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Extracellular electron transfer: Wires, capacitors, iron lungs, and more

Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA.
Geobiology (Impact Factor: 3.69). 07/2008; 6(3):225-31. DOI: 10.1111/j.1472-4669.2008.00148.x
Source: PubMed
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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.
    Frontiers in Microbiology 09/2014; 5:428. DOI:10.3389/fmicb.2014.00428 · 3.94 Impact Factor
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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.
    Biochemical Engineering Journal 07/2014; 90:294-300. DOI:10.1016/j.bej.2014.06.024 · 2.37 Impact Factor
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    • "They grow as attached biofilm on electrodes and without required contributions by planktonic cells to the current (Bond and Lovley, 2003). An understanding of how Geobacteraceae externalize electrons generated in central metabolism during electron donor oxidation is continually evolving (Lovley and Nevin., 2008), however, anode respiration likely involves multiple c-type cytochromes (Kim et al., 2008) and conductive pili (Reguera et al., 2005); both of which are required for optimal current production. The conductive pili of Geobacteraceae are necessary for biofilm formation (Reguera et al., 2006) and are hypothesized to enable respiration of the anode by cells which are not in direct contact with the anode. "
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    ABSTRACT: The efficiency of microbial fuel cells (MFCs) is affected by several factors such as activation overpotentials, ohmic losses and concentration polarization. These factors are handled in micro-sized MFCs using special electrodes with physically or chemically modified surfaces constructed with specified materials. Most of the existing μLscale MFCs show great potential in rapid screening of electrochemically-active microbes and electrode performance; although they generate significantly lower volumetric power density compared with their mL counterparts because of their high internal resistance. This review presents the development of microfluidic MFCs, with summarization of their advantages and challenges, and focuses on the efforts done to minimize the adverse effects of internal resistance (ohmic and non-ohmic) on their performance.
    Bioresource Technology 05/2013; 142:672-682. DOI:10.1016/j.biortech.2013.05.061 · 5.04 Impact Factor
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