_JExD to the inducing dyes as measured by single-cell RFP fluorescence of E. coli containing the low-copy plasmid pTR_sJExD-rfp. b Values for EC₅₀, amplitudes (y_max), and Hill-coefficients are used to characterize the response of P_JExD to cationic dyes. Colored circles in the chemical structures indicate N (blue), S (yellow), and O (red). Photographs show the corresponding inducing dyes in concentrated aqueous solutions. Values and error bars in a represent the means and standard deviation of biological triplicate measurements. Response curves (R² > 0.99) and numerical values in b were obtained by non-linear regression analysis in a 4-parameter variable slope model using average values of fluorescence measurements from three independently grown cultures