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FUNGAL BIOLOGY
A Textbook by JIM DEACON
Blackwell Publishing 2005

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CHAPTER 7: FUNGAL METABOLISM AND FUNGAL PRODUCTS

This chapter is divided into the following major sections:

how fungi obtain energy in different environmental conditions
co-ordination of metabolism: how the pathways are balanced
the mobilisable and storage compounds of fungi
the synthesis of chitin and lysine
the pathways and products of secondary metabolism

Sample text:

In this chapter we discuss the basic metabolic pathways of fungi, as a basis for understanding how fungi grow on different types of substrate and in different environmental conditions. We also cover some of the distinctive and unusual aspects of fungal metabolism, including the production of a wide range of secondary metabolites of commercial and environmental significance, such as the penicillin antibiotics and important mycotoxins like the highly carcinogenic aflatoxins and the toxic ergot alkaloids. Some of the material in this chapter will be familiar, basic biochemistry. But it is presented in the specific context of fungal biology.

Chapter 7 images. Click on the thumbnails


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Fig. 7.20a


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Fig. 7.20b


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Fig. 7.20c


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Fig. 7.20d

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Table 7.1. Some secondary metabolites derived from different pathways and precursors
Precursor Pathway Metabolites; representative organisms
Sugars   Few, e.g. muscarine (Amanita muscaria)
kojic acid (Aspergillus spp.)
Aromatic amino acids Shikimic acid Some lichen acids
Aliphatic amino acids Various, including peptide synthesis Penicillins (P. chrysogenum, P. notatum)
Fusaric acid (Fusarium spp.)
Ergot alkaloids (Claviceps, Neotyphodium)
Lysergic acid (Claviceps purpurea)
Sporidesmin (Pithomyces chartarum)
Beauvericin (Beauveria bassiana)
Destruxins (Metarhizium anisopliae)
Organic acids TCA cycle Rubratoxin (Penicillium rubrum)
Itaconic acid (Aspergillus spp.)
Fatty acids Lipid metabolism Polyacetylenes (Basidiomycota fruitbodies and hyphae)
Acetyl-CoA Polyketide Patulin (Penicillium patulum)
Usnic acid (many lichens)
Ochratoxins (Aspergillus ochraceus)
Griseofulvin (Penicillium griseofulvum)
Aflatoxins (A. parasiticus, A. flavus)
Acetyl Co-A Isoprenoid Trichothecenes (Fusarium spp.)
Fusicoccin (Fusicoccum amygdali)
Several sex hormones: sirenin, trisporic acids, oogoniol, antheridiol
Cephalosporins
(Cephalosporium and related fungi)
Viridin (Trichoderma virens)

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Table 7.2. Some representative mycotoxins in foodstuffs

Toxin

Representative fungi

Foodstuff

Effects

Aflatoxins Aspergillus flavus
A. parasiticus
Peanuts, oilseeds Nephrotoxic, hepatocarcinomas
Ergot alkaloids Claviceps purpurea
Cereals, grasses Neurotoxic
Fuminosins Fusarium moniliforme Maize Human oesophageal cancer in Africa?
Ochratoxin A Some Aspergillus and Penicillium spp.
Grain crops Nephrotoxic, kidney carcinoma
Patulin Penicillium expansum,
Aspergillus clavatus
Apples Contact oedema, haemorrhage
Sporidesmin Pithomyces chartarum Grass Facial eczema of sheep, cattle
Sterigmatocystin Aspergillus spp.
Grain, oilseeds Hepatocarcinogen
Trichothecenes Fusarium spp. Stachybotrys chartarum
Cereals Abortive, blistering, oestrogenic
Zearalenone Fusarium
Cereals Vulvovaginitis

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