Response to heavy metals in organisms – I. Excretion and accumulation of physiological and non physiological metals in Euglena gracilis.

Euglena gracilis was cultured with different concentrations of an essential metal and a non essential one: Cu and Cd. Cu even at high concentrations did not affect the growth rate, while Cd reduced it according to the concentration used. Cu concentration stayed always lower in the cells than in the medium, instead Cd was accumulated in the cells. From cells and medium of cultures treated with copper a glycopeptide which chelated copper and zinc was isolated. It was present in the control culture too, but it linked only Zn; its molecular weight is lower than 10,000 D. From cells cultured with Cd a compound of a very high molecular weight (higher than 100,000 D) was isolated: it linked Cd and Zn. The concentration of Zn in the medium and in the cells linked to the compounds is also discussed, and a model is proposed for regulation of physiological metals in organisms; it may explain how detoxification relates to regulation of heavy metals. © 1980.