Bioelectrical antimicrobial susceptivity testing (BeAST) with the budding yeastS. cerevisiae

Abstract

AbstractDue to the fundamental and universal characteristic of vital cells, the membrane potential is a useful marker for antimicrobial susceptivity testing (AST). However, the difficulties associated with measuring the membrane potential in microbes restricts its broad application. In this study, we present bioelectrical AST (BeAST) using the model eukaryotic microbeSaccharomyces cerevisiae. Using fluorescent indicators (DiBAC4(3), ThT and TMRM) we measure plasma and mitochondrial membrane-potential dynamics upon electric stimulation. We find that a 2.5-second electric stimulation induces hyperpolarisation lasting 20 minutes in vitalS. cerevisiae, but depolarisation in inhibited cells. The numerical simulation of FitzHugh-Nagumo model successfully recapitulates vitality-dependent dynamics. The model also suggests that the magnitude of hyperpolar-isation response could correlate with the degree of inhibition. To test this prediction and to examine if BeAST can be used for assessing novel anti-fungal compounds, we treat cells with biogenic silver nanoparticles (bioAgNPs) synthesised using orange fruit flavonoids and Fusarium oxysporum. Measurements of electrically triggered membrane-potential dynamics and liquid culture growth reveal a correlation between hyperpolarisation and growth rate, which is consistent with the model. These results suggest that BeAST holds promise for screening anti-fungal compounds, offering a valuable approach to tackling antimicrobial resistance.