title: Harmful effects of silver nanoparticles on a complex detrital model system.
abstract: 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.
authors.affiliation: 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 .
authors.forename: Ahmed
authors.initials: A
authors.lastname: Tlili
authors.affiliation: a Department of Experimental Limnology , Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) , Stechlin , Germany .|c Laboratoire Interdisciplinaire des Environnements Continentaux (LIEC), UMR 7360, Université de Lorraine , Campus Bridoux, Rrue du Général Delestraint , Metz , France .
authors.forename: Julien
authors.initials: J
authors.lastname: Cornut
authors.affiliation: b Department of Environmental Toxicology , Eawag: Swiss Federal Institute of Aquatic Science and Technology , Dübendorf , Switzerland .|d Department of Environmental Science , ETH Zurich , Zurich , Switzerland .
authors.forename: Renata
authors.initials: R
authors.lastname: Behra
authors.affiliation: b Department of Environmental Toxicology , Eawag: Swiss Federal Institute of Aquatic Science and Technology , Dübendorf , Switzerland .|e School of Architecture, Civil and Environmental Engineering, École Polytechnique Fédérale de Lausanne , Lausanne , Switzerland , and.
authors.forename: Carmen
authors.initials: C
authors.lastname: Gil-Allué
authors.affiliation: a Department of Experimental Limnology , Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) , Stechlin , Germany .|f Department of Ecology , Berlin Institute of Technology (TU Berlin) , Berlin , Germany.
authors.forename: Mark O
authors.initials: MO
authors.lastname: Gessner
mesh_terms: D003545:Cysteine / Q000378:metabolism; D017753:Ecosystem; D052918:Environmental Restoration and Remediation; D019015:Geologic Sediments / Q000737:chemistry / Q000382:microbiology; D007477:Ions; D053768:Metal Nanoparticles / Q000032:analysis / Q000633:toxicity*; D059013:Microbial Consortia / Q000187:drug effects*; D008962:Models, Theoretical; D018515:Plant Leaves / Q000737:chemistry / Q000382:microbiology; D012834:Silver / Q000032:analysis / Q000633:toxicity*; D012835:Silver Nitrate / Q000032:analysis / Q000633:toxicity*; D012995:Solubility
chemical_list: D007477:Ions; D012834:Silver; D012835:Silver Nitrate; D003545:Cysteine
keywords: Bacterial and fungal growth; community nanotoxicology; extracellular enzymatic activities; litter decomposition; stream ecosystem