Simulation of ΔCheY
. A] Models representing the mutants lacking CheY3 and CheY4 were simulated. The grey and the magenta model are chemotactic (they still respond to stimulus) under these conditions and the steady state of magenta model is always close to zero. These results do not correspond to experimental observation. B] The robustness of our invalidation of the grey and magenta models was tested by running 200 simulations of the model lacking CheY3 and CheY4, allowing parameters k1 - k14 to vary by ± 50%. None of these changes produced a non-chemotactic model.