FIG 1.

phoP plays a major role in mycobacterial redox stress response. (A and B) The WT H37Rv and phoP::Kan^r strains were grown in the presence of either 5 mM diamide for 48 h or 50 μM cumene hydroperoxide (CHP) for 24 h, and CFU values were enumerated. For each strain, the percentage of bacterial survival was determined relative to growth of the corresponding strain in the presence of carryover DMSO. The growth experiments were performed in biological duplicates, each with two technical repeats. (C and D) To examine whether phoP is linked to mycobacterial redox potential, we compared the intramycobacterial mycothiol redox states of the WT and phoP::Kan^r strains grown either (C) in the presence of 5 mM diamide or (D) under low-pH conditions. In this experiment, we used plasmid Mrx1-roGPF2, where mycoredoxin is fused to redox-sensitive GFP, enabling real-time measurement of the mycothiol redox state by analysis of fluorescence emission at 510 nm after excitation of the samples at 405 and 488 nm (see Materials and Methods). The results show average values from biological triplicates, each with two technical repeats (*, P ≤ 0.05; **, P ≤ 0.01).