Predicting the chemical composition and structure of Aspergillus nidulans hyphal wall surface by atomic force microscopy

In fungi, cell wall plays an important role in growth and development. Major macromolecular constituents of the aspergilli cell wall are glucan, chitin, and protein. We examined the chemical composition and structure of the Aspergillus nidulans hyphal wall surface by an atomic force microscope (AFM). To determine the composition of the cell wall surface, the adhesion forces of commercially available β-glucan, chitin, and various proteins were compared to those of corresponding fractions prepared from the hyphal wall. In both setups, the adhesion forces of β-glucan, chitin, and protein were 25–50, 1000–3000, and 125–300 nN, respectively. Adhesion force analysis demonstrated that the cell surface of the apical tip region might contain primarily chitin and β-glucan and relatively a little protein. This analysis also showed the chemical composition of the hyphal surface of the mid-region would be different from that of the apical region. Morphological images obtained by the tapping mode of AFM revealed that the hyphal tip surface has moderate roughness.