Regulatory RNAs as mediators, scaffolds, and effectors in host-phage interaction.

Regulatory RNAs have long been recognized as major post-transcriptional regulators of bacterial physiology, controlling diverse processes including metabolism, stress adaptation, quorum sensing, and virulence. Recent discoveries have expanded their functional repertoire, revealing that both bacterial and phage-encoded regulatory RNAs contribute to multiple aspects of host-(bacterio)phage interactions. Beyond regulating cellular physiology, regulatory RNAs influence bacterial defense through immune regulation, RNA-guided immunity, dormancy, and abortive infection pathways, while phage-encoded regulatory RNAs can reprogram host gene expression, promote lysogeny, and allow evasion of bacterial defense mechanisms. In this article, we discuss recent advances in the roles of regulatory RNAs during host-phage interactions, focusing on emerging mechanisms through which RNA-mediated regulation influences both bacterial defense and phage counter-defense.