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

Abstract

Urinary tract infections (UTIs) are common bacterial infections and the vast majority of UTIs are caused by extraintestinal pathogenic <i>Escherichia coli</i> (ExPEC) strains referred to as uropathogenic <i>E. coli</i> (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 <i>lux</i> under the control of the fimbrial promoter region, <i>fimS</i> and this construct was inserted into the reference UPEC strain CFT073 genome at the <i>att</i>Tn7 site. This <i>fimS</i> reporter strain was used to generate a Tn<i>10</i> 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 Δ<i>yqhG</i> 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 <i>fim</i> switch in the OFF position. Interestingly, the Δ<i>yqhG</i> mutant was more motile than the WT strain and was also significantly more sensitive to hydrogen peroxide. Taken together, loss of <i>yqhG</i> may decrease virulence in the urinary tract due to a decrease in production of type 1 fimbriae and a greater sensitivity to oxidative stress.