Cell Wall ofAspergillus fumigatus: a Dynamic Structure

Abstract

The cell wall is an essential extracellular organelle that accounts for 20 to 40% of the cellular dry weight of most fungi. Due to the pathogenicity of Aspergillus fumigatus, cell wall composition and chemical organization have been studied to identify fungal molecules involved in host-pathogen interactions, resistance to microbial killing mechanisms, and immune defenses. Polysaccharide composition of the A. fumigatus mycelium and conidial cell wall are listed in this chapter. The alkali-soluble fraction of cell wall polysaccharides is mainly composed of α-1,3-glucan. The majority of antigenic proteins are secreted proteins transiently found in the cell wall before they are secreted in the extracellular environment. A thin layer of regularly arranged rodlets covers the surface of aerial fungal conidia. The number of genes encoding α-1,3-glucan synthases and the essentiality of each individual gene vary according to the fungal species. Analysis of the common domains among the eight chitin synthases of A. fumigatus has shown two clusters of three and four genes and a singleton which are associated with chitin synthesis. The fungal cell wall of A. fumigatus is a complex organization of macromolecules resulting from several biosynthetic pathways: protein synthesis in the endoplasmic reticulum (ER), biosynthesis of mannan and glycans in the ER and Golgi complex, and synthesis of homopolysaccharide at the plasma membrane. Molecular biology methods and biochemical approaches have allowed researchers to identify genes and proteins involved in polysaccharide synthesis.