In response to biochemical requirements for iron, and the great insolubility of environmental ferric ion, microorganisms secrete siderophores (from the Greek: sideros) iron, pherein) to carry), small molecules capable of high affinity binding and transport of Fe (III). Enterobactin (1), 1 produced by E. coli and many other Gramnegative bacteria, 2 exhibits the largest binding constant (log KML) 49) for ferric ion of any natural substance. 3 It is composed of ...