Bacterial responses to Cu-doped TiO2 nanoparticles |
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Authors: | Bing Wu Yinjie J. Tang |
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Affiliation: | Department of Energy, Environmental and Chemical Engineering, One Brookings Drive, Campus Box 1180, Washington University in St. Louis, St. Louis, MO 63130, United States |
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Abstract: | The toxicity of Cu-doped TiO2 nanoparticles (NPs, 20 nm), synthesized by a flame aerosol reactor, to Mycobacterium smegmatis and Shewanella oneidensis MR-1, is the primary focus of this study. Both doped and non-doped TiO2 NPs (20 nm) tended to agglomerate in the medium solution, and therefore did not penetrate into the cell and damage cellular structures. TiO2 particles (< 100 mg/L) did not apparently interfere with the growth of the two species in aqueous cultures. Cu-doped TiO2 NPs (20 mg/L) significantly reduced the M. smegmatis growth rate by three fold, but did not affect S. oneidensis MR-1 growth. The toxicity of Cu-doped TiO2 NPs was driven by the release of Cu2+ from the parent NPs. Compared to equivalent amounts of Cu2+, Cu-doped TiO2 NPs exhibited higher levels of toxicity to M. smegmatis (P-value < 0.1). Addition of EDTA in the culture appeared to significantly decrease the anti-mycobacterium activity of Cu-doped TiO2 NPs. S. oneidensis MR-1 produced a large amount of extracellular polymeric substances (EPS) under NP stress, especially extracellular protein. Therefore, S. oneidensis MR-1 was able to tolerate a much higher concentration of Cu2+ or Cu-doped TiO2 NPs. S. oneidensis MR-1 also adsorbed NPs on cell surface and enzymatically reduced ionic copper in culture medium with a remediating rate of 61 µg/(liter?OD600? hour) during its early exponential growth phase. Since the metal reducing Shewanella species can efficiently “clean” metal-oxide NPs, the activities of such environmentally relevant bacteria may be an important consideration for evaluating the ecological risk of metal-oxide NPs. |
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Keywords: | Mycobacterium smegmatis Shewanella oneidensis EDTA EPS Remediate |
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