Bacterial Toxins in Yeast Model

The budding yeast Saccharomyces cerevisiae is a powerful model organism for the studies of basic molecular cell biological processes.  Most of these basic processes are highly conserved, making the findings in yeast applicable to higher eukaryotes.  Here, we exploit the powerful genetic system and numerous genomic tools in yeast to investigate the mechanisms of bacterial toxins in eukaryotic host cells. We also use yeast to perform functional analysis of disease-related mutations in human genes and to investigate antifungal mechanisms of natural products.

1. Characterization of cytotoxic mechanisms of a bacterial genotoxin called Cytolethal Distending Toxin (CDT) from Aggregatibacteractinomycetemcomitans: We use both candidate and genome-wide approaches to investigate the role of host genes in the cytotoxic effect of CdtB, the catalytic subunit with homology to DNase.  We conditionally express CdtB from a galactose-inducible plasmid in yeast strains with various gene mutations and in the yeast deletion library. Our findings show that genes involved in homologous recombination repair of DNA double strand breaks are necessary for cell survival upon CdtB intoxication, confirming the role of CdtB as a genotoxin.  The genome-wide screens in the yeast deletion library allow us to gain further insights into the mechanisms of CdtB.
2. Identification of novel toxins from an anaerobic pathogenic bacteria: Several pathogenic bacteria translocate effector proteins into host cells as virulence factors, however the genes encoding these effector proteins are difficult to identify. This is especially important in organisms that are difficult to cultivate.  Yeast has been successfully used to screen for potential bacterial effector genes that could inhibit yeast growth because they target conserved cellular processes in eukaryotic cells.  We employ such system in order to search for potential effector genes in an anaerobic bacterial species that associates with periodontal disease, Tannerella forsythia (Tf).
3. Investigating the antifungal mechanisms of chitosan by genome wide screening in the yeast deletion library.