@article {568, title = {Microorganisms associated with uranium bioremediation in a high-salinity subsurface sediment.}, journal = {Appl Environ Microbiol}, volume = {69}, year = {2003}, month = {2003 Jun}, pages = {3672-5}, abstract = {Although stimulation of dissimilatory metal reduction to promote the reductive precipitation of uranium has been shown to successfully remove uranium from some aquifer sediments, the organisms in the family Geobacteraceae that have been found to be associated with metal reduction in previous studies are not known to grow at the high salinities found in some uranium-contaminated groundwaters. Studies with a highly saline uranium-contaminated aquifer sediment demonstrated that the addition of acetate could stimulate the removal of U(VI) from the groundwater. This removal was associated with an enrichment in microorganisms most closely related to Pseudomonas and Desulfosporosinus species.}, keywords = {Acetates, Biodegradation, Environmental, DNA, Ribosomal, Fresh Water, Geologic Sediments, Peptococcaceae, Polymerase Chain Reaction, Pseudomonas, RNA, Ribosomal, 16S, Sodium Chloride, Uranium, Water Pollution}, issn = {0099-2240}, author = {Nevin, Kelly P and Finneran, Kevin T and Lovley, Derek R} } @article {567, title = {Rhodoferax ferrireducens sp. nov., a psychrotolerant, facultatively anaerobic bacterium that oxidizes acetate with the reduction of Fe(III).}, journal = {Int J Syst Evol Microbiol}, volume = {53}, year = {2003}, month = {2003 May}, pages = {669-73}, abstract = {To further investigate the diversity of micro-organisms capable of conserving energy to support growth from dissimilatory Fe(III) reduction, Fe(III)-reducing micro-organisms were enriched and isolated from subsurface sediments collected in Oyster Bay, VA, USA. A novel isolate, designated T118(T), was recovered in a medium with lactate as the sole electron donor and Fe(III) as the sole electron acceptor. Cells of T1 18(T) were Gram-negative, motile, short rods with a single polar flagellum. Strain T1 18(T) grew between pH 6.7 and 7.1, with a temperature range of 4-30 degrees C. The optimal growth temperature was 25 degrees C. Electron donors utilized by strain T1 18(T) with Fe(III) as the sole electron acceptor included acetate, lactate, malate, propionate, pyruvate, succinate and benzoate. None of the compounds tested was fermented. Electron acceptors utilized with either acetate or lactate as the electron donor included Fe(III)-NTA (nitrilotriacetic acid), Mn(IV) oxide, nitrate, fumarate and oxygen. Phylogenetic analysis demonstrated that strain T1 18(T) is most closely related to the genus Rhodoferax. Unlike other species in this genus, strain T1 18(T) is not a phototroph and does not ferment fructose. However, phototrophic genes may be present but not expressed under the experimental conditions tested. No Rhodoferax species have been reported to grow via dissimilatory Fe(III) reduction. Based on these physiological and phylogenetic differences, strain T1 18(T) (=ATCC BAA-621(T) = DSM 15236(T)) is proposed as a novel species, Rhodoferax ferrireducens sp. nov.}, keywords = {Acetates, Anaerobiosis, Bacterial Typing Techniques, Betaproteobacteria, Cold Temperature, Culture Media, DNA, Ribosomal, Electron Transport, Ferric Compounds, Fresh Water, Molecular Sequence Data, Oxidation-Reduction, Phylogeny, RNA, Ribosomal, 16S, Sequence Analysis, DNA}, issn = {1466-5026}, author = {Finneran, Kevin T and Johnsen, Claudia V and Lovley, Derek R} } @article {574, title = {Desulfitobacterium metallireducens sp. nov., an anaerobic bacterium that couples growth to the reduction of metals and humic acids as well as chlorinated compounds.}, journal = {Int J Syst Evol Microbiol}, volume = {52}, year = {2002}, month = {2002 Nov}, pages = {1929-35}, abstract = {Strain 853-15A(T) was enriched and isolated from uranium-contaminated aquifer sediment by its ability to grow under anaerobic conditions via the oxidation of lactate coupled to the reduction of anthraquinone-2,6-disulfonate (AQDS) to anthrahydroquinone-2,6-disulfonate (AHQDS). Lactate was oxidized incompletely to acetate and carbon dioxide according to the reaction CH3CHOHCOO(-)+ 2AQDS+H2O --> CH3COO(-)+ 2AHQDS+CO2. Additional electron donors utilized included formate, ethanol, butanol, butyrate, malate and pyruvate. Lactate also supported growth with Fe(III) citrate, Mn(IV) oxide, humic substances, elemental sulfur, 3-chloro-4-hydroxyphenylacetate, trichloroethylene or tetrachloroethylene serving as the electron acceptor. Growth was not observed with sulfate, sulfite, nitrate or fumarate as the terminal electron acceptor. The temperature optimum for growth was 30 degrees C, but growth was also observed at 20 and 37 degrees C. The pH optimum was approximately 7.0. The 16S rDNA sequence of strain 853-15A(T) suggested that it was most closely related to Desulfitobacterium dehalogenans and closely related to Desulfitobacterium chlororespirans and Desulfitobacterium frappieri. The phylogenetic and physiological properties exhibited by strain 853-15A(T) (= ATCC BAA-636(T)) place it within the genus Desulfitobacterium as the type strain of a novel species, Desulfitobacterium metallireducens sp. nov.