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Kevin VerstrepenWe focus on the physiological role and phenotypic variability of flocculation and biofilm formation in the common brewer's yeast Saccharomyces cerevisiae. Saccharomyces cells have a remarkable capacity to adhere to various surfaces, tissues and other cells. These properties are of considerable importance for the fermentation industry, where they are used to separate yeast from the bulk medium at the end of the fermentation process. In addition, adherence of the harmless brewer's yeast serves as a model for the deadly drug-resistant biofilms formed by hospital-acquired pathogenic fungi. Fungal adherence is an extremely variable phenotype, with most laboratory strains failing to show any adhesion, whereas feral and industrial isolates show various degrees of adhesion. Moreover, much remains to be discovered about the mechanism and regulation of fungal adhesion. Using various molecular and genetic techniques, we hope to answer some of the basic questions that still surround these intriguing processes. Why do yeast cells want to stick together? What regulates this process? Why are biofilms resistant to drugs? What makes adhesion such a variable phenotype? What changes accompanied the "domestication" of laboratory strains? How can we use genetic engineering to make superior strains for the fermentation industry? One fascinating finding of our research is that the yeast flocculation genes contain several internal tandem repeats — sequences of around 100 nucleotides that are repeated several times in the gene. These repeats function as hyper-variable modules, with frequent changes in repeat numbers leading to corresponding changes in flocculation and adhesion. We are currently investigating how the number of repeats influences the flocculation and adhesion properties. In addition, we are hoping to expand this area of research, to investigate just how prevalent this repeat-based generation of variability really is. Suggested reading:
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