Fungal cell wall, chitin

Other biodegradable polymers include Konjac, a water-soluble natural polysaccharide produced by FMC, Chitin, another polysaccharide that is insoluble in water, and Chitosan, which is soluble in water. Chitin is found in insect exoskeletons and in shellfish. Chitosan can be formed from chitin and is also found in fungal cell walls. Chitin is used in many biomedical applications, including dialysis membranes, bacteriostatic agents, and wound dressings. Other applications include cosmetics, water treatment, adhesives, and fungicides. ... 

The chemistry and biochemistry of polyoxins has been discussed. The structure of the neopolyoxins A, B, and C, which are potent inhibitors of fungal cell-wall chitin synthetase, has been established neopolyoxins A and B are the imidazole nucleosides (18) and (19), respectively, whereas neopolyoxin C is the corresponding uracil-1-yl nucleoside the structure of polyoxin N was also revised, the amino-acid side-chain of (18) being replaced by 2-amino-5-(9-carbamoyl-2-deoxy-L-xyIonic acid. The new antibiotic nikkomycin B also has the structure of (18), although its stereochemistry has not been fully established. Adenomycin has... 

IV. PARASITISM. Lysis by hydrolytic enzymes excreted by microorganisms is a well-known feature of mycoparasitism. Chitinase and P-l,3 glucanase (laminarase) are particularly important enzymes secreted by fungal mycoparasites capable of degrading the fungal cell wall components, chitin, and P-1,3 glucan (131-134). 

Chitin is the microfibrillar component of some fungal cell walls and is equivalent to cellulose microfibrils in plants. It is a characteristic feature of the Ascomycetes, Deuteromycetes and Basidiomycetes but is absent in the Phycomycetes, which contain cellulose as their major cell wall constituent. 

Polyoxins are inhibitors of chitin biosynthesis. Chitin is a component of fungal cell walls except in Phycomycete fungi these contain cellulose as their major cell wall constituent, hence polyoxins are inactive against Plasmopara, Pythium and Phytophthora. 

The mechanisms of metal uptake may be modified in those plants where the roots are associated with mycorrhizal fungi. Streit and Stumm (1993) suggest that metal ions might form complexes with the chitin of the fungal cell wall. However is it not clear whether this would facilitate the uptake of metals by the plant host. Some selection seems to be involved since not all the elements taken up by the fungus are released... 

Fungal cell walls are composed primarily of the highly crystalline polysaccharides, chitin and )8-glucan, and various nonhydrolyzable melanins (Peberdy, 1990). Section 8.07.5.4 describes the structure and decomposition of chitin. While chitin has been well studied, very little is known about the structure or in situ decomposition of melanins (Butler and Day, 1998). However, melanins are thought to be a possible humus precursor because of their similarities with humic acids (Saiz-Jimenez, 1996). 

Like cellulose (O Sect. 3.1), chitin imparts mechanical strength. Both chitin and cellulose form fibrils. Chitin fibrils are structural elements in the exoskeletons of insects and crustaceans. Fungal cell walls, which often contain 80-90% (dry-weight basis, db) polysaccharide, have been categorized into eight types by polysaccharide composition ... 

The primary cell-wall component of many species is chitin. At least in fungal cell walls and probably elsewhere, chitin occurs as part of a proteoglycan. 

Its fungicidal action is based on ergosterol depletion and the accumulation of ignosterol in fungal cytoplasmic membrane, which causes the fungal cell wall to thicken and chitin to be deposited. 

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