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Applied and Environmental Microbiology, February 2005, p. 955-960, Vol. 71, No. 2
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.2.955-960.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Assessment of Elasticity and Topography of Aspergillus nidulans Spores via Atomic Force Microscopy

Liming Zhao,¹ David Schaefer,² and Mark R. Marten^1*

Department of Chemical and Biochemical Engineering, University of Maryland, Baltimore County (UMBC), Baltimore,¹ Department of Physics, Astronomy, and Geosciences, Towson University, Towson, Maryland²

Received 11 August 2004/ Accepted 27 September 2004

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.

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* Corresponding author. Mailing address: Department of Chemical and Biochemical Engineering, University of Maryland, Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250. Phone: (410) 455-3439. Fax: (410) 455-1049. E-mail: marten{at}umbc.edu.

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Applied and Environmental Microbiology, February 2005, p. 955-960, Vol. 71, No. 2
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.2.955-960.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

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