Our new paper on silver nanoparticle toxicity on environmental bacteria is now available online. It is published in the Journal of Microbiology, Immunology and Infection (Elsevier). Read the article here.

Abstract

Background/Purposes

Silver nanoparticles (AgNPs) are currently important in various industrial applications. However, the impact upon their release into the environment on the microorganisms remains unclear. The aim of this study was to analyse the effect of polyvinylpyrrolidone (PVP)-capped AgNPs synthesized in this lab on two bacterial strains isolated from the environment; Gram-negative Citrobacter sp. A1 and Gram-positive Enterococcus sp. C1.

Methods

PVP-capped AgNPs were synthesized by ultrasound-assisted chemical reduction. Characterization of the AgNPs involved UV-Visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, and energy dispersive X-ray spectroscopy. Citrobacter sp. A1 and Enterococcus sp. C1 were exposed to varying concentrations of AgNPs and cell viability determined. Scanning electron microscopy was done to evaluate the morphological alteration on both species upon exposure to AgNPs at 1000 mg/L.

Results

AgNPs synthesized were spherical in shape with an average particle size of 15 nm. The AgNPs had different but prominent effects on either Citrobacter sp. A1 or Enterococcussp. C1. At 1000 mg/L AgNPs, Citrobacter sp. A1 retained viability for 6 h while Enterococcus sp. C1 only 3 h. Citrobacter sp. A1 appeared to be more resistant to AgNPs than Enterococcus sp. C1. The cell wall of both strains was found to be morphologically altered at that concentration.

Conclusions

Minute and spherical AgNPs significantly affected the viability of the two bacterial strains selected from the environment. Enterococcus sp. C1 was more vulnerable to AgNPs, probably due to its cell wall architecture and the absence of silver resistance-related genes.