Oxidative Stress Induced in<i>Saccharomyces Cerevisiae</i>Exposed to Dielectric Barrier Discharge Plasma in Air at Atmospheric Pressure

Abstract

Nonthermal plasmas are considered to be effective methods for sterilization. However, the changes that occur within the cells of microorganism during sterilization are rarely reported. This paper investigated the effects of dielectric barrier discharge air plasma at atmospheric pressure on yeast <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Saccharomyces cerevisiae</i> ATCC 4126 suspended in water. <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S. cerevisiae</i> showed extensive cell death after plasma discharge. For plasma-treated cells, intracellular protein concentration decreased, whereas extracellular nucleic acid concentration increased significantly, suggesting that intracellular protein and nucleic acids were released, possibly with leakages in cell walls and cell membrane. Furthermore, reactive species production increased linearly with plasma treatment time in pure water. In addition, treated cells showed cell cycle arrest at <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> phase that increased in a time-dependent manner, a consequence that is known to be caused by DNA damage. The concentration of reactive oxygen species in the cells increased significantly, leading to activation of superoxide dismutases and catalase, as shown by increases in enzyme specific activities in the cell extracts. Taken together, these results suggested that, besides cell surface damages directly caused by plasma, oxidative stress occurred when <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S. cerevisiae</i> cells were exposed to plasma under sublethal condition, which could possibly cause cell damage, cell mutation, and cell apoptosis.