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Time-course development of the Cd2+ hyper-accumulating phenotype in Euglena gracilis
César Avilés1, M Eugenia Torres-Márquez, David Mendoza-Cózatl
1Departamento de Bioquímica, Instituto Nacional de Cardiología, Juan Badiano No. 1, Col. Sección XVI, Tlalpan, 14080, México.
Archives of Microbiology
|September 24, 2005
Summary
Mercury pretreatment induces cadmium hyperaccumulation in Euglena gracilis after 48 hours. While glutathione and phytochelatins are involved, other mechanisms also contribute to cadmium detoxification.
Area of Science:
- Environmental microbiology
- Biochemistry
- Cellular biology
Background:
- Mercury (Hg2+) pretreatment can induce specific phenotypes in Euglena gracilis.
- Understanding cadmium (Cd2+) hyperaccumulation is crucial for bioremediation strategies.
Purpose of the Study:
- To determine the onset of the Cd2+-hyperaccumulating phenotype in Euglena gracilis after Hg2+ pretreatment.
- To analyze cellular growth, Cd2+ uptake, and intracellular compounds during culture progression.
Main Methods:
- Culturing Euglena gracilis with CdCl2 exposure.
- Analyzing cellular growth, Cd2+ uptake, and intracellular levels of sulfide, cysteine, gamma-glutamylcysteine, glutathione, and phytochelatins.
- Measuring gamma-glutamylcysteine synthetase activity.
Main Results:
- The Cd2+-hyperaccumulating phenotype became apparent after 48 hours of culture in cells exposed to 0.2 mM CdCl2.
- Significant increases in cell growth, sulfide, and thiol-compounds were observed.
- Gamma-glutamylcysteine synthetase activity was higher, but the thiol-compounds/Cd2+ ratio was insufficient for complete Cd2+ inactivation.
Conclusions:
- The glutathione and phytochelatin synthesis pathway is involved in Cd2+-hyperaccumulation in Euglena gracilis.
- Other pathways, including increased chelating molecules (di-/tricarboxylic acids, phosphates) and organelle Cd2+ compartmentation, are also implicated.
- Additional sub-cellular mechanisms contribute to the Cd2+-hyperaccumulating phenotype.