Plasticity of Candida albicans Biofilms

Abstract

SUMMARYCandida albicans, the most pervasive fungal pathogen that colonizes humans, forms biofilms that are architecturally complex. They consist of a basal yeast cell polylayer and an upper region of hyphae encapsulated in extracellular matrix. However, biofilms formedin vitrovary as a result of the different conditions employed in models, the methods used to assess biofilm formation, strain differences, and, in a most dramatic fashion, the configuration of the mating type locus (MTL). Therefore, integrating data from different studies can lead to problems of interpretation if such variability is not taken into account. Here we review the conditions and factors that cause biofilm variation, with the goal of engendering awareness that more attention must be paid to the strains employed, the methods used to assess biofilm development, every aspect of the model employed, and the configuration of theMTLlocus. We end by posing a set of questions that may be asked in comparing the results of different studies and developing protocols for new ones. This review should engender the notion that not all biofilms are created equal.

Candida albicans cell-type switching and functional plasticity in the mammalian host

“…Medical device-associated biofilms are of enormous clinical importance because of their high prevalence and intrinsic resistance to antibiotics and the mammalian immune system. C. albicans MTL a / MTL α white a /α cells form conventional biofilms in a stereotyped fashion (reviewed in 148, 149 , see the figure, part a). Biofilms are initiated when white a /α phase yeasts attach to a solid substrate.…”

“…These biofilms differ from conventional biofilms by multiple criteria, including increased permeability, decreased resistance to antibiotics and host immune cells, and promotion of chemotropism between opaque a MTL a and MTL α cells. 76, 77, 149 It has been proposed that a primary function of white a cell biofilms is to facilitate mating between sexually competent MTL a and MTL α opaque a cells. 77 …”

Fungal Biofilms: Inside Out

“…Biofilm integrity probably depends upon a balance of cell-substrate adherence and cell-cell adherence (sometimes called cohesion (97)). The importance of this balance was emphasized in studies of Cabral et al of a panel of C. albicans strains that overexpressed 531 different individual genes, including many cell wall protein genes (10).…”

“…However, the specific in vitro conditions used can have dramatic effects on biofilm properties (15, 97), and some mutations cause a biofilm defect only under a subset of in vitro conditions (85). In fact, one theme that has emerged repeatedly in all aspects of infection biology is that in vitro conditions can be poor mimics of in vivo conditions.…”

Candida albicans biofilm inactivated by cold plasma treatment in vitro and in vivo

“…Importantly, increased C. albicans infections are associated with their biofilm‐forming ability. A biofilm is a highly structured microbial community, consisting of a basal yeast cell polylayer and an upper extracellular matrix (ECM) region with hyphae encapsulated inside, attached to the biotic or abiotic surface . The complex interactions among cells in the biofilm and the tight packaging of ECM protect C. albicans from antimicrobial agents and host defenses, resulting in serious health problems and economic consequences .…”