DIFFERENTIAL TOXICOLOGICAL RESPONSE TO CADMIUM IN ANABAENA STRAIN PCC-7119 GROWN WITH NO3- OR NH4+ AS NITROGEN-SOURCE

The effect of free Cd2+ ions on growth, photosynthesis, photosynthetic pigments (chlorophyll and phycobiliproteins), nitrate and ammonium uptake and divalent cation (Mg2+, Ca2+) content in Anabaena PCC 7119 grown in a medium containing nitrate or ammonium was investigated. After 96 h of exposure, the metal causes an inhibition of photosynthesis in cells of Anabaena PCC 7119 growing in NH4+ and NO3- media and a decrease in the photosynthetic pigments. Likewise, Cd2+ toxicity elicited a reduction in the intracellular concentrations of Mg2+ and Ca2+ and an inhibition in ammonium uptake, resulting in changes in the cellular structure. The possible relation between the differential response in each culture medium and pH is discussed.