Phage are the most abundant organisms on earth, and yet little is known about how phage and bacterial hosts are influencing each other in density and evolution. In this talk, we focus on the structure of a phage plaque, a zone of killing when phage infect a lawn of bacteria. Phage lambda is a temperate phage, with a capacity for dormancy with immunity for further infection that can be modified by single gene knockouts. The stochastic bias in the lysis-lysogeny decision's probability is reflected in plaque morphologies on bacterial lawns. We present a reaction-diffusion based model for plaque morphology of both virulent and temperate phages, taking into account the underlying survival of bacterial micro-colonies . When compared with experimentally observed plaque structure, the model reproduces known plaque morphologies for many cases, but for some mutants we failed to reproduce the detailed structure. This points out necessity of further research in relation between the regulatory network and the plaque morphology. The model also speaks for the advantage of temperate phage in a spatially structured habitat.
 Namiko Mitarai, Stanley Brown, and Kim Sneppen. Journal of Bacteriology, vol. 198, no. 12, 1783-1793 (2016).