Genetic Insights into the Rheological Phenotype of Candida albicans Biofilms

The opportunistic fungal pathogen Candida albicans forms biofilms with viscoelastic properties and rheological response to flow that can significantly impact its biology and life cycle. The rheological phenotypes of fungal biofilms, however, have been neither quantified extensively nor genetically dissected. We have developed methods to quantify the rheology of fungal biofilms, and, here, we analyzed a panel of C. albicans deletion mutants impaired in cell wall structure or extracellular matrix (ECM) production for rheological phenotypes. Increased elastic moduli, indicative of higher viscoelasticity, were evident in strains singly deleted for ALG11, KRE5, and PMR1, with complementation strains showing wild-type phenotypes. The deletion mutants exhibited a smooth biofilm morphology on agar, with reduced hyphae, decreased ECM, and decreased fluconazole resistance. Transcriptional profiling of these strains identified altered expression of genes affecting cell membrane/cell wall biology, translation, protein catabolism, lipid metabolism, and filamentous development. Collectively, the data present C. albicans biofilm rheology as a distinct phenotype affected by ECM production and cell morphology, while identifying genes for the further investigation of fungal biofilm viscoelasticity.