Direct probing of the surface ultrastructure and molecular interactions ofdormant and germinating spores of Phanerochaete chrysosporium

Atomic force microscopy (AFM) has been used to probe, under physiological c onditions, the surface ultrastructure and molecular interactions of spores of the filamentous fungus Phanerochaete chrysosporium. High-resolution imag es revealed that the surface of dormant spores was uniformly covered with r odlets having a periodicity of 10 +/- 1 nm, which is in agreement with earl ier freeze-etching measurements. In contrast, germinating spores had a very smooth surface partially covered with rough granular structures. Force dis tance curve measurements demonstrated that the changes in spore surface ult rastructure during germination are correlated with profound modifications o f molecular interactions: while dormant spores showed no adhesion with the AFM probe, germinating spores exhibited strong adhesion forces, of 9 +/- 2 nN magnitude. These forces are attributed to polysaccharide binding and sug gested to be responsible for spore aggregation. This study represents the f irst direct characterization of the surface ultrastructure and molecular in teractions of living fungal spores at the nanometer scale and offers new pr ospects for mapping microbial cell surface properties under native conditio ns.