Extrusion of benzoic acid in Saccharomyces cerevisiae by an energy-dependent mechanism

When grown in the presence of benzoic acid, Saccharomyces cerevisiae was able to extrude [14C]benzoic acid when a pulse of glucose was given to preloaded cells. While octanoic, sorbic, hexanoic, salicylic, butyric and propionic acids were also inducers, ethanol and acetic acid were not. The mechanism of extrusion required energy and prior growth in the presence of the inducers. Diethylstilbestrol, an inhibitor of ATPases, prevented benzoic acid extrusion. Propionic acid was not actively extruded in cells adapted to either benzoic or propionic acid, behaving as an appropriate probe to measure intracellular pH. Even though the extrusion mechanism was active, benzoic acid entered the cells by a simple diffusion mechanism.