A Dual Rheometer-Microscope Instrument for the Quantitative Characterization of Bacterial Biofilms

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It is currently estimated that 80% of the planet's bacteria live in communities inside biofilms - a medium comprised of exopolysaccharides, DNA, proteins and various small molecules. A biofilm is a mechanically robust material that surrounds and protects the bacteria from the external world. As a result, these bacteria are generally more resistant or tolerant to antibiotics and disinfectants. The development of biofilms on medical devices, such as catheter and implants, and in living tissues, now poses some important issues, since intensive and prolonged treatments with antibiotics still often lead to treatment failure, and higher morbidity and mortality rates - this is a worldwide issue that still needs the development of efficient solutions. Biofilms also have useful properties, for example in the development of treatment processes for water and wastewater. Biofilm flocs allow the suspension of bacteria in the medium, or their adherence to inert supports onto which the biomass develops. As a result, understanding and controlling the properties of biofilms is of critical importance in these areas of research. Very recently, both interfacial and bulk rheology have been introduced as techniques to monitor quantitatively the viscoelastic properties of bacterial biofilms, which are directly related to the stability of the film. The commercial rheometer that we request in this proposal will be equipped with interfacial geometries, along with other various bulk measurement geometries, that will allow time-resolved, quantitative measurements of biofilms' viscoelastic properties, with a fluorescence microscope allowing microstructure and composition analyses. Previous work has demonstrated that this technique is particularly sensitive to biofilm composition, which can be controlled by gene knockout and by the external environment - temperature, composition of the media, etc. Since time-resolved measurements will be possible, quantifying the effects of perturbations, such as the addition of antibiotics, on the viscoelastic, microstructural and composition properties of biofilms will be possible. Finally, the installation of the rheometer in a Biosafety level 2 laboratory will allow the study of pathological strains such as Salmonella - a unique configuration in Canada. This original multidisciplinary program is a first collaboration between seven co-applicants and 4 collaborators with complementary expertises, including rheology, bacterial microbiology, interfacial science, water/wastewater treatment processes, veterinary medecine, and pediatrics, from Polytechnique Montreal, Université de Montréal, INRS Institut Armand-Frappier, and Stanford University.