Tlili Ahmed, Cornut Julien, Behra Renata, Gil-Allué Carmen, Gessner Mark O
a Department of Experimental Limnology , Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) , Stechlin , Germany .
b Department of Environmental Toxicology , Eawag: Swiss Federal Institute of Aquatic Science and Technology , Dübendorf , Switzerland .
Nanotoxicology. 2016 Aug;10(6):728-35. doi: 10.3109/17435390.2015.1117673. Epub 2016 Jan 26.
The rapid proliferation of silver nanoparticles (AgNP) in industry and the environment requires realistic toxicity assessments based on approaches that consider the biological complexity of ecosystems. Here we assessed the acute toxicity of carbonate-coated AgNP and, for comparison, AgNO3 (Ag(+)) by using a model system consisting of decomposing plant litter and the associated fungal and bacterial decomposers as central players in the functioning of stream ecosystems. Little variation in size and surface charge during the experiment indicated that the AgNP used were essentially stable. AgNP disrupted bacterial growth (≤83% reduction in protein biosynthesis, EC50 = 0.3 μM), clearly affected fungal growth (≤61% reduction in ergosterol synthesis, EC50 = 47 μM) with both endpoints more sensitive to AgNP than to Ag(+). Fungal reproduction, in contrast, was stimulated by AgNP, but not Ag(+), at concentrations up to 25 μM. Both AgNP and Ag(+ )also stimulated extracellular alkaline phosphatase but reduced leucine aminopeptidase, whereas β-glucosidase was stimulated by AgNP and reduced by Ag(+). Importantly, the provision of cysteine, a chelating ligand that complexes free Ag(+), failed to alleviate AgNP toxicity to microbial growth, clearly demonstrating particle-mediated toxicity independent of the presence of ionic silver. This contrasts with the observed inhibition of leucine aminopeptidase by Ag(+), which accounted for 2-6% of the total silver in treatments receiving AgNP. These results show that although outcomes of AgNP and Ag(+ )exposure assessed by different functional endpoints vary widely, AgNP strongly interferes with bacterial growth and a range of other microbial processes, resulting in severe consequences for natural microbial communities and ecosystem functioning.
银纳米颗粒（AgNP）在工业和环境中的迅速扩散，需要基于考虑生态系统生物复杂性的方法进行实际的毒性评估。在此，我们通过使用一个由分解植物凋落物以及相关真菌和细菌分解者组成的模型系统，来评估碳酸包覆的AgNP以及作为对照的AgNO3（Ag(+)）的急性毒性，这些分解者是溪流生态系统功能的核心参与者。实验过程中AgNP的大小和表面电荷变化很小，表明所使用的AgNP基本稳定。AgNP干扰细菌生长（蛋白质生物合成减少≤83%，半数效应浓度EC50 = 0.3 μM），明显影响真菌生长（麦角固醇合成减少≤61%，EC50 = 47 μM），这两个指标对AgNP都比对Ag(+)更敏感。相比之下，在浓度高达25 μM时，AgNP刺激真菌繁殖，但Ag(+)无此作用。AgNP和Ag(+)都刺激细胞外碱性磷酸酶，但降低亮氨酸氨肽酶，而β-葡萄糖苷酶受AgNP刺激，受Ag(+)抑制。重要的是，提供半胱氨酸（一种能与游离Ag(+)络合的螯合配体）并不能减轻AgNP对微生物生长的毒性，这清楚地证明了颗粒介导的毒性与离子银的存在无关。这与观察到的Ag(+)对亮氨酸氨肽酶的抑制形成对比，在接受AgNP处理的样本中，Ag(+)占总银含量的2 - 6%。这些结果表明，尽管通过不同功能指标评估的AgNP和Ag(+)暴露结果差异很大，但AgNP强烈干扰细菌生长和一系列其他微生物过程，对自然微生物群落和生态系统功能造成严重影响。
