| Abstract
| - Bacterial adhesion to substratum surfaces is determined by the combined action of a large number ofdifferent interactions, which have hitherto been inferred from macroscopic cell surface properties, suchas electrostatic double-layer forces, hydrophobic interactions, hydrogen bonding, and steric interactions.The origin of these interactions arises from a molecular level, but nevertheless they have always beenestimated from a macroscopic point of view. The macroscopic bacterial cell surface hydrophobicity, forinstance, is commonly inferred from water contact angles on bacterial lawns, and cell surface charge ismacroscopically determined by electrophoresis or titration methods. Although these macroscopic propertiesof bacteria have been demonstrated to correlate with bacterial adhesion of certain strains and species tosubstratum surfaces, a generalized physicochemical understanding of bacterial adhesion to surfaces doesnot yet exist. The introduction of the atomic force microscope (AFM) and its application to biologicalsurfaces has offered new possibilities to obtain microscopic, physicochemical properties of bacterial cellsurfaces. In this paper, a detailed analysis of the interaction forces between a silicon nitride AFM tip andthe surface of nine different oral bacterial strains, Streptococcus mitis, was carried out. Interestingly,microscopic features of force−distance curves could be amalgamated in such a way that relations betweenmicroscopic cell surface properties and macroscopic cell surface properties were obtained, even thoughthese relations were not fully understood.
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