Although iron (Fe) is an essential element for almost all living organisms, little is known regarding its acquisition from the insoluble Fe(III) (hydr)oxides in aerobic environments. In this study a strict aerobe, Pseudomonas mendocina, was grown in batch culture with hematite, goethite, or ferrihydrite as a source of Fe. P. mendocina obtained Fe from these minerals in the following order: goethite > hematite > ferrihydrite. Furthermore, Fe release from each of the minerals appears to have occurred in excess, as evidenced by the growth of P. mendocina in the medium above that of the insoluble Fe(III) (hydr)oxide aggregates, and this release was independent of the mineral's surface area. These results demonstrate that an aerobic microorganism was able to obtain Fe for growth from several insoluble Fe minerals and did so with various growth rates.

Growth of Pseudomonas mendocina on Fe(III) (Hydr)Oxides

Siderophore adsorption to and dissolution of kaolinite at pH 3 to 7 and 22°C

Measurement and interpretation of molecular-level forces of interaction between the siderophore azotobactin and mineral surfaces

At the most fundamental level, intermolecular forces (e.g., van der Waals, electrostatic, solvation, steric) control interactions between biological molecules and mineral surfaces. These are forces with magnitudes of piconewtons to nanonewtons, which operate in a space that is on the order of nanometers. We have used force microscopy to quantitatively probe forces, energies, and distances between crystal surfaces and living microbial cells or biological molecules in their native state. The systems we have studied include those involving: Escherichia coli, Shewanella oneidensis, siderophores, muscovite, goethite, and/or diaspore, in aqueous solutions of varying composition. Direct force measurements at the organic–inorganic interface have been interpreted with theoretical models describing interfacial forces, adhesion, and molecular dynamic calculations. A new perspective on bacterium–mineral interactions is emerging from these studies. We have discovered a world that operates under a very different set of principles than macroscopic bodies. A world where the intermolecular force, rather than gravitational attraction, is the preeminent force controlling the evolution of processes at the bacterium–mineral interface.

Forces between Minerals and Biological Surfaces in Aqueous Solution

The chemistry of iron soils and its availability to plants , The chemistry of iron soils and its availability to plants , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

The chemistry of iron soils and its availability to plants

Non‐crystalline or short‐range order Fe oxides (sometimes called amorphous Fe oxides) are of interest because of their surface area and high reactivity, and their influence on Fe availability in the soil Eight non‐crystalline Fe(III) oxides were precipitated from solutions with Si/Fe(III) molar ratios ranging from 000 to 100 These eight Fe oxides, along with goethite and hematite, were evaluated for their ability to supply Fe to an isolate of Pseudomonas obtained from grass roots Levels of siderophore in solution were significantly higher in controls (with no Fe added) and in the presence of hematite or the more‐crystalline goethite sample, than with the non‐crystalline oxide treatments The non‐crystalline oxides were indistinguishable in their ability to suppress siderophore production Greater numbers of Pseudomonas were observed in cultures amended with the non‐crystalline oxides than in the cultures amended with crystalline oxides or in the Fe‐deficient controls

J. C. Seaman

Papers

The availability of iron from various solid‐phase iron sources to a siderophore producing Pseudomonas strain