Molecular architecture of the hyphal wall of Achlya ambisexualis Raper. II. Ultrastructural analyses and a proposed model

Abstract

The surface configuration of hyphal walls and various fractions of the wall were analyzed by electron microscopy using carbon–platinum replicas. Fractionation was carried out with both enzymes and chemical solvents. Laminarinase with or without protease and acid with alkali removed the acid- and alkali-soluble glucans revealing an underlying pattern of microfibrils. The combination of cellulase, laminarinase, and protease essentially dissolved the hyphae. The cellulose solvent cadoxen removed the microfibrillar pattern which was exposed following acid and alkali treatment. The acid-soluble fraction is amorphous, the alkali-soluble and the insoluble residuum is faintly microfibrillar, and the cellulose II preparation is strongly microfibrillar. Both the cellulose I and the chitinlike fractions are uniformly microfibrillar. Morphologically, the wall consists of an outer matrix of β-1,3- and β-1,6-glucans covering an inner cellulosic protein core. Both a diagrammatic and molecular model are proposed.