Electron transfer and biofilm formation of Shewanella putrefaciens as function of anode potential

Institute of Environmental and Sustainable Chemistry, Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig, Germany.
Bioelectrochemistry (Amsterdam, Netherlands) (Impact Factor: 3.87). 05/2012; 93. DOI: 10.1016/j.bioelechem.2012.05.002

ABSTRACT Shewanellaceae are among the most widely studied electroactive microorganisms. In this report, we studied the influence of the applied electrode potential on the anodic current production of Shewanella putrefaciens NCTC 10695 under anoxic conditions. Furthermore, we used cyclic voltammetry (CV) and confocal laser scanning mi-croscopy (CLSM) to investigate the microbial electron transfer and biofilm formation. It is shown that the chro-noamperometric current density is increasing with increasing electrode potential from 3 μA cm − 2 at −0.1 V up to ~12 μA cm − 2 at +0.4 V (vs. Ag/AgCl), which is accompanied by an increasing amount of biomass deposited on the electrode. By means of cyclic voltammetry we demonstrate that direct electron transfer (DET) is dominat-ing and the planktonic cells play only a minor role.

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    ABSTRACT: Formation of biofilm on an electrode surface is usually a prerequisite for efficient electron transfer from electrogenic bacteria onto electrode, and the geometric status of the biofilm governs the generated current. In this study, we propose a real-time characterization method to track the dynamic formation process of biofilm on electrode using scanning electrochemical microscopy (SECM). Shewanella oneidensis MR-1 was chosen in this work as an electrogenic model species. A plane electrode at the bottom of a electrochemical cell filled with bacteria suspension was biased at +0.04 V vs. Ag/AgCl as the sole electron acceptor under anaerobic environment, while a movable ultramicroelectrode (UME) was employed to track the localized faradaic current generated by a redox mediator, Ru(NH3)6Cl3 above the bottom electrode. The growth rate of biofilm showed some spatial heterogeneity, which might be explained by inhomogeneous mass transfer and non-uniformity of electrode surface. The application of SECM into bacterial electrogenesis studies offered a simple and label-free monitoring method to evaluate the bacteria-electrode coupling status.
    Electroanalysis 02/2015; 27(3). DOI:10.1002/elan.201400578 · 2.50 Impact Factor
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    ABSTRACT: Sulfide is a common product of marine anaerobic respiration, and a potent reactant biologically and geochemically. Here we demonstrate the impact on microbial communities with the removal of sulfide via electrochemical methods. The use of differential pulse voltammetry revealed that the oxidation of soluble sulfide was seen at +30 mV (vs. SHE) at all pH ranges tested (from pH = 4 to 8), while non-ionized sulfide, which dominated at pH = 4 was poorly oxidized via this process. Two mixed cultures (CAT and LA) were enriched from two different marine sediments (from Catalina Island, CAT; from the Port of Los Angeles, LA) in serum bottles using a seawater medium supplemented with lactate, sulfate, and yeast extract, to obtain abundant biomass. Both CAT and LA cultures were inoculated in electrochemical cells (using yeast-extract-free seawater medium as an electrolyte) equipped with carbon-felt electrodes. In both cases, when potentials of +630 or +130 mV (vs. SHE) were applied, currents were consistently higher at +630 then at +130 mV, indicating more sulfide being oxidized at the higher potential. In addition, higher organic-acid and sulfate conversion rates were found at +630 mV with CAT, while no significant differences were found with LA at different potentials. The results of microbial-community analyses revealed a decrease in diversity for both CAT and LA after electrochemical incubation. In addition, some bacteria (e.g., Clostridium and Arcobacter) not well-known to be capable of extracellular electron transfer, were found to be dominant in the electrochemical cells. Thus, even though the different mixed cultures have different tolerances for sulfide, electrochemical-sulfide removal can lead to major population changes.
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    ABSTRACT: Quantitative proteomics from low biomass, biofilm samples is not well documented. In this study we show successful use of SWATH-MS for quantitative proteomic analysis of a microbial electrochemically active biofilm. Shewanella oneidensis MR-1 was grown on carbon cloth electrodes under continuous anodic electrochemical polarizations in a bioelectrochemical system (BES). Using lactate as the electron donor, anodes serving as terminal microbial electron acceptors were operated at three different electrode potentials (+0.71V, +0.21V & -0.19V vs. SHE) and the development of catalytic activity was monitored by measuring the current traces over time. Once maximum current was reached (usually within 21-29h) the electrochemical systems were shut off and biofilm proteins were extracted from the electrodes for proteomic assessment. SWATH-MS analysis identified 704 proteins, and quantitative comparison was made of those associated with tricarboxcylic acid (TCA) cycle. Metabolic differences detected between the biofilms suggested a branching of the S. oneidensis TCA cycle when grown at the different electrode potentials. In addition, the higher abundance of enzymes involved in the TCA cycle at higher potential indicates an increase in metabolic activity, which is expected given the assumed higher energy gains. This study demonstrates high numbers of identifications on BES biofilm samples can be achieved in comparison to what is currently reported. This is most likely due to the minimal preparation steps required for SWATH-MS. Copyright © 2014 Elsevier GmbH. All rights reserved.
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May 16, 2014