Quantitative and real time detection of pulsed electric field induced damage on Escherichia coli cells and sublethally injured microbial cells using flow cytometry in combination with fluorescent techniques

The methods employed in most previous studies to investigate the non-thermal action of pulsed electric field (PEF) on microbial cells are only capable of revealing the obvious morphological changes of microbial cells induced by PEF, or only differentiate between culturable and not culturable cells. They are totally incapable of real time detection of sublethally injured cells under stress of PEF. In this study, flow cytometry (FCM) in combination with fluorescent techniques was used for quantitative and real time detection of PEF induced damage on Escherichia coli cells and sublethally injured microbial cells. The present work confirmed the thesis that electropermeabilisation was not an all-or-nothing-event. FCM sorting of double stained cells put forward direct evidence for the occurrence of sublethally injured microbial cells under stress of PEF. This work provided quantitative and real time analysis of sublethally injured microbial cells in PEF treatment, and further revealed the underlying mechanism on synergistic effect of moderate heat and PEF on microbial inactivation.