Sublethally damaged cells of Escherichia coli by Pulsed Electric Fields: The chance of transformation and proteomic assays

Abstract The present research work comprised: (i) Escherichia coli DH5α inactivation by Pulsed Electric Field (PEF) technology (E = 15–30 kV/cm; t = 0–9000 μs); (ii) a study of sublethally damaged cells generated by PEF; (iii) a quantitative and qualitative proteomic study after PEF treatment (15 kV/cm–700 μs); and (iv) the determination of the occurrence of electrotransformant cells, based on pUC19 plasmid ampicillin resistance. All analyses were carried out with PEF inlet temperatures of 7, 16, 24, 30 and 38 °C. According to the results, a maximum of 16% of the PEF-treated population was sublethally damaged by 15 kV/cm–700 μs PEF treatment (30 °C). In the [7–24] °C temperature range, electroporation was directly affected by temperature and directly related with the sublethally damaged population. In the temperature range [16–24] °C, a transformation frequency in the range [3–23] × 10 − 9  transformants/total CFU was observed after 15 kV/cm–700 μs PEF treatment. PEF treatments combined with 38 °C showed no electrotransformant generation and low levels of sublethal damage, associated with the highest levels of inactivation. Proteomic studies revealed a significant change in the expression of some structural and metabolic proteins (ompA, gmhA, ClpA, RS6, Dut, FtnA, TufB, ftsH, putA, atpA, and sdhA) due to PEF treatment and temperature.