A mechanistic study of TiO2nanoparticle toxicity on Shewanella oneidensis MR-1 with UV-containing simulated solar irradiation: Bacterial growth, riboflavin secretion, and gene expression.
Toxicity of nanomaterials to ecological systems has recently emerged as an important field of research, and thus, many researchers are exploring the mechanisms of how nanoparticles impact organisms. Herein, we probe the mechanisms of bacteria-nanoparticle interaction by investigating how TiO2nanoparticles impact a model organism, the metal-reducing bacterium Shewanella oneidensis MR-1. In addition to examining the effect of TiO2exposure, the effect of synergistic simulated solar irradiation containing UV was explored in this study, as TiO2nanoparticles are known photocatalysts. The data reveal that TiO2nanoparticles cause an inhibition of S. oneidensis growth at high dosage without compromising cell viability, yet co-exposure of nanoparticles and illumination does not increase the adverse effects on bacterial growth relative to TiO2alone. Measurements of intracellular reactive oxygen species and riboflavin secretion, on the same nanoparticle-exposed bacteria, reveal that TiO2nanoparticles have no effect on these cell functions, but application of UV-containing illumination with TiO2nanoparticles has an impact on the level of riboflavin outside bacterial cells. Finally, gene expression studies were employed to explore how cells respond to TiO2nanoparticles and illumination, and these results were correlated with cell growth and cell function assessment. Together these data suggest a minimal impact of TiO2NPs and simulated solar irradiation containing UV on S. oneidensis MR-1, and the minimal impact could be accounted for by the nutrient-rich medium used in this work. These measurements demonstrate a comprehensive scheme combining various analytical tools to enable a mechanistic understanding of nanoparticle-cell interactions and to evaluate the potential adverse effects of nanoparticles beyond viability/growth considerations.
Department of Chemistry, University of Minnesota, 207 Pleasant St SE, Minneapolis, MN 55455, United States.
Tian A
TA
Qiu
Department of Chemistry, University of Minnesota, 207 Pleasant St SE, Minneapolis, MN 55455, United States.
Ben M
BM
Meyer
Department of Chemistry, University of Minnesota, 207 Pleasant St SE, Minneapolis, MN 55455, United States.
Ky G
KG
Christenson
School of Freshwater Sciences, University of Wisconsin Milwaukee, 600 E. Greenfield Ave, Milwaukee, WI 53204, United States.
Rebecca D
RD
Klaper
Department of Chemistry, University of Minnesota, 207 Pleasant St SE, Minneapolis, MN 55455, United States. Electronic address: chaynes@umn.edu.
Christy L
CL
Haynes
D002470:Cell Survival / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects; D008027:Light; D053768:Metal Nanoparticles / Q000633:toxicity*; D018384:Oxidative Stress / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012256:Riboflavin / Q000378:metabolism*; D020592:Shewanella / Q000187:drug effects* / Q000254:growth & development* / Q000378:metabolism; D012993:Solar Energy; D014025:Titanium / Q000633:toxicity*; D014466:Ultraviolet Rays
D017382:Reactive Oxygen Species; C009495:titanium dioxide; D014025:Titanium; D012256:Riboflavin
Gene expression; Riboflavin; Shewanella oneidensis; Simulated solar irradiation; Titanium dioxide nanoparticles; UV