Saccharomyces cerevisiae: the effect of different forms and concentrations of iodine on uptake and yeast growth.

The essentiality of iodine for humans, especially in the early stages of life, is well recognized. The chemical forms of iodine in food supplements, infant formulae and iodated salt are either iodide (KI) or iodate (KIO(3)). Because there are no or rare data about iodine uptake by yeasts, we investigated the influence of different sources of iodine, as KI, KIO(3) and periodate (KIO(4)), on its uptake in and growth of the model yeast Saccharomyces cerevisiae. KIO(3) inhibited the growth of the yeast the most and already at a 400 microM initial concentration in the growth medium; the OD was reduced by 23% in comparison with the control, where no KIO(3) was added. The uptake of different iodine sources by the yeast S. cerevisiae was minimal, in total <1%. Tracer experiments with radioactive (131)I added as KI showed that the yeast S. cerevisiae does not have the ability to transform KI into volatile species. We investigated the specificity of iodine uptake added as KIO(3) in the presence of Na(2)SeO(4) or ZnCl(2) or K(2)CrO(4) in the growth medium, and it was found that chromate had the most influence on reduction of KIO(3) uptake.