New Heterothallic species of Hansenula

Summary

As the genusHansenula is at present constituted,H. fabianii appears to be the first species of its phylogenetic line to have become independent of trees and bark beetles. It is also the last species of its line to occur in nature with the haploid, or basic, number of chromosomes. So near is it to the diploid level of evolution that a sporulation medium rich in malt extract favors the development of diploid vegetative cells in the period between conjugation of opposite sexes and the onset of sporulation. The diploid form is easily isolated from the mixture and, as long as sporulation is prevented, may be kept in pure state. Media that favor vegetative development of the species favor its occurrence as haploid vegetative cell.H. fabianii is most closely related toHansenula subpelliculosa Bedford, which occurs in nature as the diploid form. Both species have been isolated almost exclusively as contaminants of fermentations, and both have been used industrially in Oriental fermentations to make alcoholic beverages or foods.