Figure 3.

Rap1 regulates the rate of phagocytosis of FITC-E. coli. Top, Bar graph showing bacterial uptake and the average fluorescence per microgram of protein for each of the strains at the 30-min time point ± SD. Phagocytosis assays were performed as in Figure 2, except FITC-labeled E. coli was used instead of fluorescent latex beads. Bottom, Cells were incubated with FITC-labeled E. coli for 10 min, washed, and placed on a coverslip. After adding ethidium bromide (5 μg/ml) to the medium, the coverslips were mounted and viewed using either the green (F-Channel) or red (R-Channel) of a fluorescence microscope. Under these experimental conditions for all the strains examined, FITC-E. coli was readily internalized by the cells (see F-channel), but <5% of the bacteria stuck to the outside of the cell (see R-channel).