Fig. 2. Phenotype of midA^- at the vegetative stage. (A) Appropriate dilutions of wild-type and mutant Dictyostelium cells were plated in association with Klebsiella aerogenes in SM plates to determine differences in the size of the clearing zone. The plates were incubated at 22°C for the indicated times. Bar, 1 cm. (B) Growth rate in axenic medium, cell diameter and the amount of protein per cell were compared between the wild type and midA^- cells. Significance of differences is indicated by the P value shown inside the panels. (C) Proportion of cells (%) whose diameter is in the within the indicated sizes (µm). Most of the mutant cells had a diameter of 8-10 µm, whereas the majority of wild-type cells had a diameter of 10-14 µm. At least 200 cells were analyzed for each strain. (D) Axenically growing cells were exposed for 30 minutes to fluorescent beads (phagocytosis) or soluble fluorescent-dextran (macropinocytosis). The fluorimetry values were expressed as arbitrary units. The mean of three independent experiments is shown and the significance of differences indicated by the P value. (E) Representative flow-cytometry assay to determine the amount of fluorescent beads taken up by wild-type and midA^- cells. Both the total number of labeled cells and the proportion of cells with multiple beads were reduced in the mutant. For comparison, the vertical line is given as a reference.