@article {571,
	title = {OmcB, a c-type polyheme cytochrome, involved in Fe(III) reduction in Geobacter sulfurreducens.},
	journal = {J Bacteriol},
	volume = {185},
	year = {2003},
	month = {2003 Apr},
	pages = {2096-103},
	abstract = {Microorganisms in the family Geobacteraceae are the predominant Fe(III)-reducing microorganisms in a variety of subsurface environments in which Fe(III) reduction is an important process, but little is known about the mechanisms for electron transport to Fe(III) in these organisms. The Geobacter sulfurreducens genome was found to contain a 10-kb chromosomal duplication consisting of two tandem three-gene clusters. The last genes of the two clusters, designated omcB and omcC, encode putative outer membrane polyheme c-type cytochromes which are 79\% identical. The role of the omcB and omcC genes in Fe(III) reduction in G. sulfurreducens was investigated. OmcB and OmcC were both expressed during growth with acetate as the electron donor and either fumarate or Fe(III) as the electron acceptor. OmcB was ca. twofold more abundant under both conditions. Disrupting omcB or omcC by gene replacement had no impact on growth with fumarate. However, the OmcB-deficient mutant was greatly impaired in its ability to reduce Fe(III) both in cell suspensions and under growth conditions. In contrast, the ability of the OmcC-deficient mutant to reduce Fe(III) was similar to that of the wild type. When omcB was reintroduced into the OmcB-deficient mutant, the capacity for Fe(III) reduction was restored in proportion to the level of OmcB production. These results indicate that OmcB, but not OmcC, has a major role in electron transport to Fe(III) and suggest that electron transport to the outer membrane is an important feature in Fe(III) reduction in this organism.},
	keywords = {Amino Acid Sequence, Bacterial Outer Membrane Proteins, Bacterial Proteins, Cytochrome c Group, Deltaproteobacteria, Gene Expression Regulation, Bacterial, Iron, Molecular Sequence Data, Multigene Family, Mutation, Oxidation-Reduction, Sequence Homology, Amino Acid},
	issn = {0021-9193},
	author = {Leang, Ching and Coppi, M V and Lovley, D R}
}
@article {606,
	title = {Differences in Fe(III) reduction in the hyperthermophilic archaeon, Pyrobaculum islandicum, versus mesophilic Fe(III)-reducing bacteria.},
	journal = {FEMS Microbiol Lett},
	volume = {195},
	year = {2001},
	month = {2001 Feb 20},
	pages = {253-8},
	abstract = {The discovery that all hyperthermophiles that have been evaluated have the capacity to reduce Fe(III) has raised the question of whether mechanisms for dissimilatory Fe(III) reduction have been conserved throughout microbial evolution. Many studies have suggested that c-type cytochromes are integral components in electron transport to Fe(III) in mesophilic dissimilatory Fe(III)-reducing microorganisms. However, Pyrobaculum islandicum, the hyperthermophile in which Fe(III) reduction has been most intensively studied, did not contain c-type cytochromes. NADPH was a better electron donor for the Fe(III) reductase activity in P. islandicum than NADH. This is the opposite of what has been observed with mesophiles. Thus, if previous models for dissimilatory Fe(III) reduction by mesophilic bacteria are correct, then it is unlikely that a single strategy for electron transport to Fe(III) is present in all dissimilatory Fe(III)-reducing microorganisms.},
	keywords = {Cytochrome c Group, Electron Transport, Ferric Compounds, FMN Reductase, NADH, NADPH Oxidoreductases, NADP, Oxidation-Reduction, Temperature, Thermoproteaceae},
	issn = {0378-1097},
	author = {Childers, S E and Lovley, D R}
}
@article {590,
	title = {Isolation, characterization and gene sequence analysis of a membrane-associated 89 kDa Fe(III) reducing cytochrome c from Geobacter sulfurreducens.},
	journal = {Biochem J},
	volume = {359},
	year = {2001},
	month = {2001 Oct 1},
	pages = {147-52},
	abstract = {Geobacter sulfurreducens is capable of anaerobic respiration with Fe(III) as a terminal electron acceptor via a membrane-bound Fe(III) reductase activity associated with a large molecular mass cytochrome c. This cytochrome was purified by detergent extraction of the membrane fraction, Q-Sepharose ion-exchange chromatography, preparative electrophoresis, and MonoQ ion-exchange chromatography. Spectrophotometric analysis of the purified cytochrome reveals a c-type haem, with no evidence of haem a, haem b or sirohaem. The cytochrome has an M(r) of 89000 as determined by denaturing PAGE, and has an isoelectric point of 5.2 as determined by analytical isoelectric focusing. Dithionite-reduced cytochrome can donate electrons to Fe(III)-nitrilotriacetic acid and synthetic ferrihydrite, thus demonstrating that the cytochrome has redox and thermodynamic properties required for reduction of Fe(III). Analysis using cyclic voltammetry confirmed that the reduced cytochrome can catalytically transfer electrons to ferrihydrite, further demonstrating its ability to be an electron transport mediator in anaerobic Fe(III) respiration. Sequence analysis of a cloned chromosomal DNA fragment revealed a 2307 bp open reading frame (ferA) encoding a 768 amino acid protein corresponding to the 89 kDa cytochrome. The deduced amino acid sequence (FerA) translated from the open reading frame contained 12 putative haem-binding motifs, as well as a hydrophobic N-terminal membrane anchor sequence, a lipid-attachment site and an ATP/GTP-binding site. FerA displayed 20\% or less identity with amino acid sequences of other known cytochromes, although it does share some features with characterized polyhaem cytochromes c.},
