Scanning ion conductance microscopy reveals differences in the ionic environments of gram positive and negative bacteria
Scanning ion conductance microscopy reveals differences in the ionic environments of gram positive and negative bacteria
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DOI：
10.1101/2020.08.26.267849
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发表时间：
2020-08
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影响因子：
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通讯作者：
Kelsey Cremin;Bryn A. Jones;J. Teahan;Gabriele Meloni;David Perry;Christian Zerfaß;Munehiro Asally-Munehiro-Asall
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文献类型：
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作者：
Kelsey Cremin;Bryn A. Jones;J. Teahan;Gabriele Meloni;David Perry;Christian Zerfaß;Munehiro Asally-Munehiro-Asall
本文报道了使用扫描离子电导显微镜（SICM）本地映射的离子特性和电荷环境的两个活的细菌菌株：革兰氏阴性大肠杆菌和革兰氏阳性枯草芽孢杆菌。SICM结果发现细菌表面的异质性，以及革兰氏阳性菌和革兰氏阴性菌之间的显著差异。B的生物电环境。枯草芽孢杆菌被发现是相当多的负电荷相比，E。杆菌SICM测量，拟合到一个简化的有限元方法（FEM）模型，显示表面电荷值为−80至−140 mC m−2的革兰氏阴性E。杆菌革兰氏阳性B。枯草芽孢杆菌在细胞壁周围表现出更高的电导率，并且使用相同的简化模型发现表面电荷值在−350和−450 mC m−2之间。SICM还能够检测到B附近的高负电荷区域。枯草杆菌，未检测到的地形SICM响应，并归因于胞外聚合物。为了进一步探讨B.枯草杆菌细胞壁结构会影响SICM电流响应，因此，开发了一个更全面的有限元模型，考虑了革兰氏阳性细胞壁的物理特性。新模型提供了对细胞壁更真实的描述，并允许研究其关键特性与SICM电流之间的关系，为进一步研究和提高对革兰氏阳性细胞微环境的理解奠定了基础。
This paper reports on the use of scanning ion conductance microscopy (SICM) to locally map the ionic properties and charge environment of two live bacterial strains: the gramnegative Escherichia coli and the gram-positive Bacillus subtilis. SICM results find heterogeneities across the bacterial surface, and significant differences among the grampositive and -negative bacteria. The bioelectrical environment of the B. subtilis was found to be considerably more negatively charged compared to E. coli. SICM measurements, fitted to a simplified finite element method (FEM) model, revealed surface charge values of −80 to −140 mC m−2 for the gram-negative E. coli. The gram-positive B. subtilis show a much higher conductivity around the cell wall, and surface charge values between −350 and −450 mC m−2 were found using the same simplified model. SICM was also able to detect regions of high negative charge near B. subtilis, not detected in the topographical SICM response and attributed to extracellular polymeric substance. To further explore how the B. subtilis cell wall structure can influence the SICM current response, a more comprehensive FEM model, accounting for the physical properties of the gram-positive cell wall, was developed. The new model provides a more realistic description of the cell wall and allowed investigation of the relation between its key properties and SICM currents, building foundations to further investigate and improve understanding of the gram-positive cellular microenvironment.