Mercury pretreatment selects an enhanced cadmium-accumulating phenotype in Euglena gracilis.
Pre-treatment of heterotrophic cultures of Euglena gracilis with 1.5 microM HgCl(2) for at least 60 generations resulted in a cell population that showed both increased resistance to Cd(2+) and ability to accumulate it, when compared to non-Hg(2+)-pretreated Euglena. These Hg(2+)-enhanced capacities were evident in cells cultured in the dark in a medium with lactate, but not in cells cultured with glutamate plus malate. After culturing with 0.1 mM CdCl(2) through three consecutive transfers, the mercury-pretreated cells still grew and maintained high levels of glutathione-related metabolites, while the non-Hg(2+)-pretreated cells died. Cultures of Hg(2+)-pretreated cells, after transfer to media with or without cadmium, did not alter either their enhanced Cd(2+) accumulation or their increased production of glutathione-related metabolites. These observations suggested that the Hg(2+)-pretreated population underwent a permanent change that improved its Cd(2+) resistance. Several factors that contributed to the improved capacities included: (a) higher cellular malate, cysteine and glutathione levels induced by Hg(2+) before and after Cd(2+) exposure; and (b) increased storage of Cd(2+) in mitochondria along with increased intramitochondrial citrate, cysteine, and glutathione levels. These characteristics suggested that this Cd(2+) hyper-accumulating strain of E. gracilis might be a suitable candidate for Cd(2+)-bioremediation of polluted water systems.
Departamento de Bioquímica, Instituto Nacional de Cardiología, DF. 14080, México, México.
César
C
Avilés
Herminia
H
Loza-Tavera
Norman
N
Terry
Rafael
R
Moreno-Sánchez
D000818:Animals; D001673:Biodegradation, Environmental; D002104:Cadmium / Q000378:metabolism* / Q000494:pharmacology; D024881:Drug Resistance, Bacterial / Q000502:physiology*; D005056:Euglena gracilis / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D008627:Mercuric Chloride / Q000493:pharmacokinetics / Q000633:toxicity*; D010641:Phenotype
D002104:Cadmium; D008627:Mercuric Chloride