Chemical composition and ultrastructure of wild-type and white mutantAspergillus nidulans conidial walls

Abstract

Conidial walls of wild-type and white mutantAspergillus nidulans were purified. Chemical analysis showed that the conidial wall of the wild-type strain contained neutral carbohydrate, protein, chitin, melanin, and small amounts of lipid. The neutral sugars were glucose, galactose, and mannose. Chemical fractionation experiments indicated the presence of α-1,3-glucan in the wild-type conidial wall. The conidial wall of the white mutant strain lacked melanin and α-1,3-glucan, and contained twice as much galactose as that of the wild-type strain. The protein(s) of the white mutant wall contained fifteen amino acids. Transmission electron microscopy showed that the wild-type conidial wall was composed of an electron-dense outer layer, irregular in thickness and containing the α-1,3-glucan, an electron-translucent middle layer, and a thin inner layer intimately associated with the plasma membrane. Conidial walls of the white mutant strain lacked the electron-dense outer layer.