Quorum Sensing Determines the Choice of Antiphage Defense Strategy in Vibrio anguillarum

Comprehensive knowledge on bacterial antiphage strategies and their regulation is essential for understanding the role of phages as drivers of bacterial evolution and diversity. In an applied context, development of successful phage-based control of bacterial pathogens also requires detailed understanding of the mechanisms of phage protection in pathogenic bacteria. Here, we demonstrate for the first time the presence of quorum-sensing-regulated phage defense mechanisms in the fish pathogen Vibrio anguillarum and provide evidence that quorum-sensing regulation allows V. anguillarum to alternate between different phage protection mechanisms depending on population cell density. Further, our results demonstrate the prevalence of nonmutational defense mechanisms in the investigated V. anguillarum strain, which allow flexible adaptations to a dynamic phage infection pressure.