We describe a qualitative assay for yeast adhesion and agar invasion as a measure of invasive and pseudohyphal differentiation. This simple assay can be used to assess the invasive phenotype of various mutants as well as the effects environmental cues and signaling pathways on yeast differentiation.
Yeast cells display various differentiation modes according to nutrient availability and environmental conditions, including spore formation under starvation and stress conditions, filamentation under various nutrient stresses, and flocculation. Various yeasts, including S. cerevisiae and C. albicans, can also be found in biofilms formed by a diverse set of microorganisms. Though there is some correlation with filamentation and invasive behavior, it is not clear exactly how filamentation might cause invasion and colonization of surfaces and tissues. Yeast can certainly be found in both vegetative and filamentous forms in biofilms in nature as well as places where they threaten human health, such as catheters and infected human organs. 10-13 In order to understand the signaling pathways utilized by yeasts to infect animals and to participate in harmful and beneficial biofilms, we must develop accessible and reliable assays. Here we have developed an assay, adopted from already existing adhesion and invasion assays available for yeast, which allow us to qualitatively determine the adhesive and invasive phenotypes of yeast strains and mutants in various conditions. The assay presented here eliminates the requirement for streaking yeast cells onto the agar, where the mere action of streaking the agar surface changes the invasive and adhesive qualities of yeast. Digital imaging of especially the invading cells by a microscope allows for semi-quantitative assessment of the degree of invasion and adhesion. Such detection of invasive and adhesive cells is complimentary the single cell agar invasion assay developed by the Sprague lab 9 and can be adapted to do time course experiments.
We would like to thank Lisa Schneper and Katrin Duevel for their insights in developing this assay.
Material Name | Type | Company | Catalogue Number | Comment |
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Moticam 350 | Camera | Motic | discontinued (new model: Moticam 352) | A relatively cheap camera that attaches to eye pieces of microscopes and captures digital images for PC or Mac. |