The link between yeast cell wall porosity and plasma membrane permeability after PEF treatment

An investigation of the yeast cell resealing process was performed by studying the absorption of the tetraphenylphosphonium (TPP(+)) ion by the yeast Saccharomyces cerevisiae. It was shown that the main barrier for the uptake of such TPP(+) ions is the cell wall. An increased rate of TPP(+) absorption after treatment of such cells with a pulsed electric field (PEF) was observed only in intact cells, but not in spheroplasts. The investigation of the uptake of TPP(+) in PEF treated cells exposed to TPP(+) for different time intervals also showed the dependence of the absorption rate on the PEF strength. The modelling of the TPP(+) uptake recovery has also shown that the characteristic decay time of the non-equilibrium (PEF induced) pores was approximately a few tens of seconds and this did not depend on the PEF strength. A further investigation of such cell membrane recovery process using a florescent SYTOX Green nucleic acid stain dye also showed that such membrane resealing takes place over a time that is like that occurring in the cell wall. It was thus concluded that the similar characteristic lifetimes of the non-equilibrium pores in the cell wall and membrane after exposure to PEF indicate a strong coupling between these parts of the cell.