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Portela PC, Morgado L, Silva MA, Denkhaus L, Einsle O, Salgueiro CA. Exploring oxidative stress pathways in Geobacter sulfurreducens: the redox network between MacA peroxidase and triheme periplasmic cytochromes. Front Microbiol 2023; 14:1253114. [PMID: 37860142 PMCID: PMC10582990 DOI: 10.3389/fmicb.2023.1253114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Accepted: 09/11/2023] [Indexed: 10/21/2023] Open
Abstract
The recent reclassification of the strict anaerobe Geobacter sulfurreducens bacterium as aerotolerant brought attention for oxidative stress protection pathways. Although the electron transfer pathways for oxygen detoxification are not well established, evidence was obtained for the formation of a redox complex between the periplasmic triheme cytochrome PpcA and the diheme cytochrome peroxidase MacA. In the latter, the reduction of the high-potential heme triggers a conformational change that displaces the axial histidine of the low-potential heme with peroxidase activity. More recently, a possible involvement of the triheme periplasmic cytochrome family (PpcA-E) in the protection from oxidative stress in G. sulfurreducens was suggested. To evaluate this hypothesis, we investigated the electron transfer reaction and the biomolecular interaction between each PpcA-E cytochrome and MacA. Using a newly developed method that relies on the different NMR spectral signatures of the heme proteins, we directly monitored the electron transfer reaction from reduced PpcA-E cytochromes to oxidized MacA. The results obtained showed a complete electron transfer from the cytochromes to the high-potential heme of MacA. This highlights PpcA-E cytochromes' efficient role in providing the necessary reducing power to mitigate oxidative stress situations, hence contributing to a better knowledge of oxidative stress protection pathways in G. sulfurreducens.
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Affiliation(s)
- Pilar C. Portela
- Associate Laboratory i4HB – Institute for Health and Bioeconomy, NOVA School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
- UCIBIO – Applied Molecular Biosciences Unit, Department of Chemistry, NOVA School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
| | - Leonor Morgado
- Associate Laboratory i4HB – Institute for Health and Bioeconomy, NOVA School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
- UCIBIO – Applied Molecular Biosciences Unit, Department of Chemistry, NOVA School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
| | - Marta A. Silva
- Associate Laboratory i4HB – Institute for Health and Bioeconomy, NOVA School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
- UCIBIO – Applied Molecular Biosciences Unit, Department of Chemistry, NOVA School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
| | - Lukas Denkhaus
- Institut für Biochemie, Albert-Ludwigs-Universität, Freiburg, Germany
| | - Oliver Einsle
- Institut für Biochemie, Albert-Ludwigs-Universität, Freiburg, Germany
| | - Carlos A. Salgueiro
- Associate Laboratory i4HB – Institute for Health and Bioeconomy, NOVA School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
- UCIBIO – Applied Molecular Biosciences Unit, Department of Chemistry, NOVA School of Science and Technology, Universidade NOVA de Lisboa, Caparica, Portugal
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2
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Lee HS, Xin W, Katakojwala R, Venkata Mohan S, Tabish NMD. Microbial electrolysis cells for the production of biohydrogen in dark fermentation - A review. BIORESOURCE TECHNOLOGY 2022; 363:127934. [PMID: 36100184 DOI: 10.1016/j.biortech.2022.127934] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2022] [Revised: 09/01/2022] [Accepted: 09/06/2022] [Indexed: 06/15/2023]
Abstract
To assess biohydrogen for future green energy, this review revisited dark fermentation and microbial electrolysis cells (MECs). Hydrogen evolution rate in mesophilic dark fermentation is as high as 192 m3 H2/m3-d, however hydrogen yield is limited. MECs are ideal for improving hydrogen yield from carboxylate accumulated from dark fermentation, whereas hydrogen production rate is too slow in MECs. Hence, improving anode kinetic is very important for realizing MEC biohydrogen. Intracellular electron transfer (IET) and extracellular electron transfer (EET) can limit current density in MECs, which is proportional to hydrogen evolution rate. EET does not limit current density once electrically conductive biofilms are formed on anodes, potentially producing 300 A/m2. Hence, IET kinetics mainly govern current density in MECs. Among parameters associated with IET kinetic, population of anode-respiring bacteria in anode biofilms, biofilm density of active microorganisms, biofilm thickness, and alkalinity are critical for current density.