}, keywords = {Anaerobiosis, DNA, Bacterial, DNA, Ribosomal, Ecosystem, Electron Transport, Geologic Sediments, Humic Substances, Metals, Microscopy, Electron, Molecular Sequence Data, Oxidation-Reduction, Peptococcaceae, Phenotype, Phylogeny, RNA, Bacterial, RNA, Ribosomal, 16S, Species Specificity}, issn = {1466-5026}, author = {Finneran, Kevin T and Forbush, Heather M and VanPraagh, Catherine V Gaw and Lovley, Derek R} } @article {583, title = {Enrichment of members of the family Geobacteraceae associated with stimulation of dissimilatory metal reduction in uranium-contaminated aquifer sediments.}, journal = {Appl Environ Microbiol}, volume = {68}, year = {2002}, month = {2002 May}, pages = {2300-6}, abstract = {Stimulating microbial reduction of soluble U(VI) to insoluble U(IV) shows promise as a strategy for immobilizing uranium in uranium-contaminated subsurface environments. In order to learn more about which microorganisms might be involved in U(VI) reduction in situ, the changes in the microbial community when U(VI) reduction was stimulated with the addition of acetate were monitored in sediments from three different uranium-contaminated sites in the floodplain of the San Juan River in Shiprock, N.Mex. In all three sediments U(VI) reduction was accompanied by concurrent Fe(III) reduction and a dramatic enrichment of microorganisms in the family Geobacteraceae, which are known U(VI)- and Fe(III)-reducing microorganisms. At the point when U(VI) reduction and Fe(III) reduction were nearing completion, Geobacteraceae accounted for ca. 40\% of the 16S ribosomal DNA (rDNA) sequences recovered from the sediments with bacterial PCR primers, whereas Geobacteraceae accounted for fewer than 5\% of the 16S rDNA sequences in control sediments that were not amended with acetate and in which U(VI) and Fe(III) reduction were not stimulated. Between 55 and 65\% of these Geobacteraceae sequences were most similar to sequences from Desulfuromonas species, with the remainder being most closely related to Geobacter species. Quantitative analysis of Geobacteraceae sequences with most-probable-number PCR and TaqMan analyses indicated that the number of Geobacteraceae sequences increased from 2 to 4 orders of magnitude over the course of U(VI) and Fe(III) reduction in the acetate-amended sediments from the three sites. No increase in Geobacteraceae sequences was observed in control sediments. In contrast to the predominance of Geobacteraceae sequences, no sequences related to other known Fe(III)-reducing microorganisms were detected in sediments. These results compare favorably with an increasing number of studies which have demonstrated that Geobacteraceae are important components of the microbial community in a diversity of subsurface environments in which Fe(III) reduction is an important process. The combination of these results with the finding that U(VI) reduction takes place during Fe(III) reduction and prior to sulfate reduction suggests that Geobacteraceae will be responsible for much of the Fe(III) and U(VI) reduction during uranium bioremediation in these sediments.}, keywords = {Gene Library, Geologic Sediments, Iron, Oxidation-Reduction, Proteobacteria, RNA, Ribosomal, 16S, Soil Pollutants, Uranium}, issn = {0099-2240}, author = {Holmes, Dawn E and Finneran, Kevin T and O{\textquoteright}Neil, Regina A and Lovley, Derek R} } @article {577, title = {Multiple influences of nitrate on uranium solubility during bioremediation of uranium-contaminated subsurface sediments.}, journal = {Environ Microbiol}, volume = {4}, year = {2002}, month = {2002 Sep}, pages = {510-6}, abstract = {Microbiological reduction of soluble U(VI) to insoluble U(IV) has been proposed as a remediation strategy for uranium-contaminated groundwater. Nitrate is a common co-contaminant with uranium. Nitrate inhibited U(VI) reduction in acetate-amended aquifer sediments collected from a uranium-contaminated site in New Mexico. Once nitrate was depleted, both U(VI) and Fe(III) were reduced concurrently. When nitrate was added to sediments in which U(VI) had been reduced, U(VI) reappeared in solution. Parallel studies with the dissimilatory Fe(III)-, U(VI)- and nitrate-reducing microorganism, Geobacter metallireducens, demonstrated that nitrate inhibited reduction of Fe(III) and U(VI) in cell suspensions of cells that had been grown with nitrate as the electron acceptor, but not in Fe(III)-grown cells. Suspensions of nitrate-grown G. metallireducens oxidized Fe(II) and U(IV) with nitrate as the electron acceptor. U(IV) oxidation was accelerated when Fe(II) was also added, presumably due to the Fe(III) being formed abiotically oxidizing U(IV). These studies demonstrate that although the presence of nitrate is not likely to be an impediment to the bioremediation of uranium contamination with microbial U(VI) reduction, it is necessary to reduce nitrate before U(VI) can be reduced. These results also suggest that anaerobic oxidation of U(IV) to U(VI) with nitrate serving as the electron acceptor may provide a novel strategy for solubilizing and extracting microbial U(IV) precipitates from the subsurface.}, keywords = {Ferric Compounds, Ferrous Compounds, Geologic Sediments, Nitrates, Oxidation-Reduction, Proteobacteria, Soil Pollutants, Solubility, Uranium, Water Pollutants, Chemical}, issn = {1462-2912}, author = {Finneran, Kevin T and Housewright, Meghan E and Lovley, Derek R} }