CHANGES IN CHARGED GROUPS ON THE CELL SURFACE DURING DEVELOPMENT OF THE CELLULAR SLIME MOLD DICTYOSTELIUM DISCOIDEUM: AN ELECTRON MICROSCOPIC STUDY.

Abstract

The distribution of charged groups on the surface of Dictyostelium cells and their change during development were examined by electronmicroscopy using cationic and anionic ferritins. The number of anionic sites on the cell surface decreased greatly during the course of development. The whole surface of vegetative cells stained strongly with cationic ferritin (CF). On the other hand, the surface of aggregation-competent cells had fewer negative charges and these were unequally distributed, the surface of the advancing area (lobopodial region) being devoid of anionic sites. The number of anionic sites on the cell surface decreased progressively during further development, and the suface of slug cells did not stain at all with CF. The cell surface did not stain with anionic ferritin at any developmental stage, indicating the absence of detectable cationic sites. The biological significance of these findings is discussed in connection with cell adhesiveness and movement.