Respuesta al cadmio de la microalga marina "tetraselmis suecica" (kylin) butchrelación entre tolerancia y compuestos tiólicos. Aplicación de su biomasa viva para la retirada de cadmio del medio

Abstract

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.