The Fungal Wall

Functions :
  • PROTECTS the underlying protoplasm;
  • determines and MAINTAINS THE SHAPE of the fungal cell or hypha; if you remove the wall the resulting protoplast will always assume a spherical shape;
  • acts as an INTERFACE between the fungus and its environment;
  • acts as a BINDING SITE for some enzymes;
  • possesses ANTIGENIC properties - which allow interactions with other organisms.
Chemical composition of the wall:
  • POLYMERIC FIBRILS
    • chitin
    • cellulose (in the Oomycota)
  • AMORPHOUS MATRIX COMPONENTS
    • glucans
    • proteins
    • lipids
    • heteropolymers (mixed polymers) of mannose, galactose, fucose and xylose
  • The types and amounts of these various components vary amongst different groups of fungi and may even vary during the life cycle of a single species.
Arrangement of the wall components:
Diagram illustrating the arrangement of wall components.
  • The diagram above represents a section through the mature lateral wall of hyphae of Neurospora crassa.
  • In general, the inner part of the wall consists of POLYMERIC FIBRILS embedded in an AMORPHOUS MATRIX and this is covered by further layers of matrix material.
  • At the HYPHAL TIP the wall is thinner and simpler in structure, consisting of only TWO LAYERS - an inner layer of fibrils embedded in protein and outer layer of mainly protein.
  • EXTRA LAYERS of wall material are deposited in the lateral walls behind the extending apex - strengthening the wall as the hypha matures.
  • In the oldest parts of the hyphae (and in many fungal spores) LIPIDS and PIGMENTS may be desposited in the wall:
    • LIPIDS serve as a nutrient reserve and help prevent desiccation
    • PIGMENTS, such as MELANIN, help protect the protoplast against the damaging effects of UV radiation.
  • N.B. Although represented as distinct layers in the diagram above, these four zones merge into one another.

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