Structure and chemical composition of the cell walls from the haploid yeast and mycelial forms of Ustilago maydis.

Isolated or in vivo cell walls from the yeast and mycelial forms of haploid Ustilago maydis were not stained by the normal osmium procedure for electron microscopy. KMnO4 stained mycelial walls, revealing a layered structure with a loose electron-dense layer at the cell surface, but stained only the outer surface layer of yeast walls. Walls were purified from extracts obtained by ballistic and ultrasonic disruption. Chemical analysis showed that composition of yeast and mycelial walls was similar. Yeast walls contained higher amounts of neutral sugars and protein, whereas mycelial walls contained more chitin and phosphate. No chitosan or uronic acids were detected. Higher proportions of xylose and mannose were present in yeast walls, whereas the amounts of glucose and galactose were higher in mycelial walls. Fucose, arabinose, and ribose were detected in yeast walls only. Electrophoretic patterns of proteins extracted with SDS, beta 1, 3-glucanase, or chitinase were similar in walls of both morphologies, although some differential bands were identified. Most antigenic proteins appeared in the covalently bound fraction of the wall. Some were common to both morphologies, but others were stage specific.