Probing molecular interactions and mechanical properties of microbial cellsurfaces by atomic force microscopy

Knowledge of the surface properties of microbial cells is a key to gain a d etailed understanding of their functions in the natural environment and to efficiently exploit them in biotechnological processes. In this paper, we p resent force-distance curves recorded. by atomic force microscopy (AFM) in aqueous solutions, on various microbial samples: reconstituted S-layers, wh ole fungal spores and several bacterial strains. The approach and retractio n curves exhibited important differences - depending on the type of microor ganism, on the physiological state (dormancy versus germination) and on the environmental conditions (ionic strength)- which were shown to reflect dif ferences in long-range surface forces. adhesion forces and mechanical prope rties. These data illustrate the great potential of AFM force measurements to elucidate the physical properties of microbial cells and to understand. at the molecular level, biointerfacial phenomena such as cell adhesion and cell aggregation. (C) 2001 Elsevier Science B.V. All rights reserved.