MORPHOGENESIS AND ADHESION OF AUREOBASIDIUM-PULLULANS

Two strains of the dimorphic fungus Aureobasidium pullulans were grown in liquid and on solid media varying in carbon and nitrogen content, and on leaf surfaces. Hyphae were observed in all systems but comprise d a very low proportion (often below quantitative detection) of the to tal biomass. In liquid media, hyphae were found sparsely and only in t he wash-zone on walls of the culture flasks. Yeast phase growth (blast ospores) occurred in pH-buffered media that were nutrient balanced, or continuously carbon-limited (fed-batch culture), or carbon-exhausted (batch culture). Blastospores exposed to conditions with limited nitro gen but sufficient organic carbon, or to acidified media, converted to swollen cells and chlamydospores. The latter morphotypes accumulated carbon internally as lipid granules, and then externally as capsular a nd soluble extracellular polysaccharide. They were cohesive and also a dhered more strongly to cellulose membranes overlying agar media or to leaves than did blastospores. Pullulanase treatment diminished the ca psules, cohesion, and adhesion. Addition of soluble extracellular poly saccharide to blastospores enhanced their adhesion to leaves. We concl ude that extracellular polysaccharide can play a role in adhesion of A . pullulans.