Use of Single-Frequency Impedance Spectroscopy to Characterize the Growth Dynamics of Biofilm Formation in Pseudomonas aeruginosa
Jozef B. J. H. van Duurena b, Mathias Müskenc d, Bianka Kargea, Jürgen Tomasche, Christoph Wittmannb, Susanne Häußlerc d, Mark Brönstrupf g h✉
- aDepartment of Chemical Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
- bInstitute of Systems Biotechnology, Saarland University, Saarbrücken, Germany
- cDepartment of Molecular Bacteriology, Helmholtz Centre for Infection Research, Braunschweig, Germany
- dInstitute for Molecular Bacteriology, TWINCORE, Centre for Experimental and Clinical Infection Research, Hannover, Germany
- eGroup Microbial Communication, Helmholtz Centre for Infection Research, Braunschweig, Germany
- fDepartment of Chemical Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany. mark.broenstrup@helmholtz-hzi.de
- gGerman Centre for Infection Research (DZIF), Site Hannover Braunschweig, Braunschweig, Germany. mark.broenstrup@helmholtz-hzi.de
- hGerman Centre for Infection Research (DZIF), Site Hannover Braunschweig, Braunschweig, Germany
- ✉Corresponding author
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Abstract
Impedance spectroscopy has been applied in prokaryotic and eukaryotic cytometry as a label-free method for the investigation of adherent cells. In this paper, its use for characterizing the growth dynamics of P. aeruginosa biofilms is described and compared to crystal violet staining and confocal microscopy. The method allows monitoring the growth of biofilm-forming P. aeruginosa in a continuous and label-free manner over a period of 72 h in a 96 well plate format. Impedance curves obtained for P. aeruginosa PA14 wild type and mutant strains with a transposon insertion in pqsA and pelA genes exhibited distinct phases. We propose that the slope of the declining curve following a maximum at ca. 35-40 h is a measure of biofilm formation. Transplant experiments with P. aeruginosa biofilms and paraffin suggest that the impedance also reflects pellicle formation at the liquid-air interface, a barely considered contributor to impedance. Finally, the impairment of biofilm formation upon treatment of cultures with L-arginine and with ciprofloxacin, tobramycin and meropenem was studied by single frequency impedance spectroscopy. We suggest that these findings qualify impedance spectroscopy as an additional technique to characterize biofilm formation and its modulation by small molecule drugs.