Saccharomyces boulardii

Saccharomyces boulardii is a tropical yeast first isolated from lychee and mangosteen peels in 1923 by French scientist Henri Boulard. Although early reports claimed distinct taxonomic, metabolic, and genetic properties, S. boulardii is a grouping of S. cerevisiae strains, all sharing a >99% genomic relatedness. This has given rise to the synonym S. cerevisiae var. boulardii.

S. boulardii is sometimes used as a probiotic with the purpose of introducing beneficial microbes into the large and small intestines and conferring protection against pathogens. It grows at 37 °C (98.6 °F). In addition, the popular genome-editing tool CRISPR-Cas9 was proven to be effective in S. boulardii. Boulard first isolated this yeast after he observed natives of Southeast Asia chewing on the skin of lychee and mangosteen in an attempt to control the symptoms of cholera. In healthy people, S. boulardii has been shown to be nonpathogenic and nonsystemic (remaining in the gastrointestinal tract rather than spreading elsewhere in the body).