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Affiliation(s)
- Hyung-Sool Lee
- KENTECH Institute for Environmental and Climate Technology, Korea Institute of Energy Technology (KENTECH) 200 Hyeoksin-ro, Naju-si, Jeollanam-do, Republic of Korea.
| | - Wang Xin
- MOE Key Laboratory of Pollution Processes and Environmental Criteria/Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, No. 38 Tongyan Road, Jinnan District, Tianjin 300350, China
| | - Ranaprathap Katakojwala
- Bioengineering and Environmental Engineering Lab, Department of Energy and Environmental Engineering, Indian Institute of Chemical Technology, Hyderabad 500007, India
| | - S Venkata Mohan
- Bioengineering and Environmental Engineering Lab, Department of Energy and Environmental Engineering, Indian Institute of Chemical Technology, Hyderabad 500007, India
| | - Noori M D Tabish
- Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering, University of Alcala, Alcala De Henares, Madrid 28801, Spain
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3
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Frühauf‐Wyllie HM, Holtmann D. Geobacter sulfurreducens
metabolism at different donor/acceptor ratios. Microbiologyopen 2022; 11:e1322. [PMID: 36314758 PMCID: PMC9494351 DOI: 10.1002/mbo3.1322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Revised: 09/12/2022] [Accepted: 09/12/2022] [Indexed: 11/11/2022] Open
Abstract
Geobacter species have great application potential in remediation processes and electrobiotechnology. In all applications, understanding the metabolism will enable target‐oriented optimization of the processes. The typical electron donor and carbon source of the Geobacter species is acetate, while fumarate is the usual electron acceptor. Here, we could show that depending on the donor/acceptor ratio in batch cultivation of Geobacter sulfurreducens different product patterns occur. With a donor/acceptor ratio of 1:2.5 malate accumulated as an intermediate product but was metabolized to succinate subsequently. At the end of the cultivation, the ratio of fumarate consumed and succinate produced was approximately 1:1. When fumarate was added in excess, malate accumulated in the fermentation broth without further metabolization. After the addition of acetate to stationary cells, malate concentration decreased immediately and additional succinate was synthesized. Finally, it was shown that also resting cells of G. sulfurreducens could efficiently convert fumarate to malate without an additional electron donor. Overall, it was demonstrated that by altering the donor/acceptor ratio, targeted optimization of the metabolite conversion by G. sulfurreducens can be realized.
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Affiliation(s)
- Hanna Marianne Frühauf‐Wyllie
- Department of Chemical Technology DECHEMA Forschungsinstitut Frankfurt am Main Germany
- Technische Hochschule Mittelhessen, Institut für Bioverfahrenstechnik und Pharmazeutische Technologie Gießen Germany
| | - Dirk Holtmann
- Technische Hochschule Mittelhessen, Institut für Bioverfahrenstechnik und Pharmazeutische Technologie Gießen Germany
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4
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Karamash M, Stumpe M, Dengjel J, Salgueiro CA, Giese B, Fromm KM. Reduction Kinetic of Water Soluble Metal Salts by Geobacter sulfurreducens: Fe2+/Hemes Stabilize and Regulate Electron Flux Rates. Front Microbiol 2022; 13:909109. [PMID: 35783399 PMCID: PMC9248073 DOI: 10.3389/fmicb.2022.909109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 05/20/2022] [Indexed: 01/17/2023] Open
Abstract
Geobacter sulfurreducens is a widely applied microorganism for the reduction of toxic metal salts, as an electron source for bioelectrochemical devices, and as a reagent for the synthesis of nanoparticles. In order to understand the influence of metal salts, and of electron transporting, multiheme c-cytochromes on the electron flux during respiration of G. sulfurreducens, the reduction kinetic of Fe3+, Co3+, V5+, Cr6+, and Mn7+ containing complexes were measured. Starting from the resting phase, each G. sulfurreducens cell produced an electron flux of 3.7 × 105 electrons per second during the respiration process. Reduction rates were within ± 30% the same for the 6 different metal salts, and reaction kinetics were of zero order. Decrease of c-cytochrome concentrations by downregulation and mutation demonstrated that c-cytochromes stabilized respiration rates by variation of their redox states. Increasing Fe2+/heme levels increased electron flux rates, and induced respiration flexibility. The kinetic effects parallel electrochemical results of G. sulfurreducens biofilms on electrodes, and might help to optimize bioelectrochemical devices.
