Kinetics and Mechanism of Dissolution of Metal Hydroxides Promoted by Structurally Diverse Siderophores.

Siderophores are biogenic chelating agents that have high affinities for and facilitate the uptake of Fe(III). To date, more than 500 structurally diverse siderophores have been isolated. The most frequently observed functional groups include some combination of catecholate, carboxylate, or hydroxamate groups. Although siderophores are generally thought of as being specific for interacting with Fe(III), studies with the model trihydroxamate siderophore desferrioxamine B (DFOB) have demonstrated the formation of high affinity complexes with other environmentally relevant metals, including Mn(III), Co(III), and Cr(III). This observation suggests that siderophores may play important roles in the biogeochemical cycling of these trace metals. Little is known about the interactions of siderophores besides DFOB with trace metals, and the possible routes of complex production in soils. This study utilized siderophores that span the known structural diversity to examine and compare the siderophore-promoted dissolution rates and mechanisms of FeOOH, CoOOH, MnOOH, and CrOOH at environmentally relevant conditions. The results will help us to understand specific structural attributes of siderophores that favor the formation of complexes with the chosen metal ions.