Modification of the Composition and Structure of the Yeast Cell Wall by Culture in the Presence of Sulfur Amino Acids

Growth of Candida utilis and Saccharomyces cerevisiae in a medium supplemented with sulfur amino acids led to synthesis and accumulation of S-adenosylmethionine, accompanied by a reduction in the cell yield, an increased sensitivity of the cell wall to snail gut enzymes (Helix pomatia), as judged by spheroplast formation, and by a modification of the chemical composition of both the intact cells and their isolated walls. Walls of supplemented cultures of C. utilis were three times as sensitive to enzymatic digestion as walls from nonsupplemented cultures. In contrast to C. utilis, walls isolated from supplemented cultures of S. cerevisiae were digested slightly more rapidly by the purified snail extract than those from nonsupplemented cultures. Chemical modifications of the cell wall are interpreted to explain the ease with which cells from sulfur amino acid-supplemented cultures are converted to spheroplasts.