(B) The percent of ROS positive E. coli cells treated with FeSO4, H2O2 and FeSO4+DP determined by flow cytometry at 3 h after treatment. Shown are the mean percentages of ROS positive cells exceeding the fluorescence of 99% of untreated cells. Data shown are mean ± SE (n=3). *** indicates p-value < 0.001 compared with data obtained from iron treated wild type and mutant by paired student t-test. 