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We aim to establish the effect of environmental diversity in evaluating nanotoxicity to bacteria. We assessed the toxicity of 4 nm polyallylamine hydrochloride-wrapped gold nanoparticles (PAH AuNPs) to a panel of bacteria from diverse environmental niches. The bacteria experienced a range of toxicities as evidenced by the different minimum bactericidal concentrations determined; the sensitivities of the bacteria was A. vinelandii = P. aeruginosa > S. oneidensis MR-4 > A. baylyi > S. oneidensis MR-1. Interactions between gold nanoparticles and molecular components of the cell wall were investigated by TEM, flow cytometry, and computational modeling. Binding results showed a general trend that bacteria with smooth lipopolysaccharides (LPS) bind more PAH AuNPs than bacteria with rough LPS. Computational models reveal that PAH migrates to phosphate groups in the core of the LPS structure. Overall, our results demonstrate that simple interactions between nanoparticles and the bacterial cell wall cannot fully account for observed trends in toxicity, which points to the importance of establishing more comprehensive approaches for modeling environmental nanotoxicity.
Bibliographical noteFunding Information:
This work was supported by the National Science Foundation under the Center for Sustainable Nanotechnology, CHE-1503408. J. T. B. was supported by the University of Minnesota Biotechnology Training Grant Program through the National Institutes of Health under grant number 5 T32 GM 8347-24. K. M. L. was supported by a University of Minnesota UROP award. We are grateful to Tian (Autumn) Qiu for her work with the fluorescamine assay. The authors gratefully acknowledge Dr. Michael P. Schwartz, Dr. Joel A. Pedersen, and Dr. Franz M. Geiger for helpful discussion. The TEM work in this study was carried out in the Characterization Facility, University of Minnesota, which receives partial support from NSF through the MRSEC program. We thank Fang Zhou for microtome sectioning of the resin-embedded bacteria samples for TEM analysis. The authors are grateful for the University of Minnesota's University Flow Cytometry Resource for flow cytometric analysis. The computing resources necessary for this research were provided in part by the National Science Foundation through XSEDE resources on Bridges under grant number TG-CTS090079. Additional computing resources were provided by the Maryland Advanced Research Computing Center (MARCC).
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