Subtle interplay of stochasticity and deterministic dynamics pervades an evolutionary plausible genetic circuit for Bacillus subtilis competence

• Studied evolutionary plausible auto-regulated competence circuit for B. subtilis.
• Discovered competence is delivered in high noise by one single fixed point assisted by the presence of a dynamical ghost.
• Showed how circuit dynamical features affect the shape of the distribution of times spent in competence.
• Studied the consequences of imperfect time-scale separation between transcription and translation processes.
• Mathematically investigated the dynamic stability of the system and derived general rules.

Here we study the interplay of stochastic and deterministic dynamics in an evolutionary plausible candidate core genetic circuit for Bacillus subtilis competence. We find that high noise would not necessarily be detrimental to the circuit’s ability to deliver the phenotype, due to an unexpected built-in robustness that we further investigate. Also, we find that seemingly subtle deterministic dynamical features of the regulation, unstable and stable limit cycles, while in the presence of biochemical noise, would result in a distinctive new observable in the phenotype. We conduct mathematical analyses of the system’s stability at the fixed points and derive some general model-independent consequences. We also show how imperfect time-scale separation in the system would result in observables detrimental to the phenotype, that nature could have harnessed for selection.