Fig. 5. Delayed lysosome maturation in lvsB mutant cells. Cells were allowed to internalize 1-µm-diameter latex beads for 15 minutes, washed to remove non-internalized beads and incubated further for 15, 45 and 75 minutes (for a total incubation time of 30, 60 or 90 minutes), fixed and processed for immunofluorescence to detect p80 and H⁺-ATPase. (A) Typical images of internalized beads present in lysosomes (H⁺-ATPase-positive, p80-positive vacuoles; top picture; arrowhead) and in post lysosomes (H⁺-ATPase-negative, p80-positive vacuoles; bottom picture; arrow). Bar, 5 µm. (B) The percentage of internalized beads found in post lysosomes was determined. The curves show the means ± s.e.m. of three experiments. Forty cells containing internalized beads were analyzed for each cell type and at each time point in each experiment