Staphylococcus is a major pathogen recognized as the most common cause of nosocomial infections, postoperative infections, and rejection of implants and other biomaterial-related devices. Capsules are a compact layer of polysaccharides extending from the cell wall of some bacteria. Capsulated bacteria are frequently associated with biofouling, serious invasive infections, and biofilm formation. The attachment kinetics of bacteria mutant strains Staphylococcus aureus Smith diffuse (SD) and Stophylococcus aureus Smith compact (SC) were measured under well-defined, laminar flow conditions using a parallel plate flow chamber. The attachment rate of capsule-free SC to a glass slide was approximately 2 orders of magnitude greater than that of encapsulated SD bacteria from which it was derived. Ancillary physicochemical characterization supports that this marked difference in adhesion is due to the absence of a capsule outside the cell wall of SC. Electrophoresis measurements showed no statistically significant difference in the cell surface charge of the two mutant strains. In addition, contact angle measurements showed little variation in hydrophobic character and suggested that both the encapsulated and capsule-deficient strains were hydrophilic. To further quantify the affect of extracellular capsule on the adhesion of the S. aureus mutants, optical tweezers in combination with evanescent wave light scattering was used to directly measure the interaction forces upon probing a single bacterium, toward a flat surface. The force-distance profile of SD suggests steric repulsion, while that of SC illustrates the overall attraction. Therefore, differences in deposition were most likely due to steric stabilization forces from the capsular polysaccharides. This study reports the premier direct measurement of biopolymer-induced interaction forces between a single, living bacterium and a surface under physiological conditions.