Abstract: In this paper, Saccharomyces cerevisiae was used as a model fungus to study the changes in cell growth, morphology and intracellular reactive oxygen species (ROS) under the combined effects of different concentrations of ε-poly-L-lysine (ε-PL) and the exogenous antioxidant N-acetylcysteine (NAC). Meanwhile, the antifungal activity of ε-PL on S. cerevisiae was explored. The results showed that the surface of cells treated with ε-PL at sublethal concentration was unsmooth with pits and the cells exhibited an increased intracellular content of ROS. Fluorescence microscopy observation revealed phosphatidylserine externalization, chromatin pyknosis, mitochondrial transmembrane potential dissipation and DNA damage, which together indicate that the cells entered the early stage of apoptosis. Cells treated with ε-PL at lethal concentration had a rough surface with pits and dumps and showed decreased content of intracellular ROS. Moreover, the cells displayed obvious fluorescence characteristics and entered the late stage of apoptosis and even died. After adding NAC, the content of intracellular ROS was decreased and the fluorescence characteristics were attenuated. Therefore, it is suggested that ε-PL can induce an increase in intracellular ROS, consequently leading to cell apoptosis and inhibiting cell activity. In addition, NAC could reduce the antimicrobial activity of ε-PL.

Key words: ε-poly-L-lysine, Saccharomyces cerevisiae, reactive oxygen species, N-acetylcysteine, cell apoptosis