Biofilm formation by the fungal pathogen Candida albicans: Development, architecture, and drug resistance

Biofilms are a protected niche for microorganisms, where they are safe from antibiotic treatment and can create a source of persistent infection. Usin g two clinically relevant Candida albicans biofilm models formed on biopros thetic materials, we demonstrated that biofilm formation proceeds through t hree distinct developmental phases. These growth phases transform adherent blastospores to well-defined cellular communities encased in a polysacchari de matrix. Fluorescence and confocal scanning laser microscopy revealed tha t C. albicans biofilms have a highly heterogeneous architecture composed of cellular and noncellular elements. In both models, antifungal resistance o f biofilm-grown cells increased in conjunction with biofilm formation. The expression of agglutinin-like (ALS) genes, which encode a family of protein s implicated in adhesion to host surfaces, was differentially regulated bet ween planktonic and biofilm-grown cells. The ability of C. albicans to form biofilms contrasts sharply with that of Saccharomyces cerevisiae, which ad hered to bioprosthetic surfaces but failed to form a mature biofilm. The st udies described here form the basis for investigations into the molecular m echanisms of Candida biofilm biology and antifungal resistance and provide the means to design novel therapies for biofilm-based infections.