Figure 3

The input dynamic range of the araBAD operon is reduced by disrupting the NAR that controls araC. Shown is araBAD promoter activity as a function of arabinose concentration. The error bars indicate the s.e. (a) Promoter activity (dGFP/dt/OD, arbitrary units) in the parental strain (U424, with NAR). The blue squares are the experimental results. The dashed blue line is a fitted Hill function with Hill coefficient n = 1 ± 0.3 (s.e.), K = 1.1 ± 0.4 mM (s.e.), and R = 100 ± 40 (s.e.), and also the best fit solution of the full model described in Additional File 1. The black horizontal dashed lines mark the 10% and 90% promoter activity. (b) Promoter activity (dGFP/dt/OD, arbitrary units) in the mutant strain (U426, without NAR). The red circles are the experimental results. The solid red line is a fitted Hill function with Hill coefficient n = 1.9 ± 0.4 (s.e.), K = 42 ± 6 mM (s.e.), and R = 10 ± 3 (s.e.), and also the best fit solution of the full model described in Additional File 1. The black horizontal dashed lines mark the 10% and 90% promoter activity. (c) Normalized promoter activity of the two strains. The x axis is the L-Arabinose concentration divided by K per strain. This best demonstrates differences in the input dynamic range (R) between the two strains. Blue squares and dashed blue line are of the parental strain (U424, with NAR), while red circles and solid red line are of the mutant strain (U426, without NAR). Symbols are the measured results and the lines are fitted Hill functions.