Niu Bin, Zhang Gengxin
State Key Laboratory of Tibetan Plateau Earth System, Resources and Environment (TPESRE), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China.
University of Chinese Academy of Sciences, Beijing 100101, China.
Microorganisms. 2023 Feb 21;11(3):542. doi: 10.3390/microorganisms11030542.
Nanoparticles widely exist in nature and may be formed through inorganic or organic pathways, exhibiting unique physical and chemical properties different from those of bulk materials. However, little is known about the potential consequences of nanomaterials on microbes in natural environments. Herein, we investigated the interactions between microbes and nanoparticles by performing experiments on the inhibition effects of gold, ludox and laponite nanoparticles on in liquid Luria-Bertani (LB) medium at different nanoparticle concentrations. These nanoparticles were shown to be effective bactericides. Scanning electron microscopy (SEM) images revealed the distinct aggregation of cells and nanoparticles. Transmission electron microscopy (TEM) images showed considerable cell membrane disruption due to nanoparticle accumulation on the cell surfaces, resulting in cell death. We hypothesized that this nanoparticle accumulation on the cell surfaces not only disrupted the cell membranes but also physically blocked the microbes from accessing nutrients. An iron-reducing bacterium, , was tested for its ability to reduce the Fe (III) in solid ferrihydrite (HFO) or aqueous ferric citrate in the presence of laponite nanoparticles. It was found that the laponite nanoparticles inhibited the reduction of the Fe (III) in solid ferrihydrite. Moreover, direct contact between the cells and solid Fe (III) coated with the laponite nanoparticles was physically blocked, as confirmed by SEM images and particle size measurements. However, the laponite particles had an insignificant effect on the extent of aqueous Fe (III) bioreduction but slightly enhanced the rate of bioreduction of the Fe (III) in aqueous ferric citrate. The slightly increased rate of bioreduction by laponite nanoparticles may be due to the removal of inhibitory Fe (II) from the cell surface by its sorption onto the laponite nanoparticle surface. This result indicates that the scavenging of toxic heavy metals, such as Fe (II), by nanoparticles may be beneficial for microbes in the environment. On the other hand, microbial cells are also capable of detoxifying nanoparticles by coagulating nanoparticles with extracellular polymeric substances or by changing nanoparticle morphologies. Hence, the interactions between microbes and nanoparticles in natural environments should receive more attention.
纳米颗粒广泛存在于自然界中，可通过无机或有机途径形成，具有与块状材料不同的独特物理和化学性质。然而，关于纳米材料对自然环境中微生物的潜在影响，人们知之甚少。在此，我们通过在不同纳米颗粒浓度的液体Luria-Bertani（LB）培养基中进行金、硅溶胶和锂皂石纳米颗粒的抑制作用实验，研究了微生物与纳米颗粒之间的相互作用。这些纳米颗粒被证明是有效的杀菌剂。扫描电子显微镜（SEM）图像显示了细胞和纳米颗粒的明显聚集。透射电子显微镜（TEM）图像显示，由于纳米颗粒在细胞表面的积累，细胞膜受到了相当大的破坏，导致细胞死亡。我们推测，纳米颗粒在细胞表面的这种积累不仅破坏了细胞膜，还在物理上阻止了微生物获取营养物质。一种铁还原细菌，在锂皂石纳米颗粒存在的情况下，测试了其还原固体水铁矿（HFO）中的Fe（III）或柠檬酸铁水溶液中的Fe（III）的能力。发现锂皂石纳米颗粒抑制了固体水铁矿中Fe（III）的还原。此外，SEM图像和粒度测量证实，细胞与涂有锂皂石纳米颗粒的固体Fe（III）之间的直接接触在物理上被阻断。然而，锂皂石颗粒对柠檬酸铁水溶液中Fe（III）的生物还原程度影响不大，但略微提高了柠檬酸铁水溶液中Fe（III）的生物还原速率。锂皂石纳米颗粒导致生物还原速率略有增加，可能是由于其吸附到锂皂石纳米颗粒表面，从而从细胞表面去除了抑制性的Fe（II）。这一结果表明，纳米颗粒对有毒重金属（如Fe（II））的清除可能对环境中的微生物有益。另一方面，微生物细胞也能够通过用细胞外聚合物凝结纳米颗粒或改变纳米颗粒形态来使纳米颗粒解毒。因此，自然环境中微生物与纳米颗粒之间的相互作用应受到更多关注。
