Testing nanoeffect onto model bacteria: Impact of speciation and genotypes

Abstract

The gram-negative bacteria Escherichia coli (E. coli) is a very useful prokaryotic model for testing the toxicity of ZnO nanoparticles (nano-ZnO). This toxicity is often linked to Zn²⁺ released from nanoparticles in the culture medium, and nano-ZnO dissolution in different media is clearly established. Here, two model E. coli strains MG1655 and W3110 both descendant from the original K-12 showing slight differences in their genome were submitted to nano-ZnO or Zn²⁺ in order 1 > to refine the nano-ZnO toxicity mechanisms to E. coli, and 2 > to investigate whether toxicity resulted from a real “nanoparticle” effect or from the release of Zn²⁺ in solution. To do so, both strains were submitted to various concentrations (i.e., 0.1–1 mM) of nano-ZnO or Zn²⁺ in Luria Bertani (LB) medium. These toxicity studies take into account the nano-ZnO solubility in the culture medium by specifically monitoring the Zn²⁺ release in our experimental systems. In our experimental conditions, differences in tolerance to nano-ZnO or Zn²⁺ between both strains were clearly evidenced. W3110 is generally more tolerant to metal than MG1655, the latter showing no real difference in its sensitivity to the two zinc added forms unlike W3110. The differences in behavior between both strains could be attributed to differences in the two genomes as a mutation named “amber” in W3110. Moreover, by using these two closely E. coli strains, a real “nano” effect is here clearly demonstrated providing a model to study the toxicity of ZnO nanoparticles.

• Antibacterial
• Escherichia coli K12
• gram negative bacteria
• metal oxides
• MG1655
• nanoparticles
• W3110
• ZnO

Acknowledgements

The authors are grateful to Dr Sam Dukan (UMR CNRS 9043 Marseille France) and Dr Christopher Rensing (University of Arizona, USA) who kindly provided the strains Escherichia coli MG1655 and W3110, respectively. Dr Danièle Josseleau-Petit, Pr Philippe Silar are thanked for their strong support during the preparation of this manuscript. Dr Anne Badel and Pr Anne-Claude Camproux are thanked for their help for the careful statistical analysis of the data. We are also grateful to two anonymous reviewers whose insight and thorough reviews greatly improve the manuscript.

Declaration of interest

This work was supported by the Grant APR Environnement Santé Travail-07-28 of the AFSSET, by the French National program ACI-ECCO, and by the region Ile de France.

Supplementary information Supplementary Sections iii–v and Figure S1A, S2 and S3, Table 3-5.