@article {492,
	title = {Fluorescent properties of c-type cytochromes reveal their potential role as an extracytoplasmic electron sink in Geobacter sulfurreducens.},
	journal = {Environ Microbiol},
	volume = {10},
	year = {2008},
	month = {2008 Feb},
	pages = {497-505},
	abstract = {A novel fluorescence technique for monitoring the redox status of c-type cytochromes in Geobacter sulfurreducens was developed in order to evaluate the capacity of these extracytoplasmic cytochromes to store electrons during periods in which an external electron acceptor is not available. When intact cells in which the cytochromes were in a reduced state were excited at a wavelength of 350 nm, they fluoresced with maxima at 402 and 437 nm. Oxidation of the cytochromes resulted in a loss of fluorescence. This method was much more sensitive than the traditional approach of detecting c-type cytochromes via visible light absorbance. Furthermore, fluorescence of reduced cytochromes in individual cells could be detected via fluorescence microscopy, and the cytochromes in a G. sulfurreducens biofilm, remotely excited with an optical fibre, could be detected at distances as far as 5 cm. Fluorescence analysis of cytochrome oxidation and reduction of the external electron acceptor, anthraquinone-2,6-disulfonate, suggested that the extracytoplasmic cytochromes of G. sulfurreducens could store approximately 10(7) electrons per cell. Independent analysis of the haem content of the cells determined from analysis of incorporation of (55)Fe into cytochromes provided a similar estimate of cytochrome electron-storage capacity. This electron-storage capacity could, in the absence of an external electron acceptor, permit continued electron transfer across the inner membrane sufficient to supply the maintenance energy requirements for G. sulfurreducens for up to 8 min or enough proton motive force to power flagella motors for G. sulfurreducens motility. The fluorescence approach described here provides a sensitive method for evaluating the redox status of Geobacter species in culture and/or its environments. Furthermore, these results suggest that the periplasmic and outer-membrane cytochromes of Geobacter species act as capacitors, allowing continued electron transport, and thus viability and motility, for Geobacter species as they move between heterogeneously dispersed Fe(III) oxides during growth in the subsurface.},
	keywords = {Anthraquinones, Cytochromes c, Electron Transport, Ferric Compounds, Flagella, Fluorescence, Geobacter, Microscopy, Fluorescence, Oxidation-Reduction},
	issn = {1462-2920},
	doi = {10.1111/j.1462-2920.2007.01470.x},
	author = {Esteve-N{\'u}{\~n}ez, Abraham and Sosnik, Julian and Visconti, Pablo and Lovley, Derek R}
}
@article {702,
	title = {Differential protein expression in the metal-reducing bacterium Geobacter sulfurreducens strain PCA grown with fumarate or ferric citrate.},
	journal = {Proteomics},
	volume = {6},
	year = {2006},
	month = {2006 Jan},
	pages = {632-40},
	abstract = {Geobacter sulfurreducens, generally considered to be a strict anaerobe, is a predominant microbe in subsurface environments, where it utilizes available metals as electron acceptors. To better understand the metabolic processes involved in the metal-reduction capability of this microbe, the proteins expressed by cells grown anaerobically with either fumarate or ferric citrate as electron acceptor were compared. Proteins were separated by 2-DE under denaturing or nondenaturing conditions, and proteins varying in abundance with a high level of statistical significance (p<0.0001) were identified by peptide mass analysis. Denaturing 2-DE revealed significant differences in the relative abundance of the membrane proteins OmpA and peptidoglycan-associated lipoprotein, several metabolic enzymes, and, in addition, superoxide dismutase and rubredoxin oxidoreductase. Nondenaturing 2-DE revealed elevated catalase in cells grown with ferric citrate. These results suggest that, in addition to adjustments in membrane transport and specific metabolic pathways in response to these two different electron acceptors, distinct differences exist in the oxidative environment within the cell when fumarate or soluble ferric citrate is provided as electron acceptor. Although an anaerobe, G. sulfurreducens appears to have alternate mechanisms for dealing with reactive oxygen species in response to increased intracellular soluble iron.},
	keywords = {Anaerobiosis, Bacterial Proteins, Electrophoresis, Gel, Two-Dimensional, Ferric Compounds, Fumarates, Geobacter, Oxidation-Reduction, Proteomics, Reactive Oxygen Species, Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization},
	issn = {1615-9853},
	doi = {10.1002/pmic.200500137},
	author = {Khare, Tripti and Esteve-N{\'u}{\~n}ez, Abraham and Nevin, Kelly P and Zhu, Wenhong and Yates, John R and Lovley, Derek and Giometti, Carol S}
}
@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 {556,
	title = {Preferential reduction of FeIII over fumarate by Geobacter sulfurreducens.},
	journal = {J Bacteriol},
	volume = {186},
	year = {2004},
	month = {2004 May},
	pages = {2897-9},
	abstract = {The presence of Fe(III), but not that of Fe(II), resulted in ca. 20-fold-lower levels of mRNA for fumarate reductase, inhibiting fumarate reduction and favoring utilization of fumarate as an electron donor in chemostat cultures of Geobacter sulfurreducens, despite the fact that growth yield with fumarate was 3-fold higher than with Fe(III).},
	keywords = {Electrons, Fumarates, Geobacter, Iron, Oxidation-Reduction, Succinate Dehydrogenase},
	issn = {0021-9193},
	author = {Esteve-N{\'u}{\~n}ez, Abraham and N{\'u}{\~n}ez, Cinthia and Lovley, Derek R}
}
