@article {525,
	title = {Genetic characterization of a single bifunctional enzyme for fumarate reduction and succinate oxidation in Geobacter sulfurreducens and engineering of fumarate reduction in Geobacter metallireducens.},
	journal = {J Bacteriol},
	volume = {188},
	year = {2006},
	month = {2006 Jan},
	pages = {450-5},
	abstract = {The mechanism of fumarate reduction in Geobacter sulfurreducens was investigated. The genome contained genes encoding a heterotrimeric fumarate reductase, FrdCAB, with homology to the fumarate reductase of Wolinella succinogenes and the succinate dehydrogenase of Bacillus subtilis. Mutation of the putative catalytic subunit of the enzyme resulted in a strain that lacked fumarate reductase activity and was unable to grow with fumarate as the terminal electron acceptor. The mutant strain also lacked succinate dehydrogenase activity and did not grow with acetate as the electron donor and Fe(III) as the electron acceptor. The mutant strain could grow with acetate as the electron donor and Fe(III) as the electron acceptor if fumarate was provided to alleviate the need for succinate dehydrogenase activity in the tricarboxylic acid cycle. The growth rate of the mutant strain under these conditions was faster and the cell yields were higher than for wild type grown under conditions requiring succinate dehydrogenase activity, suggesting that the succinate dehydrogenase reaction consumes energy. An orthologous frdCAB operon was present in Geobacter metallireducens, which cannot grow with fumarate as the terminal electron acceptor. When a putative dicarboxylic acid transporter from G. sulfurreducens was expressed in G. metallireducens, growth with fumarate as the sole electron acceptor was possible. These results demonstrate that, unlike previously described organisms, G. sulfurreducens and possibly G. metallireducens use the same enzyme for both fumarate reduction and succinate oxidation in vivo.},
	keywords = {Culture Media, Dicarboxylic Acids, Fumarates, Geobacter, Molecular Sequence Data, Operon, Oxidation-Reduction, Recombinant Proteins, Substrate Specificity, Succinate Dehydrogenase, Succinic Acid},
	issn = {0021-9193},
	doi = {10.1128/JB.188.2.450-455.2006},
	author = {Butler, Jessica E and Glaven, Richard H and Esteve-N{\'u}{\~n}ez, Abraham and N{\'u}{\~n}ez, Cinthia and Shelobolina, Evgenya S and Bond, Daniel R and Lovley, Derek R}
}
@article {533,
	title = {Characterization of citrate synthase from Geobacter sulfurreducens and evidence for a family of citrate synthases similar to those of eukaryotes throughout the Geobacteraceae.},
	journal = {Appl Environ Microbiol},
	volume = {71},
	year = {2005},
	month = {2005 Jul},
	pages = {3858-65},
	abstract = {Members of the family Geobacteraceae are commonly the predominant Fe(III)-reducing microorganisms in sedimentary environments, as well as on the surface of energy-harvesting electrodes, and are able to effectively couple the oxidation of acetate to the reduction of external electron acceptors. Citrate synthase activity of these organisms is of interest due to its key role in acetate metabolism. Prior sequencing of the genome of Geobacter sulfurreducens revealed a putative citrate synthase sequence related to the citrate synthases of eukaryotes. All citrate synthase activity in G. sulfurreducens could be resolved to a single 49-kDa protein via affinity chromatography. The enzyme was successfully expressed at high levels in Escherichia coli with similar properties as the native enzyme, and kinetic parameters were comparable to related citrate synthases (kcat= 8.3 s(-1); Km= 14.1 and 4.3 microM for acetyl coenzyme A and oxaloacetate, respectively). The enzyme was dimeric and was slightly inhibited by ATP (Ki= 1.9 mM for acetyl coenzyme A), which is a known inhibitor for many eukaryotic, dimeric citrate synthases. NADH, an allosteric inhibitor of prokaryotic hexameric citrate synthases, did not affect enzyme activity. Unlike most prokaryotic dimeric citrate synthases, the enzyme did not have any methylcitrate synthase activity. A unique feature of the enzyme, in contrast to citrate synthases from both eukaryotes and prokaryotes, was a lack of stimulation by K+ ions. Similar citrate synthase sequences were detected in a diversity of other Geobacteraceae members. This first characterization of a eukaryotic-like citrate synthase from a prokaryote provides new insight into acetate metabolism in Geobacteraceae members and suggests a molecular target for tracking the presence and activity of these organisms in the environment.},
