@article {543,
	title = {In situ expression of nifD in Geobacteraceae in subsurface sediments.},
	journal = {Appl Environ Microbiol},
	volume = {70},
	year = {2004},
	month = {2004 Dec},
	pages = {7251-9},
	abstract = {In order to determine whether the metabolic state of Geobacteraceae involved in bioremediation of subsurface sediments might be inferred from levels of mRNA for key genes, in situ expression of nifD, a highly conserved gene involved in nitrogen fixation, was investigated. When Geobacter sulfurreducens was grown without a source of fixed nitrogen in chemostats with acetate provided as the limiting electron donor and Fe(III) as the electron acceptor, levels of nifD transcripts were 4 to 5 orders of magnitude higher than in chemostat cultures provided with ammonium. In contrast, the number of transcripts of recA and the 16S rRNA gene were slightly lower in the absence of ammonium. The addition of acetate to organic- and nitrogen-poor subsurface sediments stimulated the growth of Geobacteraceae and Fe(III) reduction, as well as the expression of nifD in Geobacteraceae. Levels of nifD transcripts in Geobacteraceae decreased more than 100-fold within 2 days after the addition of 100 microM ammonium, while levels of recA and total bacterial 16S rRNA in Geobacteraceae remained relatively constant. Ammonium amendments had no effect on rates of Fe(III) reduction in acetate-amended sediments or toluene degradation in petroleum-contaminated sediments, suggesting that other factors, such as the rate that Geobacteraceae could access Fe(III) oxides, limited Fe(III) reduction. These results demonstrate that it is possible to monitor one aspect of the in situ metabolic state of Geobacteraceae species in subsurface sediments via analysis of mRNA levels, which is the first step toward a more global analysis of in situ gene expression related to nutrient status and stress response during bioremediation by Geobacteraceae.},
	keywords = {Acetates, Biodegradation, Environmental, Culture Media, DNA, Ribosomal, Fresh Water, Gene Expression Regulation, Bacterial, Geobacter, Geologic Sediments, Nitrogenase, Petroleum, Phylogeny, Polymerase Chain Reaction, Quaternary Ammonium Compounds, Rec A Recombinases, RNA, Ribosomal, 16S, Water Pollutants, Chemical},
	issn = {0099-2240},
	doi = {10.1128/AEM.70.12.7251-7259.2004},
	author = {Holmes, Dawn E and Nevin, Kelly P and Lovley, Derek R}
}
@article {604,
	title = {N2-dependent growth and nitrogenase activity in the metal-metabolizing bacteria, Geobacter and Magnetospirillum species.},
	journal = {Environ Microbiol},
	volume = {2},
	year = {2000},
	month = {2000 Jun},
	pages = {266-73},
	abstract = {Cells of Geobacter metallireducens, Magnetospirillum strain AMB-1, Magnetospirillum magnetotacticum and Magnetospirillum gryphiswaldense showed N2-dependent growth, the first anaerobically with Fe(III) as the electron acceptor, and the latter three species microaerobically in semi-solid oxygen gradient cultures. Cells of the Magnetospirillum species grown with N2 under microaerobic conditions were magnetotactic and therefore produced magnetosomes. Cells of Geobacter metallireducens reduced acetylene to ethylene (11.5+/-5.9 nmol C2H4 produced min(-1) mg(-1) cell protein) while growing with Fe(III) as the electron acceptor in anaerobic growth medium lacking a fixed nitrogen source. Cells of the Magnetospirillum species, grown in a semi-solid oxygen gradient medium, also reduced acetylene at comparable rates. Uncut chromosomal and fragments from endonuclease-digested chromosomal DNA from these species, as well as Geobacter sulphurreducens organisms, hybridized with a nifHDK probe from Rhodospirillum rubrum, indicating the presence of these nitrogenase structural genes in these organisms. The evidence presented here shows that members of the metal-metabolizing genera, Geobacter and Magnetospirillum, fix atmospheric dinitrogen.},
	keywords = {Acetylene, DNA, Bacterial, Ethylenes, Genes, Bacterial, Iron, Nitrogen Fixation, Nitrogenase, Oxidation-Reduction, Oxidoreductases, Proteobacteria, Rhodospirillaceae},
	issn = {1462-2912},
	author = {Bazylinski, D A and Dean, A J and Sch{\"u}ler, D and Phillips, E J and Lovley, D R}
}
