@article {434,
	title = {The genome of Geobacter bemidjiensis, exemplar for the subsurface clade of Geobacter species that predominate in Fe(III)-reducing subsurface environments.},
	journal = {BMC Genomics},
	volume = {11},
	year = {2010},
	month = {2010},
	pages = {490},
	abstract = {BACKGROUND: Geobacter species in a phylogenetic cluster known as subsurface clade 1 are often the predominant microorganisms in subsurface environments in which Fe(III) reduction is the primary electron-accepting process. Geobacter bemidjiensis, a member of this clade, was isolated from hydrocarbon-contaminated subsurface sediments in Bemidji, Minnesota, and is closely related to Geobacter species found to be abundant at other subsurface sites. This study examines whether there are significant differences in the metabolism and physiology of G. bemidjiensis compared to non-subsurface Geobacter species.

RESULTS: Annotation of the genome sequence of G. bemidjiensis indicates several differences in metabolism compared to previously sequenced non-subsurface Geobacteraceae, which will be useful for in silico metabolic modeling of subsurface bioremediation processes involving Geobacter species. Pathways can now be predicted for the use of various carbon sources such as propionate by G. bemidjiensis. Additional metabolic capabilities such as carbon dioxide fixation and growth on glucose were predicted from the genome annotation. The presence of different dicarboxylic acid transporters and two oxaloacetate decarboxylases in G. bemidjiensis may explain its ability to grow by disproportionation of fumarate. Although benzoate is the only aromatic compound that G. bemidjiensis is known or predicted to utilize as an electron donor and carbon source, the genome suggests that this species may be able to detoxify other aromatic pollutants without degrading them. Furthermore, G. bemidjiensis is auxotrophic for 4-aminobenzoate, which makes it the first Geobacter species identified as having a vitamin requirement. Several features of the genome indicated that G. bemidjiensis has enhanced abilities to respire, detoxify and avoid oxygen.

CONCLUSION: Overall, the genome sequence of G. bemidjiensis offers surprising insights into the metabolism and physiology of Geobacteraceae in subsurface environments, compared to non-subsurface Geobacter species, such as the ability to disproportionate fumarate, more efficient oxidation of propionate, enhanced responses to oxygen stress, and dependence on the environment for a vitamin requirement. Therefore, an understanding of the activity of Geobacter species in the subsurface is more likely to benefit from studies of subsurface isolates such as G. bemidjiensis than from the non-subsurface model species studied so far.},
	keywords = {Aldehyde Oxidoreductases, Biodegradation, Environmental, Carbohydrate Metabolism, Carbon Dioxide, Cell Wall, Electrons, Environmental Microbiology, Fatty Acids, Frameshift Mutation, Fumarates, Genes, Bacterial, Genome, Bacterial, Geobacter, Glucose, Iron, Metabolic Networks and Pathways, Multienzyme Complexes, Multigene Family, Osmosis, Oxidation-Reduction, Oxo-Acid-Lyases, Propionic Acids, Pyruvic Acid, Species Specificity, Surface Properties},
	issn = {1471-2164},
	doi = {10.1186/1471-2164-11-490},
	author = {Aklujkar, Muktak and Young, Nelson D and Holmes, Dawn and Chavan, Milind and Risso, Carla and Kiss, Hajnalka E and Han, Cliff S and Land, Miriam L and Lovley, Derek R}
}
@article {461,
	title = {The genome sequence of Geobacter metallireducens: features of metabolism, physiology and regulation common and dissimilar to Geobacter sulfurreducens.},
	journal = {BMC Microbiol},
	volume = {9},
	year = {2009},
	month = {2009},
	pages = {109},
	abstract = {BACKGROUND: The genome sequence of Geobacter metallireducens is the second to be completed from the metal-respiring genus Geobacter, and is compared in this report to that of Geobacter sulfurreducens in order to understand their metabolic, physiological and regulatory similarities and differences.

RESULTS: The experimentally observed greater metabolic versatility of G. metallireducens versus G. sulfurreducens is borne out by the presence of more numerous genes for metabolism of organic acids including acetate, propionate, and pyruvate. Although G. metallireducens lacks a dicarboxylic acid transporter, it has acquired a second putative succinate dehydrogenase/fumarate reductase complex, suggesting that respiration of fumarate was important until recently in its evolutionary history. Vestiges of the molybdate (ModE) regulon of G. sulfurreducens can be detected in G. metallireducens, which has lost the global regulatory protein ModE but retained some putative ModE-binding sites and multiplied certain genes of molybdenum cofactor biosynthesis. Several enzymes of amino acid metabolism are of different origin in the two species, but significant patterns of gene organization are conserved. Whereas most Geobacteraceae are predicted to obtain biosynthetic reducing equivalents from electron transfer pathways via a ferredoxin oxidoreductase, G. metallireducens can derive them from the oxidative pentose phosphate pathway. In addition to the evidence of greater metabolic versatility, the G. metallireducens genome is also remarkable for the abundance of multicopy nucleotide sequences found in intergenic regions and even within genes.

