A novel atomic force microscopy-based single-cell force spectroscopy assay to quantify the adhesion of bacterial cells to surfaces was developed. The assay was applied to quantify the effect of two biofilm-degrading enzymes, the protease Subtilisin A and glycoside hydrolase cellulase, on the attachment of the biofilm-forming bacterial strain Cobetia marina. Insights on the mechanism of the initial adhesion and on the nature of the adhesion-mediating molecules were gained. The assay can be easily adapted to various other substrates, different bacterial strains and other fouling species (e.g., algae and diatoms).