Prophage-encoded hotspots of anti-phage systems. Defense Hotspots

The arms race between bacteria and phages led to the emergence of a variety of genetic systems used by bacteria to defend against viral infection, some of which were repurposed as powerful biotechnological tools. While numerous defense systems have been identified in genomic regions termed defense islands, it is believed that many more remain to be discovered. Here, we show that P2-like prophages and their P4-like satellites carry genomic hotspots that represent a significant reservoir of novel anti-phage systems. We validate the defense activity of diverse systems and describe PARIS, an abortive infection system triggered by a phage-encoded anti-restriction protein. Immunity hotspots are present across prophages of distant bacterial species and likely constitute a substantial source of novel anti-phage systems that participate in interviral competition.