CONCLUSION: The genomic evidence suggests that metabolism, physiology and regulation of gene expression in G. metallireducens may be dramatically different from other Geobacteraceae.},
	keywords = {Bacterial Proteins, DNA, Bacterial, Gene Expression Regulation, Bacterial, Genome, Bacterial, Geobacter, Phylogeny, Sequence Analysis, DNA, Species Specificity, Transcription Factors},
	issn = {1471-2180},
	doi = {10.1186/1471-2180-9-109},
	author = {Aklujkar, Muktak and Krushkal, Julia and DiBartolo, Genevieve and Lapidus, Alla and Land, Miriam L and Lovley, Derek R}
}
@article {466,
	title = {Genome-scale constraint-based modeling of Geobacter metallireducens.},
	journal = {BMC Syst Biol},
	volume = {3},
	year = {2009},
	month = {2009},
	pages = {15},
	abstract = {BACKGROUND: Geobacter metallireducens was the first organism that can be grown in pure culture to completely oxidize organic compounds with Fe(III) oxide serving as electron acceptor. Geobacter species, including G. sulfurreducens and G. metallireducens, are used for bioremediation and electricity generation from waste organic matter and renewable biomass. The constraint-based modeling approach enables the development of genome-scale in silico models that can predict the behavior of complex biological systems and their responses to the environments. Such a modeling approach was applied to provide physiological and ecological insights on the metabolism of G. metallireducens.

RESULTS: The genome-scale metabolic model of G. metallireducens was constructed to include 747 genes and 697 reactions. Compared to the G. sulfurreducens model, the G. metallireducens metabolic model contains 118 unique reactions that reflect many of G. metallireducens{\textquoteright} specific metabolic capabilities. Detailed examination of the G. metallireducens model suggests that its central metabolism contains several energy-inefficient reactions that are not present in the G. sulfurreducens model. Experimental biomass yield of G. metallireducens growing on pyruvate was lower than the predicted optimal biomass yield. Microarray data of G. metallireducens growing with benzoate and acetate indicated that genes encoding these energy-inefficient reactions were up-regulated by benzoate. These results suggested that the energy-inefficient reactions were likely turned off during G. metallireducens growth with acetate for optimal biomass yield, but were up-regulated during growth with complex electron donors such as benzoate for rapid energy generation. Furthermore, several computational modeling approaches were applied to accelerate G. metallireducens research. For example, growth of G. metallireducens with different electron donors and electron acceptors were studied using the genome-scale metabolic model, which provided a fast and cost-effective way to understand the metabolism of G. metallireducens.

CONCLUSION: We have developed a genome-scale metabolic model for G. metallireducens that features both metabolic similarities and differences to the published model for its close relative, G. sulfurreducens. Together these metabolic models provide an important resource for improving strategies on bioremediation and bioenergy generation.},
	keywords = {Biodegradation, Environmental, Biomass, Computer Simulation, Ecosystem, Electron Transport, Energy Metabolism, Genome, Bacterial, Geobacter, Iron, Metabolic Networks and Pathways, Models, Biological, Models, Genetic, Mutation, Phenotype, Species Specificity, Systems Biology},
	issn = {1752-0509},
	doi = {10.1186/1752-0509-3-15},
	author = {Sun, Jun and Sayyar, Bahareh and Butler, Jessica E and Pharkya, Priti and Fahland, Tom R and Famili, Iman and Schilling, Christophe H and Lovley, Derek R and Mahadevan, Radhakrishnan}
}
@article {460,
	title = {Selection of a variant of Geobacter sulfurreducens with enhanced capacity for current production in microbial fuel cells.},
	journal = {Biosens Bioelectron},
	volume = {24},
	year = {2009},
	month = {2009 Aug 15},
	pages = {3498-503},
