Investigating Filamentous Growth and Biofilm/Mat Formation in Budding Yeast – Content Source NCBI/NIH
In response to nutrient limitation, budding yeast can undergo filamentous growth by differentiating into elongated chains of interconnected cells. Filamentous growth is regulated by signal transduction pathways that oversee the reorganization of cell polarity, changes to the cell cycle, and an increase in cell adhesion that occur in response to nutrient limitation. Each of these changes can be easily measured. Yeast can also grow colonially atop surfaces in a biofilm or mat of connected cells. Filamentous growth and biofilm/mat formation require cooperation among individuals; therefore, studying these responses can shed light on the origin and genetic basis of multicellular behaviors. The assays introduced here can be used to study analogous behaviors in fungal pathogens, which require filamentous growth and biofilm/mat formation for virulence.
Microbial species use diverse strategies to compete for nutrients. Being nonmotile, fungal microorganisms have developed a unique behavior, called filamentous growth, in which cells change their shape and band together in chains or filaments to scavenge for nutrients. Many fungal species can also grow in interconnected mats of cells called biofilms. The budding yeast Saccharomyces cerevisiae shows these behaviors, providing a genetically tractable system to study the pathways that control nutrient-dependent foraging. Studies on filamentous growth have provided insights into how eukaryotic cells differentiate and cooperate with each other, and how genetic pathways control fungal pathogenesis. Fungal pathogens require filamentous growth and biofilm formation for virulence.
The current picture of filamentous growth is a complex one, in which multiple pathways and hundreds of targets coordinate a highly integrated response that we are only beginning to understand. Future studies of filamentous growth will aid in the understanding of the genetic basis of cell differentiation, development, and the regulation of multicellularity in eukaryotes. The assays described in the associated protocols are attractive in terms of their simplicity and potential use as teaching tools. Their versatility furthermore allows analysis of filamentous growth and biofilm formation in diverse fungal species including pathogens.