Figure 6. Colocalization of phagocytosed GFP-expressing KS20 borrelia with LysoTracker Red-stained phagolysosomes in IDE12 and DAE15 cells. IDE12 and DAE15 cells were incubated overnight with GFP-expressing KS20 borreliae, stained with LysoTracker Red, fixed with paraformaldehyde, and counterstained with DAPI to stain the DNA of spirochetes and cell nuclei. Phagocytosed borreliae are indicated by arrows. Note the loss of GFP fluorescence by phagocytosed the spirochetes (arrows) whereas GFP fluorescence is retained by extracellular spirochetes (arrowhead). Scale bar, 10 μm.