	abstract = {Geobacter sulfurreducens produces current densities in microbial fuel cells that are among the highest known for pure cultures. The possibility of adapting this organism to produce even higher current densities was evaluated. A system in which a graphite anode was poised at -400 mV (versus Ag/AgCl) was inoculated with the wild-type strain of G. sulfurreducens, strain DL-1. An isolate, designated strain KN400, was recovered from the biofilm after 5 months of growth on the electrode. KN400 was much more effective in current production than strain DL-1. This was apparent with anodes poised at -400 mV, as well as in systems run in true fuel cell mode. KN400 had current (7.6A/m(2)) and power (3.9 W/m(2)) densities that respectively were substantially higher than those of DL1 (1.4A/m(2) and 0.5 W/m(2)). On a per cell basis KN400 was more effective in current production than DL1, requiring thinner biofilms to make equivalent current. The enhanced capacity for current production in KN400 was associated with a greater abundance of electrically conductive microbial nanowires than DL1 and lower internal resistance (0.015 versus 0.130 Omega/m(2)) and mass transfer limitation in KN400 fuel cells. KN400 produced flagella, whereas DL1 does not. Surprisingly, KN400 had much less outer-surface c-type cytochromes than DL1. KN400 also had a greater propensity to form biofilms on glass or graphite than DL1, even when growing with the soluble electron acceptor, fumarate. These results demonstrate that it is possible to enhance the ability of microorganisms to electrochemically interact with electrodes with the appropriate selective pressure and that improved current production is associated with clear differences in the properties of the outer surface of the cell that may provide insights into the mechanisms for microbe-electrode interactions.},
	keywords = {Bioelectric Energy Sources, Electrochemistry, Equipment Design, Equipment Failure Analysis, Geobacter, Species Specificity},
	issn = {1873-4235},
	doi = {10.1016/j.bios.2009.05.004},
	author = {Yi, Hana and Nevin, Kelly P and Kim, Byoung-Chan and Franks, Ashely E and Klimes, Anna and Tender, Leonard M and Lovley, Derek R}
}
@article {484,
	title = {Geobacter uraniireducens sp. nov., isolated from subsurface sediment undergoing uranium bioremediation.},
	journal = {Int J Syst Evol Microbiol},
	volume = {58},
	year = {2008},
	month = {2008 May},
	pages = {1075-8},
	abstract = {A Gram-negative, rod-shaped, motile bacterium, strain Rf4T, which conserves energy from dissimilatory Fe(III) reduction concomitant with acetate oxidation, was isolated from subsurface sediment undergoing uranium bioremediation. The 16S rRNA gene sequence of strain Rf4T matched sequences recovered in 16S rRNA gene clone libraries constructed from DNA extracted from groundwater sampled at the same time as the source sediment. Cells of strain Rf4T were regular, motile rods, 1.2-2.0 microm long and 0.5-0.6 microm in diameter, with rounded ends. Cells had one lateral flagellum. Growth was optimal at pH 6.5-7.0 and 32 degrees C. With acetate as the electron donor, strain Rf4T used Fe(III), Mn(IV), anthraquinone-2,6-disulfonate, malate and fumarate as electron acceptors and reduced U(VI) in cell suspensions. With poorly crystalline Fe(III) oxide as the electron acceptor, strain Rf4T oxidized the following electron donors: acetate, lactate, pyruvate and ethanol. Phylogenetic analysis of the 16S rRNA gene sequence of strain Rf4T placed it in the genus Geobacter. Strain Rf4T was most closely related to {\textquoteright}Geobacter humireducens{\textquoteright} JW3 (95.9 \% sequence similarity), Geobacter bremensis Dfr1T (95.4 \%) and Geobacter bemidjiensis BemT (95.1 \%). Based on phylogenetic analysis and phenotypic differences between strain Rf4T and closely related Geobacter species, this strain is described as a representative of a novel species, Geobacter uraniireducens sp. nov. The type strain is Rf4T (=ATCC BAA-1134T =JCM 13001T).},
	keywords = {Bacterial Typing Techniques, DNA, Bacterial, Genes, rRNA, Genotype, Geobacter, Geologic Sediments, Molecular Sequence Data, Oxidation-Reduction, Phenotype, Phylogeny, RNA, Ribosomal, 16S, Sequence Analysis, DNA, Species Specificity, Uranium},
	issn = {1466-5026},
	doi = {10.1099/ijs.0.65377-0},
	author = {Shelobolina, Evgenya S and Vrionis, Helen A and Findlay, Robert H and Lovley, Derek R}
}
@article {508,
	title = {Geobacter pickeringii sp. nov., Geobacter argillaceus sp. nov. and Pelosinus fermentans gen. nov., sp. nov., isolated from subsurface kaolin lenses.},