	keywords = {Amino Acid Sequence, Bacterial Proteins, Chromatography, Ion Exchange, Cloning, Molecular, Cytochrome c Group, Deltaproteobacteria, DNA Primers, Electron Transport, Electrophoresis, Polyacrylamide Gel, Ferric Compounds, Gene Expression Regulation, Bacterial, Molecular Sequence Data, Molecular Weight, Nitrilotriacetic Acid, Oxidation-Reduction, Polymerase Chain Reaction, Sequence Homology, Amino Acid},
	issn = {0264-6021},
	author = {Magnuson, T S and Isoyama, N and Hodges-Myerson, A L and Davidson, G and Maroney, M J and Geesey, G G and Lovley, D R}
}
@article {615,
	title = {The periplasmic 9.6-kilodalton c-type cytochrome of Geobacter sulfurreducens is not an electron shuttle to Fe(III).},
	journal = {J Bacteriol},
	volume = {181},
	year = {1999},
	month = {1999 Dec},
	pages = {7647-9},
	abstract = {Geobacter sulfurreducens contains a 9.6-kDa c-type cytochrome that was previously proposed to serve as an extracellular electron shuttle to insoluble Fe(III) oxides. However, when the cytochrome was added to washed-cell suspensions of G. sulfurreducens it did not enhance Fe(III) oxide reduction, whereas similar concentrations of the known electron shuttle, anthraquinone-2,6-disulfonate, greatly stimulated Fe(III) oxide reduction. Furthermore, analysis of the extracellular c-type cytochromes in cultures of G. sulfurreducens demonstrated that the dominant c-type cytochrome was not the 9.6-kDa cytochrome, but rather a 41-kDa cytochrome. These results and other considerations suggest that the 9.6-kDa cytochrome is not an important extracellular electron shuttle to Fe(III) oxides.},
	keywords = {Cytochrome c Group, Electron Transport, Electrophoresis, Polyacrylamide Gel, Ferric Compounds, Gram-Negative Anaerobic Bacteria, Molecular Weight, Periplasm},
	issn = {0021-9193},
	author = {Lloyd, J R and Blunt-Harris, E L and Lovley, D R}
}
@article {651,
	title = {Geobacter metallireducens gen. nov. sp. nov., a microorganism capable of coupling the complete oxidation of organic compounds to the reduction of iron and other metals.},
	journal = {Arch Microbiol},
	volume = {159},
	year = {1993},
	month = {1993},
	pages = {336-44},
	abstract = {The gram-negative metal-reducing microorganism, previously known as strain GS-15, was further characterized. This strict anaerobe oxidizes several short-chain fatty acids, alcohols, and monoaromatic compounds with Fe(III) as the sole electron acceptor. Furthermore, acetate is also oxidized with the reduction of Mn(IV), U(VI), and nitrate. In whole cell suspensions, the c-type cytochrome(s) of this organism was oxidized by physiological electron acceptors and also by gold, silver, mercury, and chromate. Menaquinone was recovered in concentrations comparable to those previously found in gram-negative sulfate reducers. Profiles of the phospholipid ester-linked fatty acids indicated that both the anaerobic desaturase and the branched pathways for fatty acid biosynthesis were operative. The organism contained three lipopolysaccharide hydroxy fatty acids which have not been previously reported in microorganisms, but have been observed in anaerobic freshwater sediments. The 16S rRNA sequence indicated that this organism belongs in the delta proteobacteria. Its closest known relative is Desulfuromonas acetoxidans. The name Geobacter metallireducens is proposed.},
	keywords = {Cytochrome c Group, Fatty Acids, Gram-Negative Anaerobic Bacteria, Iron, Oxidation-Reduction, Phylogeny, RNA, Ribosomal, 16S},
	issn = {0302-8933},
	author = {Lovley, D R and Giovannoni, S J and White, D C and Champine, J E and Phillips, E J and Gorby, Y A and Goodwin, S}
}
@article {647,
	title = {Reduction of uranium by cytochrome c3 of Desulfovibrio vulgaris.},
	journal = {Appl Environ Microbiol},
	volume = {59},
	year = {1993},
	month = {1993 Nov},
	pages = {3572-6},
	abstract = {The mechanism for U(VI) reduction by Desulfovibrio vulgaris (Hildenborough) was investigated. The H2-dependent U(VI) reductase activity in the soluble fraction of the cells was lost when the soluble fraction was passed over a cationic exchange column which extracted cytochrome c3. Addition of cytochrome c3 back to the soluble fraction that had been passed over the cationic exchange column restored the U(VI)-reducing capacity. Reduced cytochrome c3 was oxidized by U(VI), as was a c-type cytochrome(s) in whole-cell suspensions. When cytochrome c3 was combined with hydrogenase, its physiological electron donor, U(VI) was reduced in the presence of H2. Hydrogenase alone could not reduce U(VI). Rapid U(VI) reduction was followed by a subsequent slow precipitation of the U(IV) mineral uraninite. Cytochrome c3 reduced U(VI) in a uranium-contaminated surface water and groundwater. Cytochrome c3 provides the first enzyme model for the reduction and biomineralization of uranium in sedimentary environments. Furthermore, the finding that cytochrome c3 can catalyze the reductive precipitation of uranium may aid in the development of fixed-enzyme reactors and/or organisms with enhanced U(VI)-reducing capacity for the bioremediation of uranium-contaminated waters and waste streams.},
	keywords = {Biotransformation, Chemical Precipitation, Cytochrome c Group, Desulfovibrio vulgaris, Oxidation-Reduction, Uranium, Water Pollutants, Radioactive},
	issn = {0099-2240},
	author = {Lovley, D R and Widman, P K and Woodward, J C and Phillips, E J}
}
