The σB alternative sigma factor circuit modulates noise to generate different types of pulsing dynamics
Fig 4
The system transitions through a range of behaviours as the effective dephosphorylation rate is varied.
(A) The magnitude of the two behaviours for our selected parameter set (kK2, η, pfrac, kB5, kD5) = (7.0 h-1, 0.025, 100.0 μM h-1, 3600.0 μM-1h-1, 18.0 h-1). 12 different selected values of pprod (used in B-M) are marked with grey lines. (B-M) For 12 different values of pprod a single simulation is displayed (stress added at t = 0, red dashed line). (B) For pprod small, the system does not respond. (C,D) As pprod is increased, the system exhibits a single response pulse. The amplitude increase with pprod. (E,F) For larger values of pprod, stochastic pulsing is exhibited. The frequency of the pulses increases with pprod. (G-I) As the stress is increased further, the system enters a limit cycle. (J-L) For large pprod, the system exhibits a single response pulse, and then enters a persistent state of elevated σB activity. The activity in this state increases with pprod. (M) For large enough stresses, the system saturates at some maximum activity. An expanded version of this figure, including bifurcation analysis of system steady state properties, can be found in S16 Fig. A similar transition, but generated through Gillespie algorithm simulations, can be found in S17 Fig. Parameter values and other details on simulation conditions for this figure are described in S4 and S5 Tables.