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Culture experiments with the green alga Chlamydomonas sp. in metal ion‐buffered media revealed antagonistic interactions between toxic metals (Cu and Zn) and nutrient metals (Zn and Mn) in regulating cellular Mn and Zn uptake and specific growth rate. High levels of ionic Cu 2+ and Zn 2+ inhibited cellular Mn uptake, and high Cu 2+ inhibited Zn uptake rates. These effects were associated with growth rate inhibition at combined conditions of high Zn 2+ and low Mn 2+ and at high Cu 2+ and low Zn 2+ . Zinc inhibited Mn uptake by competitively blocking Mn binding to a high‐affinity Mn uptake system which was under negative feedback regulation. Kinetic modeling suggested that Zn was taken up by this system, and as a result, cellular Zn concentrations increased as external Mn 2+ was decreased. Zinc uptake behavior was complex, and in addition to the Mn system, uptake appeared to involve a high‐affinity Zn system induced at low Zn 2+ and a separate constitutive low‐affinity system. High Cu 2+ levels inhibited zinc uptake by the high‐affinity transport system. Such complex competitive interactions among metals provide important controls on cellular metal accumulation, toxicity, and nutrition.
Sunda et al. (1998) studied this question.