FIG 2.

Role of the iprA gene in oxidative stress resistance in S. Typhimurium (ST). (A) Gene map between hemB and ddlA in the S. Typhimurium genome showing different deletion mutations constructed in this region. (B) Oxidative stress resistance assays performed on S. Typhimurium strain χ3339 derivatives containing different mutations shown in panel A. The percent survival of bacteria after the addition of stress was obtained based on the initial CFU per milliliter before stress, and a ratio of the percent survival for each strain compared to the WT strain survival was calculated and plotted. (C) S. Typhimurium strains 29629 and NCTC74 containing ΔiprA mutations were compared to the corresponding WT strains in oxidative stress assays. (D) The S. Typhimurium strain UK-1 displays inherently high oxidative stress resistance in this study (as shown in the graph of oxidative stress assay results on the left). UK-1 strains containing plasmid vector, vector plus iprA, or vector plus the dihydrofolate reductase gene (dhfr) were tested for oxidative stress resistance. Data in each panel are shown as the mean plus standard deviation, and observed differences from the WT were found to be significant (as indicated by an asterisk) at a P value of <0.05 using a t test to compare the WT and the indicated mutant sample. For panels B and D, a t test comparison between the vector and the vector plus iprA was used.