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Microbial acquisition of iron from ferric iron bearing minerals

Description: This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Iron is a universal requirement for all life forms. Although the fourth most abundant element in the geosphere, iron is virtually insoluble at physiological pH in oxidizing environments, existing mainly as very insoluble oxides and hydroxides. Currently it is not understood how iron is solubilized and made available for biological use. This research project addressed this topic by conducting a series of experiments that utilized techniques from both soil microbiology and mineral surface geochemistry. Microbiological analysis consisted of the examination of metabolic and physiological responses to mineral iron supplements. At the same time mineral surfaces were examined for structural changes brought about by microbially mediated dissolution. The results of these experiments demonstrated that (1) bacterial siderophores were able to promote the dissolution of iron oxides, (2) that strict aerobic microorganisms may use anaerobic processes to promote iron oxide dissolution, and (3) that it is possible to image the surface of iron oxides undergoing microbial dissolution.
Date: December 31, 1998
Creator: Hersman, L.E. & Sposito, G.
Partner: UNT Libraries Government Documents Department

Siderophore production and facilitated uptake of iron plutonium in p. putida.

Description: Bioremediation is a very attractive alternative for restoration of contaminated soil and ground water . This is particularly true for radionuclide contamination, which tends to be low in concentration and distributed over large surface areas . Microorganisms, through their natural metabolism, produce a large variety of organic molecules of different size and functionality . These molecules interact with contaminants present in the microbe's environment . Through these interactions bio-molecules can solubilize, oxidize, reduce or precipitate major metal contaminant in soils and ground water . We are studying these interaction for actinides and common soil subsurface bacteria . One focus has been on siderophores, small molecules that have great affinity for hard metal ions, and their potential to affect the distribution and mobility of actinide contaminants . The metal siderophores assembly can be recognized and taken up by micro-organisms through their interference with their iron uptake system . The first step in the active iron transport consists of Fe(III)-siderophore recognition by membrane receptors, which requires specific stereo orientation of the Fe(III)-siderophore complex . Recent investigations have shown that siderophores can form strong complexes with a large variety of toxic metals and may mediate their introduction inside the cell . We have previously shown that a Puhydroxamate siderophore assembly is recognized and taken up by the Microbacterium flavescens (JG-9). However, it is not clear if Pu-siderophore assemblies of other siderophores are also recognized.
Date: January 1, 2003
Creator: Boukhalfa, H. (Hakim); Lack, J. G. (Joseph G.); Reilly, S. D. (Sean D.); Hersman, L. E. (Larry E.) & Neu, M. P. (Mary P.)
Partner: UNT Libraries Government Documents Department