Fungal Super Glue: The Biofilm Matrix and Its Composition, Assembly, and Functions

Biofilms are arguably the most common state of microbial growth found in nature and in patients infected with pathogenic organisms. A canonical feature of prokaryotic and eukaryotic biofilms is their production of an extracellularmatrix (Fig 1). The matrix provides a protective environment for biofilm cells, offering a three-dimensional framework for both surface adhesion and cell cohesion [1,2]. In addition, this extracellularmaterial controls cell dispersion from the biofilm and provides a nutrient source for the community [3]. The physical barrier formed by the matrix is also clinically relevant, as it shields cells from environmental threats, including immune cells and antimicrobial drugs used for treatment [4,5]. This defensive characteristic has been demonstrated for biofilms formed by diverse fungal pathogens, including Aspergillus, Candida, Cryptococcus, and Saccharomyces, with Aspergillus fumigatus and Candida albicans being the best studied [2,5–8]. Biofilm-associatedCandida infections are the fourth cause for nosocomial infections (predominantly infectingmedical devices), which may lead to systemic infection associated with highmortality rates. Candida spp. are also the most common cause of mucosal infection of the oral and vaginal sites, where biofilm infection has been increasingly recognized.Despite the ubiquitous nature of the biofilmmatrix, we are only beginning to understand the synthesis and composition of this material for a handful of species. This reviewwill discuss select components of the extracellularmatrix of fungal biofilms, including their synthesis, structure, and function.