THE EFFECTS OF FLUID CHEMISTRY ON STICKING EFFICIENCIES OF ENTEROCOCCUS FAECALIS USING ATOMIC FORCE MICROSCOPY

Sticking efficiency a is the probability of attachment of a particle to a collector and is a function of the interfacial potential energy between these surfaces at the nanoscale. In this study, the sticking efficiencies of live Enterococcus faecalis cells in different aqueous solutions were measured using atomic force microscopy (AFM). Individual bacterial cells were attached to chemically treated silicon nitride cantilevers and brought into contact with a silica glass collector surface in aqueous solution. Contact-mode AFM was used to measure the interaction forces with picoNewton resolution as the surfaces were moved together and subsequently separated at a controlled rate. Force versus distance curves were collected under variable solution pH and ionic strength to determine the dependence of bacterial sticking efficiency on solution chemistry. Intersurface potential energies were determined by integrating force data with respect to cell-collector separation distance and sticking efficiencies were calculated from potential energy using Spielman and Friedlander’s (1974) method. Results were compared with results of a previous study that measured the sticking efficiency of carboxylated polystyrene microspheres on a glass collector surface.