The Spoilage Yeast Zygosaccharomyces bailii Forms Mitotic Spores: a Screening Method

and the type strain of this spoilage yeast show a diploid DNA content. Together with a rather peculiar life cycle in which mitotic but no meiotic spores appear to be formed, the diploid DNA content explains the observed difficulties in obtaining auxotrophic mutants. Mitotic chromosome loss induced by benomyl and selection on canavanine media resulted in three haploid strains of Z. bailii. This new set of Z. bailii strains allows the easy isolation of recessive mutants and is suitable for further molecular genetic studies. The genus Zygosaccharomyces is associated with a notorious resistance to stress environments (12, 22, 27). It includes dif-ferent species, such as Z. bailii, Z. bisporus, and Z. rouxii, which have been frequently implicated in the spoilage of food and beverages (2). A screen for yeasts highly resistant to weak carboxylic acids involving a wide range of genera revealed that the strain ISA 1307 of Z. bailii, originally isolated from con-tinuous production of sparkling wine (30), displayed an out-standing capacity to survive in such environments. Wherea