Soil bacteria as well as those infecting other organisms have developed systems to secure iron necessary for their metabolism which is generally not available in its free ionic form. As one of the possible strategies they learnt to produce secondary metabolites able to bind Fe3+ as water soluble complexes, so-called siderophores. A rather small group is based on citric acid. One of the ligand sites is the central C(OH)COOH unit, the two additional ones are carried by substituents bound to one or both of the terminal carboxyl groups. A survey will be presented.