The toxicological response of the algaAnabaena flos- aquae (cyanophyceae) to cadmium

Abstract

The toxicological response of the cyanophycean algaAnabaena flos- aquae to cadmium was investigated by three integrated approaches: 1) the determination of the incipient lethal concentration of the metal, 2) study of metal incorporation and cellular compartmentalization using X-ray energy dispersive analysis, and 3) the quantification of intracellular structural changes, after metal exposure, using morphometric analysis. After 96 hr of exposure, the incipient lethal concentration was calculated to be 0.118 ± 0.04 μM cadmium. At concentrations three orders of magnitude higher than the incipient lethal concentration, cadmium was incorporated into both the cellular cytoplasm and the cell's polyphosphate bodies. Cadmium also caused the polyphosphate bodies to lose Mg and Ca, resulting in ionic changes in the elemental composition of these cellular inclusions. The utilization of stereological techniques for electron microscopic morphometric analysis established that all concentrations of cadmium tested caused significant reductions in the surface area of the cell's thylakoids. Cadmium induced changes in the numbers and relative volume of the cell occupied by polyhedral bodies, polyphosphate bodies, lipid inclusions, cyanophycin granules, membrane limited crystalline, inclusions, and changes in the volume of the cell wall layers were also documented. The physiological significance of these findings are discussed in terms of the toxic action of cadmium and the cellular mechanisms for detoxification of cations once they enter the cell.