Whether the antibacterial properties of silver nanoparticles (AgNPs) are simply due to the release of silver ions (Ag+) or, additionally, nanoparticle-specific effects, has been debated for over a decade. We used experimental evolution of the model environmental bacterium Pseudomonas putida to ask whether bacteria respond differently to Ag+ or AgNP treatment. We pre-evolved five cultures of strain KT2440 for 70 d without Ag to reduce confounding adaptations before dividing the fittest pre-evolved culture into five cultures each, evolving in the presence of low concentrations of Ag+, well-defined AgNPs or Ag-free controls for a further 75 d. The mutations in the Ag+ or AgNP evolved populations displayed different patterns that were statistically significant. The non synonymous mutations in AgNP treated populations were mostly associated with cell surface proteins, including cytoskeletal membrane protein (FtsZ), membrane sensor and regulator (EnvZ and GacS) and periplasmic protein (PP_2758). In contrast, Ag+ treatment selected for mutations linked to cytoplasmic proteins, including metal ion transporter (TauB) and those with metal binding domains (ThiL and PP_2397). These results suggest the existence of AgNP-specific effects, either caused by sustained delivery of Ag+ from AgNP-dissolution, more proximate delivery from cell-surface bound AgNPs, or by direct AgNP action on the cell outer membrane.

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银离子与纳米颗粒应力作用下恶臭假单胞菌的实验进化

十多年来，人们一直在争论银纳米颗粒（AgNPs）的抗菌性能是仅由于银离子（Ag +）的释放还是纳米颗粒特有的作用。我们使用模型环境细菌恶臭假单胞菌的实验进化来询问细菌对Ag +或AgNP处理的反应是否不同。我们在不添加Ag的情况下将KT2440菌株的5种培养物进行了70 d的进化，以减少混杂的适应性，然后将最适度的pre-evolved培养物分为5种培养物，并在低浓度的Ag +，明确的AgNPs或无Ag的对照条件下进化再持续75 d。Ag +或AgNP进化种群中的突变显示出不同的模式，具有统计学意义。AgNP处理群体中的非同义突变主要与细胞表面蛋白有关，包括细胞骨架膜蛋白（FtsZ），膜传感器和调节剂（EnvZ和GacS）和周质蛋白（PP_2758）。相反，Ag +处理选择了与胞质蛋白相关的突变，包括金属离子转运蛋白（TauB）和具有金属结合域的蛋白（ThiL和PP_2397）。这些结果表明存在AgNP特异性效应，这可能是由于从AgNP溶解过程中持续释放Ag +，从与细胞表面结合的AgNPs更接近递送，或者是由于AgNP对细胞外膜的直接作用所致。针对与细胞质蛋白相关的突变（包括金属离子转运蛋白（TauB）和具有金属结合域的蛋白）（ThiL和PP_2397）选择的Ag +处理。这些结果表明存在AgNP特异性效应，这可能是由于从AgNP溶解过程中持续释放Ag +，从与细胞表面结合的AgNPs更接近递送，或者是由于AgNP对细胞外膜的直接作用所致。针对与细胞质蛋白相关的突变（包括金属离子转运蛋白（TauB）和具有金属结合域的蛋白）（ThiL和PP_2397）选择的Ag +处理。这些结果表明存在AgNP特异性效应，这可能是由于从AgNP溶解过程中持续释放Ag +，从与细胞表面结合的AgNPs更接近递送，或者是由于AgNP对细胞外膜的直接作用所致。