ABSTRACT
A result of increasing industrial activity, more and more recalcitrant elements are being deposited in soil ecosystems, where they are expected to remain for periods of up to several hundreds of years. The presence of these elements with soil and the exposure of the soil ecosystem to them for the prolonged periods envisaged have stimulated discussion and research on the interactions between soil microorganisms and radionuclides. Under laboratory conditions, exudates, such as siderophores or metal-binding proteins modify the transport properties of trace metals in the immediate vicinity of cellular membranes, but their effect in a natural large-scale system remains unknown. In a soil environment, complex formation is probably the factor most influenced by microorganisms. Microorganisms may degrade a complex organic via several different metabolic pathways. Iron is an essential element for the metabolism of microorganisms, plants, and animals. Many types of siderophores are produced, and they have been classified according to the microorganism of origin and by their binding groups.
