Rapid multitarget metabolic inhibition precedes silver ion-induced irreversible cytotoxicity in Saccharomyces cerevisiae

Although silver is widely used as an antimicrobial agent, its primary mechanism of antimicrobial action remains unclear. Therefore, this study aimed to investigate the rapid multitarget metabolic inhibition induced by silver ions in Saccharomyces cerevisiae . Silver nitrate was added to yeast suspensions, and changes in glycolysis- and dehydrogenase-dependent reduced nicotinamide adenine dinucleotide phosphate [NAD(P)H] fluorescence intensity, as well as inhibition of glucose-induced proton release, were measured. Yeast viability was subsequently evaluated by liquid culture. The addition of 100 μM silver nitrate to yeast suspensions caused an irreversible decrease in NAD(P)H fluorescence and completely inhibited proton release and subsequent growth. In contrast, silver nitrate at concentrations of 10 μM or lower did not cause an irreversible decrease in NAD(P)H fluorescence and did not completely inhibit growth. Silver ions rapidly inhibit energy metabolism involving NAD(P)H production and proton pumping, thereby disrupting intracellular redox potential, membrane potential, and pH homeostasis, ultimately leading to irreversible cytotoxicity.