Promotion by Zinc of the Formation of Cytochromes in Ustilago sphaerogena.

Ustilago sphaerogena is a smut fungus which is parasitic on the grass Echinochloa crus-galli but may be cultured saprophytically in the sporidial stage of its life cycle. The form, rate of growth, and color of the sporidia were found (29) to be dependent upon the medium in which the fungus is grown. In a medium containing 2 % yeast extract and 2 % sucrose, large, rapidly growing pink sporidia which bud in the manner of yeasts are produced in shakeculture. However, in other organic and inorganic media, filamentous, slower growing, white sporidia are produced. The difference in color is striking and was found (29) to be due to the pigment, cytochrome c. The effect of the nutrient medium on the production of other cytochromes and cytochrome oxidase as well as cytochrome c is presented here. Evidence is given that the substance in yeast extract responsible for the high level of cytochrome in this organism is zinc.