Zonal centrifuge analysis of a transformation in Ustilago controlled by zinc.

Abstract

Zonal centrifuge rotors are relatively large, hollow rotors containing density gradients and offer the possibility of quantitative separation of qtualitatively pure particulate components of biological systems (1, 2). The possibility is a consequence of the principles of centrifugation in density gradients but to achieve it, we shall have to fashion improved techniques of zonal centrifugation on the anvils of specific biochemical and physiological problems. A physiological transformation in Ustilago sphaerogena possesses features that led us to examine it with the zonal centrifuge. Grimm and Allen (9) reported that the yeast-like sporidia of this smut fungus can be made to accumulate enormous amounts of cytochrome c (up to 1 % dry wt) if one provides high levels of zinc in the growth medium. The concentrations of other cytochromes were also reported to be increased by zinc. Since the cytochromes of heterotrophic, eucaryotic cells appear to be associated principally with mitochondria (10), we thought that the changes controlled by zinc in Ustilago might well involve the mitochondria of this organism. Consistent with this lnotionl was the report (15) that high-zinc cells were richer in phospholipid than low-zinc cells. 'T'he pturpose of this investigation was therefore 2fold: to explore the idea that a zinc-controlled process in Ustilago involved mitochondria, and to test zonal centrifuges on a problem with a yeast-like organism.