Figure 4.
Phagocytosis in shk1 mutant cell lines. (A) Cells grown axenically in log phase were adjusted to a concentration of 1 × 106 cells/mL in a suspension of GFP-tagged E. coli. Samples were taken at the time points shown, and Dictyostelium cells were isolated by differential centrifugation. The cells were fixed, and bacterial uptake was quantified fluorometrically. The label Comp. shk1 null refers to shk1 null cells complemented with FLAG–SHK1. (B) The cells were adjusted to a concentration of 1 × 106 cells/mL in an E. coli suspension. The ability of the cells to grow on bacteria was quantified by measuring uptake and degradation of bacteria from the growth medium. (C) 1 × 105 axenically grown cells were placed on a glass slide in a suspension of Na/K phosphate buffer, and 2-μm FluoSphere beads were added to the suspension (to a final concentration of 2 × 103% solids). Bead internalization was monitored by DIC and fluorescence microscopy and digitally recorded.