Cell wall as a target for bacteria inactivation by pulsed electric fields

Abstract

The integrity and morphology of bacteria is sustained by the cell wall, the target of the main microbial inactivation processes. One promising approach to inactivation is based on the use of pulsed electric fields (PEF). The current dogma is that irreversible cell membrane electro-permeabilisation causes the death of the bacteria. However, the actual effect on the cell-wall architecture has been poorly explored. Here we combine atomic force microscopy and electron microscopy to study the cell-wall organization of living Bacillus pumilus bacteria at the nanoscale. For vegetative bacteria, exposure to PEF led to structural disorganization correlated with morphological and mechanical alterations of the cell wall. For spores, PEF exposure led to the partial destruction of coat protein nanostructures, associated with internal alterations of cortex and core. Our findings reveal for the first time that the cell wall and coat architecture are directly involved in the electro-eradication of bacteria.

Biological Effect and Inactivation Mechanism of Bacillus subtilis Exposed to Pulsed Magnetic Field: Morphology, Membrane Permeability and Intracellular Contents

“…Bansal et al [34] found that the PMF treatment of Zygosaccharomyces bailii resulted in irreversible electroporation of cell membrane and leakage of cellular debris. Pillet et al [35] reported that exposure of Bacillus pumilus to PEF led to structural disorganization correlated with morphological and mechanical alterations of the cell wall. The disruption of cell wall and membrane may lead to loss of the cytosol and DNA from the PMF treated cells, which emphasizes the importance of further investigation.…”

Atomic Force Microscopy to Explore Electroporation Effects on Cells

“…Atomic Force Microscopy (AFM) is an imaging technology developed in the 80 th by physicists [5][6][7] . It has been more and more applied on biological samples (virus, bacteria, mammalian cells, DNA, proteins…) since the 90 th8 and recently to explore the effects of EP on cells morphology and nanomechanical properties [9][10][11][12][13] .…”

Moderate and high intensity pulsed electric fields : Effect on microbial inactivation, shelf life and quality of fruit juices

“…The capacity of PEF to induce cell electroporation to inactivate micro-organisms was demonstrated first by Sale and Hamilton (Hamilton & Sale, 1967;. Later, the membrane electroporation was investigated and reported to effect the lipid domain (Teissié, Golzio & Rols, 2005;Weaver & Chizmadzhev, 1996), protein channels, transport systems or transport pumps (Tsong, 1990) or cell wall (Pillet et al, 2016).…”

“…The capacity of high intensity PEF to induce cell electroporation to inactivate micro-organisms was demonstrated first by . Later, studies on the membrane electroporation effect of high intensity PEF reported to occur at the lipid domain (Teissié, Golzio & Rols, 2005;Weaver & Chizmadzhev, 1996), in the protein channel (Tsong, 1990) or cell wall (Pillet et al, 2016). Moderate intensity PEF conditions, defined in this study as conditions with an electric field strength E < 5 kV/cm, have been extensively studied as a pre-step in mass transfer phenomena in food and biotechnological processes, aiming to mildly disintegrate plant cells (Donsì, Ferrari & Pataro, 2010).…”

“…Recent work of Pillet et al (2016) showed changes in coat, cortex and core structure after PEF treatment when using electric field strength of 2.0 -7.5 kV/cm. Apart from the structural characteristics, intrinsic microbial resistance showed to play an important role in PEF resistance, as illustrated by the large diversity in PEF resistance between different strains within the same species (Cebrián et al, 2009;Gurtler et al, 2010;Lado & Yousef, 2003).…”