Isolation, composition, and structure of cell walls of filamentous and yeast-like forms of Mucor rouxii

Abstract

Chemically intact cell walls of filamentous and yeast-like forms of Mucor rouxii were isolated. Comparative studies were made on their composition and structure to explore possible morphogenetic implications. Both types of cell walls exhibited a complex chemical composition consisting of polysaccharides (glucosamine, galactose, mannose and fucose), phosphate, proteins (at least 13 common amino acids), lipids (readily extracted and bound), purines and pyrimidines (RNA type), Mg 2+ and Ca 2+. Chitosan was the most abundant component of both types of cell walls. Chitin was present in smaller quantities. No qualitative differences were found between the two types of cell walls. Major quantitative differences were found in protein, purine-pyrimidine, and especially mannose content, all of which were higher in the yeast walls. Electron microscopy of ultrathin section of whole cells showed pronounced differences in thickness and fine structure of the walls. Whereas yeast walls were seemingly composed of two layers, no distinct layering was apparent in filamentous walls, which were only one tenth as thick as yeast walls.