Table_1_yqhG Contributes to Oxidative Stress Resistance and Virulence of Uropathogenic Escherichia coli and Identification of Other Genes Altering Expression of Type 1 Fimbriae.DOCX

Urinary tract infections (UTIs) are common bacterial infections and the vast majority of UTIs are caused by extraintestinal pathogenic Escherichia coli (ExPEC) strains referred to as uropathogenic E. coli (UPEC). Successful colonization of the human urinary tract by UPEC is mediated by secreted or surface exposed virulence factors—toxins, iron transport systems, and adhesins, such as type 1 fimbriae (pili). To identify factors involved in the expression of type 1 fimbriae, we constructed a chromosomal transcriptional reporter consisting of lux under the control of the fimbrial promoter region, fimS and this construct was inserted into the reference UPEC strain CFT073 genome at the attTn7 site. This fimS reporter strain was used to generate a Tn10 transposon mutant library, coupled with high-throughput sequencing to identify genes that affect the expression of type 1 fimbriae. Transposon insertion sites were linked to genes involved in protein fate and synthesis, energy metabolism, adherence, transcriptional regulation, and transport. We showed that YqhG, a predicted periplasmic protein, is one of the important mediators that contribute to the decreased expression of type 1 fimbriae in UPEC strain CFT073. The ΔyqhG mutant had reduced expression of type 1 fimbriae and a decreased capacity to colonize the murine urinary tract. Reduced expression of type 1 fimbriae correlated with an increased bias for orientation of the fim switch in the OFF position. Interestingly, the ΔyqhG mutant was more motile than the WT strain and was also significantly more sensitive to hydrogen peroxide. Taken together, loss of yqhG may decrease virulence in the urinary tract due to a decrease in production of type 1 fimbriae and a greater sensitivity to oxidative stress.

尿路感染（Urinary Tract Infections, UTIs）是常见的细菌性感染，绝大多数UTI由肠外致病性大肠杆菌（Extraintestinal Pathogenic Escherichia coli, ExPEC）菌株引发，该类菌株又被称为尿路致病性大肠杆菌（Uropathogenic E. coli, UPEC）。UPEC对人类尿路的成功定植，依赖于其分泌型或表面暴露的毒力因子——包括毒素、铁转运系统以及黏附素（如1型菌毛（type 1 fimbriae，pili））。为鉴定参与1型菌毛表达的相关因子，本研究构建了以菌毛启动子区域fimS调控lux基因的染色体转录报告系统，并将该重组构建体插入至参考尿路致病性大肠杆菌菌株CFT073基因组的attTn7位点。利用该fimS报告菌株构建Tn10转座子突变体文库，并结合高通量测序技术，筛选得到影响1型菌毛表达的相关基因。转座子插入位点所关联的基因，涉及蛋白质命运与合成、能量代谢、黏附、转录调控以及物质转运等多个通路。本研究证实，YqhG作为一种预测的周质蛋白，是导致尿路致病性大肠杆菌CFT073菌株中1型菌毛表达下调的重要介导因子之一。ΔyqhG突变株的1型菌毛表达水平显著降低，且其定植小鼠尿路的能力也出现下降。1型菌毛的表达下调，与fim开关偏向处于关闭（OFF）状态的比例升高呈显著相关性。值得注意的是，ΔyqhG突变株的运动能力较野生型（WT）菌株更强，同时对过氧化氢的敏感性也显著升高。综上，yqhG基因的缺失可通过降低1型菌毛的生成以及提升菌株对氧化应激的敏感性，进而减弱其在尿路中的毒力。