Figure 2

Theoretical analysis of the dynamics of the mar circuit and associated modifications.

(A) MarR response upon induction with 0.5 mM salicylate normalized by the steady state (ss) value (starting from [MarR] = [MarA] = 0 in the absence of the signal). We compared the dynamics of the wild-type circuit (solid blue line) with those of two circuit variants without the positive (dashed blue line; a circuit lacking MarA) or negative (dotted blue line; a circuit lacking MarR in presence of salicylate) feedback, respectively, and with a third system exhibiting a constitutively controlled response (black line, this represents a null reference model of the dynamics, see main text). All simulations performed by using nominal parameter values (Table S1). (B) MarA dynamics (relative to the ss value) for different degradation rates of this protein (δ) upon induction with 0.5 mM salicylate. When MarA is unstable (as it is the case in the natural system), the protein dynamics follows the pulse-like behavior of the promoter activity (see also Fig. 3; note that the cell growth rate is μ < 10⁻² min⁻¹).