Diverse phage communities are maintained stably on a clonal bacterial host

Bacteriophages are the most abundant and phylogenetically diverse biological entities on Earth, yet the ecological mechanisms that sustain this extraordinary diversity remain unclear. In this study, we discovered that phage diversity consistently outstripped the diversity of their bacterial hosts under simple experimental conditions. We assembled and passaged dozens of diverse phage communities on a single, nonevolving strain of <i>Escherichia coli</i> until the phage communities reached equilibrium. In all cases, we found that two or more phage species coexisted stably, despite competition for a single, clonal host population. Phage coexistence was supported through host phenotypic heterogeneity, whereby bacterial cells adopting different growth phenotypes served as niches for different phage species. Our experiments reveal that a rich community ecology of bacteriophages can emerge on a single bacterial host.