Theoretical Analysis of the Starvation Response under Substrate Pulses

A simulation model was constructed in which two model bacteria competed with each other in a closed system to which periodic substrate additions were made. One bacterium responded to starvation by entering into a dormant state characterized by a decreased death rate; the other bacterium did not make this transition. The periodicity of substrate addition was varied, and the magnitude of selection for one bacterial type was calculated. For model parameters typical of those measured in Escherichia coli, positive selection for the bacterium capable of the starvation response only occurred if the time interval of substrate addition exceeded 54 times the minimum doubling time of the bacterium. The magnitude of the selection coefficient was most sensitive to two model parameters: the time constant for conversion of dormant cells back to actively growing ones, and the magnitude of the death rate of cells which did not undergo the starvation response.