Lack of production of electron-shuttling compounds or solubilization of Fe(III) during reduction of insoluble Fe(III) oxide by Geobacter metallireducens

Studies with the dissimilatory Fe(III)-reducing microorganism Geobacter met allireducens demonstrated that the common technique of separating Fe(III)-r educing microorganisms and Fe(III) oxides with semipermeable membranes in o rder to determine whether the Fe(III) reducers release electron-shuttling c ompounds and/or Fe(III) chelators is invalid. This raised doubts about the mechanisms for Fe(III) oxide reduction by this organism. However, several e xperimental approaches indicated that G. metallireducens does not release e lectron-shuttling compounds and does not significantly solubilize Fe(III) d uring Fe(III) oxide reduction. These results suggest that G. merallireducen s directly reduces insoluble Fe(III) oxide.