Seminar über aktuelle Fragen zur Dynamik komplexer Fluide: Quantitative Imaging of E. coli Biofilms Reveals Heterogeneity within localized regions of the Extracellular Polymeric Substances
10:15 - 11:15
- University of Toronto, Canada
Max-Planck-Institut für Dynamik und Selbstorganisation (MPIDS)
Bacteria in adhesive contact with surfaces secrete a conglomeration of various sticky substances, which surround and glue cells together, creating intricate communities of bacterial biofilms. These extracellular polymeric substances (EPS) provide the three-dimensional structural stability in biofilms, mediate substrate adhesion, serves as reservoir of nutrients, and allows for information exchange in between cells, among other functions. These functionalities of the EPS contribute significantly to severe implications caused by biofilms in biomedical settings. Despite the crucial role EPS fulfill in development and maturation of a biofilm, little is known about the physical parameters that dictate the glue’s morphology and nanomechanics (stability, elasticity, adhesivity). To this day, quantitative imaging of biofilms has been elusive due to their inherent complexity. Consequently, the microscopic morphology of the biofilm at the experimental location remains unclear and a correlation between the structure of the EPS and its physical parameters is difficult to acquire.
Here we present a robust and quantitative protocol that allows for simultaneous imaging of E. coli biofilm morphology and nanomechanical properties with atomic force microscopy on length scales below the size of individual bacteria. Along with our experimental methodology, we developed an analysis algorithm based on linearized Hertzian contact mechanics that allows for extraction of the biofilms’ nanomechanical properties, reproducibly. The algorithm allows for detecting the EPS layer covering the bacteria and to extract its elasticity (Young’s modulus). As such, we are able to unravel properties of the EPS alone, separate from the bacteria it covers, and we provide direct evidence of EPS heterogeneities, which are not evident on topography images alone. These toolkits enable us to directly study the effects of drugs on the nanomechanical properties of the biofilm and its individual components.