Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada.
PLoS One. 2009 Sep 30;4(9):e7285. doi: 10.1371/journal.pone.0007285.
In Escherichia coli, MinD-GFP fusion proteins show rapid pole to pole oscillations. The objective was to investigate the effects of extracellular cations on the subcellular oscillation of cytoplasmic MinD within Escherichia coli.
METHODOLOGY/PRINCIPAL FINDINGS: We exposed bacteria to the extracellular cations Ca(++), Mg(++), the cationic antimicrobial peptide (CAP) protamine, and the cationic aminoglycoside gentamicin. We found rapid and substantial increases in the average MinD oscillation periods in the presence of any of these polyvalent cations. For Ca(++) and Mg(++) the increases in period were transient, even with a constant extracellular concentration, while increases in period for protamine or gentamicin were apparently irreversible. We also found striking interdependence in the action of the small cations with protamine or gentamicin, distorted oscillations under the action of intermediate levels of gentamicin and Ca(++), and reversible freezing of the Min oscillation at high cationic concentrations.
CONCLUSIONS/SIGNIFICANCE: Intracellular Min oscillations provide a fast single-cell reporter of bacterial response to extracellular polycations, which can be explained by the penetration of polycations into cells.
在大肠杆菌中，MinD-GFP 融合蛋白表现出快速的极向振荡。本研究旨在探讨细胞外阳离子对大肠杆菌细胞质内 MinD 亚细胞振荡的影响。
方法/主要发现：我们使细菌暴露于细胞外阳离子 Ca(++)、Mg(++)、阳离子抗菌肽（CAP）鱼精蛋白和阳离子氨基糖苷类抗生素庆大霉素中。我们发现，在存在这些多价阳离子的任何一种情况下，MinD 的平均振荡周期都会迅速且显著增加。对于 Ca(++)和 Mg(++)，周期的增加是短暂的，即使在恒定的细胞外浓度下，而对于鱼精蛋白或庆大霉素，周期的增加显然是不可逆的。我们还发现，小分子阳离子与鱼精蛋白或庆大霉素的作用具有显著的相互依赖性，在庆大霉素和 Ca(++)的中等水平作用下，振荡会发生扭曲，而在高阳离子浓度下，Min 振荡会发生可逆冻结。
结论/意义：细胞内 Min 振荡为细菌对外界多阳离子反应提供了快速的单细胞报告器，这可以用多阳离子穿透细胞来解释。
