Cohesion is a primary factor affecting the balance between growth and detachment of biofilms. Thus the quantification of cohesion is essential to understanding, predicting and modeling biofilm development, whether on medical implants or waste water treatment media. But cohesion is one of the most difficult material properties to measure. Fundamentally the quantity has units of energy per unit volume; but it is more commonly measured as yield force per unit area, using custom tools.  In this work we developed an AFM methodology for reproducibly measuring, in situ, the cohesive energy density of moist biofilms.Thick biofilms were grown from activated sludge. The thin volume of biofilm displaced by abrasive raster scanning, and the frictional energy dissipation necessary to produce this abrasion, provided a measurement of cohesive energy density. This quantity reproducibly increases with calcium and polysaccharide concentration, as well as biofilm depth (from different macro-slices, as grown on aerated membranes).

AFM-based tribology as a probe of biofilm cohesion

244th National Meeting (2012)

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