FIG. 4.

Lysis of Dictyostelium cells exposed to Pseudomonas supernatants. Dictyostelium cells were exposed to culture supernatants of wild-type (wt) strain PT5 (A, upper panels) and the double mutant PT531 (A, lower panels) and observed with a phase-contrast microscope. Arrows indicate individual Dictyostelium cells being lysed by wild-type supernatant during the indicated time frame. The kinetics of cell lysis induced by supernatants of the wild type (PT5), the lasR-rhlR double mutant (PT531) and the rhlA mutant (PT712) was determined by counting Dictoystelium cells under the microscope in a field containing approximately 100 cells at time zero (B).