Abstract:
<p align="justify"> Certain species of microorganisms have been found to accumulate surprisingly large quantities of important metals, involved in the toxicity provoked by human activities (Cd, Pb, Hg) and metals of economic values (Ag, Au). Microbiological methods are applied to large-scale recovery or removal of metallic ions from aqueous solutions. These applications involved the removal of heavy metals from sewage sludge, industrial effluents, and mine or wastewaters. This process has been developed using immobilized extracellular or cellular ligands or more simple chemical models based upon them. The uptake of metal ions on the cell surface and their translocations into the cell are well-known natural processes. These adsorption processes could be expressed using Langmuir isotherms. Fe₂₊ and Mn₂₊ appeared to .be the most effective cations for adsorption by Bacillus subtilis, Pseudomonas aeruginosa, even by Saccharomyces cerevisiae, while the Zn₂₊ cation, in spite of a great value of maximum adsorption, has a toxic action on microorganisms and the 'detoxification" mechanism depends on genetic control. </p>