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UBC Theses and Dissertations

The effect of polyunsaturated fatty acids and growth temperature on the differentiation of the cellular slime mold Dicyostelium discoideum Mohan Das, D.V.


Cells of Dictyostelium discoideum grown on media containing polyunsaturated fatty acids (PUFA) exhibit impaired differentiation when placed on a solid surface in the absence of all nutrients. The temper-rature dependence studies on the rates of growth and differentiation were performed to test if this was due to increased plasma membrane fluidity. PUFA had no adverse effect on cell growth at temperatures at or below the optimum growth temperature, 22°C. At 25°C however, there was considerable inhibition and at 27°C growth was completely eliminated in the presence of PUFA. However, differentiation in PUFA cells was inhibited at all temperatures and although the inhibition was somewhat less pronounced at low temperatures there was no decrease in the optimum temperature of differentiation. Furthermore, although the in vitro aggregation of vegetative cells and the reaggregation of dispersed aggregation - phase cells were markedly temperature dependent, PUFA supplementation did not markedly influence this dependence. These data are not consistent with the hypothesis that impaired differentiation is due to increased plasma membrane fluidity. The differentiation of Dictyostelium discoideum, Ax-2, an axenic strain is markedly influenced by the temperature at which the cells are grown. This temperature adaptation was not accomplished by an alteration in the fatty acid composition of the organism. In contrast, the wild type strain Dictyostelium discoideum NC-4, differentiated optimally at 25°C - 27°C, regardless of the temperature of growth.

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