Effect of reduced levels of RsbX on stress activation of σB. Three data-sets from Völker et al. (1997)  were digitized in which the level of RsbX is controlled by the addition of IPTG (BSA46 [wild type], squares; BSA337+1 mM IPTG [RsbX reduced], diamonds; BSA337+0.1 mM IPTG [RsbX low], triangles). The simulation was performed with the ‘product activation’ model. The responses of experiment and simulation are normalised to the maximum response of the wild type. The lines represent simulations with parameters as listed in Tables 1 and 3 but with appropriately adapted dephosphorylation probabilities (kdps), wt with kdps=1 (continuous line); reduced RsbX with kdps=0.6 (dashed line); low RsbX with kdps=0.1 (dashed-dotted line). The activation of the stressosome by ethanol (experiment) or by increase in kphr (simulation) both took place at 20 min.