Genotypic and Physiological Characterization of Saccharomyces boulardii , the Probiotic Strain of Saccharomyces cerevisiae

Abstract

Saccharomyces boulardii, a yeast that was isolated from fruit in Indochina, has been used as a remedy for diarrhea since 1950 and is now a commercially available treatment throughout Europe, Africa, and South America. Though initially classified as a separate species of Saccharomyces, recent publications have shown that the genome of S. boulardii is so similar to Saccharomyces cerevisiae that the two should be classified as conspecific. This raises the question of the distinguishing molecular and phenotypic characteristics present in S. boulardii that make it perform more effectively as a probiotic organism compared to other strains of S. cerevisiae. This investigation reports some of these distinguishing characteristics including enhanced ability for pseudohyphal switching upon nitrogen limitation and increased resistance to acidic pH. However, these differences did not correlate with increased adherence to epithelial cells or transit through mouse gut. Pertinent characteristics of the S. boulardii genome such as trisomy of chromosome IX, altered copy number of a number of individual genes, and sporulation deficiency have been revealed by comparative genome hybridization using oligonucleotide-based microarrays coupled with a rigorous statistical analysis. The contributions of the different genomic and phenotypic features of S. boulardii to its probiotic nature are discussed.

Saccharomyces cerevisiae var. boulardii – Probiotic Yeast

“…Higher optimal growth temperature (~37 °C) Lower optimal growth temperature (~30 °C) Higher resistance to low pH [11] Lower resistance to low pH [11] The karyotypes of Sb are very similar to those of S. cerevisiae…”

“…It has been shown that yeast pathogenicity correlates with survival in oxidative stress [20] which could be triggered by transcription factor Rds2 [21] or activation of MAP kinases and variability in the polyglutamine tract of Slt2 [22]. Probiotic properties are also strain specific, which is the case for Sb used as probiotic [11,12]. Thus there is a need for a valuable molecular markers able to distinguish among strains and establish appropriate methods for the identification of probiotic strains of the Sb.…”

“…summarizes some results of the investigation on differences and similarities between Sb and S. cerevisiae. Although S. boulardii strains differ significantly from laboratory strains of S. cerevisiae [11], finally according to current nomenclature like International Code of Botanical Nomenclature (ICBN) Sb yeasts should be referred to as S. cerevisiae var. boulardii [16].…”

“…Thus there is a need for a valuable molecular markers able to distinguish among strains and establish appropriate methods for the identification of probiotic strains of the Sb. Such a method could be, for example, microsatellite length polymorphism, having a discriminatory power of 99% [15,23], restriction fragment length polymorphism [24], full genome hybridization [14], randomly amplified polymorphic DNA [25], GeneChip hybridization [11], artificial neural network-assisted Fourier-transform infrared spectroscopy [26] or multilocus enzyme electrophoresis [27]. These identification methods enable the discrimination between various strains but are not necessarily related to mechanisms of probiotic activity.…”

“…Typing RFLPs or PCR-(ex 5.8S rDNA) failed to distinguish Sb from S. cerevisiae [12] Do not use galactose [13] Use galactose Asporogenous in contrast to S. cerevisiae but may produce fertile hybrids with of S. cerevisiae strains [11] Sporogenous Lost all intact Ty1/2 elements [14]. Contains several Ty1/2 elements Microsatellite typing shows genotypic differences [15] Trisomic for chromosome IX There are stable strains with various ploidy Table 1.…”