Biofilm Exopolysaccharides of Pathogenic Fungi: Lessons from Bacteria

Abstract

Exopolysaccharides play an important structural and functional role in the development and maintenance of microbial biofilms. Although the majority of research to date has focused on the exopolysaccharide systems of biofilm-forming bacteria, recent studies have demonstrated that medically relevant fungi such as Candida albicans and Aspergillus fumigatus also form biofilms during infection. These fungal biofilms share many similarities with those of bacteria, including the presence of secreted exopolysaccharides as core components of the extracellular matrix. This review will highlight our current understanding of fungal biofilm exopolysaccharides, as well as the parallels that can be drawn with those of their bacterial counterparts.

What's on the Outside Matters: The Role of the Extracellular Polymeric Substance of Gram-negative Biofilms in Evading Host Immunity and as a Target for Therapeutic Intervention

“…Another approach for disruption of biofilms formed by Pa has involved the use of glycoside hydrolases to target exopolysaccharides present within the EPS, as the enzymes PelA h , PslG h , and Sph3 h can disrupt existing Pa biofilms in vitro (77,78). The accompanying review by Sheppard and Howell discusses this class of enzymes in more detail (79). Likewise, the enzyme Dispersin B in combination with an AMP showed synergistic antibiofilm/ antibacterial activity in a chronic wound model of Pa infection (80).…”

Microbiological, biochemical, physicochemical surface properties and biofilm forming ability ofBrettanomyces bruxellensis

“…All these results suggest distinct wall composition and metabolism traits which can 304 possibly affect the biofilm production capacity. Indeed, the wall polysaccharides are the first and most 305 abundant component of the cell which comes in contact with the surfaces and can affect the microbial 306 colonization ability (Ghafoor et al, 2011;Sheppard and Howell 2016). According to previous studies, they 307 may contribute positively or negatively to biofilm formation (Legras et al 2016;Verstrepen and Klis 2006).…”

Both galactosaminogalactan and α-1,3-glucan contribute to aggregation ofAspergillus oryzaehyphae in liquid culture

“…In Aspergillus species, the cell wall is composed of α-glucan (mainly α-1,3-glucan), β-1,3/1,6-glucan, galactomannan, and chitin (6–8). Cell walls of some filamentous fungi are covered with extracellular matrix, which is composed mainly of polysaccharides, including α-glucan (α-1,3-glucan with a small amount of α-1,4-glucan), galactomannan, or galactosaminogalactan (GAG) (9, 10).…”

“…GAG is a hetero-polysaccharide composed of linear α-1,4-linked galactose (Gal), N -acetylgalactosamine (GalNAc), and galactosamine (GalN). GAG is an important pathogenetic factor in the human pathogen A. fumigatus (14, 15); it is involved in adherence to host cells, biofilm formation, and avoidance of immune response by masking β-1,3-glucan and chitin (9, 16). Disruption of genes encoding the transcription factors StuA and MedA significantly decreases GAG content and has led to identification of the uge3 (UDP-glucose 4-epimerase) gene (16).…”

“…In stuA and medA gene disruptants, these five genes are downregulated, suggesting that they are co-regulated by StuA and MedA (17). GAG biosynthesis by the five encoded proteins is predicted in A. fumigatus (9, 18). First, the epimerase Uge3 produces UDP-galactopyranose (Gal p ) from UDP-glucose and UDP- N -GalNAc from UDP- N -acetylglucosamine (GlcNAc) (16, 19).…”