| Cells exhibit diverse and dynamic responses to stress. However, in many cases it remains unclear what the dynamics are, how they are generated, and why they are beneficial to the cell or organism. To investigate these issues we studied the General Stress Response in B. subtilis, a critical, conserved stress signaling pathway, mediated by the alternative sigma factor, σB. First, we find that σB activates with stochastic, frequency modulated pulses in response to energy stress. We explore the mechanism behind this striking response and find that a small, compact circuit facilitates this behavior. Second, we find that σB activates with a single-homogenous pulse of activity exposed to environmental stress, in contrast to energy stress dynamics. We also find that activation is rate-responsive, and show how this property may separate broad and specific regulatory modes. Lastly, we present some preliminary work toward a synthetic sigma factor activation circuit. Combined, these results present a comprehensive study of σB activation and generate a platform by which other dynamic stress response systems can be understood. |
