Lovley, D. R. Extracellular electron transfer: wires, capacitors, iron lungs, and more. Geobiology 6, 225-231

Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA.
Geobiology (Impact Factor: 3.83). 07/2008; 6(3):225-31. DOI: 10.1111/j.1472-4669.2008.00148.x
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    • "This reduction in diversity and selection for 176 Geobacteraceae and Proteobacteria is similar to other examples of soil based MFCs where 177 anthropogenically affected soils have lesser diversity (Dunaj et al. 2012). Members of 178 Geobacteraceae have been shown to partake in the degradation of organic contaminants and 179 several types of extracellular electron transfer including Fe(II) (Lovley 2008; Reguera et al. 180 2005; Kato et al. 2010; Kato, Hashimoto, and Watanabe 2012). Here we see communities such 181 as the soil sample at 6m depth from the center of the plume dominated by 31.0% of the family 182 Geobacter and 12.0% of family Desulfobulbaceae (Figure 2b). "
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    ABSTRACT: We have used geophysics, microbiology, and geochemistry to link large-scale (30+ m) geophysical self-potential (SP) responses at a groundwater contaminant plume with its chemistry and microbial ecology of groundwater and soil from in and around it. We have found that microbially mediated transformation of ammonia to nitrite, nitrate, and nitrogen gas was likely to have promoted a well-defined electrochemical gradient at the edge of the plume, which dominated the SP response. Phylogenetic analysis demonstrated that the plume fringe or anode of the geobattery was dominated by electrogens and biodegradative microorganisms including Proteobacteria alongside Geobacteraceae, Desulfobulbaceae, and Nitrosomonadaceae. The uncultivated candidate phylum OD1 dominated uncontaminated areas of the site. We defined the redox boundary at the plume edge using the calculated and observed electric SP geophysical measurements. Conductive soils and waste acted as an electronic conductor, which was dominated by abiotic iron cycling processes that sequester electrons generated at the plume fringe. We have suggested that such geoelectric phenomena can act as indicators of natural attenuation processes that control groundwater plumes. Further work is required to monitor electron transfer across the geoelectric dipole to fully define this phenomenon as a geobattery. This approach can be used as a novel way of monitoring microbial activity around the degradation of contaminated groundwater plumes or to monitor in situ bioelectric systems designed to manage groundwater plumes.
    Full-text · Article · Nov 2015
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    • "Some microorganisms have physiological adaptations that enable them to utilize insoluble forms of ferric iron as electron acceptors. Several such mechanisms have been described in mesophilic Gram-negative bacteria, particularly for Geobacter sulfurreducens and Shewanella putrefaciens (Lovley et al., 2004; Shi et al., 2007, 2009; Lovley, 2008). The physiology of Gram-positive and archaeal iron reducers is much less understood (Gavrilov et al., 2012). "
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    ABSTRACT: The ability of microorganisms to thrive under oxygen-free conditions in subsurface environments relies on the enzymatic reduction of oxidized elements, such as sulfate, ferric iron, or CO2, coupled to the oxidation of inorganic or organic compounds. A broad phylogenetic and functional diversity of microorganisms from subsurface environments has been described using isolation-based and advanced molecular ecological techniques. The physiological groups reviewed here comprise iron-, manganese-, and nitrate-reducing microorganisms. In the context of recent findings also the potential of chlorate and perchlorate [jointly termed (per)chlorate] reduction in oil reservoirs will be discussed. Special attention is given to elevated temperatures that are predominant in the deep subsurface. Microbial reduction of (per)chlorate is a thermodynamically favorable redox process, also at high temperature. However, knowledge about (per)chlorate reduction at elevated temperatures is still scarce and restricted to members of the Firmicutes and the archaeon Archaeoglobus fulgidus. By analyzing the diversity and phylogenetic distribution of functional genes in (meta)genome databases and combining this knowledge with extrapolations to earlier-made physiological observations we speculate on the potential of (per)chlorate reduction in the subsurface and more precisely oil fields. In addition, the application of (per)chlorate for bioremediation, souring control, and microbial enhanced oil recovery are addressed.
    Full-text · Article · Sep 2014 · Frontiers in Microbiology
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    • "In recent years microbial fuel cell (MFC) research has scaled several new heights. There has been a remarkable improvement in power density and cell structure [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]. For several years, researchers used synthetic wastewater and/or real wastewater as substrate and were able to degrade up to 98% of chemical oxygen demand (COD) [12,13,3,14–22]. "
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    ABSTRACT: The present study evaluates the performance of air-cathode microbial fuel cells (MFCs) under alternating open circuit/closed circuit (OC/CC) modes and its effect on independent-electrode and full-cell potentials, power output (at different external resistances) and the polarization behaviour of the electrodes. Three different types of feeds were evaluated using this approach: (1) phosphorus buffer solution (PBS) with acetate as carbon source, (2) glucose-rich synthetic wastewater, and (3) sewage from wastewater treatment plant enriched with fermented molasses. When MFCs were suddenly switched to CC from CC and then again back to CC from CC, the behaviour of the anodes vs reference electrode (Ag/AgCl,3 M KCl) was monitored. When electric circuit of the MFCs was switched from open to closed circuit, for all cases: (a) the anode potential-shift (vs Ag/AgCI) reallocated in the positive direction in about 200-400 mV, (b) the air-cathode potential-shift (vs Ag/AgCI) reallocated in the negative direction in about 10-25 mV, and (c) the cell-potential difference started at around 0 mV and progressively increased as the MFC reached stability. This behaviour was consistently reproduced during different OC/CC cycles. The systems studied delivered good performance with both controlled media and industrial wastewater. Additionally, this study provides insightful characterization of the independent-electrode behaviours.
    Full-text · Article · Jul 2014 · Biochemical Engineering Journal
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