Host-Parasite Coexistence: The Role of Spatial Refuges in Stabilizing Bacteria-Phage Interactions

Abstract

We manipulated a bacteria-phage model system to investigate empirical and theoretical conditions allowing for the coexistence of an Escherichia coli host with each of two virulent phage species, a T1-like phage (T1X) and λvir. In minimal medium in the laboratory, bacteria coexisted with each phage species in continuous (chemostat) culture; however, in serial culture, T1X rapidly became extinct in all cases and λvir became extinct in most cases. When we refined a previously developed mechanistic model of bacteria-phage interactions in continuous culture, this model failed to predict our laboratory observations of long-term stability of bacteria and phage in chemostats. A serial transfer version of this model, however, came much closer to predicting bacteria-phage dynamics. To investigate why models of continuous culture failed, we tested hypotheses for phage persistence by manipulating experimental culture conditions. We found that wall populations of bacteria strongly influenced the stability of both phag...