@article {531,
	title = {Adaptation to disruption of the electron transfer pathway for Fe(III) reduction in Geobacter sulfurreducens.},
	journal = {J Bacteriol},
	volume = {187},
	year = {2005},
	month = {2005 Sep},
	pages = {5918-26},
	abstract = {Previous studies demonstrated that an outer membrane c-type cytochrome, OmcB, was involved in Fe(III) reduction in Geobacter sulfurreducens. An OmcB-deficient mutant was greatly impaired in its ability to reduce both soluble and insoluble Fe(III). Reintroducing omcB restored the capacity for Fe(III) reduction at a level proportional to the level of OmcB production. Here, we report that the OmcB-deficient mutant gradually adapted to grow on soluble Fe(III) but not insoluble Fe(III). The adapted OmcB-deficient mutant reduced soluble Fe(III) at a rate comparable to that of the wild type, but the cell yield of the mutant was only ca. 60\% of that of the wild type under steady-state culturing conditions. Analysis of proteins and transcript levels demonstrated that expression of several membrane-associated cytochromes was higher in the adapted mutant than in the wild type. Further comparison of transcript levels during steady-state growth on Fe(III) citrate with a whole-genome DNA microarray revealed a significant shift in gene expression in an apparent attempt to adapt metabolism to the impaired electron transport to Fe(III). These results demonstrate that, although there are many other membrane-bound c-type cytochromes in G. sulfurreducens, increased expression of these cytochromes cannot completely compensate for the loss of OmcB. The concept that outer membrane cytochromes are promiscuous reductases that are interchangeable in function appears to be incorrect. Furthermore, the results indicate that there may be different mechanisms for electron transfer to soluble Fe(III) and insoluble Fe(III) oxides in G. sulfurreducens, which emphasizes the importance of studying electron transport to the environmentally relevant Fe(III) oxides.},
	keywords = {Adaptation, Physiological, Bacterial Outer Membrane Proteins, Base Sequence, Cytochromes c, DNA Primers, Electron Transport, Ferric Compounds, Gene Expression Regulation, Bacterial, Geobacter, Kinetics, Oxidation-Reduction, Reverse Transcriptase Polymerase Chain Reaction},
	issn = {0021-9193},
	doi = {10.1128/JB.187.17.5918-5926.2005},
	author = {Leang, Ching and Adams, L A and Chin, K-J and Nevin, K P and Meth{\'e}, B A and Webster, J and Sharma, M L and Lovley, D R}
}
@article {548,
	title = {Direct correlation between rates of anaerobic respiration and levels of mRNA for key respiratory genes in Geobacter sulfurreducens.},
	journal = {Appl Environ Microbiol},
	volume = {70},
	year = {2004},
	month = {2004 Sep},
	pages = {5183-9},
	abstract = {The predominance of Geobacter species in environments in which Fe(III) reduction is important has suggested that Fe(III) reduction rates might be estimated in Geobacter-dominated environments by assessing in situ activity with molecular techniques. To determine whether mRNA levels of key respiratory genes might be correlated with respiration rates in Geobacter sulfurreducens, studies were conducted with fumarate as the electron acceptor and acetate as the limiting electron donor in anaerobic continuous cultures. Levels of mRNA for a fumarate reductase gene, frdA, quantified by real-time reverse transcription-PCR were directly correlated with fumarate reduction rates. In similar studies with Fe(III) as the electron acceptor, mRNA levels for omcB, a gene for an outer membrane c-type cytochrome involved in Fe(III) reduction, were positively correlated with Fe(III) reduction rates. Levels of mRNA for frdA and omcB were also positively correlated with fumarate and Fe(III) reduction rates, respectively, when growth was limited by the availability of fumarate or Fe(III), but mRNA levels were higher than in acetate-limited cultures. Levels of mRNA for omcC, which encodes a c-type cytochrome highly similar to OmcB but not necessary for Fe(III) reduction, followed patterns different than those of omcB. This agrees with the previous finding that OmcC is not involved in Fe(III) reduction and suggests that changes in mRNA levels of omcB are related to its role in Fe(III) reduction. These results demonstrate that mRNA levels for respiratory genes might be used to estimate in situ Fe(III) reduction rates in Geobacter-dominated environments but suggest that information on environmental conditions and/or the metabolic state of Geobacter species is also required for accurate rate estimates.},
	keywords = {Anaerobiosis, Base Sequence, DNA Primers, Geobacter, Kinetics, Oxygen Consumption, Polymerase Chain Reaction, RNA, Messenger},
	issn = {0099-2240},
	doi = {10.1128/AEM.70.9.5183-5189.2004},
	author = {Chin, Kuk-Jeong and Esteve-N{\'u}{\~n}ez, Abraham and Leang, Ching and Lovley, Derek R}
}
