El sulfato como nutriente esencial en la protección contra los efectos citotóxicos del cadmio en la microalga dulceacuícula "Chlamydomonas moewussii" Gerloff

Abstract

Sulphate is the main source of sulphur for microalgae and, therefore, an essential nutrient for these organisms. The knowledge of the optimal concentration of nutrients is an important issue that helps to develop efficient growth systerns; in fact, the study of the kinetics of growth of microalgae is an indispensable tool in all fields of phycology. In tbe present study, using as a model the microalga Chlamydomonas moewusii, the effects of this nutrient were studied and a kinetic model was obtained to relate the growth of this microalga with sulphate. Although this nutrient has many biological functions, it was also dernostrated in this work that it has important implications in processes of tolerance to cadmium toxicity due to the existence of an interaction between both compounds. The reason for this is that sulphur compounds, rich in thiols (cysteine, y-Glu-Cys, glutathione and phytochelatins), are a mechanism of tolerance against the toxicity of this metal. It was demonstrated that higher levels of sulphate allowed a higher biosynthesis of thiols and, therefore, a higher toleran ce to this toxicity. However, an excess of this nutrient had an opposite effect causing toxicity and a higher toxic effect of cadmium.