Changes in mycoparasite-Fusarium hosts interfaces in response to hostile environment as revealed by water contact angle and atomic force microscopy

The aim of this study is to characterize the mycoparasitic attributes of fungal surface hydrophobicity and topography influenced by nutrient conditions and dryness in Sphaerodes-Fusarium dual culture assays. This study presents detailed methods to study fungal cell surface texture or roughness under atomic force microscopy (AFM) and hydrophobicity measured by water contact angle (WCA). The differential expression of the WCA depicted a hydrophilic nature of S. mycoparasitica mycoparasite compared to highly hydrophobic F. proliferatum and low hydrophobic F. redolens plant pathogens showing antagonistic and biotrophic interactions, respectively. A shift in WCA induced by potato dextrose agar (PDA) versus nitrogen rich synthetic-ICI medium greatly affected a level of mycoparasitism as measured by the changes in fungal radial growth. The AFM portrayed differential changes in cell wall topography with possible cell-cell adhesion when exposed to desiccation. These findings propose that changes in fungal cell wall topography and hydrophobicity may foster more/less conductive microenvironment for mycoparasitism as related to physicochemical properties of the fungus-fungus interfaces. Furthermore, hostile environment exposed to dryness and/or limited nutrient supply may dictate the effectiveness of the mycoparasite in controlling plant pathogenic Fusarium hosts.