Elastic Properties of Aspergillus nidulans Studied with Atomic Force Microscopy

Abstract

An atomic force microscopy (AFM) was used as a nanoindentor to measure cell wall mechanical properties of the model fungus Aspergillus nidulans in both hyphal and spore forms. Hyphae and spores were immobilized on polylysine-coated cover slips and AFM was used to investigate surface topography and to obtain force-displacement curves. For fungal hyphae the nanoindentation data were compared to finite element analysis (FEMLAB v3.0, Burlington MA) to simulate AFM indentation because no suitable analytical models were available. The elastic modulus of wild type hyphae grown in complete medium was determined to be 110 ± 10 MPa. This decreased to 64 ± 4 MPa when grown in 0.6 M KCl, implying growth medium osmotic conditions have significant effects on cell wall elasticity. These values are comparable with other microbial systems (e.g., yeast and bacteria). Comparisons with a mutant strain (DcsmA) further indicate that the differences in mechanical properties may be dependent on varying molecular structure of hyphal cell walls as opposed to wall composition.