Bacteria and bacteriophages are ubiquitous. Obligate parasites of bacteria, bacteriophages significantly alter the diversity and the dynamics of bacterial populations. Understanding the interactions between bacteria and bacteriophages in order to predict and control their evolution, has many interests in ecology, industry, and public health. The coexistence of bacteria and bacteriophages is partly due to antagonistic coevolution dynamics that established between them. Here, we chose to study the genetic constraints limiting the coevolution between Escherichia coli and PhiX174. Studying the ecological niche of PhiX174, we found that the sensitive strains to this bacteriophage, were both rare and remarkable for their phylogenetic diversity. Moreover, while the lipopolysaccharide (LPS) is recognized as the receptor of PhiX174, we demonstrated that PhiX174 can lyse bacteria displaying a variety of LPS, compelling the bacterial population to resist except by amending its receptor. Then, modifying the genotype of the bacterial host inoculated with PhiX174, we have profoundly altered the duration of the bacteria-phage coexistence. Finally, we established a protocol of coevolution between E. coli and PhiX174 which allowed us to discuss the evolution of the selection pressure induced by bacteriophages on bacterial population and the existence of a compromise between virulence and infectivity. It seems, ultimately, that epistatic relationships between genes involved in bacteriabacteriophage interactions are strong genetic constraints limiting the antagonistic coevolution between E. coli and PhiX174, in addition to ecological constraints already described.