	keywords = {Amino Acid Sequence, Citrate (si)-Synthase, Culture Media, Deltaproteobacteria, DNA, Bacterial, Eukaryotic Cells, Geobacter, Kinetics, Molecular Sequence Data, Phylogeny, Sequence Analysis, DNA},
	issn = {0099-2240},
	doi = {10.1128/AEM.71.7.3858-3865.2005},
	author = {Bond, Daniel R and Mester, T{\"u}nde and Nesb{\o}, Camilla L and Izquierdo-Lopez, Andrea V and Collart, Frank L and Lovley, Derek R}
}
@article {540,
	title = {Evidence for involvement of an electron shuttle in electricity generation by Geothrix fermentans.},
	journal = {Appl Environ Microbiol},
	volume = {71},
	year = {2005},
	month = {2005 Apr},
	pages = {2186-9},
	abstract = {In experiments performed using graphite electrodes poised by a potentiostat (+200 mV versus Ag/AgCl) or in a microbial fuel cell (with oxygen as the electron acceptor), the Fe(III)-reducing organism Geothrix fermentans conserved energy to support growth by coupling the complete oxidation of acetate to reduction of a graphite electrode. Other organic compounds, such as lactate, malate, propionate, and succinate as well as components of peptone and yeast extract, were utilized for electricity production. However, electrical characteristics and the results of shuttling assays indicated that unlike previously described electrode-reducing microorganisms, G. fermentans produced a compound that promoted electrode reduction. This is the first report of complete oxidation of organic compounds linked to electrode reduction by an isolate outside of the Proteobacteria.},
	keywords = {Acetates, Bacteria, Bioelectric Energy Sources, Electricity, Electrodes, Electron Transport, Graphite, Microscopy, Electron, Scanning, Oxidation-Reduction},
	issn = {0099-2240},
	doi = {10.1128/AEM.71.4.2186-2189.2005},
	author = {Bond, Daniel R and Lovley, Derek R}
}
@article {559,
	title = {Electron transfer by Desulfobulbus propionicus to Fe(III) and graphite electrodes.},
	journal = {Appl Environ Microbiol},
	volume = {70},
	year = {2004},
	month = {2004 Feb},
	pages = {1234-7},
	abstract = {Desulfobulbus propionicus was able to grow with Fe(III), the humic acids analog anthraquinone-2,6-disulfonate (AQDS), or a graphite electrode as an electron acceptor. These results provide an explanation for the enrichment of Desulfobulbaceae species on the surface of electrodes harvesting electricity from anaerobic marine sediments and further expand the diversity of microorganisms known to have the ability to use both sulfate and Fe(III) as an electron acceptor.},
	keywords = {Culture Media, Deltaproteobacteria, Electrodes, Electron Transport, Ferric Compounds, Graphite, Oxidation-Reduction, Pyruvic Acid, Sulfates},
	issn = {0099-2240},
	author = {Holmes, Dawn E and Bond, Daniel R and Lovley, Derek R}
}
@article {552,
	title = {Graphite electrodes as electron donors for anaerobic respiration.},
	journal = {Environ Microbiol},
	volume = {6},
	year = {2004},
	month = {2004 Jun},
	pages = {596-604},
	abstract = {It has been demonstrated previously that Geobacter species can transfer electrons directly to electrodes. In order to determine whether electrodes could serve as electron donors for microbial respiration, enrichment cultures were established from a sediment inoculum with a potentiostat-poised graphite electrode as the sole electron donor and nitrate as the electron acceptor. Nitrate was reduced to nitrite with the consumption of electrical current. The stoichiometry of electron and nitrate consumption and nitrite accumulation were consistent with the electrode serving as the sole electron donor for nitrate