Geobacter hydrogenophilus, Geobacter chapellei and Geobacter grbiciae, three new, strictly anaerobic, dissimilatory Fe(III)-reducers.

Coates, John D.; Bhupathiraju, Vishvesh K.; Achenbach, Laurie A.; Mclnerney, Michael J.; Lovley, Derek R.

doi:10.1099/00207713-51-2-581

Cited by 205 publications

(98 citation statements)

References 23 publications

(24 reference statements)

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“…S4). The predominant Geobacter species were most closely related to the subsurface isolates G. psychrophilus and G. chapellei, which were isolated from an acetate-impacted aquifer [37] and a deep subsurface site [38], respectively. This contrasts with the predominance of Geobacter species most closely related to strain M18 on the 2007 electrode suggesting growth of different Geobacter species in the subsurface may be favored under different environmental conditions.…”

Section: Current Production Following Long-term Acetate Amendmentmentioning

confidence: 99%

Electrode-Based Approach for Monitoring In Situ Microbial Activity During Subsurface Bioremediation

Williams

Nevin

Franks

et al. 2009

Environ. Sci. Technol.

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Current production by microorganisms colonizing subsurface electrodes and its relationship to substrate availability and microbial activity was evaluated in an aquifer undergoing bioremediation. Borehole graphite anodes were installed downgradient from a region of acetate injection designed to stimulate bioreduction of U(VI); cathodes consisted of graphite electrodes embedded at the ground surface. Significant increases in current density (≤50 mA/m 2 ) tracked delivery of acetate to the electrodes, dropping rapidly when acetate inputs were discontinued. An upgradient control electrode not exposed to acetate produced low, steady currents (≤0.2 mA/m 2 ). Elevated current was strongly correlated with uranium removal but minimal correlation existed with elevated Fe(II). Confocal laser scanning microscopy of electrodes revealed firmly attached biofilms, and analysis of 16S rRNA gene sequences indicated the electrode surfaces were dominated (67-80%) by Geobacter species. This is the first demonstration that electrodes can produce readily detectable currents despite long-range (6 m) separation of anode and cathode, and these results suggest that oxidation of acetate coupled to electron transfer to electrodes by Geobacter species was the primary source of current. Thus it is expected that current production may serve as an effective proxy for monitoring in situ microbial activity in a variety of subsurface anoxic environments.

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Section: Current Production Following Long-term Acetate Amendmentmentioning

confidence: 99%

Electrode-Based Approach for Monitoring In Situ Microbial Activity During Subsurface Bioremediation

Williams

Nevin

Franks

et al. 2009

Environ. Sci. Technol.

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“…Since the first report on the ability of some Fe(III) reducing bacteria to enzymatically reduce U(VI) (Lovley et al, 1991), the number of known U(VI) reducing microorganisms has increased (Shelobolina et al, 2004;. As shown in Figure 2, more than 25 species of phylogenetically diverse prokaryotes are known to mediate enzymatic U(VI) reduction, including a hyperthermophilic archaeon (Kashefi and Lovley, 2000), thermophilic bacteria (Kieft et al, 1999), mesophilic Fe(III) reducing bacteria (Lovley et al, 1991, Coates et al, 1998Coates et al, 2001), mesophilic sulfate reducing bacteria (Lovley and Phillips, 1992;Lovley et al, 1993;Tebo and Obraztsova, 1998;Suzuki et al, 2005), fermentative bacteria (Francis et al, 1994;Sani et al, 2002), a heterotrophic bacterium (McLean and Beveridge, 2001), and an acidotolerant bacterium (Shelobolina et al, 2004). Some of these have been shown to grow using U(VI) as a sole terminal electron acceptor (Lovley et al, 1991;Tebo and Obraztsova, 1998;Pietzsch et al, 1999).…”

Section: Direct Enzymatic Control Of the Redox Transformations Of Umentioning

confidence: 99%

Geomicrobiological factors that control uranium mobility in the environment: Update on recent advances in the bioremediation of uranium-contaminated sites

