Under iron restricted condition many bacteria produced iron chealating molecules called siderophore. Siderophore chealate iron and supply to bacterial cell by outer membrane receptors.
A great variation is seen in siderophore structure produced by many bacteria. There are three main kinds of siderophores known as hydroxamate, catecholate and carboxylate.
Siderophore and their derivative have large application in agriculture as to increase soil fertility and biocontrol for fungal pathogen. In medicine the most important application is selective drug delivery, a Trojan horse strategy, to defeat drug resistant bacteria.