John D. Weete

Lipid biochemistry of fungi and other organisms

1 Introduction to Lipids.- Definition and classification.- Nomenclature of lipids.- Historical aspects of fungal lipid research.- 2 Fungal Lipids.- Total lipid content.- Vegetative hyphae and yeast cells.- Spores and sclerotia.- Lipid composition.- Lipid functions.- Subcellular distribution of lipids.- Cell wall.- Protoplast.- Relation of culture conditions to fungal growth and lipid production.- Temperature.- Carbon source.- Inorganic nutrients.- pH.- Aeration (oxygen).- Growth factors.- Fungal growth and lipid production.- 3 Fatty Acids.- Nomenclature and structure.- Fatty acids in fungi.- Phycomycetes.- Ascomycetes and Fungi Imperfecti.- Basidiomycetes.- Fatty acids of cell walls and membranes.- Cell wall.- Plasmalemma and mitochondrial membranes.- 4 Fatty Acid Metabolism.- Fatty acid biosynthesis.- Origin of substrates for fatty acid biosynthesis.- De novo fatty acid synthesis.- Regulation of de novo fatty acid synthesis.- Fatty acid elongation.- Biosynthesis of unsaturated fatty acids.- Biosynthesis of unusual fatty acids.- Fatty acid degradation.- 5 Acylglycerols and Related Lipids.- to acylglycerols.- Structure and nomenclature.- Occurrence in fungi.- Biosynthesis of triacylglycerides.- Lipases.- Glycosylglycerides and other glycolipids.- Methyl, ethyl, and sterol esters.- 6 Glycerophospholipids.- Nomenclature and structure.- Occurrence in fungi.- Yeasts.- Filamentous fungi.- Glycerophospholipids of subcellular fractions.- Acyl groups of glycerophospholipids.- Biosynthesis.- Phosphatidic acid.- Phosphatidylcholine.- Phosphatidylethanolamine.- Phosphatidylserine.- Phosphatidylinositol.- Diphosphatidylglycerol (cardiolipin).- Plasmanic and plasmenic acid derivatives.- Degradation.- 7 Sphingolipids.- Structure and nomenclature.- Occurrence.- Bacteria, plants, and animals.- Fungi.- Sphingolipid metabolism.- Biosynthesis.- Degradation.- 8 Aliphatic Hydrocarbons.- Occurrence in fungi.- Hydrocarbon biosynthesis.- Oxidation of hydrocarbons.- Cornynebacterium 7EIC.- Pseudomonas olevorans.- Mammals.- Yeasts.- Higher plants.- 9 Sterols, Carotenoids, and Polyprenols.- Sterols.- Structure and nomenclature.- Occurrence in fungi.- Phycomycetes.- Ascomycetes and Deuteromycetes (Fungi Imperfecti).- Basidiomycetes.- Sterols of photosynthetic plants and bacteria.- to carotenoids.- Structure and nomenclature.- Occurrence in fungi.- Polyprenols.- 10 Biosynthesis of Sterols, Carotenoids, and Polyprenols.- to sterol biosynthesis.- Formation of squalene.- Conversion of squalene to lanosterol.- Terminal reactions of sterol biosynthesis.- Demethylation.- C-24 alkylation and other side-chain modifications.- Nuclear double bond shift, formation, and reduction.- Pathway of ergosterol biosynthesis.- Carotenoid biosynthesis.- Biosynthesis of polyprenols.- 11 Lipid Metabolism During Fungal Development.- Spore germination.- Lipophilic stimulators of spore germination.- Electron microscopic observations of lipid bodies in fungal spores.- Lipid metabolism during germination.- Reproductive growth.- Lipid metabolism during sporulation.- References.

Sterols of the fungi - Distribution and biosynthesis.

The importance of sterols in the growth and reproduction in fungi is becoming increasingly apparent. This article concerns the composition and biosynthesis of ergosterol in these organisms. Comparison to plant and animal sterol formation are made.

Structure and Function of Sterols in Fungi

Publisher Summary This chapter discusses the structure and function of sterols in fungi. The distribution of sterols among fungi follows the taxonomic separation of fungi at the subdivision level. The Mastigomycotina, or lower fungi, produce mainly cholesterol and/or its C-24 alkyl and/or alkylidene derivatives, but no ergosterol. There is less distinction among fungi at the class level with respect to sterol composition among the Mastigomycotina. Fucosterol is a major sterol of many sterol-producing Oomycetes and may be accompanied by cholesterol and 24-methylene cholesterol. Cholesterol is produced by some but not all Chytridiomycetes, which, along with the Hypochytriomycetes, have 24-alkyl rather than 24-alkylidene derivatives as major sterols. It is well-known that the pythiaceous fungi (Oomycetes) do not produce sterols because they cannot carry out the epoxidation of squalene, and it is believed that Plasmodiophoromycetes, which are obligate parasites, also do not produce sterols. Sterols are synthesized by enzymes located mainly in the endoplasmic reticulum, but they do not tend to accumulate there or in endomembranes derived from the endoplasmic reticulum.

