Control of dimorphism in a biochemical variant of Candida albicans

The cellular morphology of a biochemical variant of Candida albicans could be controlled by the ratio of carbon dioxide to oxygen in the culture system or by individual amino acids. Predominantly pseudohyphal morphology was observed (i) at a CO(2) to O(2) ratio of 2:1 and (ii) without the addition of carbon dioxide, when either glycine, d- or l-ornithine, l-serine, l-methionine, l-phenylalanine, or l-tyrosine was the sole nitrogen source in the culture medium. When ammonium chloride, ammonium sulfate, l-glutamic acid, l-glutamine, or l-proline was the nitrogen source, yeastlike growth was observed in the presence or absence of CO(2). More adenosylmethionine was present in pseudohyphal than in yeastlike cells, and pseudohyphal cell wall preparations contained less methionine than cell walls from the yeastlike form. These results suggest a correlation between sulfur amino acid metabolism and dimorphism.