Assessing Effects of Nano-Titanium Dioxide on Freshwater Microbial Communities
Wednesday, February 24, 2016
John Kelly, PhD
John Kelly, Ph.D.
Professor and Associate Chairperson
Department of Biology
Loyola University Chicago
Abstract: Nano-TiO2 is an engineered nanomaterial that is found in a wide range of commercial products. Production of nano-TiO2 has increased rapidly over the last several decades, raising concerns about the release of this material into the environment. Aquatic habitats are especially at risk for nano-TiO2 contamination due to inputs from urban and suburban runoff and domestic wastewater. Nano-TiO2 has been shown to be toxic to a variety of aquatic organisms due primarily to its production of reactive oxygen species (ROS) when illuminated. Within freshwater habitats the interactions of nano-TiO2 with microorganisms are a topic of specific concern due to the significant contributions that microbes make to the function of these ecosystems. We are using a range of approaches to assess the interactions of nano-TiO2 with freshwater microbial communities, including field surveys, high-throughput screening (HTS), and model stream experiments. We quantified the release of TiO2 in effluent from an urban wastewater treatment plant as ~3.4 tons per year and characterized the phase composition of the TiO2 as 29% anatase and 61% rutile. We have used HTS to demonstrate that the toxicity of nano-TiO2 to microbes depends on the type and morphology of the nano-TiO2 as well as on the properties of the aqueous matrix. Our HTS experiments have also revealed that different bacterial and algal species vary in their sensitivity/tolerance to nano-TiO2 exposure, and that nano-TiO2 exposure can alter the taxonomic composition of freshwater microbial communities. Finally, our model stream experiments have shown that nano-TiO2 added either as a single pulse or as daily additions of a low, environmentally relevant concentration had negative effects on microbial abundance, with chronic exposure also resulting in lower metabolic activity and altered algal and bacterial community composition. These data indicate the potential for nano-TiO2 to negatively affect the structure and function of freshwater microbial communities and the critical ecosystem services they provide.