CRISPR-Cas系统是细菌和古菌的后天免疫系统，防御噬菌体入侵，同时参与调控内源性基因表达而影响细菌毒力、耐药性和生物膜的形成。但细菌如何调控CRISPR系统却知之甚少。项目前期通过低通量sRNA文库筛选获得34个sRNA与CRISPR基因座相结合，其中PhrS和pant463 sRNA激活该基因座转录合成pre-crRNA，参与CRISPR免疫应答，而pant391抑制该过程。在此基础上，本项目运用已建立的TSRT-seq方法在全基因组水平鉴定参与CRISPR-Cas转录的sRNA，解析噬菌体入侵sRNA与CRISPR系统的关系，揭示PhrS、pant463和pant391的生物学功能，阐明PhrS介导抑制Rho依赖的转录终止调控pre-crRNA转录的机制。本项目有望首次阐明sRNA作为CRISPR-Cas系统的新型调节因子，控制细菌的生理功能，为研究细菌耐药性和致病性提供新思路。

CRISPR-Cas systems not only endow prokaryotes with adaptive and heritable immunity against bacteriophages, but also control endogenous genes expression to affect bacterial virulence, drug resistance and biofilm formation. However, it is unknown how bacteria regulate CRISPR-Cas systems. Our preliminary work showed using proximity ligation by T4 RNA 1 ligase search for a 274 sRNAs library to identify those RNAs that target type I-F CRISPR-Cas system and demonstrate that 34 sRNAs can bind to CRISPR loci. And 34 sRNA are found to impact transcription levels of CRISPR locus, with enhancement by sRNA PhrS and pant463 but inhibition by pant391. We then identify PhrS as a major regulator of CRISPR-Cas to promotes transcription of a specific CRISPR locus to generate crRNA and subsequently activating CRISPR-Cas adaptive immunity against bacteriophage invasion. In this project, we will establish approach named Total small RNA target by T4 RNA ligase and Illumina sequencing (TSRT-seq) to identify new sRNAs that target CRISPR-Cas system, especially to sRNA expression pattern during plasmid infection. Meanwhile, we will clarify how PhrS suppresses Rho-dependent transcription termination to control CRISPR-Cas transcriptions. Our findings identify sRNAs as a new type of regulators of CRISPR-Cas, extending the role of sRNAs in controlling bacterial physiology by priming CRISPR-Cas adaptive immunity.