Ultrastructure and composition of the conidial wall of Cladosporium cladosporioides.

Transmission electron microscopy revealed that the conidial wall of Cladosporium cladosporioides was constituted of an electron-lucent inner layer and an electron-dense outer layer. The conidial surface is covered by rodlet fascicles which can be removed by ultrasonication. Ultrastructurally, the 100,000 X g ultracentrifugation pellet of the ultrasonicated extract containing the rodlet layer appeared as an amorphous structure containing probably internal wall material anchoring the rodlet fascicles on the wall. The total conidial wall was essentially composed of beta(1----3)glucans and melanin. Lipid, salt, and galactan represented the main components of the 100,000 X g ultracentrifugation pellet of the ultrasonicated extract. Cladosporium cladosporioides produced melanin via the pentaketide pathway. Tricyclazole inhibited melanin synthesis but did not interfere with allergen production. This suggests that the wall components associated with melanin are not allergenic factors.