reduction. Analysis of 16 rRNA gene sequences demonstrated that the electrodes supplied with current were specifically enriched in microorganisms with sequences most closely related to the sequences of known Geobacter species. A pure culture of Geobacter metallireducens was shown to reduce nitrate to nitrite with the electrode as the sole electron donor with the expected stoichiometry of electron consumption. Cells attached to the electrode appeared to be responsible for the nitrate reduction. Attached cells of Geobacter sulfurreducens reduced fumarate to succinate with the electrode as an electron donor. These results demonstrate for the first time that electrodes may serve as a direct electron donor for anaerobic respiration. This finding has implications for the harvesting of electricity from anaerobic sediments and the bioremediation of oxidized contaminants.},
	keywords = {Anaerobiosis, Electrodes, Electrons, Fumarates, Geobacter, Geologic Sediments, Graphite, Kinetics, Microscopy, Electron, Scanning, Nitrates, Phylogeny, RNA, Ribosomal, 16S, Sequence Analysis, DNA},
	issn = {1462-2912},
	doi = {10.1111/j.1462-2920.2004.00593.x},
	author = {Gregory, Kelvin B and Bond, Daniel R and Lovley, Derek R}
}
@article {546,
	title = {Potential role of a novel psychrotolerant member of the family Geobacteraceae, Geopsychrobacter electrodiphilus gen. nov., sp. nov., in electricity production by a marine sediment fuel cell.},
	journal = {Appl Environ Microbiol},
	volume = {70},
	year = {2004},
	month = {2004 Oct},
	pages = {6023-30},
	abstract = {Previous studies have shown that members of the family Geobacteraceae that attach to the anodes of sediment fuel cells are directly involved in harvesting electricity by oxidizing organic compounds to carbon dioxide and transferring the electrons to the anode. In order to learn more about this process, microorganisms from the anode surface of a marine sediment fuel cell were enriched and isolated with Fe(III) oxide. Two unique marine isolates were recovered, strains A1(T) and A2. They are gram-negative, nonmotile rods, with abundant c-type cytochromes. Phylogenetic analysis of the 16S rRNA, recA, gyrB, fusA, rpoB, and nifD genes indicated that strains A1(T) and A2 represent a unique phylogenetic cluster within the Geobacteraceae. Both strains were able to grow with an electrode serving as the sole electron acceptor and transferred ca. 90\% of the electrons available in their organic electron donors to the electrodes. These organisms are the first psychrotolerant members of the Geobacteraceae reported thus far and can grow at temperatures between 4 and 30 degrees C, with an optimum temperature of 22 degrees C. Strains A1(T) and A2 can utilize a wide range of traditional electron acceptors, including all forms of soluble and insoluble Fe(III) tested, anthraquinone 2,6-disulfonate, and S(0). In addition to acetate, both strains can utilize a number of other organic acids, amino acids, long-chain fatty acids, and aromatic compounds to support growth with Fe(III) nitrilotriacetic acid as an electron acceptor. The metabolism of these organisms differs in that only strain A1(T) can use acetoin, ethanol, and hydrogen as electron donors, whereas only strain A2 can use lactate, propionate, and butyrate. The name Geopsychrobacter electrodiphilus gen. nov., sp. nov., is proposed for strains A1(T) and A2, with strain A1(T) (ATCC BAA-880(T); DSM 16401(T); JCM 12469) as the type strain. Strains A1(T) and A2 (ATCC BAA-770; JCM 12470) represent the first organisms recovered from anodes that can effectively couple the oxidation of organic compounds to an electrode. Thus, they may serve as important model organisms for further elucidation of the mechanisms of microbe-electrode electron transfer in sediment fuel cells.},
	keywords = {Bioelectric Energy Sources, Cytochromes, Deltaproteobacteria, Electron Transport, Genes, Bacterial, Geologic Sediments, Microscopy, Electron, Molecular Sequence Data, Phylogeny, RNA, Bacterial, RNA, Ribosomal, 16S, Temperature},
	issn = {0099-2240},
