Figure 7.

Response of the Tar-only mutant to both pH and chemical (MeAsp) stimuli, as predicted by an extended Ising-type model (with details in the Supporting Material). The mutant was preadapted to pH₀ = 7.0 and [MeAsp]₀ = 10⁻¹K₁^I,c before being stimulated to the new state (pH, [MeAsp]), where the dissociation constant K₁^I,c = 18 μM. (A) Each point in the surface represents the Tar response to a combined stimuli (pH, [MeAsp]). (B) The contour plot of panel A on the space (pH, [MeAsp]) (dashed line corresponds to the neutral response curve along which the responses to the pH and chemoattractant changes cancel out).