Plasma membrane H+ and K+ transporters are involved in the weak-acid preservative response of disparate food spoilage yeasts

Abstract

The food spoilage yeastsZygosaccharomyces bailiiandSaccharomyces cerevisiaehave been proposed to resist weak-acid preservative stress by different means;Z. bailiiby limiting influx of preservative combined with its catabolism,S. cerevisiaeby active extrusion of the preservative weak-acid anion and H+. Measurement of H+extrusion by exponential-phaseZ. bailiicells suggest that, in common withS. cerevisiae, this yeast uses a plasma membrane H+-ATPase to expel H+when challenged by weak-acid preservative (benzoic acid). Simultaneous measurement ofZ. bailiinet H+and K+fluxes showed that net K+influx accompanies net H+efflux during acute benzoic acid stress. Such ionic coupling is known forS. cerevisiaein short-term preservative stress. Both yeasts significantly accumulated K+on long-term exposure to benzoic acid. Analysis ofS. cerevisiaeK+transporter mutants revealed that loss of the high affinity K+uptake systemTrk1confers sensitivity to growth in preservative. The results suggest that cation accumulation is an important factor in adaptation to weak-acid preservatives by spoilage yeasts and thatZ. bailiiandS. cerevisiaeshare hitherto unsuspected adaptive responses at the level of plasma membrane ion transport.