Figure 5.

nlpD deletion attenuates bacterial survival within IFN-γ-activated macrophages

Transmitted images with overlays of bacteria in green (left), fluorescent bacteria (center), and pseudocolor images of the 410:470 excitation ratio (right) of nonactivated (A) and IFN-γ–activated (B) macrophages 24 h after infection with WT, the ΔnlpD mutant, and the complemented mutant are shown. Scale bar, 10 μm. (C) Sensitivities of C. sakazakii strains to pH 4.5. (D) Sensitivities of C. sakazakii strains to 200 mM hydrogen peroxide (H₂O₂). (E) Sensitivities of C. sakazakii strains to a combination of 200 mM hydrogen peroxide (H₂O₂) and pH 4.5. To initiate experiments, C. sakazakii strains were cultured in Luria-Bertani (LB) overnight at 37°C. In all cases, the estimated initial bacterial densities were 0.1 optical density at 600 nm. Optical densities or CFU counts of C. sakazakii were determined immediately before (time zero) and at the indicated time points. All data represent the mean and standard deviation of three biological repeats.