A benzimidazole-based ruthenium(IV) complex inhibits Pseudomonas aeruginosa biofilm formation by interacting with siderophores and the cell envelope, and inducing oxidative stress

Abstract

Pseudomonas aeruginosa biofilm-associated infections are a serious medical problem, and new compounds and therapies acting through novel mechanisms are much needed. Herein, the authors report a ruthenium(IV) complex that reduces P. aeruginosa PAO1 biofilm formation by 84%, and alters biofilm morphology and the living-to-dead cell ratio at 1 mM concentration. Including the compound in the culture medium altered the pigments secreted by PAO1, and fluorescence spectra revealed a decrease in pyoverdine. Scanning electron microscopy showed that the ruthenium complex did not penetrate the bacterial cell wall, but accumulated on external cell structures. Fluorescence quenching experiments indicated strong binding of the ruthenium complex to both plasmid DNA and bovine serum albumin. Formamidopyrimidine DNA N-glycosylase (Fpg) protein digestion of plasmid DNA isolated after ruthenium(IV) complex treatment revealed the generation of oxidative stress, which was further proved by the observed upregulation of catalase and superoxide dismutase gene expression.

Keywords:

• Ruthenium complex
• biofilm
• benzimidazole
• Pseudomonas aeruginosa PAO1
• fluorescence quenching
• cell surface hydrophobicity

Acknowledgements

The authors would like to thank Karol Szary from the Division of Molecular Physics in Jan Kochanowski University for technical assistance with the confocal microscope.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was supported by BS/UJK – Jan Kochanowski Univeristy [grant no 612076]. Some of the experiments were run on apparatus purchased with EU grant 2.2 Innovation Industry. The potential utilisation of the complex presented herein has been patented under number PL228178.