Surface Hydrophobicity Changes of Two Candida albicans Serotype B mnn4 Δ Mutants

Abstract

Cell surface hydrophobicity (CSH) of Candida species enhances virulence by promoting adhesion to host tissues. Biochemical analysis of yeast cell walls has demonstrated that the most significant differences between hydrophobic and hydrophilic yeasts are found in the acid-labile fraction of Candida albicans phosphomannoprotein, suggesting that this fraction is important in the regulation of the CSH phenotype. The acid-labile fraction of C. albicans is unique among fungi, in that it is composed of an extended polymer of ␤-1,2-mannose linked to the acid-stable region of the N-glycan by a phosphodiester bond. C. albicans serotype A and B strains both contain a ␤-1,2-mannose acid-labile moiety, but only serotype A strains contain additional ␤-1,2-mannose in the acid-stable region. A knockout of the C. albicans homolog of the Saccharomyces cerevisiae MNN4 gene was generated in two serotype B C. albicans patient isolates by using homologous gene replacement techniques, with the anticipation that they would be deficient in the acid-labile fraction and, therefore, demonstrate perturbed CSH. The resulting mnn4⌬-deficient derivative has no detectable phosphate-linked ␤-1,2-mannose in its cell wall, and hydrophobicity is increased significantly under conditions that promote the hydrophilic phenotype. The mnn4⌬ mutant also demonstrates an unanticipated perturbation in the acid-stable mannan fraction. The present study reports the first genetic knockout constructed in a serotype B C. albicans strain and represents an important step for dissecting the regulation of CSH.The modification of proteins by carbohydrate is conserved throughout eukaryotic species. The stepwise addition of carbohydrate to nascent proteins occurs shortly after translocation of the polypeptide into the endoplasmic reticulum, and posttranslational glycosylation is limited to a subset of total cellular proteins that transit through the secretory pathway. Core carbohydrate addition to specific amino acid residues is essentially identical in all eukaryotes. However, the maturation of glycans is variable between species and can vary between cell types in a single organism. The addition of glycan to a protein plays various functional roles for the protein and increases the apparent molecular mass of the protein. The dissection of carbohydrate maturation pathways has been accomplished by the parallel use of biochemical analysis of glycosylation in many cell types and the identification of microbial mutants defective in carbohydrate addition.The cell walls of fungi are composed of highly branched polymers of glycan with embedded, highly glycosylated proteins and serve an essential role in maintaining the structural integrity of the cell (46). The addition of glycans to cell wall glycoproteins in the budding yeast Saccharomyces cerevisiae has been elucidated by the identification of a panel of viable loss-of-function mutants at various points in the pathway (see, e.g., references 3-7, 20, and 45), and the basic enzymology of carbohydrate addition is essentially c...

Insight into the Antiadhesive Effect of Yeast Wall Protein 1 of Candida albicans

“…Various assays have suggested that deletion of YWP1 increases the surface hydrophobicity of yeast cells (unpublished observations), but efforts to reliably quantify this effect have been unsuccessful, in part because wild-type parental strain SC5314 is already relatively hydrophobic (38). Such an antihydrophobicity effect might be due to the abundance of Ywp1 if Ywp1 is indeed hydrophilic, but the mechanistic relationship between glycans, hydrophobicity, and adhesion remains complex and enigmatic at this time (38,55). Alternatively, the effect may be more specific.…”

Antifungal and post-antifungal effects of chlorhexidine, fluconazole, chitosan and its combinations on Candida albicans

“…Yeast suspensions were mixed with chloroform (volume relationship 5:1); the mixture was agitated for 1 minute and put to rest during 10 min at 37ºC. CSH was defined as the difference between absorbances at 520 nm of the aqueous phase before and after the confronting C. albicans suspension and the organic phase, ∆Abs (5).…”

“…The first stage of the infection includes adhesion to cellular surfaces. Adhesion of yeast has been studied using buccal epithelial cells, different cell lines, and plastic materials (3,4), with the cell surface hydrophobicity of fungus (CSH) as the main force implied in this process (5). Besides, C. albicans is capable of secreting exoenzymes, such as phospholipase (PL), and of developing hyphae, which allows penetration in oral tissues and, in turn, the infection process (6,7).…”

Eap1p, an Adhesin That Mediates Candida albicans Biofilm Formation In Vitro and In Vivo

“…Attachment of C. albicans cells to materials is mediated by nonspecific interactions, such as hydrophobic and electrostatic forces, as well as by specific adhesin-ligand bonds (8,10,26,44,45,50). Cell hydrophobicity and charge also depend on cell growth morphology and cell surface structure (27).…”