The antimicrobial activity and mechanism of silver ions (Ag⁺) have gained broad attention in recent years. However, dynamic studies are rare in this field. Here, we report our measurement of the effects of Ag⁺ ions on the dynamics of histone-like nucleoid structuring (H-NS) proteins in live bacteria using single-particle tracking photoactivated localization microscopy (sptPALM). It was found that treating the bacteria with Ag⁺ ions led to faster diffusive dynamics of H-NS proteins. Several techniques were used to understand the mechanism of the observed faster dynamics. Electrophoretic mobility shift assay on purified H-NS proteins indicated that Ag⁺ ions weaken the binding between H-NS proteins and DNA. Isothermal titration calorimetry confirmed that DNA and Ag⁺ ions interact directly. Our recently developed sensing method based on bent DNA suggested that Ag⁺ ions caused dehybridization of double-stranded DNA (i.e., dissociation into single strands). These evidences led us to a plausible mechanism for the observed faster dynamics of H-NS proteins in live bacteria when subjected to Ag⁺ ions: Ag⁺-induced DNA dehybridization weakens the binding between H-NS proteins and DNA. This work highlighted the importance of dynamic study of single proteins in the live cells for understanding the functions of antimicrobial agents to the bacteria.

Importance As "superbug" bacteria resistant to commonly prescribed antibiotics become a global threat to the public threat in recent years, noble metals, such as silver, in various forms have been attracting broad attention due to their antimicrobial activities. However, most of the existing literature relied on the traditional bioassays for studying the antimicrobial mechanism of silver; in addition, temporal resolution is largely missing for understanding the effects of silver the molecular dynamics inside the bacteria. Here, we report our study on the antimicrobial effect of silver ions at the nanoscale on the diffusive dynamics of histone-like nucleoid structuring (H-NS) proteins in live bacteria using single-particle tracking photoactivated localization microscopy. This work highlights the importance of dynamic study of single proteins in the live cells for understanding the functions of antimicrobial agents to the bacteria.

近年来，银离子（Ag ⁺）的抗菌活性和机理受到广泛关注。但是，动态研究在该领域很少见。在这里，我们报告使用单粒子跟踪光激活定位显微镜（sptPALM）来测量我们的Ag ⁺离子对活细菌中组蛋白样核糖结构化（H-NS）蛋白动力学的影响。发现用Ag ⁺离子处理细菌可导致H-NS蛋白更快的扩散动力学。使用了几种技术来了解观察到的更快动力学的机制。纯化的H-NS蛋白的电泳迁移率迁移分析表明Ag ⁺离子会削弱H-NS蛋白与DNA之间的结合。等温滴定热法证实DNA和Ag ⁺离子直接相互作用。我们最近开发的基于弯曲DNA的传感方法表明，Ag ⁺离子引起了双链DNA的去杂化（即解离成单链）。这些证据使我们找到了一个可行的机制，可以观察到活细菌中H-NS蛋白在受到Ag ⁺离子作用时的更快动力学：Ag ⁺诱导的DNA去杂化作用减弱了H-NS蛋白与DNA之间的结合。这项工作强调了对活细胞中的单个蛋白质进行动态研究对于理解抗菌剂对细菌的功能的重要性。

重要性近年来，随着对常用抗生素具有抗性的“超级细菌”细菌成为对公众威胁的全球威胁，各种形式的贵金属（如银）由于其抗菌作用而受到广泛关注。然而，大多数现有文献依靠传统的生物测定方法来研究银的抗菌机理。此外，由于缺乏了解银对细菌内部分子动力学的影响的时间分辨率，因此在很大程度上缺乏这种方法。在这里，我们报告我们的研究使用单粒子跟踪光激活的定位显微镜在纳米级的银离子对活细菌中的组蛋白样核糖结构化（H-NS）蛋白扩散动力学的抗菌作用的研究。