Polyphosphate kinase 1-coding gene (ppk1) is involved in the oxidative stress resistance in uropathogenic Escherichia coli by modulating the expression of katG and katE genes / 中华微生物学和免疫学杂志

ABSTRACT

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.