Microbiological implications of electric field effects. II. Inactivation of yeast cells and repair of their cell envelope.

The inactivation of yeast cells in different growth phases by an electric field pulse was investigated. Cells of Saccharomyces cerevisiae in the logarithmic growth phase were found to be much more sensitive with respect to an electric discharge than those in the stationary phase. The influence of the electric field pulse characteristics on the inactivation as well as possible secondary effects were studied. The polyene antibiotic perhydrohexafungin (PHF) is used as a tool to sense defects in the yeast cell envelope brought about by electric field action. The repair kinetics of these defects was followed after the impulse. At least two repair stages can be distinguished, a fast one in the second range and a slower one which takes place after plating the cells on a nutrient medium. The obtained results are discussed in connection with current theories of reversible dielectric breakdown in biological membrane systems.