INFLUENCE OF MICROORGANISMS ON THE ENVIRONMENTAL FATE OF RADIONUCLIDES

Microorganisms have a significant influence on the environmental fate of radionuclides in aquatic and terrestrial ecosystems with a multipli city of physico-chemical and biological mechanisms effecting changes i n mobility and speciation, Physico-chemical mechanisms of removal incl ude association with extracellular materials, metabolites and cell wal ls which are features of living and dead organisms, In living cells, s ome physico-chemical processes are reversible, influenced by metabolis m and changing environmental conditions, Metabolism-dependent mechanis ms of radionuclide immobilization include sulphide precipitation, tran sport and intracellular compartmentation and/or sequestration by prote ins and peptides, In addition, chemical reduction to less soluble form s can result in immobilization, Microbial processes involved in radion uclide solubilization include autotrophic and heterotrophic leaching, and complexation by siderophores and other metabolites, Such mechanism s are important components of biogeochemical cycles for radionuclides and should be considered in any analyses of environmental radionuclide contamination. In addition, several microorganism-based biotechnologi es are receiving interest as potential treatment methods.