Research utilizing the model soil nematode Caenorhabditis elegans has revealed that agriculturally relevant nanoparticles (NP), such as zinc oxide NP (ZnONP), cause toxicity at low concentrations and disrupt molecular pathways of pathogen resistance. However, in most nanotoxicity assessments, model organisms are exposed to a single stressor but in nature organisms are affected by multiple sources of stress, including infections, which might exacerbate or mitigate negative effects of NP exposure. Thus, to expand our understanding of the environmental consequences of released NP, this project examined the synergistic/antagonistic effects of ZnONP on C. elegans infected with a common pathogen, Klebsiella pneumoniae. Individual exposures of C. elegans to ZnONP, zinc sulfate (Zn2+ ions) or K. pneumoniae significantly decreased nematode reproduction compared to controls. To assess the combined stress of ZnONP and K. pneumoniae, C. elegans were exposed to equitoxic EC30 concentrations of ZnONP (or Zn ions) and K. pneumoniae. After the combined exposure there was no decrease in reproduction. This complete elimination of reproductive toxicity was unexpected because exposures were conducted at EC30 Zn concentrations and reproductive toxicity due to Zn should have occurred. Amelioration of the pathogen effects by Zn are partially explained by the Zn impact on the K. pneumoniae biofilm. Quantitative assessments showed that external biofilm production and estimated colony forming units (CFU) of K. pneumoniae within the nematodes were significantly decreased. Taken together, our results suggest that during the combined exposure of C. elegans to both stressors Zn in ionic or particulate form inhibits K. pneumoniae ability to colonize nematode's intestine through decreasing pathogen biofilm formation. This highlights the unpredictable nature of combined stressor effects, calling into question the utility of exposures in simplified laboratory media.
|Journal||Science of the Total Environment|
|State||Published - Mar 20 2023|
Bibliographical noteFunding Information:
We acknowledge the assistance of T. Smith, S. Shrestha, K. Chheang, and P. Ngy, N. Briot, J. Cramer, and J. Pu. Caenorhabditis elegans strains were provided by the Caenorhabditis Genetics Center, which is funded by the NIH Office of Research Infrastructure Programs ( P40 OD010440 ). Additionally, acquisition of SEM and TEM images was funded by KY-INBRE grant P20 GM103436 . A portion of this project was funded by USDA NIFA multistate project NC1194 and Hatch Project KY006133 . Chemical analyses were supported by UK-CARES through NIEHS Grant P30 ES026529 . Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIEHS. JC was supported by the University of Kentucky , Department of Plant and Soil Sciences through a graduate research assistantship.
© 2022 Elsevier B.V.
- Antagonistic effects
- Internal colonization
- Multiple stressors
ASJC Scopus subject areas
- Environmental Engineering
- Environmental Chemistry
- Waste Management and Disposal