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

Abstract

The pink pigment of U. sphaerogena sporidia grown in 1% yeast extract (Y.E.)-1% sucrose medium is shown to be cytochrome (cyt.) c, which may constitute as much as 1% of the dry wt. of the cells. Sporidia grown in a simple synthetic medium are white and contain a max. of 0.08% cyt. c, although the yield of cell material is comparable with that obtained in Y.E. and the QO2 of the cells is similar to that of the pink cells. Y.E. also enhances the production of cyt. a and b and of cyt. oxidase. The substance in Y. E. responsible for high cyt. c production is Zn. Although only 0.001 ppm Zn is required for opt. growth, 1.0 ppm is opt. for pigment formation, which can be obtained in a completely synthetic medium. The addition of 2.0 ppm thiamin results in a further increase in cyt. formation in the presence of 1.0 ppm Zn, but it is without effect in the absence of Zn and is not a required growth factor Cyt. a and b and cyt. oxidase are also increased by the addition of zinc to a synthetic medium, but not to the high levels produced in Y.E. Their production is not affected by thiamin. Y. E. also has an effect on cell morphology which is partially reproduced by Zn. Ammonium ion is specifically required for the enhanced production of cyt. in the presence of Zn and thiamin. It cannot be replaced by nitrate or amino acids although these are adequate sources of N for growth. A spectro-photometric method for the quantitative determination of cyto-chrome c in suspensions of intact cells is described.