Structure and chemical composition of yeast chlamydospores of Aureobasidium pullulans.

Abstract

Cellular form in Aureobasidium pullulons can be partially controlled by nitrogen nutrition. Ammonium nitrogen supports a mixture of filamentous and yeastlike growth, whereas only a few filaments develop on nitrate nitrogen. On nitrate 97% of the cell material consists of a mixture of yeastlike cells and chlamydospores. Chlamydospores are produced on both nitrogen sources; however, with ammonium nitrogen chlamydospores occur in an intercalar position, whereas nitrate nitrogen supports development of chlamydospores as separate structures containing one, two, or occasionally three cells. This mode of production allows separation of yeast chlamydospores from other cell types and subsequent isolation of their cell walls. Yeast chlamydospores and filaments have an electron dense, melanin-rich, granular, outer cell-wall layer which yeastlike cells lack. This granular material is also found in cross walls of filaments and chlamydospores. Glucose is the main component of chlamydospore walls and accounts for 36% of the dry weight. Yeastlike cell walls contain only 13% glucose, but more mannose, galactose, and bound lipid. Most of the glucan portion of chlamydospore walls is insoluble in dilute alkali; methylation analysis indicates that this material contains linear chains of (1 → 3) and (1 → 6) linked glucose. About one residue in five forms a branch point having both (1 → 3) and (1 → 6) linkages.