THE METABOLISM OF YEAST SPORULATION: V. STIMULATION AND INHIBITION OF SPORULATION AND GROWTH BY NITROGEN COMPOUNDS

Abstract

The effects of a variety of nitrogen compounds, mainly amino acids, on ascus production by S. cerevisiae in sporulation media containing several carbon sources were compared. With acetate, glucose, ethanol, pyruvate, and lactate all the amino acids (0.01 M) and most other nitrogen compounds inhibited sporulation. With dihydroxyacetone fewer nitrogen compounds inhibited and alanine, phenylalanine, glycine, and lysine (especially the latter) increased sporulation, even at low concentrations (0.0001 M). Sporulation in buffer resembled sporulation in dihydroxyacetone in its response to amino acids. For greatest inhibition of sporulation the simultaneous presence of carbon and nitrogen sources was necessary. With dihydroxyacetone as carbon source, glutamic acid increased the average number of spores per ascus, but decreased it with all other carbon sources.No correlation was evident between the effects of the amino acids on sporulation and their value as nitrogen sources for growth or with changes in the oxygen uptake of cells in their presence. Dihydroxyacetone did not support growth when the nitrogen source was ammonium sulphate, but slow growth resulted when ammonium sulphate was replaced by glutamic acid or casein hydrolyzate.A sporulation medium is recommended containing, in water (or buffer) agar, 0.02 M dihydroxyacetone and 0.01 M lysine.