Rauch Cyril, Leigh James
School of Veterinary Medicine and Science, University of Nottingham, College Road, Sutton Bonington, LE12 5RD, UK.
School of Veterinary Medicine and Science, University of Nottingham, College Road, Sutton Bonington, LE12 5RD, UK.
Biochim Biophys Acta. 2015 Apr;1850(4):595-601. doi: 10.1016/j.bbagen.2014.12.004. Epub 2014 Dec 11.
Electroporation 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.
We 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.
It is demonstrated herein that for a bonding energy of about ~1-10 k(B)T between peptidoglycan monomers an intra-wall pressure of about ~5-120 k(B)T/nm(3) generates spherical defects of radius ~0.1-1 nm diverging in size to create pores.
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.
电穿孔是一种用于转化活细胞的首选方法。电穿孔使小分子或大分子化学物质穿过真核细胞或革兰氏阴性菌的脂质双分子层膜的能力，依赖于跨膜形成的瞬时孔。这些孔的存在依赖于一种绝缘体（双分子层膜）以及由外部电场介导的膜两侧的电位差。然而，在革兰氏阳性菌中，细胞壁不是绝缘体，但施加电场时仍可形成孔。过去的研究表明，磷壁酸（一种主要的细胞壁成分）的静电荷，在施加外部电场时会使细胞壁对孔的形成敏感化。这些结果表明，磷壁酸介导了革兰氏阳性菌细胞壁中缺陷的形成。
我们对施加电场时嵌入由肽聚糖组成的细菌细胞壁中的磷壁酸之间的静电排斥进行建模。磷壁酸之间的排斥产生一种应力压力，当达到阈值时能够使细胞壁破裂。这种小缺陷的尺寸会发散，导致孔的形成。
本文证明，对于肽聚糖单体之间约1 - 10 k(B)T 的结合能，约5 - 120 k(B)T/nm(3) 的壁内压力会产生半径约为0.1 - 1 nm 的球形缺陷，其尺寸发散以形成孔。
细菌细胞壁静电空化理论有可能突出磷壁酸在孔形成中的作用，为理解革兰氏阳性菌中的电穿孔提供新的进展，而无需使用绝缘体。
