Time-course development of the Cd2+ hyper-accumulating phenotype in Euglena gracilis.
To determine the onset of the Cd2+-hyperaccumulating phenotype in Euglena gracilis, induced by Hg2+ pretreatment (Avilés et al. in Arch Microbiol 180:1-10, 2003), the changes in cellular growth, Cd2+ uptake, and intracellular contents of sulfide, cysteine, gamma-glutamylcysteine, glutathione and phytochelatins during the progress of the culture were analyzed. In cells exposed to 0.2 mM CdCl2, the Cd2+-hyperaccumulating phenotype was apparent only after 48 h of culture, as indicated by the significant increase in cell growth and higher internal contents of sulfide and thiol-compounds, along with a higher gamma-glutamylcysteine synthetase activity. However, the stiochiometry of thiol-compounds/Cd2+ accumulated was similar for both control and Hg2+-pretreated cells. Moreover, the value for this ratio was 2.1 or lower after 48-h culture, which does not suffice to fully inactivate Cd2+. It is concluded that, although the glutathione and phytochelatin synthesis pathway is involved in the development of the Cd2+-hyperaccumulating phenotype in E. gracilis, apparently other pathways and sub-cellular mechanisms are also involved. These may be an increase in other Cd2+ chelating molecules such as di- and tricarboxylic acids, phosphate and polyphosphates, as well as Cd2+ compartmentation into organelles.
Avilés
César
C
Departamento de Bioquímica, Instituto Nacional de Cardiología, Juan Badiano No. 1, Col. Sección XVI, Tlalpan, 14080, México.
Torres-Márquez
M Eugenia
ME
Mendoza-Cózatl
David
D
Moreno-Sánchez
Rafael
R
D000818:Animals; D001673:Biodegradation, Environmental; D002104:Cadmium / Q000378:metabolism*; D003545:Cysteine / Q000378:metabolism; D004151:Dipeptides / Q000378:metabolism; D004351:Drug Resistance; D005056:Euglena gracilis / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D005721:Glutamate-Cysteine Ligase / Q000302:isolation & purification / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D008628:Mercury / Q000494:pharmacology; D010641:Phenotype; D054811:Phytochelatins; D013438:Sulfhydryl Compounds / Q000378:metabolism; D013440:Sulfides / Q000378:metabolism
D004151:Dipeptides; D013438:Sulfhydryl Compounds; D013440:Sulfides; D002104:Cadmium; D054811:Phytochelatins; D005721:Glutamate-Cysteine Ligase; D008628:Mercury; D005978:Glutathione; D003545:Cysteine; C017341:gamma-glutamylcysteine