Figure 1. ObgE* increases intracellular ROS concentrations.

(a) Cultures of E. coli pBAD33, E. coli pBAD33-obgE or E. coli pBAD33-obgE* were stained with the redox-sensitive probe H₂DCFDA that can be oxidized to form the fluorescent H₂DCF. ObgE* expression increases H₂DCF fluorescence, even when the signal is corrected for cell size, and thus causes oxidative stress. PC = Positive Control, E. coli pBAD33 + 100 μM H₂O₂. (b) ObgE* activates GFP expression from the ROS-responsive promoters P_soxS and P_dps and therefore leads to increased ROS concentrations. PC = Positive Control, E. coli pBAD33 + 20 mM PQ for P_soxS and E. coli pBAD33 + 100 μM H₂O₂ for P_dps. Representative results of three repeats are shown. (c) Average GFP expression from the ROS-responsive promoters P_soxS and P_dps shows that ObgE* expression leads to increased ROS concentrations. Averages of three repeats are shown. Error bars represent the standard error of the mean, n = 3. Student’s t test: ^#p-value < 0.05, ^##p-value < 0.01 in comparison with the vector control.