From environmental signals to adaptive phenotypes: signal-responsive regulation and network logic of bacterial small RNAs.

Bacterial regulatory small RNAs (sRNAs) are integral components of posttranscriptional control, shaping environmental adaptation, metabolic homeostasis, and virulence. Advances in transcriptomics and RNA technologies have greatly expanded the repertoire of bacterial sRNAs and revealed their extensive roles in posttranscriptional regulatory networks. This review provides an updated framework for the biogenesis of bacterial sRNAs and their regulatory roles within posttranscriptional networks. Crucially, we describe the regulatory pathways controlling sRNA expression, including environmental signal sensing and regulation mediated by σ factors and transcription factors, to illustrate how sRNAs respond dynamically to changing conditions. Expanding beyond expression control, we further discuss the diverse roles of sRNA-mediated regulation in metabolic adaptation, stress responses, and bacterial virulence, emphasizing their importance in linking environmental changes to cellular phenotypes. Concurrently, we review current experimental and computational methods used for sRNA discovery and target identification. Overall, this review provides an integrated perspective on how bacterial sRNAs connect environmental sensing with adaptive cellular responses and highlights the broader significance of RNA-mediated regulation in bacterial physiology.