Axenic Growth of Dictyostelium discoideum Wild-type NC-4 Cells and its Relation to Endocytotic Ability

Abstract

A method for the axenic growth of Dictyostelium discoideum wild-type strain NC-4 is described. There were some differences between the nutritional requirements of strain NC-4 and an axenic strain Ax-2 derived from NC-4. Of the numerous components in growth media, the nature and concentration of the peptone was especially critical for axenic growth of NC-4 cells; 3% Bacteriological-peptone (Oxoid) giving the best growth rate and yield. NC-4 cells seemed to require more vitamin B12 than Ax-2 cells. Other vitamins like folic acid, biotin, and riboflavin also stimulated axenic growth of NC-4 cells. Pinocytosis was examined by the use of FITC-dextran and the results showed that the above peptone considerably enhanced the pinocytotic activity of both NC-4 and Ax-2 cells. Bacto-peptone (Difco) also enhanced pinocytosis to a similar extent, though it never supported axenic growth of NC-4 cells. Therefore, stimulation of pinocytosis may be necessary for nutrient uptake, but is not sufficient for axenic growth. The pinocytotic ability of cells decreased conspicuously during the course of development, particularly just before aggregation. The biological significance of this is discussed in relation to cell differentiation.