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

Zoiial cenitrifuge rotors are relatively large, hollow rotors containing dlensitv gra(lients ani(l offer the poszib)ility of qjumltitative se)aration of qualitatively pure particulate comlpollents of liological systemis (1, 2). The possibility is a con.seq(uenlce of the principles of centrifugationi in density gradients but to achieve it, xve shall have to fashioin inlprove(l tecliiqu1es of zonal cenitrifugationi on the anvils of specific biochemical ali(l physiological problemiis. A physiological traiisforniiatioll i Ustilago spl/aerogeoi l possesses features that led us to examinie it witlh the zonal centrifuge. Grimm and(i Allen (9) rel)orted that the yeast-like sporidia of this smllUt funigus canl he made to accumulate enormiious amiiounts of cvtochrome c (up to 1 % dry wvt) if onie provides high levels of zinlc in the growth miediumii. The concenitrations of other cvtochrome. ; were also reported to le increased by zinlc. Sinice the cytochrolmies of heterotrophic, eucarvotic cells appear to be associated l)rincipally wAith imiitochonidria (10). we tlhought that the clhanges controlled bv zilnc in (Ustilago might well involve the mlitocholndria of this organism. Conisistenit with this notioni was the report (15) that high-zinic cells sere richer in phospholipid thanl low-zilnc cells. Th'le purpose of this investigationi was therefore 2fold: to explore the idea thalt a zinic-conitrolledI process in Ustilago ilnvolve(d mitoclhoindria, and to test zonal cenitrifutges on a prol)lem xwitlh a yeast-like orgaiiislii.