Effects of hexavalent chromium on two strains of Euglena gracilis

ROCCHETTA I., RUIZ L., MAGAZ G., CONFORTI V

BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY

Springer

Lugar: Nueva York; Año: 2003 vol. 70 p. 1045 - 1051

0007-4861

  Among the industrial waste discharged into aquatic systems, heavy metals are one of the most important and dangerous contaminants. Chromium is an environmental contaminant usually released into waters by metallurgical, tanning and other industries. Aquatic ecosystems can be altered by the cytotoxic effects that this metal has on animals and plants, since it is easily absorbed by biological membranes (Levis et al., 1978). Hexavalent chromium has also been reported to have a mutagenic effect on humans, being the source of skin and lung diseases, and different types of cancer (Mertz, 1969). Chromium bioconcentration studies on the food chain showed that plankton accumulated a great amount of this metal (NRCC, 1976). It is known that the toxicity of chromium depends on its physicochemical properties (Hamilton and Weeterhahn, 1987); hence it is very important to understand the interaction between Cr(VI) and the living systems. The oxidation properties of the CrO4-2 ion, and its structural similarity to biologically important inorganic anions, such as SO4-2 and PO4-3, seem to be responsible for the chromate interactions with cell components (Riedel, 1985). Moreover, hexavalent chromium effects are generally associated to the reduction of Cr(VI) to Cr(III) that occurred within cells (Cieslak-Golonka, 1996, Cervantes et al., 2001). Previous studies on phytoplankton from the Matanza River –one of the most polluted rivers of Buenos Aires, Argentina– showed that euglenoids are one of the most important groups of this community. For decades, the quality of this River has been deteriorating due to the high discharges of different pollutants derived from untreated sewage, solid wastes and petroleum, and especially tanning industries (Conforti, 1991, Conforti et al. 1995). According to these reports, euglenoids are resistant to contaminated water systems. On the other hand, bioassays carried out with different strains of Euglena gracilis have shown that they were affected by low heavy metal concentrations (Gajdosova and Reichrtova, 1996). Based on this information, we decided to compare the behavior of two strains of Euglena gracilis; UTEX 364 (from the Culture Collection of the Texas University), and MAT (isolated from the Matanza River). Both were exposed to different concentrations of hexavalent chromium. Taking into account the source of MAT, we worked on the hypothesis that it would show higher resistance to the heavy metal.