AVS 46th International Symposium
    Biomaterial Interfaces Group Tuesday Sessions
       Session BI-TuA

Paper BI-TuA7
Direct Probing of the Surface Ultrastructure and Molecular Interactions of Living Microbial Cells with Atomic Force Microscopy

Tuesday, October 26, 1999, 4:00 pm, Room 613/614

Session: Characterization of Biomaterial Interfaces
Presenter: Y.F. Dufrene, Universite Catholique de Louvain, Belgium
Authors: Y.F. Dufrene, Universite Catholique de Louvain, Belgium
C.J.P. Boonaert, Universite Catholique de Louvain, Belgium
P.G. Rouxhet, Universite Catholique de Louvain, Belgium
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Understanding biointerfacial phenomena such as cell aggregation and cell adhesion requires knowledge of the surface structure and physico-chemical properties of living cells with a nanometer scale resolution. In this work, atomic force microscopy (AFM) was used to determine, in physiological conditions, the ultrastructure and molecular interactions at the surface of living spores of Phanerochaete chrysosporium and their changes during germination. Cell immobilization was achieved by mechanical trapping in porous membranes. High-resolution images recorded on dormant spores showed that the surface was uniformly covered with a regular pattern of rodlets. These structures were several hundreds nm in length and had a periodicity of about 10 nm, in excellent agreement with freeze-etching characterization. Force-distance curves recorded between a silicon nitride probe and the spore surface showed no adhesion forces upon retraction. Dramatic changes of cell surface ultrastructure and molecular interactions occurred during germination. Germinating spores had a very smooth surface, partially covered with granular structures which were the residues of the rodlet layer. Force-distance curves recorded on smooth areas showed strong adhesion forces. These are attributed to binding of polysaccharides, which have been detected by X-ray photoelectron spectroscopy (XPS) and considered to be responsible for spore aggregation. The approach presented here offers new possibilities for probing the local surface properties of prokaryotic, animal and plant cells in the native state.