Mercury uptake and removal by Euglena gracilis

Abstract.

The uptake and removal of mercury (added as HgCl₂) from the culture medium by Euglena gracilis was studied. In cultures initiated in the light, cells accumulated a small fraction of the added heavy metal (5–13%). Mercury was both biologically and nonbiologically volatilized, and cell growth was partially inhibited; under these conditions the glutathione content was 3.2 nmol/10⁶ cells. In contrast, in cultures initiated in the dark, mercury uptake by cells was two to three times higher, biological volatilization remained unchanged and nonbiological volatilization and growth were negligible; the glutathione content diminished to 1.4 nmol/10⁶ cells. Biological mercury volatilization depended on cell density and metal concentration, but was light-independent. Thus, volatilization of mercury by Euglena appeared not to be an effective mechanism of resistance, whereas a high intracellular level of glutathione and a low mercury uptake seemed necessary for successful tolerance.