Estimating Optimal Lysogenic Propensity for Viruses in Stressed Environments

Abstract. H aving infected a bacterial cell, a temperate phage has to make a choice between (a) integrating itself into the bacterial genome, i.e. lysogeny , and (b) using the bacterial machinery to create multiple copies of itself and lysing the cell in the process, i.e. lysis . In order to maximize its long-term growth rate, phages need to ensure that they do not wipe off their bacterial hosts. Temperate phages have been observed to exhibit lysogenic propensities dependent on the MoI (Multiplicity of Infection), among other factors. We propose a model to estimate the propensity of lysogeny opted for by the phages in order to maximize coexistence. One possible approach to do so is to adopt a strategy that would help to attain and maintain an approximately equal proportion of phages with respect to their host. We find that the optimal fraction of phages opting for lysogeny follows a sigmoidal relationship with the MoI and is comparable to results obtained experimentally. We further assess the impact of phage and bacterial environmental stresses on the lysogenic propensity. Our results indicate that the optimal value of lysogenic propensity is greatly dependent on the intensity of these stresses.