GENERAL MICROBIOLOGY - T.P. Pyrog - 2004

8. FUNGI

8.7. BIOLOGICALLY ACTIVE METABOLITES OF FUNGI

8.7.4. Fungal Toxins

This group comprises metabolites of diverse chemical nature, including acids, sterol derivatives, and Aromatic Compounds. Toxins synthesized by Fungi affect humans, animals, and plants. The most extensively studied are those causing toxicosis in humans and farm animals. The science of mycotoxicology emerged in the 1940s to study the toxic properties of fungi, their distribution, associated diseases, as well as the chemical Structure and properties of the toxins themselves. To date, several hundred mycotoxins produced by 600 fungal species have been identified.

Stachybotryotoxins. This is a complex of toxins produced by the fungus Stachybotrys alternans. The resulting disease, known as stachybotryotoxicosis, is caused by feeding animals contaminated fodder, primarily straw and less frequently hay. Before their toxic properties were discovered, species of the genus Stachybotrys were described in literature as saprophytic. Humans can contract this disease through direct contact with infected fodder. Stachybotrytoxin also exerts a toxic effect on plants, causing necrosis and dieback. Chemically, this toxin is a steroid. Stachybotrytoxin is stable during storage, withstanding temperatures up to 120º С for up to 2 hours without loss of toxicity. It is resistant to mineral acids, potassium permanganate, and UV radiation, but unstable in alkaline environments; Treatment of straw or the toxin itself with a 0.5% alkali solution results in its inactivation.

Dendrodochins. These are toxins produced by the fungus Dendrodochium toxicum, causing the disease known as dendrodochiotoxicosis. A characteristic feature of this condition is the rapid death of animals—within 12–24 hours after consuming a lethal dose of toxic feed (350–450 g of fungus-infested chaff for a horse). Dendrodochins also exhibit antifungal activity, inhibiting the growth of certain phytopathogenic fungi and Yeasts. Among yeasts, Candida stellatoidea and Saccharomyces vini are the most sensitive, and they have been proposed as test cultures for the Quantitative determination of dendrodochin. Chemically, dendrodochins are trichothecenes (macrocyclic compounds).

Sporofusariotoxins. Produced by the fungus Fusarium sporotrichiella. Chemically, they belong to the trichothecenes.

Aflatoxins. Produced by fungi of the Aspergillus flavus-oryzae group. The investigation of their toxic properties originated from outbreaks of disease in ducklings and turkey poults. Aflatoxins are derivatives of dihydrofuran (coumarin). While certain species of fungi and yeasts are resistant to aflatoxin, strains of Bacillus brevis are the most sensitive.