Fig. 3

Modelling of the ppGpp-based biosensor in normal, non-FA-producing E. coli lines. a. Dependence of steady state GFP fluorescence on ppGpp concentrations. Each data point was calculated at different ppGpp concentration. b. Timecourses of ppGpp, GFP and lim in the model during nutrient upshift (shown by arrow) at the end of phase 1. c. Dependence of the response time of GFP fluorescence (T _0.5,GFP ) on the fold increase of the rate constant k _GFP of GFP protein degradation (black) or fold decrease of the rate constant Ki _I of the inhibition of GFP expression by the inhibitor I (blue). T _0.5,GFP was calculated as the time required for 2-fold decrease of GFP fluorescence after the nutrient upshift. Red circle indicates the value of T _0.5,GFP corresponding to k _GFP  = 0.1 min⁻¹ and Ki _I  = 0.3 used in a, b