细菌可摄取外源DNA从而增强其适应性。同时，它也面临外源DNA入侵的风险。启动CRISPR/Cas系统可选择性地识别并降解入侵的DNA。对数期大肠杆菌中，拟核相关蛋白H-NS可调控CRISPR/Cas系统，但尚未发现其同源蛋白StpA具此功能。申请人前期研究揭示稳定期大肠杆菌可建立自然感受态，摄取外源质粒；发现StpA调控自然感受态大肠杆菌中CRISPR/Cas系统表达，提示质粒摄取时存在新的调控CRISPR/Cas系统的模式。但该条件下CRISPR/Cas系统调控机制尚不清楚。本项目中，申请人拟基于前期自行建立的大肠杆菌自然转化体系，构建检测CRISPR/Cas系统表达和功能的报告体系，揭示StpA调控CRISPR/Cas系统的机制及相关调控网络，为认识细菌利用CRISPR/Cas系统防御外源DNA入侵的机制奠定基础，为拓展CRISPR/Cas系统在生物体中应用范围提供依据。

Bacteria are able to take up exogenous DNA to increase its adaptability. Meanwhile, they face the risk of exogenous DNA invasion. The activation of the CRISPR/Cas system can selectively recognize and degrade the invasive DNA. In exponentially growing Escherichia coli, the nucleoid-associated protein H-NS regulates the CRISPR/Cas system. But the role of its homologue StpA remains undiscovered in the regulation of the CRISPR/Cas system. In previous work, the applicant revealed that stationary phase E. coli is able to establish natural competence for the uptake of the exogenous plasmid DNA, and discovered that StpA regulates the expression of the CRISPR/Cas system in naturally competent E. coli, implicating the presence of a new mode of regulation of the CRISPR/Cas system during plasmid uptake. However, the regulation mechanism of the CRISPR/Cas system remains unclear under such conditions. Based on the self-established transformation system, the applicant plans to uncover how StpA regulates the CRISPR/Cas system and the involved regulation network, providing a foundation for understanding how bacteria utilize the CRISPR/Cas system in defending against the invasion of extracellular DNA, and for extending the application scope of the CRISPR/Cas system in organism.