The influence of copper and silver ions on Cupriavidus metallidurans biofilm formation and development

Abstract

Bacterial biofilm formation is a widely known problem for water storage and distribution systems since it often leads to recurring contamination and water spoilage. Cupriavidus metallidurans strains, such as NA4, have been discovered aboard the International Space Station (ISS). Their presence is notable, especially in water supplies, because of the absence of nutrients and the presence of water decontaminants such as silver. C. metallidurans, and in particular strain CH34, is mostly studied for its metal resistance. Both C. metallidurans CH34 and NA4 are able to form biofilms.

The aim of this Master's thesis was to study C. metallidurans biofilms in the presence of various concentrations of copper (Cu2+) and silver (Ag+), since these metal ions are frequently used as water disinfectants. Biofilm formation and development were studied in Lysogeny Broth (LB) medium and Tris-buffered (284) medium.

In order to determine the effect of silver and copper ions on biofilm formation and development; optical density (OD) measurements, crystal violet (CV) quantification, RNA extraction, and scanning electron microscopy (SEM) were carried out.

Attempts to evaluate the effect of Cu2+ and Ag+ on biofilms, have shown inconsistent results for LB medium. For 284 medium, more consistent data were obtained. RNA extraction of biofilms was performed, but further optimization of the RNA extraction protocol is needed. Furthermore, SEM visualised some interesting structural differences in CH34 and NA4 biofilm formation.