title: Symbiosis between nitrogen-fixing bacteria and Medicago truncatula is not significantly affected by silver and silver sulfide nanomaterials.
abstract: Silver (Ag) engineered nanomaterials (ENMs) are being released into waste streams and are being discharged, largely as Ag2S aged-ENMs (a-ENMs), into agroecosystems receiving biosolids amendments. Recent research has demonstrated that biosolids containing an environmentally relevant mixture of ZnO, TiO2, and Ag ENMs and their transformation products, including Ag2S a-ENMs, disrupted the symbiosis between nitrogen-fixing bacteria and legumes. However, this study was unable to unequivocally determine which ENM or combination of ENMs and a-ENMs was responsible for the observed inhibition. Here, we examined further the effects of polyvinylpyrollidone (PVP) coated pristine Ag ENMs (PVP-Ag), Ag2S a-ENMs, and soluble Ag (as AgSO4) at 1, 10, and 100 mg Ag kg(-1) on the symbiosis between the legume Medicago truncatula and the nitrogen-fixing bacterium, Sinorhizobium melliloti in biosolids-amended soil. Nodulation frequency, nodule function, glutathione reductase production, and biomass were not significantly affected by any of the Ag treatments, even at 100 mg kg(-1), a concentration analogous to a worst-case scenario resulting from long-term, repeated biosolids amendments. Our results provide additional evidence that the disruption of the symbiosis between nitrogen-fixing bacteria and legumes in response to a mixture of ENMs in biosolids-amended soil reported previously may not be attributable to Ag ENMs or their transformation end-products. We anticipate these findings will provide clarity to regulators and industry regarding potential unintended consequences to terrestrial ecosystems resulting from of the use of Ag ENMs in consumer products.
authors.affiliation: Commonwealth Science and Industry Research Organization (CSIRO), Land and Water, Environmental Contaminant Mitigation and Technologies Research Program, Waite Campus, Waite Road, Urrbrae, 5064 South Australia, Australia. Electronic address: jonathan.judy@csiro.au.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Judy
authors.affiliation: Commonwealth Science and Industry Research Organization (CSIRO), Land and Water, Environmental Contaminant Mitigation and Technologies Research Program, Waite Campus, Waite Road, Urrbrae, 5064 South Australia, Australia.
authors.forename: Jason K
authors.initials: JK
authors.lastname: Kirby
authors.affiliation: Commonwealth Science and Industry Research Organization (CSIRO), Land and Water, Environmental Contaminant Mitigation and Technologies Research Program, Waite Campus, Waite Road, Urrbrae, 5064 South Australia, Australia.
authors.forename: Mike J
authors.initials: MJ
authors.lastname: McLaughlin
authors.affiliation: Department of Plant and Soil Sciences, University of Kentucky, Lexington, 40546 Kentucky, United States.
authors.forename: David
authors.initials: D
authors.lastname: McNear
authors.affiliation: Department of Plant and Soil Sciences, University of Kentucky, Lexington, 40546 Kentucky, United States; Center for the Environmental Implications for Nanotechnology, Duke University, Durham, 27708 North Carolina, USA; Commonwealth Science and Industry Research Organization (CSIRO), Land and Water, Ecosciences Precinct, 41 Boggo Road, Dutton Park, 4102, Queensland, Australia.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Bertsch
mesh_terms: D000383:Agriculture / Q000379:methods; D018533:Biomass; D017753:Ecosystem; D004784:Environmental Monitoring / Q000379:methods; D046913:Medicago truncatula / Q000187:drug effects / Q000254:growth & development / Q000382:microbiology*; D053758:Nanoparticles / Q000032:analysis* / Q000633:toxicity; D000072738:Nitrogen-Fixing Bacteria / Q000187:drug effects / Q000254:growth & development*; D018030:Silver Compounds / Q000032:analysis* / Q000633:toxicity; D012987:Soil / Q000737:chemistry / Q000592:standards; D012989:Soil Pollutants / Q000032:analysis* / Q000633:toxicity; D013559:Symbiosis / Q000187:drug effects*
chemical_list: D018030:Silver Compounds; D012987:Soil; D012989:Soil Pollutants; C013251:silver sulfide
keywords: Nanoparticles; Nanotechnology; Nanotoxicology