革兰氏阴性菌对多粘菌素的耐药问题已引起全球关注。小RNA（sRNA）在细菌对抗生素应答中起重要调控作用。我们前期研究发现，多粘菌素诱导下大肠杆菌MicA（一个sRNA）的表达大幅度增加，其调控的下游基因表达改变，且临床分离大肠杆菌耐药株中存在MicA核苷酸区突变，表明MicA在多粘菌素诱导和耐药中起重要作用，但机制不明确。基于前期研究结果，本项目拟：1）利用高通量转录组测序等方法，结合已报道的MicA下游基因，在模式菌中系统阐述与多粘菌素作用相关的MicA下游基因并验证；2）在临床分离多粘菌素耐药株中，检测MicA及其与多粘菌素作用相关下游基因的突变和表达变化，验证和筛选有意义的目标下游基因；3）构建目标基因突变株和回补株，进行表型和功能研究，从而阐明MicA及其调控的下游基因在多粘菌素诱导和耐药中的作用机制。本项目有助于完善临床分离株的多粘菌素耐药产生机制，为药物靶标的发掘提供理论基础。

Polymyxin resistance in Gram-negative bacteria has becoming a worldwide concerned antimicrobial resistance problem. Small RNA (sRNA) plays an important regulation role in antibiotic response in bacteria. Our studies have demonstrated that the expression of Escherichia coli MicA (a sRNA) significantly increased when induced by polymyxin, and several MicA regulated genes have changed expression. We also find micA mutation in some of clinical isolated polymyxin resistant E. coli. All these results have demonstrated an important function of MicA in polymyxin induce and resistance. But we don’t know the exact mechanism. Based on the previous studies, this project will, 1) Employ high throughput transcriptome and other methods, combined with the reported MicA regulated genes, to explore and demostrate the MicA regulated downstream genes which are related to polymyxin effect; 2) Demonstrate and select the meaningful genes through identify the mutation and expression of the clinical isolated polymyxin resistant E. coli; 3) Construct the mutants and complementation strains of the target genes to figure out the phenotypes and functions, so that we can explain the proper function mechanism of MicA and its regulated genes in polymyxin induce and resistance. Through this study, we will provide the theoretical basis for the mechanism of polymyxin-resistant bacteria and for the exploration of new drug targets.