Atomic force microscopy study of the adhesion of Saccharomyces cerevisiae

An atomic force microscope (AFM) has been used to quantify directly the adh esion of metabolically active Saccharomyces cerevisiae cells at a hydrophil ic mica surface, a mica surface with a hydrophobic coating, and a protein-c oated mica surface in an aqueous environment. The measurements used "cell p robes" constructed by immobilizing a single cell at the apex of a tipless A FM cantilever. Adhesion was quantified from force-distance data for the ret raction of the cell from the surface. The data indicated stretching and seq uential bond-breaking as the cell probe was retracted from all of the surfa ces. Detailed studies were made for physiologically active cells, which wer e shown to have different adhesion properties to glutaraldehyde-treated cel ls. Greatest cell adhesion was measured at the hydrophobic surface. Prior a dsorption of a bovine serum albumin protein layer at the hydrophilic surfac e did not significantly affect cell adhesion. Changes in yeast surface hydr ophobicity and zeta-potential with yeast cell age were correlated with diff erences in adhesion. Cells from the stationary phase adhered most strongly to a mica surface. Time of surface contact was demonstrated to be important . Both the force needed to detach a cell from a hydrophilic mica surface an d the length of the adhesive interaction increased after 5 min contact. The AFM cell probe technique gives unique insights into primary colonization e vents in biofilm formation. It will continue to aid both fundamental studie s and the assessment of new procedures that are designed to lower cell adhe sion at surfaces relevant to biotechnology, medicine, and dentistry. (C) 20 01 Academic Press.