Assessment of Elasticity and Topography of Aspergillus nidulans Spores via Atomic Force Microscopy
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2004-09-27
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Liming Zhao, David Schaefer, Mark R. Marten, Assessment of Elasticity and Topography of Aspergillus nidulans Spores via Atomic Force Microscopy, Applied and Environmental Microbiology, p. 955–960, 2005 , DOI: 10.1128/AEM.71.2.955-960.2005
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Abstract
Previous studies have described both surface morphology and adhesive properties of fungal spores, but little
information is currently available on their mechanical properties. In this study, atomic force microscopy
(AFM) was used to investigate both surface topography and micromechanical properties of Aspergillus nidulans
spores. To assess the influence of proteins covering the spore surface, wild-type spores were compared with
spores from isogenic rodA⁺ and rodA⁻ strains. Tapping-mode AFM images of wild-type and rodA⁺ spores in
air showed characteristic “rodlet” protein structures covering a granular spore surface. In comparison, rodA
spores were rodlet free but showed a granular surface structure similar to that of the wild-type and rodA⁺
spores. Rodlets were removed from rodA⁺ spores by sonication, uncovering the underlying granular layer. Both
rodlet-covered and rodlet-free spores were subjected to nanoindentation measurements, conducted in air,
which showed the stiffnesses to be 110 ± 10, 120 ± 10, and 300 ± 20 N/m and the elastic moduli to be 6.6 ±
0.4, 7.0 ± 0.7, and 22 ± 2 GPa for wild-type, rodA⁺ and rodA⁻ spores, respectively. These results imply the
rodlet layer is significantly softer than the underlying portion of the cell wall.