@article {527,
	title = {Outer membrane c-type cytochromes required for Fe(III) and Mn(IV) oxide reduction in Geobacter sulfurreducens.},
	journal = {Appl Environ Microbiol},
	volume = {71},
	year = {2005},
	month = {2005 Dec},
	pages = {8634-41},
	abstract = {The potential role of outer membrane proteins in electron transfer to insoluble Fe(III) oxides by Geobacter sulfurreducens was investigated because this organism is closely related to the Fe(III) oxide-reducing organisms that are predominant in many Fe(III)-reducing environments. Two of the most abundant proteins that were easily sheared from the outer surfaces of intact cells were c-type cytochromes. One, designated OmcS, has a molecular mass of ca. 50 kDa and is predicted to be an outer membrane hexaheme c-type cytochrome. Transcripts for omcS could be detected during growth on Fe(III) oxide, but not on soluble Fe(III) citrate. The omcS mRNA consisted primarily of a monocistronic transcript, and to a lesser extent, a longer transcript that also contained the downstream gene omcT, which is predicted to encode a second hexaheme outer membrane cytochrome with 62.6\% amino acid sequence identity to OmcS. The other abundant c-type cytochrome sheared from the outer surface of G. sulfurreducens, designated OmcE, has a molecular mass of ca. 30 kDa and is predicted to be an outer membrane tetraheme c-type cytochrome. When either omcS or omcE was deleted, G. sulfurreducens could no longer reduce Fe(III) oxide but could still reduce soluble electron acceptors, including Fe(III) citrate. The mutants could reduce Fe(III) in Fe(III) oxide medium only if the Fe(III) chelator, nitrilotriacetic acid, or the electron shuttle, anthraquinone 2,6-disulfonate, was added. Expressing omcS or omcE in trans restored the capacity for Fe(III) oxide reduction. OmcT was not detected among the sheared proteins, and genetic studies indicated that G. sulfurreducens could not reduce Fe(III) oxide when omcT was expressed but OmcS was absent. In contrast, Fe(III) oxide was reduced when omcS was expressed in the absence of OmcT. These results suggest that OmcS and OmcE are involved in electron transfer to Fe(III) oxides in G. sulfurreducens. They also emphasize the importance of evaluating mechanisms for Fe(III) reduction with environmentally relevant Fe(III) oxide, rather than the more commonly utilized Fe(III) citrate, because additional electron transfer components are required for Fe(III) oxide reduction that are not required for Fe(III) citrate reduction.},
	keywords = {Amino Acid Sequence, Bacterial Outer Membrane Proteins, Bacterial Proteins, Base Sequence, Cytochromes c, DNA Primers, Ferric Compounds, Geobacter, Kinetics, Manganese Compounds, Molecular Sequence Data, Oxidation-Reduction, Oxides, Peptide Fragments},
	issn = {0099-2240},
	doi = {10.1128/AEM.71.12.8634-8641.2005},
	author = {Mehta, T and Coppi, M V and Childers, S E 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}
}
