A number of substances that directly or indirectly affect the cell walls of fungi have been identified. Those that actively interfere with the synthesis or degradation of polysaccharide components share the property of being produced by soil microbes as secondary metabolites. Compounds specifically interfering with chitin or beta-glucan synthesis have proven effective in studies of preclinical models of mycoses, though they appear to have a restricted spectrum of coverage. Semisynthetic derivatives of some of the natural products have offered improvements in activity, toxicology, or pharmacokinetic behavior. Compounds which act on the cell wall indirectly or by a secondary mechanism of action, such as the azoles, act against diverse fungi but are usually fungistatic in nature. Overall, these compounds are attractive candidates for further development.

Compounds active against cell walls of medically important fungi.

The cell wall is commonly regarded as an assemblage of polymers, mainly polysaccharides, that occurs outside the plasma membrane of cells of plants, fungi, and bacteria. Because of its rigidity it maintains the shape of the cell and offers resistance to unlimited influx of water into the cell. In addition it offers protection and, being the outermost cover of cells, often contains molecules involved in interaction between cells.

Fungal Cell Walls: A Survey

Major insights into sexual development and cryptic sexuality within filamentous fungi have been gained from investigations using Aspergillus species Here, an overview is first given into sexual morphogenesis in the aspergilli, describing the different types of sexual structures formed and how their production is influenced by a variety of environmental and nutritional factors It is argued that the formation of cleistothecia and accessory tissues, such as Hulle cells and sclerotia, should be viewed as two independent but co-ordinated developmental pathways Next, a comprehensive survey of over 75 genes associated with sexual reproduction in the aspergilli is presented, including genes relating to mating and the development of cleistothecia, sclerotia and ascospores Most of these genes have been identified from studies involving the homothallic Aspergillus nidulans, but an increasing number of studies have now in addition characterized 'sex-related' genes from the heterothallic species Aspergillus fumigatus and Aspergillus flavus A schematic developmental genetic network is proposed showing the inter-relatedness between these genes Finally, the discovery of sexual reproduction in certain Aspergillus species that were formerly considered to be strictly asexual is reviewed, and the importance of these findings for cryptic sexuality in the aspergilli as a whole is discussed

Sexual development and cryptic sexuality in fungi: insights from Aspergillus species

https://mmbr.asm.org/content/mmbr/43/2/117.full.pdf

Biosynthesis of cell walls of fungi.

Trichoderma harzianum secretes α-1,3-glucanases when it is grown on polysaccharides, fungal cell walls, or autoclaved mycelium as a carbon source (simulated antagonistic conditions). We have purified and characterized one of these enzymes, named AGN13.1. The enzyme was monomeric and slightly basic. AGN13.1 was an exo-type α-1,3-glucanase and showed lytic and antifungal activity against fungal plant pathogens. Northern and Western analyses indicated that AGN13.1 is induced by conditions that simulated antagonism. We propose that AGN13.1 contributes to the antagonistic response of T. harzianum.

B.J.M. Zonneveld

Papers

Morphogenesis in aspergillus nidulans The significance of α-1,3-glucan of the cell wall and α-1,3-glucanase for cleistothecium development☆