Trading robustness and precision through noise in genetic circuits

Dynamical processes within cells can often be generated by multiple gene regulation circuits with different coupling architectures. The question then arises as to what are the criteria used by evolution to select a particular circuit architecture over another. Here we investigate this issue in the excitable genetic circuit that drives transient differentiation towards competence in the bacterium B. subtili s under nutritional stress. Interestingly, the architecture of this excitable circuit is very different from standard excitable systems in other areas, such as neurobiology and surface chemistry. How did this novel excitable architecture emerge? We have addressed this problem by means of a combination of single-cell tracking via time-lapse fluorescence microscopy, and mathematical modeling. Our results show that the natural competence architecture maximizes noise in the dynamics of the circuit, which in turn enhances the robustness of the cell\\\'s behavior with respect to variability in the stress conditions. The alternative circuit, on the other hand, maximizes precision, and indeed its architecture is more common among genetic oscillators.

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