CELL-WALL PROTEIN AND GLYCOPROTEIN CONSTITUENTS OF ASPERGILLUS-FUMIGATUS THAT BIND TO POLYSTYRENE MAY BE RESPONSIBLE FOR THE CELL-SURFACE HYDROPHOBICITY OF THE MYCELIUM

Cell surface hydrophobicity (C5H) of Aspergillus fumigatus grown both in complex medium (yeast extract/peptone/dextrose;YPD) and minimal (Vo gel's N) medium was monitored by assessing attachment of polystyrene m icrospheres to the cell surface. It was found that mature mycelium was hydrophobic, Treatment of intact mycelium with beta-mercaptoethanol ( beta ME) abolished binding of the microspheres to hyphal elements, and coating of the microspheres with beta ME extracts from mycelium inhib ited their attachment to intact mycelial cells, A, fumigatus mycelium was tagged in vivo with biotin and treated with beta ME, The beta ME e xtracts were analysed by SDS-PAGE and Western blotting with both perox idase-conjugated-ExtrAvidin and concanavalin A (ConA). This procedure allowed identification of cell wall surface proteins and glycoproteins . Rabbit polyclonal antisera were raised against beta ME extracts obta ined from cells grown in YPD and Vogel's N media. These antisera defin ed some major cell-wall-bound antigens, SDS-PAGE and Western blotting analysis of the cell wall material released by beta ME and adsorbed on polystyrene microspheres revealed about 19 protein species with appar ent molecular masses ranging from 20 to 70 kDa, and two high-molecular -mass glycoproteins of 115 and 210 kDa. Treatment of cells grown in YP D, but not those grown in Vogel's N medium, with beta ME released a 55 kDa polypeptide able to adsorb to polystyrene microspheres that was d etectable with the antisera, The ability to bind to polystyrene partic les exhibited by several protein and glycoprotein species released by beta ME treatment suggested that these cell wall moieties possess expo sed hydrophobic domains that could be responsible for the CSH of mycel ium.