Hansenula angusta, an Excellent Species for Demonstration of the Coexistence of Haploid and Diploid Cells in a Homothallic Yeast

Abstract

H. angusta is a species of yeast associated with deciduous trees and disseminated by bark beetles and fruit flies. It exists in nature predominantly in the haploid form but a small percentage of diploid cells are present. Ascospores impart a red color to the colonies when 4 to 8 days old. Diploid colonies have a denser color than the haploid colonies because diploid cells sporulate sooner and more abundantly than haploid cells. Asci produced by diploid cells are not conjugated; asci produced by haploid cells are conjugated. The diploid form returns to haploid when it sporulates, and the haploid form becomes diploid at a slow rate while growing vegetatively.