Optimising dormancy vs. virulence decisions in bacteriophage

Abstract

Bacteriophages are the most abundant organisms on the planet and play key roles as shapers of ecosystems and drivers of bacterial evolution. Temperate phages can choose between (i) lysis: exploiting their bacterial hosts to produce multiple offspring phage and releasing them by lysing the host cell, and (ii) lysogeny: establishing a mutually beneficial relationship with the host by integrating their chromosome into the host cell’s genome. I will describe how we combine dynamical systems and game theory to model the  competition of phage mutants that have different lysogeny propensities. We find that there is a narrow range of optimal propensity values that phages can evolve, and this predicted range covers the values observed for various phage species. Our results also offer an explanation for why temperate phages tend to utilize bistable switches that can incorporate the number of infecting phage into the lysis-lysogeny decision. If there is time, I will describe other work that examines the range of network structures that can produce such functionality.