Relationships between fungal spore morphologies and surface properties forentomopathogenic members of the genera Beauveria, Metarhizium, Paecilomyces,Tolypocladium, and Verticillium

The surface properties of aerial conidia (AC) from 24 strains of entomopath ogenic fungi were studied and compared using the salt-mediated aggregation and sedimentation (SAS) assay, electron microscopy, FITC-labelled lectins, and spore dimensions. Spores with rugose surfaces were hydrophobic, whereas hydrophilic spores had smooth surfaces. Correlation analysis found no link between spore dimensions and either hydrophobicity or surface carbohydrate s. However, there was a strong positive correlation between spore hydrophob icity and surface carbohydrates. The three spore types of Beauveria bassian a were all shown to possess discrete surface hydrophobicities, which were a lso strongly linked to surface carbohydrate profiles. Various chemical trea tments had pronounced effects on spore surface properties, with sodium dode cyl sulfate (SDS) and formic acid (FA) reducing both lectin binding and sur face hydrophobicity. When FA-protein extracts were separated and analysed u sing SDS-PAGE, only the hydrophobic spores had low molecular weight hydroph obin-like peptides that were unglycosylated and contained disulfide bonds. The strains with hydrophilic AC had much lower levels of FA-extractable pro tein per spore dry weight compared to their more hydrophobic counterparts. Moreover, extracts of the more hydrophobic spores tended to have greater pr otein:carbohydrate ratios.