The rodlet layer from aerial and submerged conidia of the entomopathogenic fungus Beauveria bassiana contains hydrophobin

The entomopathogenic fungus Beauveria bassiana produces aerial conidia, submerged conidia or blastospores depending on the culture conditions. Rodlets are observed on aerial and submerged conidia but not on blastospores. Cell wall rodlets were removed by sonication and the proteins dissolved with formic acid. A single major 9·7 kDa protein was found in rodlets of aerial and submerged conidia and showed N terminal sequence similarities to the hydrophobin class of fungal proteins. Hydrophobin could not be recovered from blastospores. Oxidation of the hydrophobin with performic acid produced a protein of higher molecular weight (14·0 kDa). The rodlet layer could not be removed from intact conidia by boiling in sodium dodecyl sulphate (SDS) but could be removed with formic acid. Formic acid treated conidia retained the ability to bind to insect cuticles and retained hydrophobicity as indicated by a phase exclusion assay.