STEROLS OF THE PHYLUM ZYGOMYCOTA - PHYLOGENETIC IMPLICATIONS

The sterol composition of 42 fungal species representing six of the ei ght orders of the Zygomycota was determined using gas-liquid chromatog raphy-mass spectrometry to assess whether the distribution of major st erols in this phylum has taxonomic or phylogenetic relevance, Ergoster ol, 22-dihydroergosterol, 24-methyl cholesterol, cholesterol, and desm osterol 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 a ppeared to be the characteristic sterol of the Mortierellaceae (Mucora les), 24-Methyl cholesterol was the major sterol of the Entomophthoral es genera Entomophthora, Conidiobolus and Basidiobolus, but cholestero l was the sole sterol detected in Delacroixia coronatus. The Kickxella les species analyzed in this study were characterized by 22-dihydroerg osterol 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 m ight be arranged in the order Kickxellales (C-28 Delta(5,7)) --> Dimar garitales, Zoopagales and Mucorales (C-28 Delta(5,7,22)) 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 C-28 Del ta(5), it is not apparent from these data that members of the Zygomyco ta with ergosterol or its precursors as major sterols evolved from thi s taxon or the Chytridiomycota.