Weak organic
acids are an important class of
food preservatives that are particularly efficacious towards yeast and fungal spoilage. While
acids with small aliphatic chains appear to function by acidification of the cytosol and are required at high concentrations to inhibit growth, more hydrophobic organic
acids such as sorbic and
benzoic acid have been suggested to function by perturbing membrane dynamics and are growth-inhibitory at much lower concentrations. We previously demonstrated that
benzoic acid has selective effects on membrane trafficking in Saccharomyces cerevisiae.
Benzoic acid selectively blocks macroautophagy in S. cerevisiae while
acetic acid does not, and
sorbic acid does so to a lesser extent. Indeed, while both
benzoic acid and
nitrogen starvation are
cytostatic when assayed separately, the combination of these treatments is cytocidal, because macroautophagy is essential for survival during
nitrogen starvation. In this report, we demonstrate that Zygosaccharomyces bailii, a food spoilage yeast with relatively high resistance to weak
acid stress, also exhibits a cytocidal response to the combination of
benzoic acid and
nitrogen starvation. In addition, we show that
nitrogen starvation can be replaced by
caffeine supplementation.
Caffeine induces a
starvation response that includes the induction of macroautophagy, and the combination of
caffeine and
benzoic acid is cytocidal, as predicted from the
nitrogen starvation data.