Siderophores are low molecular weight organic ligands that are released by aerobic microorganisms to acquire Fe. We investigated the role of siderophores in Fe acquisition from the mineral hematite by Pseudomonas mendocina ymp, an obligate aerobic bacterium previously shown to secrete siderophore(s). Using a mutant incapable of producing functional siderophores (i.e., siderophore (-) strain), it was shown that siderophores are necessary for appreciable growth in the presence of hematite. However, a large excess of small-molecule reductant (ascorbate) alone could restore the siderophore(-) culture to WT growth levels. We also observed that siderophores and reductant could work synergistically. Excess carboxylic acid (oxalate) alone had little effect on mutant growth, but oxalate had a pronounced effect when siderophores were present (either WT or added siderophores). Our results demonstrate that the process of Fe acquisition from mineral substrates can involve a complex array of natural organic ligands typically found in soil environments.

Role(s) of siderophores and other natural organic ligands in Fe acquisition from hematite by an aerobic soil microorganism

239th National Meeting (2010)

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