Glycogen and trehalose mobilization by acetic acid in Phycomyces blakesleeanus: dependence on the anion form

Trehalose and glycogen are reserve carbohydrates that were shown to accumulate in mycelia of the filamentous fungus Phycomyces blakesleeanus. Both carbohydrates were mobilized under glucose starvation or in the presence of acetate. Glycogen was mobilized faster than trehalose in the presence of acetate. In all cases, glycogen and trehalose mobilization followed single exponential decay. There was a direct relationship between glycogen mobilization and the concentration of the dissociated form of external acetic acid. The half-life of glycogen mobilization increased as the concentration of the external acetate anion decreased, so the dissociated form of acetate was the stressor causing glycogen mobilization. Mobilization was not due to transfer to poor carbon sources, as the dissociated form of other weak acids (butyrate, lactate, pyruvate and propionate) also produced glycogen mobilization. Previous exposure of the mycelia to a lower acetate concentration decreased glycogen mobilization by subsequent exposure to a high acetate concentration. Glycogen mobilization by acetate may be involved in production of ATP necessary for acetate uptake as well as for maintenance of the internal pH homeostasis.