title: Statistical analysis of long- and short-range forces involved in bacterial adhesion to substratum surfaces as measured using atomic force microscopy.
abstract: Surface thermodynamic analyses of microbial adhesion using measured contact angles on solid substrata and microbial cell surfaces are widely employed to determine the nature of the adhesion forces, i.e., the interplay between Lifshitz-van der Waals and acid-base forces. While surface thermodynamic analyses are often viewed critically, atomic force microscopy (AFM) can also provide information on the nature of the adhesion forces by means of Poisson analysis of the measured forces. This review first presents a description of Poisson analysis and its underlying assumptions. The data available from the literature for different combinations of bacterial strains and substrata are then summarized, leading to the conclusion that bacterial adhesion to surfaces is generally dominated by short-range, attractive acid-base interactions, in combination with long-range, weaker Lifshitz-van der Waals forces. This is in line with the findings of surface thermodynamic analyses of bacterial adhesion. Comparison with single-molecule ligand-receptor forces from the literature suggests that the short-range-force contribution from Poisson analysis involves a discrete adhesive bacterial cell surface site rather than a single molecular force. The adhesion force arising from these cell surface sites and the number of sites available may differ from strain to strain. Force spectroscopy, however, involves the tedious task of identifying the minor peaks in the AFM retraction force-distance curve. This step can be avoided by carrying out Poisson analysis on the work of adhesion, which can also be derived from retraction force-distance curves. This newly proposed way of performing Poisson analysis confirms that multiple molecular bonds, rather than a single molecular bond, contribute to a discrete adhesive bacterial cell surface site.
authors.affiliation: W. J. Kolff Institute, Department of Biomedical Engineering, University Medical Center Groningen and University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands.
authors.forename: Yun
authors.initials: Y
authors.lastname: Chen
authors.forename: Henk J
authors.initials: HJ
authors.lastname: Busscher
authors.forename: Henny C
authors.initials: HC
authors.lastname: van der Mei
authors.forename: Willem
authors.initials: W
authors.lastname: Norde
mesh_terms: D001419:Bacteria / Q000378:metabolism / Q000648:ultrastructure; D001422:Bacterial Adhesion / Q000502:physiology*; D002462:Cell Membrane / Q000648:ultrastructure; D018625:Microscopy, Atomic Force / Q000379:methods*; D016012:Poisson Distribution; D013499:Surface Properties; D013816:Thermodynamics