Sterols in Growth and Reproduction of Fungi

Abstract

Fungi are cukaryotic organisms, which are characterized by cellular or­ ganelles such as nuclei and mitochondria. Eukaryotic organisms are gener­ ally considered to synthesize and cont::tin sterols, whereas prokaryotic orga­ nisms �;t]ch as hacteria (see 20) and hlm'-green algae (74, 103) are gener­ ally considered not to contain or need sterols. Although sterols and related compounds (tetracyclic triterpenes) occur in tremendous variety in the various taxonomic groups of plants and ani­ mals (17, 54, 55, 127), is usually considered to be the principal sterol in fungi. This conception probably arose because of the commercial interest in as provitamin D and as a precursor for the synthesis of clinically important steroids. Yeasts and certain other fungi frequently used in industrial fermentations are readily available sources of ergosterol. Yeasts and a few other fungi are also useful in studies of the biosynthesis of sterols (20, 43-45). Deeper penetrations into these areas demonstrate anew the folly of gener­ alizations based on few data. At least some bacteria (132, 133) and blue­ green algae (34, 124) in the prokaryotic group apparently do synthesize sterols. Another prokaryotic group, the pathogenic Mycoplasma, does not synthesize sterols but has a nutritional requirement for �hem (119). Eukar­ yotic organisms which cannot synthesize sterols hut require them include probably all insects (28), at least some nematodes (29, 71), and some proto­ zoa (20, 75, 78). Adequate charactcrizations of the sterols extracted from fungi are few. Frequently ergosterol contents of fungi are given with no attempt to prove the structure. The use of in physiological experiments with aquatic Phycomycetes on the assumption that is the fungal sterol is unfortunate, because is much more susceptible to autoxidation than sterols lacking the extra double bonds. Furthermore, the elegant study by McCorkindale and co-workers (108) shows that species of the Sapro­ legniales· and Leptomitales may be expected to contain cholesterol, desmos­ terol, 24-methylenecholesterol, or fucosterol rather than compounds such as which have a pair of conjugated double bonds in ring B. Other