Figure 5

Colocalization of P. aeruginosa with a probe that labels acidic compartments. J774 macrophages were infected with PAO1 and ∆oprF strains expressing GFP. After 2.5 h of gentamicin treatment, infected J774 cells were incubated with Lysotracker for 10 min, a red fluorescent weak base that accumulates in acidic compartments. Cells were then fixed and imaged with fluorescence microscope. (A) The image shows individual panels for Differential Interference Contrast (DIC), lysosomal compartment (red), bacteria expressing GFP (green), the nucleus (blue) and merged image of all channels. White arrows show colocalization of bacteria with lysotracker while yellow arrows show non-colocalization. Scale bar is equivalent to 5 µm. (B) Values indicate the percentage of bacteria that colocalized with Lysotracker red (white arrows). Data are the mean (± SEM) of 3 independent experiments, with a minimum of 100 bacteria counted per experiment for each sample. *, p ≤ 0.05 (Two-tailed unpaired t test).