Cell wall of Fusarium sulphureum. II. Chemical composition of the conidial and chlamydospore walls.

Abstract

Examination of the conidial and chlamydospore walls of Fusarium sulphureum by electron microscopy showed the presence of two distinct layers of differing electron densities. These include a relatively narrow outer electron-dense layer and a broader more transparent inner layer. Both chlamydospore cell wall layers were thicker than the conidial wall. The outer wall of the chlamydospore wall was 30% thicker while the inner cell wall layer was 250% thicker than the corresponding cell wall layers in the conidia. During conidial differentiation to form chlamydospores there was a considerable augmentation of all cell wall components which varied from 7 to 26-fold per cell. The augmentation of the major cell wall constituents (N-acetylglucoseamine (NAG), glucose, and protein) and the vast increase in the inner cell wall of the chlamydospore wall indicated that these newly synthesized constituents are predominently located in the inner cell wall layer.The major carbohydrate constituents on a dry weight basis in both the conidial and chlamydospore walls were glucose, glucuronic acid, and N-acetylglycosamine (NAG). However, the proportion of these and the other carbohydrate constituents were different for both spore walls. Thus, the conidial wall contained about 50% less NAG and glucuronic acid but twice the glucose content of the chlamydospore wall. Protein was a major component of both spore walls (21.6%, conidial wall; 28.5%, chlamydospore wall). Amino acid analysis indicated differences in the types of protein present in the two spore walls. The lipid content of both conidia and chlamydospore was low (1–2%).