FIG. 4.
GFP expression from a PsifB::gfp transcriptional fusion, analyzed by flow cytometry of Salmonella strains grown overnight at 37°C in MgM. (A) Histogram plot of fluorescence intensity due to GFP (relative units) versus number of particles for 105 bacterium-sized particles of each strain analyzed. The peaks (from right to left) are plots of the following strains carrying PsifB::gfp: wild type (black); ΔslyA mutant (black, dashed); ompR mutant (red); ompR ΔslyA double mutant (red, dashed); ssrA mutant (blue); ssrA ΔslyA double mutant (blue, dashed). The leftmost peak (grey) is the nonfluorescent negative control (wild type carrying pFPV25, a promoterless gfp construct). The results are the results of a single representative experiment. (B) Geometric mean GFP fluorescence of the strains shown in panel A, using the same color coding. The error bars indicate the standard errors of the means (n = 6). WT, wild type.