	doi = {10.1128/AEM.70.10.6023-6030.2004},
	author = {Holmes, Dawn E and Nicoll, Julie S and Bond, Daniel R and Lovley, Derek R}
}
@article {573,
	title = {Electricity production by Geobacter sulfurreducens attached to electrodes.},
	journal = {Appl Environ Microbiol},
	volume = {69},
	year = {2003},
	month = {2003 Mar},
	pages = {1548-55},
	abstract = {Previous studies have suggested that members of the Geobacteraceae can use electrodes as electron acceptors for anaerobic respiration. In order to better understand this electron transfer process for energy production, Geobacter sulfurreducens was inoculated into chambers in which a graphite electrode served as the sole electron acceptor and acetate or hydrogen was the electron donor. The electron-accepting electrodes were maintained at oxidizing potentials by connecting them to similar electrodes in oxygenated medium (fuel cells) or to potentiostats that poised electrodes at +0.2 V versus an Ag/AgCl reference electrode (poised potential). When a small inoculum of G. sulfurreducens was introduced into electrode-containing chambers, electrical current production was dependent upon oxidation of acetate to carbon dioxide and increased exponentially, indicating for the first time that electrode reduction supported the growth of this organism. When the medium was replaced with an anaerobic buffer lacking nutrients required for growth, acetate-dependent electrical current production was unaffected and cells attached to these electrodes continued to generate electrical current for weeks. This represents the first report of microbial electricity production solely by cells attached to an electrode. Electrode-attached cells completely oxidized acetate to levels below detection (<10 micro M), and hydrogen was metabolized to a threshold of 3 Pa. The rates of electron transfer to electrodes (0.21 to 1.2 micro mol of electrons/mg of protein/min) were similar to those observed for respiration with Fe(III) citrate as the electron acceptor (E(o){\textquoteright} =+0.37 V). The production of current in microbial fuel cell (65 mA/m(2) of electrode surface) or poised-potential (163 to 1,143 mA/m(2)) mode was greater than what has been reported for other microbial systems, even those that employed higher cell densities and electron-shuttling compounds. Since acetate was completely oxidized, the efficiency of conversion of organic electron donor to electricity was significantly higher than in previously described microbial fuel cells. These results suggest that the effectiveness of microbial fuel cells can be increased with organisms such as G. sulfurreducens that can attach to electrodes and remain viable for long periods of time while completely oxidizing organic substrates with quantitative transfer of electrons to an electrode.},
	keywords = {Culture Media, Deltaproteobacteria, Electricity, Electrodes, Electron Transport, Microscopy, Electron, Scanning, Oxidation-Reduction},
	issn = {0099-2240},
	author = {Bond, Daniel R and Lovley, Derek R}
}
@article {588,
	title = {Electrode-reducing microorganisms that harvest energy from marine sediments.},
	journal = {Science},
	volume = {295},
	year = {2002},
	month = {2002 Jan 18},
	pages = {483-5},
	abstract = {Energy in the form of electricity can be harvested from marine sediments by placing a graphite electrode (the anode) in the anoxic zone and connecting it to a graphite cathode in the overlying aerobic water. We report a specific enrichment of microorganisms of the family Geobacteraceae on energy-harvesting anodes, and we show that these microorganisms can conserve energy to support their growth by oxidizing organic compounds with an electrode serving as the sole electron acceptor. This finding not only provides a method for extracting energy from organic matter, but also suggests a strategy for promoting the bioremediation of organic contaminants in subsurface environments.},
	keywords = {Aerobiosis, Anaerobiosis, Anthraquinones, Benzoates, Biodegradation, Environmental, Carbon Dioxide, Colony Count, Microbial, Deltaproteobacteria, DNA, Ribosomal, Electricity, Electrodes, Electrons, Energy Metabolism, Geologic Sediments, Oxidation-Reduction, RNA, Ribosomal, 16S, Seawater, Sodium Acetate},
