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.