Kumar Niraj, Palmer Gerald R, Shah Vishal, Walker Virginia K
Department of Biology, Queen's University, Kingston, Ontario, Canada.
Department of Biology, Dowling College, Oakdale, New York, United States of America.
PLoS One. 2014 Jun 13;9(6):e99953. doi: 10.1371/journal.pone.0099953. eCollection 2014.
The impact of silver nanoparticles (NPs) and microparticles (MPs) on bacterial and fungal assemblages was studied in soils collected from a low arctic site. Two different concentrations (0.066% and 6.6%) of Ag NPs and Ag MPs were tested in microcosms that were exposed to temperatures mimicking a winter to summer transition. Toxicity was monitored by differential respiration, phospholipid fatty acid analysis, polymerase chain reaction-denaturing gradient gel electrophoresis and DNA sequencing. Notwithstanding the effect of Ag MPs, nanosilver had an obvious, additional impact on the microbial community, underscoring the importance of particle size in toxicity. This impact was evidenced by levels of differential respiration in 0.066% Ag NP-treated soil that were only half that of control soils, a decrease in signature bacterial fatty acids, and changes in both richness and evenness in bacterial and fungal DNA sequence assemblages. Prominent after Ag NP-treatment were Hypocreales fungi, which increased to 70%, from only 1% of fungal sequences under control conditions. Genera within this Order known for their antioxidant properties (Cordyceps/Isaria) dominated the fungal assemblage after NP addition. In contrast, sequences attributed to the nitrogen-fixing Rhizobiales bacteria appeared vulnerable to Ag NP-mediated toxicity. This combination of physiological, biochemical and molecular studies clearly demonstrate that Ag NPs can severely disrupt the natural seasonal progression of tundra assemblages.
在从北极低地采集的土壤中，研究了银纳米颗粒（NPs）和微米颗粒（MPs）对细菌和真菌群落的影响。在模拟冬夏过渡温度的微观环境中，测试了两种不同浓度（0.066%和6.6%）的银纳米颗粒和银微米颗粒。通过差异呼吸、磷脂脂肪酸分析、聚合酶链反应-变性梯度凝胶电泳和DNA测序来监测毒性。尽管银微米颗粒有影响，但纳米银对微生物群落有明显的额外影响，突出了颗粒大小在毒性方面的重要性。这种影响在以下方面得到了证明：0.066%银纳米颗粒处理的土壤中差异呼吸水平仅为对照土壤的一半，标志性细菌脂肪酸减少，以及细菌和真菌DNA序列组合的丰富度和均匀度发生变化。银纳米颗粒处理后，肉座菌目真菌显著增加，从对照条件下真菌序列的仅1%增加到70%。该目内以其抗氧化特性闻名的属（虫草属/棒束孢属）在添加纳米颗粒后主导了真菌群落。相比之下，归因于固氮根瘤菌目的序列似乎易受银纳米颗粒介导的毒性影响。这种生理、生化和分子研究的结合清楚地表明，银纳米颗粒会严重破坏苔原群落的自然季节性进程。
