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Figure 4 | BMC Systems Biology

Figure 4

From: Dynamics of the quorum sensing switch: stochastic and non-stationary effects

Figure 4

Cell response distribution to autoinducer induction in the stochastic model. Cell response probability after 10 hours (top: A, B) and 100 hours (middle: C, D) of induction at different autoinducer concentrations for the lux01 (left: A, C) and lux02 (right: B, D) operons in the stochastic model. The distribution reveals the coexistence of two subpopulations with low and high GFP expression when the cells are induced at intermediate autoinducer concentrations. The region of bistability (precision) is defined by the range of c A for which the response is bimodal according to the following criterion: the lower/upper limit of the bistable region (orange lines) is defined by the value of c A for which 90% of the cells are in the low/high state. The black line stands for the concentration of GFP (normalized) as a function of c A in the deterministic model at the steady state. After 10 hours of induction (top: A, B) most cells are still in a transient state if c A <70nM. After 100 hours of induction (middle: C, D), the bimodality region shrinks and the precision increases. The population average curves of the induction and dilution experiments in the stochastic model (bottom: E, F, dashed lines) show that the intrinsic noise allows cells to jump to the high state inside the deterministic bistable region. On the other hand, the transition from high to low follows the deterministic path thus indicating that the switching rate in this case is close to zero.

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