Suzuki

Suko

2006

Journal of Mineralogical and Petrological Sciences

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Understanding the behavior of uranium (U) in the environment is essential not only for the protection of aquifers from U contamination but also for predicting the fate of U and other actinides disposed of in deep geological settings. It has long been believed that the redox chemistry of U can be simply predicted by thermodynamics and that the development of a low redox potential is a sufficient condition for U reduction. However, recent studies have demonstrated that redox transformations of U are controlled by kinetic factors that are strongly influenced by microbial activity. Although abiological U oxidation proceeds efficiently under oxygenic conditions, abiological reduction of U is inhibited by the formation of negatively charged U(VI) CO 3 complexes that prevail in nature. Phylogenetically diverse microorganisms are capable of enzymatically reducing U(VI) CO 3 complexes to form U(IV) bearing minerals such as uraninite (UO 2+x . This complex is mainly produced by the microbial reduction of Fe(III) in natural systems. Thus, U(VI) reduction is controlled both directly and indirectly, at least in part, by microbial activity. Several mechanisms of U oxidation under anoxic conditions have been revealed recently by laboratory and field studies. U(IV) is abiologically oxidized by Fe(III) and Mn(IV) oxides. Microbial reduction of nitrate to molecular nitrogen, which occurs following the depletion of O 2 , produces nitrogen intermediates including nitrite (NO 2 -), nitrous oxide (NO), and nitric oxide (N 2 O). Although the nitrogen intermediates oxidize U(IV), poorly crystalline Fe(III) oxide minerals resulting from the oxidation of aqueous Fe(II) species by the nitrogen intermediates oxidize U(IV) more efficiently than the nitrogen intermediates alone. Remarkably, the formation of Ca U(VI) CO 3 complexes resulting from increased levels of Ca 2+ and/or HCO 3 -leads to the reoxidation of bioreduced U(IV) under reducing conditions. These geomicrobiological factors pose challenges in manipulating and/or predicting the mobility and fate of U in complex and heterogeneous environmental settings.

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“…Members of the family Geobacteraceae are major iron-reducing microorganisms in subsurface environments (Lonergan et al, 1996) and their prevalence in benzene-degrading sediments and enrichments is not of surprise as several species are known to degrade aromatic hydrocarbons like toluene (Lovley et al, 1993;Coates et al, 2001a). No further isolate or lineage was hypothesized to date to be involved in anaerobic benzene degradation under iron-reducing conditions.…”

Section: Desulfitobacterium Chlororespirans (T) U68528 Desulfosporosmentioning

confidence: 99%

The use of stable isotope probing to identify key iron-reducing microorganisms involved in anaerobic benzene degradation

2007

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Here, we present a detailed functional and phylogenetic characterization of an iron-reducing enrichment culture maintained in our lab with benzene as sole carbon and energy source. We used DNA-stable isotope probing to identify microbes within the enrichment most active in the assimilation of 13 C-label. When 12 C 6 -and 13 C 6 -benzene were added as comparative substrates, marked differences in the quantitative buoyant density distribution became apparent especially for uncultured microbes within the Gram-positive Peptococcaceae, closely related to environmental clones retrieved from contaminated aquifers world wide and only distantly related to cultured representatives of the genus Thermincola. Prominent among the other constituents of the enrichment were uncultured Deltaproteobacteria, as well as members of the Actinobacteria. Although their presence within the enrichment seems to be stable they did not assimilate 13 C-label as significantly as the Clostridia within the time course of our experiment. We hypothesize that benzene degradation in our enrichment involves an unusual syntrophy, where members of the Clostridia primarily oxidize benzene. Electrons from the contaminant are both directly transferred to ferric iron by the primary oxidizers, but also partially shared with the Desulfobulbaceae as syntrophic partners. Alternatively, electrons may also be quantitatively transferred to the partners, which then reduce the ferric iron. Thus our results provide evidence for the importance of a novel clade of Gram-positive iron-reducers in anaerobic benzene degradation, and a role of syntrophic interactions in this process. These findings shed a totally new light on the factors controlling benzene degradation in anaerobic contaminated environments.

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Geobacter hydrogenophilus, Geobacter chapellei and Geobacter grbiciae, three new, strictly anaerobic, dissimilatory Fe(III)-reducers.

Cited by 205 publications

References 23 publications

Electrode-Based Approach for Monitoring In Situ Microbial Activity During Subsurface Bioremediation

Electrode-Based Approach for Monitoring In Situ Microbial Activity During Subsurface Bioremediation

Geomicrobiological factors that control uranium mobility in the environment: Update on recent advances in the bioremediation of uranium-contaminated sites

The use of stable isotope probing to identify key iron-reducing microorganisms involved in anaerobic benzene degradation

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