Application of atomic force microscopy to microbial surfaces: from reconstituted cell surface layers to living cells

The application of atomic force microscopy (AFM) to probe the ultrastructur e and physical properties of microbial cell surfaces is reviewed. The uniqu e capabilities of AFM can be summarized as follows: imaging surface topogra phy with (sub)nanometer lateral resolution; examining biological specimens under physiological conditions; measuring local properties and interaction forces. AFM is being used increasingly for: (i) visualizing the surface ult rastructure of microbial cell surface layers, including bacterial S-layers, purple membranes, porin OmpF crystals and fungal rodlet layers; (ii) monit oring conformational changes of individual membrane proteins; (iii) examini ng the morphology of bacterial biofilms, (iv) revealing the nanoscale struc ture of living microbial cells, including fungi, yeasts and bacteria, (v) m apping interaction forces at microbial surfaces, such as van der Waals and electrostatic forces, solvation forces, and steric/bridging forces; and (vi ) probing the local mechanical properties of cell surface layers and of sin gle cells. (C) 2000 Elsevier Science Ltd. All rights reserved.