Antimicrobial effects of commercial silver nanoparticles are attenuated in natural streamwater and sediment
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Given the demonstrated antimicrobial properties of silver nanoparticles (AgNPs), and the key role that microorganisms play in performing critical ecosystem functions such as decomposition and nutrient cycling, there is growing concern that AgNP pollution may negatively impact ecosystems. We examined the response of streamwater and sediment microorganisms to commercially available 21 ± 17 nm AgNPs, and compared AgNP impacts to those of dissolved-Ag added as AgNO3. We show that in streamwater, AgNPs and AgNO3 decreased respiration in proportion to dissolved-Ag concentrations at the end of the incubation (r2 = 0.78), while in sediment the only measurable effect of AgNPs was a 14 % decrease in sulfate concentration. This contrasts with the stronger effects of dissolved-Ag additions in both streamwater and sediment. In streamwater, addition of dissolved-Ag at a level equivalent to the lowest AgNP dose led to respiration below detection, a 55 % drop in phosphatase enzyme activity, and a 10-fold increase in phosphate concentration. In sediment, AgNO3 addition at a level equivalent to the highest AgNP addition led to a 34 % decrease in respiration, a 55 % increase in microbial biomass, and a shift in bacterial community composition. The results of this study suggest that, in similar freshwater environments, the short-term biological impacts of AgNPs on microbes are attenuated by the physical and chemical properties of streamwater and sediment.
KeywordsSilver nanoparticles Microbial biomass Microbial respiration Enzyme activity Environment
The authors would like to thank Sam Johnson, Medora Burke-Scoll, Brooke Hassett, Curt Richardson, Claudia Gunsch, and Christina Arnaout for their discussions and laboratory assistance. This work was funded through the Center for the Environmental Implications of Nanotechnology (CEINT), which is supported by funding from the National Science Foundation (NSF) and the US Environmental Protection Agency (EPA). Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF or the EPA. This work has not been subjected to EPA review and no official endorsement should be inferred.
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