Compensatory role of KatG in defending H2O2stress inmsrdeletion strain ofSalmonellaTyphimurium

Abstract

AbstractKatG and Msrs are important enzymes associated with ROS homeostasis and bacterial survival under oxidative stress. Consistent to this notion, mutant strains in these enzymes showed hypersensitivity to oxidants and accumulates elevated levels of ROS. In current study we observed that a panmsrdeletion (Δ5msrmutant) strain ofS.Typhimurium accumulates significantly higher levels of ROS. However, unexpectedly, as compared toS.Typhimurium, the Δ5msrmutant strain exhibits more than 2000 folds resistance to H2O2. Transcriptional and mass spectrometry analyses reveal the upregulation of KatG in Δ5msrmutant strain. Further, Δ5msrmutant strain exhibits ∼6 folds higher KatG activity. Supplementation of Δ5msrmutant culture with reduced glutathione resulted in ROS neutralization, decreased KatG activity and abrogation of H2O2resistance. However, Δ5msrmutant strain showed negligible KatE and KatN activities. The findings of current study suggest that theSalmonellahave evolved the mechanism to upregulate one antioxidant gene in absence of others to mitigate oxidative stress.