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 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 att Tn7 site. This fimS reporter strain was used to generate a Tn 10 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 yqhG 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 Δ yqhG 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.

The RyfA small RNA regulates oxidative and osmotic stress responses and virulence in uropathogenic Escherichia coli

“…We previously generated a transposon (Tn) library in UPEC reference strain CFT073 [ 28 ]. The library was subjected to osmotic and oxidative stresses as a selection for potentially decreased fitness in an environment in which the bacteria encounter host-derived stresses including osmolarity in urine and interactions with host immune cells.…”

“…It is interesting that there is a link between sensitivity to oxidative stress and altered expression of type 1 fimbriae. Previous studies reported that mutations in other genes, including yeaR , rpoS , ibeA and yqhG , increased sensitivity to oxidative stress and concomitantly decreased expression of type 1 fimbriae [ 28 , 49 – 51 ]. Importantly, assembly of type 1 fimbriae is dependent on the oxidative state of subunit proteins in the periplasm and involves the coordinated folding of subunits through action of the oxidoreductase DsbA and the chaperone FimC, underscoring the potential effects of oxidative imbalances on fimbrial biogenesis [ 52 ].…”

“…Motility assays were done using UPEC strains CFT073 and 536 and its mutant derivatives as previously described [ 28 , 36 ] with modifications. Following overnight growth at 37°C, strains were cultured at 37°C in LB broth to mid-log phase.…”

Coordinate overexpression of two RND efflux systems, ParXY and TtgABC, is responsible for multidrug resistance in Pseudomonas putida

“…A variety of proteins are able to sense α‐ketoglutarate including a 2CS named KguSR whose activity influences expression of α‐ketoglutarate dehydrogenase, succinyl CoA synthetase and type 1 fimbriae in uropathogenic E . coli (Cai et al ., 2013; Huergo and Dixon, 2015; Bessaiah et al ., 2019). Whether HK PpeS plays a similar role in P .…”

“…In E. coli, besides its well-known roles in carbon and nitrogen metabolic pathways, α-ketoglutarate is considered as a master regulator able to activate α-ketoglutarate-sensing regulatory proteins, and that modulates cAMP (Huergo and Dixon, 2015). A variety of proteins are able to sense α-ketoglutarate including a 2CS named KguSR whose activity influences expression of α-ketoglutarate dehydrogenase, succinyl CoA synthetase and type 1 fimbriae in uropathogenic E. coli (Cai et al, 2013;Huergo and Dixon, 2015;Bessaiah et al, 2019). Whether HK PpeS plays a similar role in P. putida in spite of its low sequence similarity with KguS (10% identity) warrants further investigations.…”