Iron oxide dissolution and solubility in the presence of siderophores

Abstract

Abstract.Iron is an essential trace nutrient for most known organisms. The iron availability is limited by the solubility and the slow dissolution kinetics of iron-bearing mineral phases, particularly in pH neutral or alkaline environments such as carbonatic soils and ocean water. Bacteria, fungi, and plants have evolved iron acquisition systems to increase the bioavailability of iron in such environments. A particularly efficient iron acquisition system involves the solubilization of iron by siderophores. Siderophores are biogenic chelators with high affinity and specificity for iron complexation.This review focuses on the geochemical aspects of biological iron acquisition. The significance of iron-bearing minerals as nutrient source for siderophore-promoted iron Aquat. Sci. 66 (2004) Dübendorf, 2004 Aquatic Sciences acquisition has been confirmed in microbial culture studies. Due to the extraordinary thermodynamic stability of soluble siderophore-iron complexes, siderophores have a pronounced effect on the solubility of iron oxides over a wide pH range. Very small concentrations of free siderophores in solution have a large effect on the solution saturation state of iron oxides. This siderophore induced disequilibrium can drive dissolution mechanisms such as protonpromoted or ligand-promoted iron oxide dissolution. The adsorption of siderophores to oxide surfaces also induces a direct siderophore-promoted surface-controlled dissolution mechanism. The efficiency of siderophores for increasing the solubility and dissolution kinetics of iron oxides are compared to other natural and anthropogenic ligands.3-18 1015-1621/04/010003-16 DOI 10.1007/s00027-003-0690-5 © EAWAG,

Dust iron dissolution in seawater: Results from a one‐year time‐series in the Mediterranean Sea

“…[19] So far, it has been demonstrated experimentally that iron-binding ligands affect iron dissolution rates when siderophore ligands, artificial [Kraemer, 2004] or from natural bacterial cultures [Yoshida et al, 2002], are added to pure iron (hydr)oxides. Here, in natural conditions, we show that this applies to the dissolution of iron from dust particles when they enter the sea surface.…”

“…Ligands have been demonstrated to be in excess compared to dissolved iron and to form strong iron-complexes (K cond Fe 0 L $ 10 12 ) [Van den Berg, 1995]. Several experimental studies have pointed out that ''natural strong iron binding ligands'' enhance the dissolution of iron (hydr)oxides in aquatic systems [e.g., Kraemer, 2004]. Iron binding ligands compose a part of the complex dissolved organic matter (DOM) pool, whose content in seawater is related to the biogeochemical conditions.…”

Review on iron availability in soil: interaction of Fe minerals, plants, and microbes

“…The insoluble Fe sources mainly subjected to weathering by MS s are Fe-containing primary silicates and Fe (hydr)oxides (Kraemer 2004). It has been observed that the smaller the particles, the greater (tenfold) the dissolution rate of these particles; in particular, those with sub-10 nm size are particularly available to aerobic microbes and, following the attack by MS s , able to guarantee sufficient Fe for bacterial growth (Treeby et al 1989).…”

Identification, isolation, and analysis of a gene cluster involved in iron acquisition by Pseudomonas mendocina ymp

“…Ferric minerals serve as primary sources of nutritional iron for a variety of microbes, including water-borne pathogens and environmental species. Their iron-scavenging activities contribute to global Fe cycling as well as mineral instability over geological time (Cornell and Schwertmann 1996;Hersman et al 2001;Kraemer 2004). …”

“…In spite of the inherent interest in and attention given to this strain, nothing was known of P. mendocina's genetic potential for metal metabolism prior to the beginning of this work. Little is known of the molecular details of nutritional iron acquisition from mineral sources in general (Kraemer 2004). P. mendocina is at the same time a member of an environmentally ubiquitous, economically important, and metabolically diverse genus.…”