Rampant prophage movement among transient competitors drives rapid adaptation during infection

Interactions between bacteria, their close competitors, and viral parasites are common in infections but understanding of these eco-evolutionary dynamics is limited. Most examples of adaptations caused by phage lysogeny are through the acquisition of new genes. However, integrated prophages can also insert into functional genes and impart a fitness benefit by disrupting their expression, a process called active lysogeny. Here, we show that active lysogeny can fuel rapid, parallel adaptations in establishing a chronic infection. These recombination events repeatedly disrupted genes encoding global regulators, leading to increased cyclic-di-GMP levels and elevated biofilm production. The implications of prophage-mediated adaptation are broad, as even transient members of microbial communities can alter the course of evolution and generate persistent phenotypes associated with poor clinical outcomes. One Sentence SummaryBacteriophage act as genetic regulators that are key to establishing chronic infections and are rapidly shared among co-infecting strains.