Abstract
The nanotechnology industry is growing rapidly, leading to concerns about the potential ecological consequences of the release of engineered nanomaterials (ENMs) to the environment. One challenge of assessing the ecological risks of ENMs is the incredible diversity of ENMs currently available and the rapid pace at which new ENMs are being developed. High-throughput screening (HTS) is a popular approach to assessing ENM cytotoxicity that offers the opportunity to rapidly test in parallel a wide range of ENMs at multiple concentrations. However, current HTS approaches generally test one cell type at a time, which limits their ability to predict responses of complex microbial communities. In this study toxicity screening via a HTS platform was used in combination with next generation sequencing (NGS) to assess responses of bacterial communities from two aquatic habitats, Lake Michigan (LM) and the Chicago River (CR), to short-term exposure in their native waters to several commercial TiO2 nanomaterials under simulated solar irradiation. Results demonstrate that bacterial communities from LM and CR differed in their sensitivity to nano-TiO2, with the community from CR being more resistant. NGS analysis revealed that the composition of the bacterial communities from LM and CR were significantly altered by exposure to nano-TiO2, including decreases in overall bacterial diversity, decreases in the relative abundance of Actinomycetales, Sphingobacteriales, Limnohabitans, and Flavobacterium, and a significant increase in Limnobacter. These results suggest that the release of nano-TiO2 to the environment has the potential to alter the composition of aquatic bacterial communities, which could have implications for the stability and function of aquatic ecosystems. The novel combination of HTS and NGS described in this study represents a major advance over current methods for assessing ENM ecotoxicity because the relative toxicities of multiple ENMs to thousands of naturally occurring bacterial species can be assessed simultaneously under environmentally relevant conditions.
Highlights
Engineered nanomaterials (ENMs) have at least one dimension less than 100 nm, which leads to unique chemical and physical properties, including high reactivity and conductivity
P25 showed the highest toxicity to Lake Michigan (LM) bacteria, with concentrations at or above 2.5 mg L21 resulting in significant decreases in bacterial viability as compared to the 0 mg L21 control
The results of this study indicate that short-term exposure of bacterial communities from two aquatic habitats, Lake Michigan (LM) and the Chicago River (CR), to several different forms of nano-TiO2 in their native waters under simulated solar illumination resulted in significant decreases in the relative abundance of viable bacterial cells
Summary
Engineered nanomaterials (ENMs) have at least one dimension less than 100 nm, which leads to unique chemical and physical properties, including high reactivity and conductivity. The manufacture of titanium dioxide (TiO2) nanoparticles is a significant niche industry and demand for these materials is strong. By 2015 production of nano-TiO2 is projected to increase to 201,500 tons [2]. There is growing concern that ENMs will have adverse effects on aquatic ecosystems, as previous studies have demonstrated ENM toxicity to aquatic organisms including fish, invertebrates and microorganisms (for reviews see [5,6]). The toxicity of nano-TiO2, for example, is caused primarily by its photo-induced production of reactive oxygen species (ROS), which are powerful oxidizing agents that can damage a variety of cell components [7,8]
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