Cyclic Accumulation of Zinc by Candida utilis during Growth in Batch Culture

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Abstract
Intracellular accumulation of Zn by C. utilis NRRL-Y-7634 was mediated by an energy- and temperature-dependent, highly specific process exhibiting saturation kinetics. In Zn-supplemented medium, uptake occurred only during the lag and late-exponential phases; this type of transport did not occur with Zn in bacteria nor with Fe in either yeast or bacteria. Cells of C. utilis did not possess a Zn-efflux system; they could reduce their level of intracellular Zn only by dilution of the metal into daughter cells. Zn-deficient organisms accumulated 12 times more Zn than did cells of the same culture age grown in Zn-supplemented medium. The varied, but experimentally reproducible levels of intracellular Zn that occurred in response to the physiological and environmental parameters had no detectable effects on respiration, rate of growth, total cell yield or cell viability. Neither the mechanism underlying the cyclic accumulation of Zn nor the function of such behavior are understood.

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