Abstract
Bacteria are used in ecotoxicology for their important role in marine ecosystems and their quick, reproducible responses. Here we applied a recently proposed method to assess the ecotoxicity of nanomaterials on the ubiquitous marine bacterium Vibrio anguillarum, as representative of brackish and marine ecosystems. The test allows the determination of 6-h EC50 in a wide range of salinity, by assessing the reduction of bacteria actively replicating and forming colonies. The toxicity of copper oxide nanoparticles (CuO NPs) at different salinities (5-20-35 ‰) was evaluated. CuSO4 5H2O and CuO bulk were used as reference toxicants (solubility and size control, respectively). Aggregation and stability of CuO NP in final testing dispersions were characterized; Cu2+ dissolution and the physical interactions between Vibrio and CuO NPs were also investigated. All the chemical forms of copper showed a clear dose-response relationship, although their toxicity was different. The order of decreasing toxicity was: CuSO4 5H2O > CuO NP > CuO bulk. As expected, the size of CuO NP aggregates increased with salinity and, concurrently, their toxicity decreased. Results confirmed the intrinsic toxicity of CuO NPs, showing modest Cu2+ dissolution and no evidence of CuO NP internalization or induction of bacterial morphological alterations. This study showed the V. anguillarum bioassay as an effective tool for the risk assessment of nanomaterials in marine and brackish environments.
Highlights
The metal nanoparticles, including metal oxides, represent one of the major classes of commercial nanomaterials, which are manufactured on a large scale for both industrial and household applications (Chang et al, 2012)
In order to provide a useful tool for NP toxicity assessments in marine environments, we recently developed a new bioassay with the marine bacterium Vibrio anguillarum and demonstrated its effectiveness in evaluating the toxicity of a reference toxicant (Rotini et al, 2017)
The Zeta (ζ-) potential and average volume-weighted diameters (Table 1) of the CuO NP dispersions were measured by DLS in the reference medium and the saline solutions (0.5-2.0-3.5% NaCl) used as exposure media
Summary
The metal nanoparticles, including metal oxides, represent one of the major classes of commercial nanomaterials, which are manufactured on a large scale for both industrial and household applications (Chang et al, 2012). The wide variety of applications entails the risk of environmental contamination, as a consequence of the environmental release of CuO NP during their production, use and disposal (Weinberg et al, 2011; Sanchís et al, 2013; Fan et al, 2014) This kind of contamination could bias both organisms and Salinity-Based Toxicity of Cu Forms to Bacteria ecosystems (Gambardella et al, 2013), as CuO NPs can exert toxic effects and antimicrobial activity on (environmental) microbes (Bondarenko et al, 2013; Rossetto et al, 2014); they could seriously affect estuarine and coastal environments, considered the ultimate sink for different kinds of NPs (Canesi et al, 2012). L. et al, 2015; Gonçalves et al, 2017), with few EC50 identifications, it is mandatory to define the hazard of CuO NPs in environment and human health and enhance their safe use
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