QCM-D for non-destructive real-time assessment of Pseudomonas aeruginosa biofilm attachment to the substratum during biofilm growth

[Display omitted] •Biofilm growth resulted in positive frequency shifts in the QCM-D.•Growth of wild-type strain produced much larger frequency shifts than ΔpilA mutant.•QCM-D signals during growth could not be explained by differences in biomass alone.•TIRF indicates different mechanisms in the two...

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Veröffentlicht in:Colloids and surfaces, B, Biointerfaces B, Biointerfaces, 2015-12, Vol.136, p.928-934
Hauptverfasser: Olsson, Adam L.J., Mitzel, Michael R., Tufenkji, Nathalie
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Sprache:eng
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Zusammenfassung:[Display omitted] •Biofilm growth resulted in positive frequency shifts in the QCM-D.•Growth of wild-type strain produced much larger frequency shifts than ΔpilA mutant.•QCM-D signals during growth could not be explained by differences in biomass alone.•TIRF indicates different mechanisms in the two strains' surface approach.•QCM-D offers direct non-disruptive measurements of the biofilm/substratum interface. Quartz crystal microbalance with dissipation monitoring (QCM-D) was used to investigate initial adhesion and subsequent biofilm growth of wild-type Pseudomonas aeruginosa PAO1 and a pili-deficient (ΔpilA) mutant PAO1 strain. Clean, sterilized, silica-coated QCM-D crystals were pre-coated with lysogeny broth (LB), seeded with a PAO1 strain and allowed to grow for 20h at 37°C in fresh LB injected at 100μL/min. QCM-D signals obtained for the wild-type PAO1 strain during the seeding period depict a large positive frequency shift that returns to baseline after ∼20min that is absent in the ΔpilA mutants, suggesting a dynamic pili-mediated attachment event for the wild-type PAO1 strain. During the subsequent growth period, significant and characteristic differences in the acquired QCM-D signals were observed between the wild-type and the ΔpilA mutant. Confocal laser scanning microscopy (CLSM) of the biofilm on the crystal surface showed that these differences could not be explained by differences in the extent of biofilm growth alone. When interpreted according to a coupled resonance model, the QCM-D observations suggest that pili are essential for coupling the developing biomass to the sensor surface. Total internal reflection fluorescence microscopy (TIRF) supports the hypothesis that the characteristic QCM-D signal is indicative of a dynamic attachment event, mediated by pili cell surface appendages pulling the wild-type PAO1 closer to the surface during the seeding period. We show that QCM-D offers direct, non-disruptive, in situ measurements of biofilm-substrate attachment. This technique has the potential to improve the current understanding of biofilm formation phenomena.
ISSN:0927-7765
1873-4367
DOI:10.1016/j.colsurfb.2015.10.032