Chemotactic behavior of gefQ⁻ cells. (A) Computer-generated cell tracks of gefQ⁻ and AX2 cells during chemotactic migration in a spatial cAMP gradient using DIAS. Arrowheads indicate turns initiated by formation of lateral pseudopods in gefQ⁻ cells. (B) Shape changes of aggregation-competent gefQ⁻ and AX2 cells during chemotactic migration were analyzed by DIAS. Images were taken every 6 s but only every third frame is shown. The green areas indicate new membrane protrusions, the red areas indicate retractions, and the arrows indicate the direction of migration.