ABSTRACT
Siderophores are iron chelating agents that are secreted by microorganisms and graminaceous plants in response to iron deficiency. Given the essential requirement for iron by almost all living organisms, these compounds are not only important for iron nutrition but are also speculated to function in the ecology of microorganisms in the plant rhizosphere (1). Siderophores have been studied for their importance in plant disease suppression by mediating nutritional competition for iron (2,3) and contribute directly to the rhizosphere competence of root colonizing bacteria (4). In research on plant ecology, siderophores have been investigated in relation to calcicole and calcifuge plant species and as one of the factors that may explain the distribution of various plant species in different soils (5). Most recently, with the growing interest in using plant-microbe systems for phytoremediation of heavy metals, new research is examining the role of siderophores and phytosiderophores in facilitating heavy metal uptake and food chain transfer of metals (6,7).
