Abstract
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.
Highlights
Over the last 25 years, both consumers and industrialists have benefited from the technological breakthroughs associated with the manufacture of nanoparticles (NPs)
Three treatment groups showed respiration that was lower than the mean differential respiration of the untreated, control soil (230 ppm CO2): NPL, NPH, and MPH microcosms showed mean differential CO2 levels of 128, 55 and 60 ppm, respectively
There were only a few white threads in the NPL -treated soil. This was not seen in the other microcosms, nor has it been observed in previous experiments where arctic soils were exposed to either temperature perturbations or metal exposure [14], [25], but not both stresses coincidently
Summary
Over the last 25 years, both consumers and industrialists have benefited from the technological breakthroughs associated with the manufacture of nanoparticles (NPs) Due to their antimicrobial activities, silver NPs are popular in textiles, food contact surfaces, building materials, vehicle interiors, cosmetics, paints, air conditioners, and medical applications [1], [2], [3], [4]. This explains a global production of Ag NPs, estimated to be more than 500 tonnes annually [5]. Atmospheric deposition, in addition to the melting of the ice pack coincident with the ‘opening’ of the Arctic will only increase the probability of such contamination
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