| Autor: |
Wang J; Department of Natural Resource Sciences, McGill University, 21111 Lakeshore Road, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada., Jia Y; Department of Natural Resource Sciences, McGill University, 21111 Lakeshore Road, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada.; Harrow Research and Development Centre, Agriculture and Agri-Food Canada, 2585 Essex County Rd 20, Harrow, ON N0R 1G0, Canada., Whalen JK; Department of Natural Resource Sciences, McGill University, 21111 Lakeshore Road, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada., McShane H; Department of Natural Resource Sciences, McGill University, 21111 Lakeshore Road, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada., Driscoll BT; Department of Natural Resource Sciences, McGill University, 21111 Lakeshore Road, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada., Sunahara GI; Department of Natural Resource Sciences, McGill University, 21111 Lakeshore Road, Ste-Anne-de-Bellevue, QC H9X 3V9, Canada. |
| Abstrakt: |
When nano-sized titanium dioxide (nano-TiO 2 ) absorbs ultra-violet (UV-A) radiation, it produces reactive oxygen species that can be toxic to bacteria. We used the agronomically beneficial nitrogen-fixing bacterium Sinorhizobium meliloti strain 1021 as a model microorganism to detect nano-TiO 2 toxicity. Sinorhizobium meliloti was exposed to aqueous dispersions of micrometer-sized TiO 2 (micron-TiO 2 , 44 μm) or nanometer-sized TiO 2 (nano-TiO 2 , 21 nm) at nominal concentrations of 0, 100, 300, 600, 900, and 1800 mg TiO 2 /L. There were fewer viable S. meliloti cells after exposure to nano-TiO 2 under dark and UV-A light conditions. Nano-TiO 2 was more toxic to S. meliloti with UV-A irradiation (100% mortality at 100 mg TiO 2 /L) than under dark conditions (100% mortality at 900 mg TiO 2 /L). Micron-TiO 2 concentrations less than 300 mg TiO 2 /L had no effect on S. meliloti viability under dark or UV-A light conditions. Exposure to 600 mg/L or more of micron-TiO 2 under UV-A light could also photo-kill S. meliloti cells (100% mortality). Further studies are needed to ascertain whether nano-TiO 2 interferes with the growth of N 2 -fixing microorganisms in realistic agricultural environments. |
