IDENTIFICATION AND PHYLOGENETIC IMPLICATIONS OF FATTY ACIDS AND STEROLS IN THREE GENERA OF AQUATIC PHYCOMYCETES

Abstract

Allomyces macrogynus, A. arbuscula, A. javanicus, Allomyces male and female hybrid strains, Blastocladia ramosa and Monoblepharella sp. were examined for their fatty acid and sterol compositions by GLC and combined GLC/MS. All the organisms produce a range of fatty acids 12 to 20 carbon atoms in length. Palmitic, stearic, and arachidic acid represent the highest concentrations of saturated fatty acids; oleic, linoleic, and arachidonic acid the highest unsaturated fatty acids. B. ramosa synthesizes only two polyunsaturates, linoleic and linolenic, but Allomyces and Monoblepharella are capable of desaturation as far as arachidonic acid. Cholesterol is produced by all the isolates and is the dominant sterol in Allomyces. 24‐Methyl and 24‐ethyl derivatives of cholesterol are the dominant sterols of Monoblepharella. B. ramosa contains a more complex sterol mixture representing changes which occur in the formation of cholesterol from lanosterol: 24‐dihydrolanosterol, 14α‐methyl Δ8‐cholestenol, Δ8(9)‐cholestenol, 14α‐methyl Δ7‐cholestenol, Δ7‐cholestenol and cholesterol. Δ7‐cholestenol, 24‐dihydrolanosterol, and 14α‐methyl Δ8‐choIestenol appear to be the major components. This is the first time that 14α‐methyl Δ8 and 14α‐methyl Δ7‐cholestenol have been reported as naturally occurring sterols.