@article {499,
	title = {Involvement of Geobacter sulfurreducens SfrAB in acetate metabolism rather than intracellular, respiration-linked Fe(III) citrate reduction.},
	journal = {Microbiology},
	volume = {153},
	year = {2007},
	month = {2007 Oct},
	pages = {3572-85},
	abstract = {A soluble ferric reductase, SfrAB, which catalysed the NADPH-dependent reduction of chelated Fe(III), was previously purified from the dissimilatory Fe(III)-reducing micro-organism Geobacter sulfurreducens, suggesting that reduction of chelated forms of Fe(III) might be cytoplasmic. However, metabolically active spheroplast suspensions could not catalyse acetate-dependent Fe(III) citrate reduction, indicating that periplasmic and/or outer-membrane components were required for Fe(III) citrate reduction. Furthermore, phenotypic analysis of an SfrAB knockout mutant suggested that SfrAB was involved in acetate metabolism rather than respiration-linked Fe(III) reduction. The mutant could not grow via the reduction of either Fe(III) citrate or fumarate when acetate was the electron donor but could grow with either acceptor if either hydrogen or formate served as the electron donor. Following prolonged incubation in acetate : fumarate medium in the absence of hydrogen and formate, an {\textquoteright}acetate-adapted{\textquoteright} SfrAB-null strain was isolated that was capable of growth on acetate : fumarate medium but not acetate : Fe(III) citrate medium. Comparison of gene expression in this strain with that of the wild-type revealed upregulation of a potential NADPH-dependent ferredoxin oxidoreductase as well as genes involved in energy generation and amino acid uptake, suggesting that NADPH homeostasis and the tricarboxylic acid (TCA) cycle were perturbed in the {\textquoteright}acetate-adapted{\textquoteright} SfrAB-null strain. Membrane and soluble fractions prepared from the {\textquoteright}acetate-adapted{\textquoteright} strain were depleted of NADPH-dependent Fe(III), viologen and quinone reductase activities. These results indicate that cytoplasmic, respiration-linked reduction of Fe(III) by SfrAB in vivo is unlikely and suggest that deleting SfrAB may interfere with growth via acetate oxidation by interfering with NADP regeneration.},
	keywords = {Acetates, Amino Acid Transport Systems, Bacterial Proteins, Cell Membrane, Citric Acid Cycle, Cytoplasm, Energy Metabolism, Ferric Compounds, Formic Acids, Fumarates, Gene Deletion, Gene Expression Profiling, Geobacter, Hydrogen, NADH, NADPH Oxidoreductases, Oligonucleotide Array Sequence Analysis},
	issn = {1350-0872},
	doi = {10.1099/mic.0.2007/006478-0},
	author = {Coppi, Maddalena V and O{\textquoteright}Neil, Regina A and Leang, Ching and Kaufmann, Franz and Meth{\'e}, Barbara A and Nevin, Kelly P and Woodard, Trevor L and Liu, Anna and Lovley, Derek 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 {592,
	title = {Isolation and characterization of a soluble NADPH-dependent Fe(III) reductase from Geobacter sulfurreducens.},
	journal = {J Bacteriol},
	volume = {183},
	year = {2001},
	month = {2001 Aug},
	pages = {4468-76},
	abstract = {NADPH is an intermediate in the oxidation of organic compounds coupled to Fe(III) reduction in Geobacter species, but Fe(III) reduction with NADPH as the electron donor has not been studied in these organisms. Crude extracts of Geobacter sulfurreducens catalyzed the NADPH-dependent reduction of Fe(III)-nitrilotriacetic acid (NTA). The responsible enzyme, which was recovered in the soluble protein fraction, was purified to apparent homogeneity in a four-step procedure. Its specific activity for Fe(III) reduction was 65 micromol. min(-1). mg(-1). The soluble Fe(III) reductase was specific for NADPH and did not utilize NADH as an electron donor. Although the enzyme reduced several forms of Fe(III), Fe(III)-NTA was the preferred electron acceptor. The protein possessed methyl viologen:NADP(+) oxidoreductase activity and catalyzed the reduction of NADP(+) with reduced methyl viologen as electron donor at a rate of 385 U/mg. The enzyme consisted of two subunits with molecular masses of 87 and 78 kDa and had a native molecular mass of 320 kDa, as determined by gel filtration. The purified enzyme contained 28.9 mol of Fe, 17.4 mol of acid-labile sulfur, and 0.7 mol of flavin adenine dinucleotide per mol of protein. The genes encoding the two subunits were identified in the complete sequence of the G. sulfurreducens genome from the N-terminal amino acid sequences derived from the subunits of the purified protein. The sequences of the two subunits had about 30\% amino acid identity to the respective subunits of the formate dehydrogenase from Moorella thermoacetica, but the soluble Fe(III) reductase did not possess formate dehydrogenase activity. This soluble Fe(III) reductase differs significantly from previously characterized dissimilatory and assimilatory Fe(III) reductases in its molecular composition and cofactor content.},
	keywords = {Amino Acid Sequence, Bacterial Proteins, Deltaproteobacteria, Ferric Compounds, FMN Reductase, Molecular Sequence Data, NADH, NADPH Oxidoreductases, NADP, Nitrilotriacetic Acid, Sequence Analysis, Protein, Sequence Homology, Amino Acid, Solubility},
	issn = {0021-9193},
	doi = {10.1128/JB.183.15.4468-4476.2001},
	author = {Kaufmann, F and Lovley, D R}
}
@article {613,
	title = {Characterization of a membrane-bound NADH-dependent Fe(3+) reductase from the dissimilatory Fe(3+)-reducing bacterium Geobacter sulfurreducens.},
	journal = {FEMS Microbiol Lett},
	volume = {185},
	year = {2000},
	month = {2000 Apr 15},
	pages = {205-11},
	abstract = {Geobacter sulfurreducens produces a single, membrane-associated Fe(3+) reductase activity when grown on fumarate or Fe(3+). The activity was initially isolated by solubilization of membranes with the non-ionic detergent dodecyl-beta-D-maltoside, and partially purified by a combination of ion exchange chromatography and preparative non-denaturing gel electrophoresis. Molecular mass of the reductase, as determined by gel filtration chromatography, was approximately 300 kDa. Cofactor analysis of the purified reductase demonstrates that it contains a hemoprotein and flavin adenine dinucleotide. Kinetic and inhibitor studies show that the reductase is specific for NADH as electron donor, and confirm that the reductase enzymatically reduces Fe(3+). The cytochrome associated with the complex undergoes a reoxidation upon addition of Fe(3+) compounds, indicating an ability to pass reducing equivalents to Fe(3+). This is the first description of a purified NADH-dependent Fe(3+) reductase from a microorganism capable of coupling Fe(3+) reduction to growth.},
	keywords = {Cell Membrane, Deltaproteobacteria, Ferric Compounds, FMN Reductase, NADH, NADPH Oxidoreductases, Oxidation-Reduction},
	issn = {0378-1097},
	author = {Magnuson, T S and Hodges-Myerson, A L and Lovley, D R}
}
