Probabilistic safety and optimal control for survival analysis of Bacillus subtilis

We introduce a methodological framework based on the concepts of safety and optimality to interpret organismal strategies that are intrinsically related to survival behaviors. We focus on the production of the antibiotic subtilin by the bacterium Bacillus subtilis, which is one among a set of possible responses to environmental stress that are elicited by the bacterium, and we investigate the activation strategies over the genes involved in the process. We argue that these activation strategies can be synthesized as the outcome of an optimal control problem that yields a survival probability. This optimization procedure is generated from a probabilistic safety problem, which is formally related to the survival probability. We claim that a proper choice of the value function for the optimization problem that encodes the survival analysis can be related to the activation mechanisms for subtilin production.