	journal = {Int J Syst Evol Microbiol},
	volume = {57},
	year = {2007},
	month = {2007 Jan},
	pages = {126-35},
	abstract = {The goal of this project was to isolate representative Fe(III)-reducing bacteria from kaolin clays that may influence iron mineralogy in kaolin. Two novel dissimilatory Fe(III)-reducing bacteria, strains G12(T) and G13(T), were isolated from sedimentary kaolin strata in Georgia (USA). Cells of strains G12(T) and G13(T) were motile, non-spore-forming regular rods, 1-2 mum long and 0.6 mum in diameter. Cells had one lateral flagellum. Phylogenetic analyses using the 16S rRNA gene sequence of the novel strains demonstrated their affiliation to the genus Geobacter. Strain G12(T) was most closely related to Geobacter pelophilus (94.7 \%) and Geobacter chapellei (94.1 \%). Strain G13(T) was most closely related to Geobacter grbiciae (95.3 \%) and Geobacter metallireducens (95.1 \%). Based on phylogenetic analyses and phenotypic differences between the novel isolates and other closely related species of the genus Geobacter, the isolates are proposed as representing two novel species, Geobacter argillaceus sp. nov. (type strain G12(T)=ATCC BAA-1139(T)=JCM 12999(T)) and Geobacter pickeringii sp. nov. (type strain G13(T)=ATCC BAA-1140(T)=DSM 17153(T)=JCM 13000(T)). Another isolate, strain R7(T), was derived from a primary kaolin deposit in Russia. The cells of strain R7(T) were motile, spore-forming, slightly curved rods, 0.6 x 2.0-6.0 microm in size and with up to six peritrichous flagella. Strain R7(T) was capable of reducing Fe(III) only in the presence of a fermentable substrate. 16S rRNA gene sequence analysis demonstrated that this isolate is unique, showing less than 92 \% similarity to bacteria of the Sporomusa-Pectinatus-Selenomomas phyletic group, including {\textquoteright}Anaerospora hongkongensis{\textquoteright} (90.2 \%), Acetonema longum (90.6 \%), Dendrosporobacter quercicolus (90.9 \%) and Anaerosinus glycerini (91.5 \%). On the basis of phylogenetic analysis and physiological tests, strain R7(T) is proposed to represent a novel genus and species, Pelosinus fermentans gen. nov., sp. nov. (type strain R7(T)=DSM 17108(T)=ATCC BAA-1133(T)), in the Sporomusa-Pectinatus-Selenomonas group.},
	keywords = {Bacterial Typing Techniques, Base Composition, DNA, Bacterial, DNA, Ribosomal, Ferric Compounds, Genes, rRNA, Geobacter, Geologic Sediments, Georgia, Kaolin, Molecular Sequence Data, Oxidation-Reduction, Phylogeny, RNA, Ribosomal, 16S, Russia, Sequence Analysis, DNA, Species Specificity},
	issn = {1466-5026},
	doi = {10.1099/ijs.0.64221-0},
	author = {Shelobolina, Evgenya S and Nevin, Kelly P and Blakeney-Hayward, Jessie D and Johnsen, Claudia V and Plaia, Todd W and Krader, Paul and Woodard, Trevor and Holmes, Dawn E and Vanpraagh, Catherine Gaw and Lovley, Derek R}
}
@article {532,
	title = {Geobacter bemidjiensis sp. nov. and Geobacter psychrophilus sp. nov., two novel Fe(III)-reducing subsurface isolates.},
	journal = {Int J Syst Evol Microbiol},
	volume = {55},
	year = {2005},
	month = {2005 Jul},
	pages = {1667-74},
	abstract = {Fe(III)-reducing isolates were recovered from two aquifers in which Fe(III) reduction is known to be important. Strain Bem(T) was enriched from subsurface sediments collected in Bemidji, MN, USA, near a site where Fe(III) reduction is important in aromatic hydrocarbon degradation. Strains P11, P35(T) and P39 were isolated from the groundwater of an aquifer in Plymouth, MA, USA, in which Fe(III) reduction is important because of long-term inputs of acetate as a highway de-icing agent to the subsurface. All four isolates were Gram-negative, slightly curved rods that grew best in freshwater media. Strains P11, P35(T) and P39 exhibited motility via means of monotrichous flagella. Analysis of the 16S rRNA and nifD genes indicated that all four strains are delta-proteobacteria and members of the Geobacter cluster of the Geobacteraceae. Differences in phenotypic and phylogenetic characteristics indicated that the four isolates represent two novel species within the genus Geobacter. All of the isolates coupled the oxidation of acetate to the reduction of Fe(III) [iron(III) citrate, amorphous iron(III) oxide, iron(III) pyrophosphate and iron(III) nitrilotriacetate]. All four strains utilized ethanol, lactate, malate, pyruvate and succinate as electron donors and malate and fumarate as electron acceptors. Strain Bem(T) grew fastest at 30 degrees C, whereas strains P11, P35(T) and P39 grew equally well at 17, 22 and 30 degrees C. In addition, strains P11, P35(T) and P39 were capable of growth at 4 degrees C. The names Geobacter bemidjiensis sp. nov. (type strain Bem(T)=ATCC BAA-1014(T)=DSM 16622(T)=JCM 12645(T)) and Geobacter psychrophilus sp. nov. (strains P11, P35(T) and P39; type strain P35(T)=ATCC BAA-1013(T)=DSM 16674(T)=JCM 12644(T)) are proposed.},
