10.6084/m9.figshare.7218110.v2 Shufeng Liu Shufeng Liu Ming Wang Ming Wang Tingting Li Tingting Li Qian Chen Qian Chen Response of an aerobic denitrifier to titanium dioxide nanoparticles exposure Taylor & Francis Group 2018 TiO2 nanoparticles aerobic denitrification napA nirS aggregation 2018-11-01 06:44:38 Journal contribution https://tandf.figshare.com/articles/journal_contribution/Response_of_an_aerobic_denitrifier_to_Titanium_dioxide_nanoparticles_exposure/7218110 <p>The cytotoxicity of titanium dioxide nanoparticles (TiO<sub>2</sub> NPs) to microorganisms has attracted great attention over the past few decades. As an important participator in the nitrogen cycle, aerobic denitrifiers have been proven to be negatively affected by TiO<sub>2</sub> NPs, but the mechanism of this effect remains unclear. In this study, the bacteria-nanoparticle interaction was investigated by exposing an aerobic denitrifier, <i>Pseudomonas stutzeri</i> PCN-1 to different concentrations of TiO<sub>2</sub> NPs at the dark condition, in order to investigate the cytotoxicity mechanism. The results illustrated that aerobic denitrification was inhibited at different TiO<sub>2</sub> NPs concentrations from 1 to 128 mg/L, accompanied by the postponement of nitrate reduction and the accumulations of nitrite and nitrous oxide. But this inhibitory effect was mitigated with increasing TiO<sub>2</sub> NPs concentrations. Further studies revealed that expressions of aerobic denitrification genes were also inhibited with the presence of TiO<sub>2</sub> NPs, and the inhibition effect on <i>napA</i> and <i>nirS</i> genes was more significant than that on <i>nosZ</i> and <i>cnorB</i>, which might directly bring about the delayed nitrate reduction and hindered nitrite transfer. Moreover, the decreased toxicities at higher TiO<sub>2</sub> NPs concentrations could be attributed to the formation of larger aggregates (>1000 nm), which greatly reduced the chance for direct interactions between NPs and bacterial membranes, as well as the interruption of denitrifying genes expressions. These findings were meaningful for the formation of deep insights into the mechanism of TiO<sub>2</sub> NPs cytotoxicity as well as the development of strategies to control the negative effect of nanoparticles in the environment.</p> <p>Aerobic denitrification characteristics of strain PCN-1 under different carbon sources.</p>