	issn = {1095-9203},
	doi = {10.1126/science.1066771},
	author = {Bond, Daniel R and Holmes, Dawn E and Tender, Leonard M and Lovley, Derek R}
}
@article {580,
	title = {Harnessing microbially generated power on the seafloor.},
	journal = {Nat Biotechnol},
	volume = {20},
	year = {2002},
	month = {2002 Aug},
	pages = {821-5},
	abstract = {In many marine environments, a voltage gradient exists across the water sediment interface resulting from sedimentary microbial activity. Here we show that a fuel cell consisting of an anode embedded in marine sediment and a cathode in overlying seawater can use this voltage gradient to generate electrical power in situ. Fuel cells of this design generated sustained power in a boat basin carved into a salt marsh near Tuckerton, New Jersey, and in the Yaquina Bay Estuary near Newport, Oregon. Retrieval and analysis of the Tuckerton fuel cell indicates that power generation results from at least two anode reactions: oxidation of sediment sulfide (a by-product of microbial oxidation of sedimentary organic carbon) and oxidation of sedimentary organic carbon catalyzed by microorganisms colonizing the anode. These results demonstrate in real marine environments a new form of power generation that uses an immense, renewable energy reservoir (sedimentary organic carbon) and has near-immediate application.},
	keywords = {Bacteria, Bioelectric Energy Sources, Biotechnology, Carbon, Conservation of Energy Resources, DNA, Ribosomal, Electricity, Electrodes, Environmental Microbiology, Geologic Sediments, Molecular Sequence Data, New Jersey, Oceans and Seas, Oregon, Oxidation-Reduction, RNA, Bacterial, RNA, Ribosomal, 16S, Sulfides},
	issn = {1087-0156},
	doi = {10.1038/nbt716},
	author = {Tender, Leonard M and Reimers, Clare E and Stecher, Hilmar A and Holmes, Dawn E and Bond, Daniel R and Lowy, Daniel A and Pilobello, Kanoelani and Fertig, Stephanie J and Lovley, Derek R}
}
@article {585,
	title = {Reduction of Fe(III) oxide by methanogens in the presence and absence of extracellular quinones.},
	journal = {Environ Microbiol},
	volume = {4},
	year = {2002},
	month = {2002 Feb},
	pages = {115-24},
	abstract = {Five methanogens (Methanosarcina barkeri MS, Methanosphaera cuniculi 1R7, Methanobacterium palustre F, Methanococcus voltaei A3 and Methanolobus vulcani PL-12/M) were investigated for their ability to reduce Fe(III) oxide and the soluble quinone anthraquinone-2,6-disulphonate (AQDS). Two species (M. barkeri and M. voltaei) reduced significant amounts of Fe(III) oxide using hydrogen as the electron donor, and 0.1 mM AQDS greatly accelerated Fe(III) reduction by these organisms. Although Fe(III) appeared to inhibit growth and methanogenesis of some strains, hydrogen partial pressures under donor-limited conditions were much lower (<0.5 Pa) in the presence of Fe(III) than in normal media (1-10 Pa) for all species except for M. vulcani. These results demonstrate that electrons were transferred to Fe(III) by hydrogen-utilizing methanogens even when growth and methanogenesis were inhibited. All species except the obligate methylotroph M. vulcani were able to reduce AQDS when their growth substrates were present as electron donors, and rates were highest when organisms used hydrogen as the electron donor. Purified soil humic acids could also be reduced by the AQDS-reducing methanogens. The ability of methanogens to interact with extracellular quinones, humic acids and Fe(III) oxides raises the possibility that this functional group of organ-isms contributes to Fe(III) and humic acid reduction under certain conditions in the environment and provides an alternative explanation for the inhibition of methanogenesis in some Fe(III)-containing ecosystems.},
	keywords = {Anthraquinones, Euryarchaeota, Ferric Compounds, Humic Substances, Oxidation-Reduction, Species Specificity},
	issn = {1462-2912},
	author = {Bond, Daniel R and Lovley, Derek R}
}
