FIGURE 9.

Accumulation of ethidium bromide in WT and efflux mutants of Escherichia coli, Klebsiella pneumonia, and P. aeruginosa, and in Staphylococcus aureus with CCCP. (A) E. coli MG1655 (dark red circles) had an average fluorescence of 8310 RFU and was significantly lower (fourfold) than its ΔacrB (red circles) equivalent at 33233 RFU. Klebsiella pneumoniae ecl8 (dark blue squares) had an average RFU of 3225, 14-fold lower than its acrB::Gm inactivated strain with a RFU of 46764. P. aeruginosa strain PA14 (gray diamonds) had ethidium bromide fluorescence of 8401 RFU which was significantly lower than the fluorescence for its ΔmexA strain at RFU (threefold difference). (B) S. aureus ethidium bromide accumulation was measured in the absence (pink) and presence (brown) of CCCP. In the presence of CCCP, accumulation was threefold higher (P < 0.0001). 4 biological replicates for each strain are shown, with a long bar to show the mean and standard error of the mean (SEM) error bars. Statistical tests were unpaired T-tests between individual WT and efflux deficient strain. Results were considered significantly different if p-value ≤ 0.05. ^∗∗ and ^**** correspond to P-values shown in Supplementary Table S3.