[en] The cadmium inhibits the growth of the marine microalga Tetraselmis suecica. The effective concentration (EC50 value) for this microalga was estimated as 7.9±1 mg/l of cadmium after six days of exposure to this metal Tetraselmis suecica cells synthesize thiol compounds when they are exposed to cadmium, most of the intracellular metal was bond to these compounds. Part of these thiol compounds have been identified as phytochelatins. A new capillary electrophoresis (CZE) technique was developed for the identification of these thiolic compounds previously derivatized with mBrB in biological complex samples. The electrophoretic conditions used to optimize the separation were: - Electrolyte: 150 mm H3PO4 pH 1.60 and 2.5 % methanol (v/v). - CZE conditions: uncoated fused-silica capillary, 30 cm effective length x 50 ?m ID (38 cm total length); samples introduced by pressure (50 mbar) for 17 s; applied voltage, 13 kV; detection wavelength, 390 nm. The established conditions allow a rapid, reproducible and sensitive analysis of thiolic compounds. The synthesis of phytochelatins is a mechanism of effective defense in the response to cadmium but with concentrations of the metal below the values of the EC50. When the concentration of cadmium exceeds this value, the poisonous effect of the cadmium blocks the synthesis of phytochelatins, being the amino acid cysteine the principal chelant agent. Nevertheless, the cysteine presents a low chelation capacity of the metal, therefore, this amino acid would not avoid the toxicity provoked by high concentrations of cadmium. A second family of thiolic peptides was characterized in Tetraselmis suecica: desglicyl phytochelatins. T. suecica was found to have good accumulation properties for cadmium. The presence of a significant amount of this metal in its cells and the high tolerance to this metal suggested the possibility of using this microalgae in bioremediation processes in seawater polluted with cadmium.

[gl] O cadmio inhibe o crecemento da microalga mariña Tetraselmis suecica, sendo o seu EC50 despois de 6 días de exposición a cadmio de 7.9 mg Cd/L. Como consecuencia da exposición ó cadmio, as células de Tetraselmis suecica sintetizan compostos que presentan grupos tiol, uníndose a maior parte do metal intracelular a estos compostos. Parte de estos compostos identificáronse como fitoquelatinas. Desenvolveuse unha nova técnica de electroforesis capilar para a identificación de estos compostos tiólicos derivatizados con mBrB en mostras biolóxicas complexas. As condicions electroforéticas usadas para optimizar a separación foron: - Electrolito: 150 mM H3PO4 pH 1.60 y 2.5 % metanol (v/v). - Condiciones da electroforesis capilar: 13 kV, capilar (50 µm d.i. x 375 µm d.e) de 30 cm de lonxitude efectiva, inxección mediante presión de 50 mbar durante 17s, detección a unha lonxitude de onda de 390 nm. As condicions establecidas permiten un análise rápido, reproducible e sensible de compostos tiólicos. A síntese de fitoquelatinas é un mecanismo de defensa efectiva na resposta a cadmio pero con concentraciones do metal por debaixo dos valores da EC50. Cando a concentración de cadmio sobrepasa este valor o efecto tóxico do cadmio bloquea a síntese de fitoquelatinas, sendo o aminoácido cisteína o principal axente quelante. Sen embargo, a cisteína presenta unha capacidade baixa de quelación do metal polo que non evitaría a toxicidade provocada por concentraciones altas de cadmio. Unha segunda familia de péptidos tiólicos foi caracterizada en Tetraselmis suecica, as fitoquelatinas desgliciladas. As células de Tetraselmis suecica mostraron unha gran capacidade de extracción do cadmio. A gran resistencia de Tetraselmis suecica ó cadmio, e a sua capacidade de acumulación deste metal, fan de esta microalga unha boa candidata para poder ser utilizada nos procesos de extracción de cadmio de augas contaminadas.