[Differences in the pattern of macromolecules between vegetative and aggregation Competent Cells in Dictyostelium...

1. As a preliminary study on the molecular basis of cell aggregation, the soluble macromolecular fractions of growing (vegetative) and aggregation competent cells ofD. discoideum were compared. a) Zone electrophoresis in agar-gel revealed gross differences in proteins, PAS-positive substances (polysaccharides), and sudan black stainable (lipid containing) constituents. b) Byimmunoelectrophoresis 26 antigens were distinguished with antisera against vegetative and aggregation competent cells. With this technique, 8 of these antigens were found only in cells harvested in the growth phase. 9 antigens were found only in aggregation competent cells and another 9 were found in both stages. c) With tests which can provide more information (Osserman technique and stimulation of antibody synthesis), not one of the detected antigens proved to be limited completely to vegetative cells. Only 4 antigens proved to be specific for aggregation competent cells. 2. Additionally, two UV induced mutants with disturbed cell contact formation were analyzed by immunoelectrophoresis. Both these mutants were defective with regard to certain of the antigens which have been found to be specific for aggregation competent cells in the wild type. It is most likely that the presence of these antigens is directly related to the morphogenetic functions of these cells.