John Wiley & Sons, Ltd.

Common freshwater bacteria vary in their responses to short‐term exposure to nano‐TiO2

Nanostructured titania (nano‐TiO2) is an engineered nanomaterial that can be cytotoxic primarily due to its ability to generate reactive oxygen species when illuminated. Production of nano‐TiO2 has increased rapidly over the last decade, leading to concerns about its release into aquatic environments. To address the possible ecological impacts of nano‐TiO2, we used high‐throughput screening to assess the responses of four bacteria representative of genera common in freshwater to short‐term exposure (1‐2 h) in two natural aqueous media (stream water and lake water) to two widely‐used titania products, Pigment White 6 (PW6) and P25. Under simulated solar illumination PW6 and P25 reduced the abundance of viable Bacillus subtilis and Aeromonas hydrophila, confirming the cytotoxicity of nano‐TiO2. In contrast PW6 and P25 stimulated growth of Arthrobacter sp. and Klebsiella sp., which we hypothesize was driven by oxidation of organic material in these natural waters into more labile compounds. This hypothesis is supported by data demonstrating PW6 photo‐oxidation of organic matter in stream water, which subsequently supported enhanced bacterial growth. The results of this study indicate that bacterial responses to nano‐TiO2 can be species‐specific, suggesting that nano‐TiO2 may alter bacterial community composition and function. Finally, our results indicate that bacterial responses to nano‐TiO2 are influenced by the water matrix, emphasizing the importance of assessing bacterial responses to nanomaterials in natural environmental media. Environ Toxicol Chem © 2013 SETAC

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