'Fusel' alcohols induce hyphal-like extensions and pseudohyphal formation in yeasts.

At a concentration of 0.5% (v/v), isoamyl alcohol induced the formation of hyphal-like extensions in haploid and diploid strains of Saccharomyces cerevisiae in liquid complex medium. These extensions, which develop via bud initiation and elongation, undergo DNA replication and nuclear division and appear similar in many respects to an aberrant form of the cell division cycle. However, in 0.25% (v/v) isoamyl alcohol, S. cerevisiae formed pseudohyphae. Other 'fusel' alcohols (which are the products of amino acid catabolism) also induced hyphal-like extensions in this yeast, with n-amyl alcohol being as equally effective as isoamyl alcohol. Isoamyl alcohol induced the formation of pseudohyphae in two species of Candida and both hyphal-like extensions and pseudohyphae in Brettanomyces anomalus, suggesting a close relationship or a common basis to the development of the two morphologies.