Identification of a sterol mutant of Neurospora crassa deficient in delta 14,15-reductase activity.

A mutant (erg-3) of Neurospora crassa resistant to the polyene antibiotic nystatin was compared with its sensitive, wild-type parent to detect differences in sterol composition using gas chromatography-mass spectrometry. The major sterol in wild-type mycelia, comprising 80% of the total, was ergosterol. The major sterols in mutant mycelia, comprising 86% of the total, were delta 8,14-sterols. It is proposed that the nystatin-resistant strain is unable to synthesize ergosterol because it lacks delta 14,15-reductase activity as a result of a mutation in the erg-3 gene.