THE CELL WALL POLYSACCHARIDES OF CANDIDA ALBICANS: GLUCAN, MANNAN, AND CHITIN

Abstract

Cells of Candida albicans, a pathogenic yeast, have been shown to contain, in addition to chitin, a glucan ([α]_D − 30°) and a mannan ([α]_D + 78°) in the approximate ratio of 1.00:0.64. The two polysaccharides were easily distinguishable by moving boundary electrophoresis in borate buffer and were separated from each other by fractionation of their copper complexes. Methylation and hydrolysis of the glucan yielded the following O-methyl ethers of D-glucose: 2,3,4,6-tetra-O-methyl (7 moles); 2,3,4-tri-O-methyl (13 moles); 2,4,6-tri-O-methyl (trace); 2,4-di-O-methyl (6 moles); and 2-O-methyl (1 mole). It was concluded that the glucan was a highly branched polysaccharide containing β 1 → 6 and β 1 → 3 linked residues. Periodate oxidation of the glucan supported this conclusion.Methylation and hydrolysis of the mannan yielded the following O-methyl ethers of D-mannose: 2,3,4,6-tetra-O-methyl (1.65 moles); 3,4,6-tri-O-methyl (1.00 mole); 2,3,6-tri-O-methyl (0.18 mole); 3,4-di-O-methyl (1.90 moles). The mannan was therefore a highly branched polysaccharide with short chains of α 1 → 2 linked mannose residues joined together by α 1 → 6 linkages. Results of periodate oxidation agreed with this structure.The differences between these two polysaccharides and glucans and mannans found in other yeasts are discussed.