Community participation in biofilm matrix assembly and function

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 112; no. 13; pp. 4092 - 4097
• Main Authors: Mitchell, Kaitlin F., Zarnowski, Robert, Sanchez, Hiram, Edward, Jessica A., Reinicke, Emily L., Nett, Jeniel E., Mitchell, Aaron P., Andes, David R.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 31.03.2015; National Acad Sciences
• Subjects: antifungal agents; Antifungal Agents - chemistry; biofilm; Biofilms; Biological Sciences; Biosynthesis; Candida albicans; Candida albicans - metabolism; Carbohydrates; Carbohydrates - chemistry; Cell Wall - metabolism; Cells; Coculture Techniques; Community involvement; community service; Drug resistance; Enzyme-Linked Immunosorbent Assay; extracellular matrix; Extracellular Matrix - metabolism; Fluconazole - chemistry; Fungi; Glucose - chemistry; lifestyle; Mannose - chemistry; Matrix; Microscopy, Electron, Scanning; Microscopy, Electron, Transmission; pathogens; Polysaccharides - chemistry; Saccharides; polysaccharide; matrix; Candida; resistance; biofilm
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.1421437112

Biofilms of the fungus Candida albicans produce extracellular matrix that confers such properties as adherence and drug resistance. Our prior studies indicate that the matrix is complex, with major polysaccharide constituents being α-mannan, β-1,6 glucan, and β-1,3 glucan. Here we implement genetic, biochemical, and pharmacological approaches to unravel the contributions of these three constituents to matrix structure and function. Interference with synthesis or export of any one polysaccharide constituent altered matrix concentrations of each of the other polysaccharides. Each of these was also required for matrix function, as assessed by assays for sequestration of the antifungal drug fluconazole. These results indicate that matrix biogenesis entails coordinated delivery of the individual matrix polysaccharides. To understand whether coordination occurs at the cellular level or the community level, we asked whether matrix-defective mutant strains could be coaxed to produce functional matrix through biofilm coculture. We observed that mixed biofilms inoculated with mutants containing a disruption in each polysaccharide pathway had restored mature matrix structure, composition, and biofilm drug resistance. Our results argue that functional matrix biogenesis is coordinated extracellularly and thus reflects the cooperative actions of the biofilm community. Significance Candida albicans is the most common fungal pathogen and frequently grows as a biofilm. These adherent communities tolerate extremely high concentrations of antifungals due in large part to the protective extracellular matrix. The present studies observe a novel reliance on multiple matrix constituents for structure and function. Furthermore, the results demonstrate how the biofilm community assembles these matrix components in the extracellular space. Our findings reveal a coordinated mechanism by which the defining trait of the biofilm lifestyle arises and identify a number of potential therapeutic targets.