Eradication of Bacteria Via Electropulsation

The behavior of bacteria can be strongly affected when pulsed electric fields are delivered on a microbial culture (electropulsation). Fields can be applied either continuously or during a short duration (electric pulse). Electropulsation is one of the most successful methods to introduce foreign molecules in living cells in vitro to assist the extraction of high-value compounds from microorganisms or to affect their viability. This last aspect was first described in the late 1960s. Strong (about 20 kV/cm) but short (a few microseconds) pulses were delivered on a suspension of vegetative bacteria. The treatment was observed to be lethal. Death of the organisms was not due to the products of electrolysis; the temperature rise of the suspension was too small and short-lived to cause lethality. Membrane damage was demonstrated by the lysis of protoplasts, the leakage of intracellular contents, and the loss of the ability of Escherichia coli to undergo plasmolysis in a hypertonic medium. Lethality levels increase with the pulse length, the number of pulses, and the field strength in the suspension. It was proposed that, on cells, the field modulated the transmembrane potential. The induced potential would trigger conformational changes in the membrane structure, resulting in the observed loss of its permeability barrier properties. The molecular processes are more complicated in bacteria as a cell wall alteration is detected.