Effects of triazoles on fungi: II. Lipid composition of Taphrina deformans

Abstract The effects of CGA-64250, a triazole inhibitor of fungal growth, on the lipid composition of Taphrina deformans (D1) were examined using Chromatographic and, in some cases, mass spectrometric techniques. Beginning 8–10 h after inoculation, the total lipid content of cells treated with 0.073 μg/ml averaged 30% more than controls. This was accounted for in part by sterols, which comprised over 2.3 times more of the total lipid from treated cells than from controls. Brassicasterol (ergosta-5,22-dienol) was the principal sterol of T. deformons , at 82% of the total sterol fraction. Ergosterol (ergosta-5,7,22-trienol) was not detected. Methyl sterols such as lanosterol and 24-methylene-dihydrolanosterol represented about 70% of the total in CGA-64250-treated cells, suggesting that this triazole inhibitor blocks the C-14 demethylation of lanosterol. Other responses that appear to be common in fungi treated with C-14 demethylation inhibitors were also observed in CGA-64250-treated T. deformans cells. This included an increased free fatty acid content by a factor of 6.8, and higher degree of lipid unsaturation, as indicated by C 18:1 C 18:2 +C 18:3 ratios of 0.2–0.4 compared to 2.1–2.7 for non-treated cells.

Selectivity and mode of action of carfentrazone-ethyl, a novel phenyl triazolinone herbicide

Post-emergence application of carfentrazone-ethyl at rates as low as 2.2 g ha -1 caused greater leaf injury and growth reduction in ivyleaf morningglory (Ipomoea hederacea) and velvetleaf (Abutilon theophrasti) than in soybean (Glycine max). The herbicide was more rapidly metabolized in the crop than in the weed species, with 26.7, 54.3 and 60.6% of the parent compound remaining in soybean, ivyleaf morningglory and velvetleaf, respectively, 24 h after exposure. The free acid metabolite, carfentrazone, was present in all species and accounted for 21.2-27.4% of the total radioactivity. Unknown metabolites (R f 0 and 0.22) were four to five times more abundant in soybean than in the weed species. Carfentrazone-ethyl induced more leakage from leaf discs from the weeds than those from soybean and the degree of injury correlated with the amount of protoporphyrin IX (Proto IX) present in the treated tissues. Both carfentrazone-ethyl and carfentrazone were potent inhibitors of protoporphyrinogen oxidase (Protox). Therefore, the selectivity of this herbicide may, at least in part, be attributed to the lower accumulation of Proto IX in soybean than in the weeds, probably because of the ability of soybean to metabolize more carfentrazone into unknown metabolites than the weeds.

lipids and Ultrastructure of Thraustochytrium sp. ATCC 26185

As a representative of a genus with species considered to be potential commercial producers of the nutritionally important polyunsaturated fatty acid docosahexaenoic acid (DHA), Thraustochytrium sp. ATCC 26185 was investigated to determine its potential for DHA production and lipid composition. Cells from liquid shake cultures contained 32% (w/w) lipid, 18% of which was nonsaponifiable lipid. The major saturated fatty acids (14∶0 and 16∶0) comprised up to 59% of the total fatty acids, and DHA was up to 25% after 6 d incubation. Squalene represented 63% of the nonsaponifiable lipid, and cholesterol composed 41% of the total sterols. The phospholipids expected for eucaryotic microbes were detected with phosphatidylcholine as the major phospholipid at 76% of the total. The ultrastructure of this species was similar to other Thraustochytrium species except that the cells did not have surface scales and they contained unusual membrane-like structures that appeared to be associated with oil formation.

