CodY Regulates Thiol Peroxidase Expression as Part of the Pneumococcal Defense Mechanism against H2O2 Stress

We identified pneumococcal thiol peroxidase as the key enzyme for enzymatic removal of H2O2, and showed that TpxD synthesis is up-regulated upon exposure to H2O2

Barak Hajaj; Hasan Yesilkaya; Sulman Shafeeq; Xiangyun Zhi; Rachel Benisty; Shiran Tchalah; Oscar P. Kuipers; Nurith Porat

2017

Scholarcy highlights

  • Streptococcus pneumoniae commonly causes severe infections such as pneumonia, meningitis, and septicemia
  • We have previously shown that the pneumococcal surface adhesion D gene, psaD, encodes a functional thiol peroxidase, which scavenges directly H2O2, and renamed it as tpxD. tpxD expression and synthesis were significantly up-regulated under aerobic compared to anaerobic conditions, and in the presence of exogenously added H2O2
  • In a previous study, we showed that thiol peroxidase is an efficient H2O2 scavenger, and that its expression is up-regulated under aerobic compared to anaerobic growth conditions
  • In order to isolate the effect of H2O2 from other reactive oxygen species formed under aerobic environment, D39 and tpxD were challenged with sub-lethal H2O2 concentrations under anaerobic conditions
  • Microarray profiling of D39 challenged with 1 mM H2O2 revealed that 217 genes were differentially expressed by a factor of 1.8 or more compared to unchallenged bacteria: 146 were downregulated and 71 were up-regulated
  • In the current study we show that pneumococcal response to high H2O2 levels depends on TpxD, and that tpxD expression is regulated by the global transcription factor CodY
  • We demonstrate that some of the genes involved in oxidative stress response, which are known to be regulated by CodY, were not affected by high H2O2 levels in tpxD mutants tpxD and TpxDC58S), signifying that active-thiol peroxidase is required for CodY function as a transcription factors under oxidative stress conditions

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