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Objective To investigate the role and the mechanism of ppk1 gene (coding for polyphosphate kinase 1) in oxidative stress resistance in uropathogenic Escherichia coli (UPEC).MethodsMutant strains with ppk1-deletion (△pk1) and complemented strains (△pk1-C) were constructed based on the UPEC strain CFT073.A comparative analysis was conducted to analyze survival rates of CFT073, △pk1 and △pk1-C strains at different time points while they were under oxidative stress.Differences in protein expression between CFT073 and △pk1 strains were analyzed using mass spectrometric analysis.Differences between CFT073 and △pk1 strains in expression of katG and katE genes were analyzed using real-time quantitative RT-PCR.Results The survival rate of △pk1 strains was lower than that of CFT073 strains at every time point, while the survival rate of △pk1-C strains was basically the same as that of CFT073 strains.Gel image analysis and mass spectrometric analysis revealed that six proteins were down-regulated and one was up-regulated in △pk1 strains as compared with those in CFT073 strains.Expression of the catalase-coding genes katG and katE in △pk1 strains were respectively (20.5±8.2)% and (20.9±6.9)% of those in CFT073 strains (P<0.05).Conclusion The ppk1 gene plays an important role in oxidative stress resistance in UPEC by modulating the expression of catalase-coding genes katG and katE.
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Objective To explore the role of ppk1 gene in E.coli CFT073 strain during urinary tract infection (UTI). Methods C57BL/6 mouse models of acute UTI with the wild-type(CFT073) and ppk1 mutant (△pk1) infected, were used to compare the bacteria colonization and inflammation induction abilities of bladder tissues. Results In the mouse models, the △pk1 strain showed a significantly lower infection rate (73.3% vs 93.3%) and lower adhesion frequency of bladder (0.01%vs 0.5%) than those of the CFT073 strain. The expression of IL-6 and TNF-αwere reduced in the bladder of △pk1 infected group (P<0.05). Hematoxylin-Eosin tissue staining showed that the damage degree of bladders in △pk1 infected mice were less serious than the CFT073 infected mice. Conclusion ppk1 gene plays an important role in E.coli colonization to bladder and the inflammation induction ability.
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<p><b>OBJECTIVE</b>To study the changes in biological behaviors of meningitis E. coli K1 strain E44 after deletion of polyphosphate kinase 1 (ppk1) gene and explore the role of ppk1 in the pathogenesis of E. coli K1-induced meningitis.</p><p><b>METHODS</b>The wild-type strain E. coli K1 and ppk1 deletion mutant were exposed to heat at 56 degrees celsius; for 6 min, and their survival rates were determined. The adhesion and invasion of the bacteria to human brain microvascular endothelial cells (HBMECs) were observed using electron microscopy and quantitative tests. HBMECs were co-incubated with wild-type strain or ppk1 deletion mutant, and the cytoskeleton rearrangement was observed under laser scanning confocal microscope.</p><p><b>RESULTS</b>The survival rate of the ppk1 deletion mutant was significantly lower than that of the wild-type strain after heat exposure. The ppk1 deletion mutant also showed lowered cell adhesion and invasion abilities and weakened ability to induce cytoskeleton rearrangement in HBMECs.</p><p><b>CONCLUSIONS</b>ppk1 gene is important for E.coli K1 for heat resistance, cell adhesion and invasion, and for inducing cytoskeletal rearrangement in HBMECs.</p>
Subject(s)
Humans , Brain , Cell Biology , Cells, Cultured , Cytoskeleton , Endothelial Cells , Cell Biology , Microbiology , Escherichia coli , Genetics , Physiology , Escherichia coli Proteins , Genetics , Gene Deletion , Phosphotransferases (Phosphate Group Acceptor) , GeneticsABSTRACT
Objective To construct a Polyphosphate kinase 1 ( ppk1) gene deletion mutant of uro-pathogenic Escherichia coli (E.coli) CFT073, and to explore the biological properties of the mutant strain . Methods The ppk1 gene deletion strain (△pk1) was constructed based on CFT073 E.coli strain by usingλRed homologous recombination technology .A comparison analysis was conducted on adhesive and invasive abilities between CFT073 wild type strain and △pk1 strain in in vitro model of human bladder cancer epithe-lial cell 5637 .Crystal violet staining method was used to evaluate the influences of ppk1 gene deletion on biofilm formation.Results The CFT073 ppk1 deletion mutant strain was successfully constructed .Com-pared with the wild type strain ,△pk1 strain showed impaired adhesive and invasive abilities to 5637 cells. Moreover , the absorbance values of crystal violet at 570 nm at each time point of the mutant strain group were also lower than those of the wild-type strain group .Conclusion The ppk1 gene deletion mutant of uro-pathogenic E.coli CFT073 could be successfully constructed by Red homologous recombination technology and its biological properties indicates that ppk1 gene plays an important role in the pathogenesis of uropatho-genic E.coli infection through regulating the abilities of adhesion , invasion and biofilm formation .