ASaccharomyces boulardii strain, which does not carry any auxotrophic markers, was transformed with knockout constructs for the genes HIS3 and ADE2 using the dominant antibiotic marker genes encoding for kanamycin/G418- and nourseothricin/NATR resistance. Thereby, homozygous derivatives that were histidine or adenine deficient were obtained. Histidine prototrophy was easily reconstituted by transforming his-defective diploid derivatives with yeast plasmids carrying the HIS3 gene. Despite different attempts, for example, by creating a rme1::KANX rme1::NATR double-deleted S. boulardii yeast strain (RME1 encodes for Regulator of Meiosis), no visible sporulation to obtain haploid derivatives could be obtained. Besides, no filamentation properties of S. boulardii were observed. As previously mentioned, this yeast strain was confirmed to thrive at 37°C, a temperature disliked by some but not all S. cerevisiae strains used in the laboratory. S. boulardii is a diploid derivative of S. cerevisiae that does not sporulates and survives at temperatures as those found in the human gut. It can be easily manipulated by using conventional yeast methods to introduce auxotrophic markers and obtain heterozygous diploid knockout derivatives that can be transformed with yeast plasmids following conventional yeast protocols, thereby it could be even suited for biochemical and genetic research purposes.
Part of the book: The Yeast Role in Medical Applications