STEROLS OF THE PHYLUM ZYGOMYCOTA : PHYLOGENETIC IMPLICATIONS

The sterol composition of 42 fungal species representing six of the eight orders of the Zygomycota was determined using gas-liquid chromatography-mass spectrometry to assess whether the distribution of major sterols in this phylum has taxonomic or phylogenetic relevance. Ergosterol, 22-dihydroergosterol, 24-methyl cholesterol, cholesterol, and desmosterol were detected as the major sterols among the species studied. Ergosterol was the major sterol of the Dimargaritales, Zoopagales, and 13 of the 14 Mucorales families included in this study. Desmosterol appeared to be the characteristic sterol of the Mortierellaceae (Mucorales). 24-Methyl cholesterol was the major sterol of the Entomophthorales genera Entomophthora, Conidiobolus and Basidiobolus, but cholesterol was the sole sterol detected in Delacroixia coronatus. The Kickxellales species analyzed in this study were characterized by 22-dihydroergosterol as the major sterol. These results suggest that certain orders of the Zygomycota may be distinguished on the basis of major sterol. Also, if sterol structure has phylogenetic implications, then orders might be arranged in the order Kickxellales (C28Δ5,7) → Dimargaritales, Zoopagales and Mucorales (C28Δ5,7,22) on the basis of evolution of the predominant and presumably most competent sterol, ergosterol. Although the Entomophthorales would be expected to be more primitive than the above orders based on the predominance of C28Δ5,, it is not apparent from these data that members of the Zygomycota with ergosterol or its precursors as major sterols evolved from this taxon or the Chytridiomycota.

Distribution of sterols in the fungi I. Fungal spores

The freely extractable sterols of spores ofLinderina pennispora, Spicaria elegans, Penicillium claviforme, Aspergillus niger, Ustilago nuda, U. maydis, Puccinia graminis, andP. striiformis were examined using mass spectrometric techniques. Each species contained at least 3–5 detectable sterol components in the 4-desmethyl sterol fraction, and, when present, ergosterol was generally the most abundant sterol produced by an individual species. Smaller relative concentrations of fungisterol (ergost-Δ7-enol) di- and tetraunsaturated C28 sterols also were found. In some species, fungisterol was the most abundant sterol. In uredospores of rust fungi, stigmast-Δ7-enol (C29) was predominant and was accompanied by lower relative concentrations of a diunsaturated C29 sterol and fungisterol. Cholesterol was found only in the teliospores of the corn smut fungus (U. maydis). Application of glass capillary columns to the separation of yeast sterols by gas liquid chromatography is illustrated.

Behavior of sulfentrazone in ionic exchange resins, electrophoresis gels, and cation-saturated soils.

Abstract Sulfentrazone persistence in soil requires many crop rotational restrictions. The sorption and mobility of sulfentrazone play an important role in its soil persistence. Thus, a series of laboratory experiments were conducted to mimic the soil properties of cation and anion exchange with different intermediates. The molecular characterization and ionization shift of sulfentrazone from a neutral molecule to an anion were determined using a three-dimensional graphing technique and titration curve, respectively. Sorption and mobility of 2.6 × 10−5 M 14C-sulfentrazone were evaluated using a soil solution technique with ion exchange resins and polyacrylamide gel electrophoresis, respectively. Solution pH ranged from 4.0 to 7.4. As pH increased, sulfentrazone sorption to an anion resin increased and its sorption to a cation resin decreased. Percent sulfentrazone in solution was pH-dependent and ranged between 0 to 18% and 54 to 88% for the anion and cation resins, respectively. Mobility of sulfentrazone on a 20% polyacryalmide gel resulted in Rf values of +0.02 and +0.39 for pH of 4.0 and 7.4, respectively. A double peak for sulfentrazone was detected in the polyacrylamide gel when the pH (6.0 and 6.8) was near the reported pKa of 6.56. There was no clear interaction for the sorption of sulfentrazone at 1.0 mg kg−1 to Congaree loamy sand or Decatur silty clay loam saturated with either calcium or potassium. Sulfentrazone behavior with the polyacrylamide electrophoresis gels and ion resins indicate the potential for this herbicide to occur as a polar or Zwitter ion. Sulfentrazone was adsorbed by potassium, calcium, and sodium saturated resins and subsequently desorbed using variable pH solutions. The level of sulfentrazone adsorption will vary among soil types and the amount of desorption into solution may be soil cation-dependent. Nomenclature: Sulfentrazone.

Aliphatic hydrocarbons of the fungi.

Abstract The presence of paraffinic hydrocarbons throughout the plant and animal kingdom has received considerable attention during the past decade. Hydrocarbons have been recently reported for the spores of phytopathogenic fungi and are found to be structurally very similar to the alkanes of higher plants. It appears that the hydrocarbon components of the few mycelial and yeast forms reported resemble the distribution found in bacteria. The occurrence and distribution of these compounds in the fungi are reviewed.