Effect of n-Alkanols on Acidification Curves of Aureobasidium pullulans Suspensions

Moragues, M. D., Estevez, J. J., Rementerı́a, A., and Sevilla, M. J. 1994. Effect of n-alkanols on acidification curves of Aureobasidium pullulans suspensions. Experimental Mycology 18, 1-6. n -Alkanols, from methanol to 1-hexanol, induce yeast-to-hyphae transition in the dimorphic fungus Aureobasidium pullulans. In order to elucidate whether triggering of the morphogenetic event is membrane related, we have studied the effect of the morphogenetic n-alkanols on the pH of suspensions of A. pullulans, with no external carbon source. n -Alkanols, at their hyphal inducing concentration or higher, caused a decrease in the initial acidification rate (C) of yeast-phase cell suspensions of A. pullulans. From this effect on C, an inhibition coefficient (K) was deduced, specific for each alcohol. These coefficients were directly related to the lipid/buffer partition coefficients of the alkanols. On the other hand, germ tubes of A. pullulans, obtained in the presence of n-propanol, showed a much slower acidification rate in water than yeast cells. Moreover, 1-propanol or 1-butanol did not significantly affect the initial acidification rate of germ tubes. The latter observation was interpreted as an adaptation of cells grown in the presence of alcohol. The results of all these experiments support our hypothesis that the plasma membrane is a target of the morphogenetic effects of n-alkanols.