MOLECULAR DETERMINANTS OF BACTERIAL ADHESION MONITORED BY ATOMIC-FORCE MICROSCOPY

Bacterial adhesion and the subsequent formation of biofilm are major c oncerns in biotechnology and medicine. The initial step in bacterial a dhesion is the interaction of cells with a surface, a process governed by long-range forces, primarily van der Waals and electrostatic inter actions. The precise manner in which the force of interaction is affec ted by cell surface components and by the physiochemical properties of materials is not well understood. Here, we show that atomic force mic roscopy can be used to analyze the initial events in bacterial adhesio n with unprecedented resolution. Interactions between the cantilever t ip and confluent monolayers of isogenic strains of Escherichia coli mu tants exhibiting subtle differences in cell surface composition were m easured. It was shown that the adhesion force is affected by the lengt h of core lipopolysaccharide molecules on the E. coli cell surface and by the production of the capsular polysaccharide, colanic acid. Furth ermore, by modifying the atomic force microscope tip we developed a me thod for determining whether bacteria are attracted or repelled by vir tually any biomaterial elf interest. This information will be critical for the design of materials that are resistant to bacterial adhesion.