The cell wall of the oleaginous yeast Trichosporon cutaneum

SUMMARY: The cell wall of Trichosporon cutaneum consists of 11% protein, 63% neutral carbohydrate, 9% glucosamine and 13% glucuronic acid. The sugars include glucose (32%), mannose (6%) and traces of xylose and galactose. The cell wall was fractionated with alkali to yield a mixture of alkali-soluble matrix components, and an alkali-insoluble glucan associated with chitin. The alkali-insoluble glucan contained a mixture of (1-3) and (1-6) glycosidic linkages. It was only partly susceptible to digestion by the β(1-3) glucanase, Zymolyase. The alkali-soluble fraction contained glucan, mannan and acidic polymers. The glucan was (1-3)-linked with no (1-6) linkages and only trace amounts of (1-3-6)-linked glucose. It was resistant to digestion by Zymolyase. Extensive hydrolysis of this fraction with trifluoroacetic acid released a high-molecular-mass glucuronan which had 1H- and 13C-NMR profiles matching those of the β(1-4) glucuronan, mucoric acid. Xylomannan was purified from isolated cell walls and from whole cells. It contained glucose, mannose, xylose, and D-glucuronic acid. It was very similar in composition and structure to the capsular polysaccharides of Cryptococcus neoformans, and to an extracellular polysaccharide produced by another yeast described as T. cutaneum. Electron microscopy showed that the cell wall of T. cutaneum has a lamellar structure characteristic of a basidiomycetous yeast rather than the electron-dense ‘fuzzy coat’ seen in Candida albicans.