FIG 1

The pH of the phagolysosome does not affect the cytosolic translocation of M. marinum. (A) Electron micrograph of a THP-1 cell infected with M. marinum for 24 h in the presence of ConB showing M. marinum in the cytosol without membrane and CD63 labeling. CD63 immunolabeling indicated by 10-nm gold particles is present on the multivesicular lysosome in the top left corner. (A′) Schematic representation of the micrograph in panel A, with blue lines representing host membranes, black dots representing CD63 labeling indicated by 10-nm gold particles, and orange representing bacteria. (B) Quantification of the percentage of M. marinum bacteria in the cytosol 24 and 48 h after infection using immunogold labeling for CD63 (see also Fig. S2A in the supplemental material). Cells were treated with ConB to raise the lysosomal pH, which did not affect the percentage of cytosolic M. marinum bacteria. Error bars represent the standard deviations from 3 experiments.