Isolation and chemical characterization of plasma membranes from the yeast and mycelial forms of Candida albicans

Abstract

It has been possible to induce the yeast-mycelium transformation in Candida albicans by growth of the organism under completely defined conditions in batch culture. Protoplasts have been obtained from the two forms by using a lytic enzyme preparation from Streptomyces violaceus. A plasma membrane fraction was prepared by osmotic lysis of these protoplasts and fractionated by using a combination of differential and discontinuous sucrose density-gradient flotation centrifugation. The purity of this fraction was determined by radioactive dansylation and iodination of plasma membranes of intact protoplasts followed by localization of the radioactivity upon fractionation. This procedure demonstrated less than 4% contamination of the plasma membrane fraction with other cell membranes. Chemical analysis of this fraction revealed that the major components were protein and lipid. Membranes from the yeast form contained (w/w): 50% protein, 45% lipid, 9% carbohydrate and 0.3% nucleic acid. Plasma membranes from the mycelial form contained significantly more carbohydrate and were found to be composed of (w/w): 43% protein, 31% lipid, 25% carbohydrate and 0.5% nucleic acid. Marked differences were also observed between the phospholipid, free and esterified sterols, and total fatty acids of membranes from the two forms of the organism.