Yeast Saccharomyces cerevisiae is ubiquitous in nature and has been associated with humans for thousands of years. It is present in food as well as on or in humans and many other environments. Although it is classified among microorganisms with the GRAS status, it can cause certain diseases in people with compromised immune systems. Researchers identify S. cerevisiae as an opportunistic pathogen. Both, natural and laboratory strains have properties that allow the differentiation of vegetative cells and spores. By manipulating these properties, haploid strains can be prepared for further analysis. In this diploma work, we developed a method for the selection of haploid strains capable of colonizing the human body. The method involves the preparation of heterothallic strains and the selection of haploid spores with heat shock. We identified 55°C as the optimal heat shock temperature, which enriches the culture consisting of vegetative cells and sporulated cells with spores.
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