17. Bacterial Siderophores and their Biotechnological applications

Siderophore is the Greek phrase for “iron bearer” and is applied to molecules that can bind metals at very high affinities. Marine bacteria as do their terrestrial counterparts, secrete siderophores, which are small peptide molecules, readily assembled by short dedicated metabolic pathways which contain side chains and functional groups that can provide a high affinity set of ligands for coordination of ferric ions. In the marine environment bacterial growth depends in part upon the availability of iron, which is an essential requirement for most microorganisms. Although heterotrophic bacteria require conditions of up to one micro molar iron for growth, the total amount of iron in surface ocean water is subnanomolar. This limiting amount of iron has implications in the biogeochemical cycling of carbon and in limiting phytoplankton growth. Marine bacteria can successfully compete for this limited nutrient using a specialized iron transport system, including the production and release of siderophores, which mediate iron transport into the cell by specific membrane receptor proteins and transport systems (Lewin, 1984; Messenger and Ratledge, 1985; Reid and Butler, 1991)