Siderophores of bacteria and fungi.

Siderophore-mediated iron assimilation systems are widely distributed in bacteria and fungi. The systems are comprised of low molecular weight ferric-ion specific ligands (siderophores) and cognate cell-bound receptor and utilization components. Most siderophores are classed chemically as hydroxamic acids or catechols; expression of both types is regulated by iron. Of the various siderophore systems present in E. coli, the enterobactin and aerobactin genes, encoded on the chromosome and pColV respectively, have been the most intensively studied to date as regards their molecular genetics.