Experimental Evolution of Magnetite Nanoparticle Resistance in Escherichia coli

Akamu J Ewunkem; LaShunta Rodgers; Daisha Campbell; Constance Staley; Kiran Subedi; Sada Boyd; Joseph L Graves Jr

doi:10.3390/nano11030790

Experimental Evolution of Magnetite Nanoparticle Resistance in Escherichia coli

Nanomaterials (Basel). 2021 Mar 19;11(3):790. doi: 10.3390/nano11030790.

Authors

Akamu J Ewunkem¹, LaShunta Rodgers², Daisha Campbell³, Constance Staley⁴, Kiran Subedi⁵, Sada Boyd⁶, Joseph L Graves Jr⁷

Affiliations

¹ Department of Nanoscience, University of North Carolina at Greensboro, Greensboro, NC 27401, USA.
² Department of Biology, University of North Carolina at Greensboro, Greensboro, NC 27412, USA.
³ Department of Chemical, Biological, and Bioengineering, North Carolina A&T State University, Greensboro, NC 27411, USA.
⁴ Department of Chemistry, Bennett College, Greensboro, NC 27401, USA.
⁵ College of Agricultural and Environmental Sciences (CAES), North Carolina A&T State University, Greensboro, NC 27411, USA.
⁶ Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095, USA.
⁷ Department of Biology, North Carolina A&T State University, Greensboro, NC 27411, USA.

Abstract

Both ionic and nanoparticle iron have been proposed as materials to control multidrug-resistant (MDR) bacteria. However, the potential bacteria to evolve resistance to nanoparticle bacteria remains unexplored. To this end, experimental evolution was utilized to produce five magnetite nanoparticle-resistant (FeNP_1-5) populations of Escherichia coli. The control populations were not exposed to magnetite nanoparticles. The 24-h growth of these replicates was evaluated in the presence of increasing concentrations magnetite NPs as well as other ionic metals (gallium III, iron II, iron III, and silver I) and antibiotics (ampicillin, chloramphenicol, rifampicin, sulfanilamide, and tetracycline). Scanning electron microscopy was utilized to determine cell size and shape in response to magnetite nanoparticle selection. Whole genome sequencing was carried out to determine if any genomic changes resulted from magnetite nanoparticle resistance. After 25 days of selection, magnetite resistance was evident in the FeNP treatment. The FeNP populations also showed a highly significantly (p < 0.0001) greater 24-h growth as measured by optical density in metals (Fe (II), Fe (III), Ga (III), Ag, and Cu II) as well as antibiotics (ampicillin, chloramphenicol, rifampicin, sulfanilamide, and tetracycline). The FeNP-resistant populations also showed a significantly greater cell length compared to controls (p < 0.001). Genomic analysis of FeNP identified both polymorphisms and hard selective sweeps in the RNA polymerase genes rpoA, rpoB, and rpoC. Collectively, our results show that E. coli can rapidly evolve resistance to magnetite nanoparticles and that this result is correlated resistances to other metals and antibiotics. There were also changes in cell morphology resulting from adaptation to magnetite NPs. Thus, the various applications of magnetite nanoparticles could result in unanticipated changes in resistance to both metal and antibiotics.

Keywords: Escherichia coli; antibiotics; cell morphology; genomics; magnetite nanoparticles; metals; pleiotropy.

Abstract

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