Aerobic isolation of an ERG24 null mutant of Saccharomyces cerevisiae

The ERG24 gene, encoding the C-14 sterol reductase, has been reported to be essential to the aerobic growth of Saccharomyces cerevisiae. We report here, however, that strains with null mutations in the ERG24 gene can grow on defined synthetic media in aerobic conditions. These sterol mutants produce ignosterol (ergosta-8,14-dienol) as the principal sterol, with no traces of ergosterol. In addition, we mapped the ERG24 gene to chromosome XIV between the MET2 and SEC2 genes. Our results indicate that ignosterol can be a suitable sterol for aerobic growth of S. cerevisiae on synthetic media and that inactivation of ERG24 is only conditionally lethal.