Nutritional requirements for growth and yeastlike development of Mucor rouxii under carbon dioxide.

Unlike five other strains of Mucor rouxii previously studied, certain nutritional factors must be present for rapid growth and completely yeastlike development of M. rouxii (National Regional Research Laboratory 1894) under CO(2); high CO(2) tensions markedly inhibit growth of this strain. Addition of yeast extract, peptone, or enzymatically hydrolyzed casein in substrate amounts to a basal medium (containing acid-hydrolyzed casein) completely relieved CO(2) inhibition of growth and permitted yeastlike development. The "CO(2) growth factor" activity of these supplements proved to be dialyzable and acid labile. These findings, together with the results of gel filtration and amino acid analysis, suggested that CO(2) growth factor activity can be attributed to small peptides.