@article {625, title = {Recovery of humic-reducing bacteria from a diversity of environments.}, journal = {Appl Environ Microbiol}, volume = {64}, year = {1998}, month = {1998 Apr}, pages = {1504-9}, abstract = {To evaluate which microorganisms might be responsible for microbial reduction of humic substances in sedimentary environments, humic-reducing bacteria were isolated from a variety of sediment types. These included lake sediments, pristine and contaminated wetland sediments, and marine sediments. In each of the sediment types, all of the humic reducers recovered with acetate as the electron donor and the humic substance analog, 2,6-anthraquinone disulfonate (AQDS), as the electron acceptor were members of the family Geobacteraceae. This was true whether the AQDS-reducing bacteria were enriched prior to isolation on solid media or were recovered from the highest positive dilutions of sediments in liquid media. All of the isolates tested not only conserved energy to support growth from acetate oxidation coupled to AQDS reduction but also could oxidize acetate with highly purified soil humic acids as the sole electron acceptor. All of the isolates tested were also able to grow with Fe(III) serving as the sole electron acceptor. This is consistent with previous studies that have suggested that the capacity for Fe(III) reduction is a common feature of all members of the Geobacteraceae. These studies demonstrate that the potential for microbial humic substance reduction can be found in a wide variety of sediment types and suggest that Geobacteraceae species might be important humic-reducing organisms in sediments.}, keywords = {Acetic Acid, Anthraquinones, Base Sequence, DNA Primers, Electron Transport, Fresh Water, Gram-Negative Anaerobic Bacteria, Humic Substances, Iron, Molecular Sequence Data, Phylogeny, Polymerase Chain Reaction, RNA, Bacterial, RNA, Ribosomal, 16S, Seawater, Sulfur-Reducing Bacteria, Water Microbiology}, issn = {0099-2240}, author = {Coates, J D and Ellis, D J and Blunt-Harris, E L and Gaw, C V and Roden, E E and Lovley, D R} } @article {648, title = {Composition of Non-Microbially Reducible Fe(III) in Aquatic Sediments.}, journal = {Appl Environ Microbiol}, volume = {59}, year = {1993}, month = {1993 Aug}, pages = {2727-9}, abstract = {The production of small quantities of Fe(II) during the initial phase of microbial Fe(III) reduction greatly increased the amount of Fe(III) that could be extracted from freshwater sediments with oxalate. This finding and other evidence suggest that the oxalate-extractable Fe(III) that is unavailable for microbial reduction in anoxic sediments is not in the form of mixed Fe(III)-Fe(II) forms, as was previously suggested, but rather is in the form of highly crystalline Fe(III) oxides.}, issn = {0099-2240}, author = {Phillips, E J and Lovley, D R and Roden, E E} } @article {650, title = {Dissimilatory Fe(III) Reduction by the Marine Microorganism Desulfuromonas acetoxidans.}, journal = {Appl Environ Microbiol}, volume = {59}, year = {1993}, month = {1993 Mar}, pages = {734-42}, abstract = {The ability of the marine microorganism Desulfuromonas acetoxidans to reduce Fe(III) was investigated because of its close phylogenetic relationship with the freshwater dissimilatory Fe(III) reducer Geobacter metallireducens. Washed cell suspensions of the type strain of D. acetoxidans reduced soluble Fe(III)-citrate and Fe(III) complexed with nitriloacetic acid. The c-type cytochrome(s) of D. acetoxidans was oxidized by Fe(III)-citrate and Mn(IV)-oxalate, as well as by two electron acceptors known to support growth, colloidal sulfur and malate. D. acetoxidans grew in defined anoxic, bicarbonate-buffered medium with acetate as the sole electron donor and poorly crystalline Fe(III) or Mn(IV) as the sole electron acceptor. Magnetite (Fe(3)O(4)) and siderite (FeCO(3)) were the major end products of Fe(III) reduction, whereas rhodochrosite (MnCO(3)) was the end product of Mn(IV) reduction. Ethanol, propanol, pyruvate, and butanol also served as electron donors for Fe(III) reduction. In contrast to D. acetoxidans, G. metallireducens could only grow in freshwater medium and it did not conserve energy to support growth from colloidal S reduction. D. acetoxidans is the first marine microorganism shown to conserve energy to support growth by coupling the complete oxidation of organic compounds to the reduction of Fe(III) or Mn(IV). Thus, D. acetoxidans provides a model enzymatic mechanism for Fe(III) or Mn(IV) oxidation of organic compounds in marine and estuarine sediments. These findings demonstrate that 16S rRNA phylogenetic analyses can suggest previously unrecognized metabolic capabilities of microorganisms.}, issn = {0099-2240}, author = {Roden, E E and Lovley, D R} }