Figure 4. Oxidative and nitrostative challenge assays.

A) Oxidative stress response of kpnO mutant. The ability of WT, ΔkpnO to combat different levels of hydrogen peroxide stress (3%, 10% and 30%) was measured by disc diffusion assay. The kpnO mutant displayed greater sensitivity to 30% H₂O₂ (inhibition zone  = 55±2.0 mm) than the wild-type (inhibition zone  = 34±0.0 mm). The data is the means of measurements made in triplicate and performed three times. *, Significant difference (P<0.05, Student t test). B) Effect of SNP at 10 mM, 20 mM and 30 mM concentration on growth of WT and ΔkpnO. Growth kinetics of ΔkpnO cells were ∼7 fold lower than the WT in the presence of 10 mM SNP, ΔkpnO exhibited ∼100 fold stunted growth at 20 mM and 30 mM SNP. C) Growth pattern of WT, ΔkpnO in the presence of sodium nitrite. In the presence of 10 mM NO donor, growth kinetics of ΔkpnO cells was ∼4.0 fold and ∼64.0 fold lower as compared to WT at pH 7.0 and pH 6.0 respectively.