Isolation and characterization of extracellular three-lamellar structures ofSporotrichum pulverulentum

Transmission electron microscopic investigations revealed extracellular three-lamellar and tubuli-like structures formed by the white rot fungusSporotrichum pulverulentum, which was grown with glucose on a rotary shaker. These structures, originating from the outermost fungal cell wall layer, were isolated by digesting the purified cell walls with snail enzyme. The resistant structures contained in the outer cell wall layer were harvested and chemically analyzed. They were composed of 80–90% carbohydrates, primarily glucose monomeres; 5–10% proteins, including five fractions with molecular weights between 30 000 and 200 000; and, finally, 5–10% lipids, none of which were phospholipids. Chemical analysis of the components after treatment with 2-mercaptoethanol/EDTA, followed by TEM observations, however, suggests that these structures consist of almost equal amounts of carbohydrate, protein, and lipid and that the additional carbohydrate is attached to them without any structural function. Several hypothesis concerning the biological function of the structures are made.