GEOC 94 |
| Although abundant in nature, iron's (Fe) extreme insolubility under oxic conditions at circumneutral pH renders it difficult – it would seem – for microorganisms and plants to acquire it for their essential, Fe-dependent, metabolic processes. Yet, they do acquire Fe with relative ease. Our interest has been to describe the process(es) used by common soil microorganisms for the initial dissolution of Fe bearing minerals, such as hematite, goethite, ferrihydrite and clay minerals under aerobic conditions. We have found that Pseudomonas mendocina is able to acquire Fe with relatively high efficiency, when its growth on those minerals is compared to growth on chelated Fe sources (e.g., EDTA, NTA, and citrate). P. mendocina also responded differently to those minerals, not only growing at different rates, but also varying its metabolic response. Specifically, growth was best on goethite, followed hematite, ferrihydrite and clay minerals. In addition to producing siderophore (Fe specific chelators), this organism also produced a low molecular weight reductant, and varied the relative amount of siderophore and reductant depending on which source of Fe was present in the growth medium. Our most recent results lead us to speculate that the reductant and siderophore work in strong concert during Fe dissolution. In fact, the combinatorial dissolution rates far exceed the sum of dissolution by either the siderophore or reductant alone. |
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Physical Chemistry of Soil and Aquifer Systems: A Symposium in Honor of Garrison Sposito
1:30 PM-4:45 PM, Tuesday, 12 September 2006 Moscone Center -- Room 256, Oral
Sci-Mix
Division of Geochemistry |