The Effects of the Chelating Agent Ethylenediamine Tetra-acetic Acid on Cell Adhesion in the Slime Mould Dictyostelium discoideum

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Abstract
Vegetative myxamoebae and pseudoplasmodia of the slime mould Dictyostelium discoideum were treated with the chelating agent ethylenediamine tetra-acetic acid. The myxamoebae first respond by rounding up, and then by throwing out active, continuously moving, hyaline lobopodia. At high concentrations of EDTA the cells are unable to migrate, although cellular ‘writhing’ continues for hours. At lower concentrations writhing also occurs, but the cells are able to move together into loose heaps. A migratory pseudoplasmodium immersed in 5 mM EDTA begins disaggregating rapidly. Its smooth surface breaks down and individual cells exhibit membrane activity similar to that described above. The cells lose their attachments to one another, and are maintained in a loose pile only by a tenuous matrix in which they appear to be embedded. Mild agitation now easily separates them into single cells and small clumps of cells. The effects noted on both myxamoebae and pseudoplasmodia are reversible by replacing the EDTA with Bonner’s solution. Moreover, preparations treated with EDTA in the presence of equimolar concentrations of calcium chloride are unaffected. How the removal of cations from cells might result in their dissociation from one another is discussed. It is suggested that EDTA may have its effects by (a) dissolving extra-cellular ground substance or sheath material, and (b) producing a state of instability in the cell membrane allowing continuous pseudopodia! activity and distortion of relations between apposed cell surfaces.