	keywords = {Bacterial Proteins, Bacterial Typing Techniques, Cold Temperature, DNA, Bacterial, DNA, Ribosomal, Ferric Compounds, Fresh Water, Genes, rRNA, Geobacter, Geologic Sediments, Massachusetts, Minnesota, Molecular Sequence Data, Oxidation-Reduction, RNA, Ribosomal, 16S, Species Specificity, Water Supply},
	issn = {1466-5026},
	doi = {10.1099/ijs.0.63417-0},
	author = {Nevin, Kelly P and Holmes, Dawn E and Woodard, Trevor L and Hinlein, Erich S and Ostendorf, David W and Lovley, Derek R}
}
@article {569,
	title = {Thermophily in the Geobacteraceae: Geothermobacter ehrlichii gen. nov., sp. nov., a novel thermophilic member of the Geobacteraceae from the "Bag City" hydrothermal vent.},
	journal = {Appl Environ Microbiol},
	volume = {69},
	year = {2003},
	month = {2003 May},
	pages = {2985-93},
	abstract = {Little is known about the microbiology of the "Bag City" hydrothermal vent, which is part of a new eruption site on the Juan de Fuca Ridge and which is notable for its accumulation of polysaccharide on the sediment surface. A pure culture, designated strain SS015, was recovered from a vent fluid sample from the Bag City site through serial dilution in liquid medium with malate as the electron donor and Fe(III) oxide as the electron acceptor and then isolation of single colonies on solid Fe(III) oxide medium. The cells were gram-negative rods, about 0.5 micro m by 1.2 to 1.5 micro m, and motile and contained c-type cytochromes. Analysis of the 16S ribosomal DNA (rDNA) sequence of strain SS015 placed it in the family Geobacteraceae in the delta subclass of the Proteobacteria. Unlike previously described members of the Geobacteraceae, which are mesophiles, strain SS015 was a thermophile and grew at temperatures of between 35 and 65 degrees C, with an optimum temperature of 55 degrees C. Like many previously described members of the Geobacteraceae, strain SS015 grew with organic acids as the electron donors and Fe(III) or nitrate as the electron acceptor, with nitrate being reduced to ammonia. Strain SS015 was unique among the Geobacteraceae in its ability to use sugars, starch, or amino acids as electron donors for Fe(III) reduction. Under stress conditions, strain SS015 produced copious quantities of extracellular polysaccharide, providing a model for the microbial production of the polysaccharide accumulation at the Bag City site. The 16S rDNA sequence of strain SS015 was less than 94\% similar to the sequences of previously described members of the Geobacteraceae; this fact, coupled with its unique physiological properties, suggests that strain SS015 represents a new genus in the family Geobacteraceae. The name Geothermobacter ehrlichii gen. nov., sp. nov., is proposed (ATCC BAA-635 and DSM 15274). Although strains of Geobacteraceae are known to be the predominant Fe(III)-reducing microorganisms in a variety of Fe(III)-reducing environments at moderate temperatures, strain SS015 represents the first described thermophilic member of the Geobacteraceae and thus extends the known environmental range of this family to hydrothermal environments.},
	keywords = {Base Composition, Cytochromes, Deltaproteobacteria, DNA, Bacterial, DNA, Ribosomal, Drug Resistance, Bacterial, Ecosystem, Electron Transport, Geologic Sediments, Hot Temperature, Hydrogen-Ion Concentration, Iron, Microscopy, Electron, Molecular Sequence Data, Oxidation-Reduction, Pacific Ocean, Phylogeny, Seawater, Sodium Chloride, Species Specificity},
	issn = {0099-2240},
	author = {Kashefi, Kazem and Holmes, Dawn E and Baross, John A 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 {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}
}
