Figure 6. Experimental confirmation of dynamically invariant response behavior of the chemotaxis pathway in E. coli upon a perturbation indicated by in Fig. 4.

Shown are the effects of a decreasing ratio between the concentrations of CheY-YFP and CheZ-CFP and the remaining signaling proteins by 2-fold (red line) and -fold (black line), whereby CheY-YFP/CheZ-CFP were expressed in LL4 cells at or M IPTG induction, respectively. Cells were stimulated by addition and subsequent removal of M MeAsp. The y-axis shows the normalized change in FRET signal, which is to good approximation proportional to the signaling output, , as explained in the main text. The base line of zero activity was determined by addition of saturating amounts of attractant.