Cyclic accumulation of zinc by Candida utilis during growth in batch culture.

Intracellular accumulation of zinc by Candida utilis NRRL-Y-7634 was mediated by an energy-and temperature-dependent, highly specific process exhibiting saturation kinetics. In zinc-supplemented medium, uptake occured only during the lad and late-exponential phases; this type of transport did not occur with zinc in bacteria nor with iron in either yeast or bacteria. Cells of C. utilis did not possess a zinc-efflux system; they could reduce their level of intracellular zinc only by dilution of the metal into daughter cells. Zinc-deficient organisms accumulated 12 times more zinc than did cells of the same culture age grown in zinc-supplemented medium. The varied, but experimentally reproducible levels of intracellular zinc that occured 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 sinc nor the function of such behaviour are understood.