Theoretical evaluation of wall teichoic acids in the cavitation-mediated pores formation in Gram-positive bacteria subjected to an electric field

Cyril Rauch,James Leigh

doi:10.1016/j.bbagen.2014.12.004

Cyril Rauch, James Leigh

Open Access

https://doi.org/10.1016/j.bbagen.2014.12.004

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Abstract

BackgroundElectroporation is a method of choice to transform living cells. The ability of electroporation to transfer small or large chemicals across the lipid bilayer membrane of eukaryotic cells or Gram-negative bacteria relies on the formation of transient pores across the membrane. To exist, these pores rely on an insulator (the bilayer membrane) and the presence of a potential difference on either side of the membrane mediated by an external electric field. In Gram-positive bacteria, however, the wall is not an insulator but pores can still form when an electric field is applied. Past works have shown that the electrostatic charge of teichoic acids, a major wall component; sensitizes the wall to pore formation when an external electric field is applied. These results suggest that teichoic acids mediate the formation of defects in the wall of Gram-positive bacteria. MethodsWe model the electrostatic repulsion between teichoic acids embedded in the bacterial wall composed of peptidoglycan when an electric field is applied. The repulsion between teichoic acids gives rise to a stress pressure that is able to rupture the wall when a threshold value has been reached. The size of such small defects can diverge leading to the formation of pores. ResultsIt is demonstrated herein that for a bonding energy of about ~1−10kBT between peptidoglycan monomers an intra-wall pressure of about ~5−120kBT/nm3 generates spherical defects of radius ~0.1−1nm diverging in size to create pores. ConclusionThe electrostatic cavitation of the bacterial wall theory has the potential to highlight the role of teichoic acids in the formation pores, providing a new step in the understanding of electroporation in Gram-positive bacteria without requiring the use of an insulator.

Highlights

As a tool, the electroporation technique has been used over the last two decades to deliver gene to cells [1] or in animal or plant tissues [2,3,4,5], to promote drug uptake by cells [6] and to implement food safety measures via electroporation-related sterilization mechanisms that are independent of temperature [7].The ability of electroporation to transfer small chemicals or large protein complexes across the bilayer membrane of cells rely on the formation of transient pores [8]
How an electric field can create transient pores is still incomplete in the case of Gram-positive bacteria and electroporation protocols are usually developed through lengthy trial and error procedures
Given the heterogeneity of living organisms, there is no guaranty that understanding the physical impact of electroporation in human cells can be transferred to Gram-positive bacteria, for example

Summary

Background

The ability of electroporation to transfer small or large chemicals across the lipid bilayer membrane of eukaryotic cells or Gram-negative bacteria relies on the formation of transient pores across the membrane To exist, these pores rely on an insulator (the bilayer membrane) and the presence of a potential difference on either side of the membrane mediated by an external electric field. Past works have shown that the electrostatic charge of teichoic acids, a major wall component; sensitizes the wall to pore formation when an external electric field is applied These results suggest that teichoic acids mediate the formation of defects in the wall of Gram-positive bacteria. The repulsion between teichoic acids gives rise to a stress pressure that is able to rupture the wall when a threshold value has been reached The size of such small defects can diverge leading to the formation of pores. Conclusion: The electrostatic cavitation of the bacterial wall theory has the potential to highlight the role of teichoic acids in the formation pores, providing a new step in the understanding of electroporation in Gram-positive bacteria without requiring the use of an insulator

Introduction

Repulsive electrostatic energy in the bacterial wall

The nucleation of several stable small defects is not an option

Electroporation of the bacterial wall

Findings

Discussion