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Affiliation(s)
- Maksym Karamash
- Department of Chemistry, University of Fribourg, Fribourg, Switzerland
| | - Michael Stumpe
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Jörn Dengjel
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Carlos A. Salgueiro
- Associate Laboratory i4HB – Institute for Health and Bioeconomy, School of Science and Technology, NOVA University Lisbon, Costa da Caparica, Portugal
- UCIBIO – Applied Molecular Biosciences Unit, Chemistry Department, School of Science and Technology, NOVA University Lisbon, Costa da Caparica, Portugal
| | - Bernd Giese
- Department of Chemistry, University of Fribourg, Fribourg, Switzerland
- *Correspondence: Bernd Giese,
| | - Katharina M. Fromm
- Department of Chemistry, University of Fribourg, Fribourg, Switzerland
- Katharina M. Fromm,
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5
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Guo G, Li Z, Chen L, Ling Q, Zan F, Isawi H, Hao T, Ma J, Wang Z, Chen G, Lu H. Advances in elemental sulfur-driven bioprocesses for wastewater treatment: From metabolic study to application. WATER RESEARCH 2022; 213:118143. [PMID: 35149365 DOI: 10.1016/j.watres.2022.118143] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 01/17/2022] [Accepted: 01/30/2022] [Indexed: 06/14/2023]
Abstract
Elemental sulfur (S0) is known to be an abundant, non-toxic material with a wide range of redox states (-2 to +6) and may serve as an excellent electron carrier in wastewater treatment. In turn, S0-driven bioprocesses, which employ S0 as electron donor or acceptor, have recently established themselves as cost-effective therefore attractive solutions for wastewater treatment. Numerous related processes have, to date, been developed from laboratory experiments into full-scale applications, including S0-driven autotrophic denitrification for nitrate removal and S0-reducing organic removal. Compared to the conventional activated sludge process, these bioprocesses require only a small amount of organic matter and produce very little sludge. There have been great efforts to characterize chemical and biogenic S0 and related functional microorganisms in order to identify the biochemical pathways, upgrade the bioprocesses, and assess the impact of the operating factors on process performance, ultimately aiming to better understand and to optimize the processes. This paper is therefore a comprehensive overview of emerging S0-driven biotechnologies, including the development of S0-driven autotrophic denitrification and S0-based sulfidogenesis, as well as the associated microbiology and biochemistry. Also reviewed here are the physicochemical characteristics of S0 and the effects that environmental factors such as pH, influent sulfur/nitrate ratio, temperature, S0 particle size and reactor configurations have on the process. Research gaps, challenges of process applications and potential areas for future research are further proposed and discussed.
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Affiliation(s)
- Gang Guo
- School of Environmental Science and Engineering, Key Laboratory of Water and Wastewater Treatment (HUST), MOHURD, Huazhong University of Science and Technology (HUST), Wuhan 430074, China
| | - Zhaoling Li
- School of Environmental Science and Engineering, Key Laboratory of Water and Wastewater Treatment (HUST), MOHURD, Huazhong University of Science and Technology (HUST), Wuhan 430074, China
| | - Lei Chen
- School of Environmental Science and Engineering, Key Laboratory of Water and Wastewater Treatment (HUST), MOHURD, Huazhong University of Science and Technology (HUST), Wuhan 430074, China
| | - Qingshan Ling
- School of Environmental Science and Engineering, Key Laboratory of Water and Wastewater Treatment (HUST), MOHURD, Huazhong University of Science and Technology (HUST), Wuhan 430074, China
| | - Feixiang Zan
- School of Environmental Science and Engineering, Key Laboratory of Water and Wastewater Treatment (HUST), MOHURD, Huazhong University of Science and Technology (HUST), Wuhan 430074, China
| | - Heba Isawi
- Desert Research Center, Water Resources and Desert Soils Division, Egyptian Desalination Research Center of Excellence (EDRC), Cairo, Egypt
| | - Tianwei Hao
- Department of Civil and Environmental Engineering, Faculty of Science and Technology, University of Macau, Macau, China.
| | - Jie Ma
- School of Environmental Science and Engineering, Key Laboratory of Water and Wastewater Treatment (HUST), MOHURD, Huazhong University of Science and Technology (HUST), Wuhan 430074, China
| | - Zongping Wang
- School of Environmental Science and Engineering, Key Laboratory of Water and Wastewater Treatment (HUST), MOHURD, Huazhong University of Science and Technology (HUST), Wuhan 430074, China
| | - Guanghao Chen
- Department of Civil & Environmental Engineering, The Hong Kong University of Science and Technology, Hong Kong, China
| | - Hui Lu
- School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, China.
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6
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Jessen GL, Chen LX, Mori JF, Nelson TEC, Slater GF, Lindsay MBJ, Banfield JF, Warren LA. Alum Addition Triggers Hypoxia in an Engineered Pit Lake. Microorganisms 2022; 10:microorganisms10030510. [PMID: 35336086 PMCID: PMC8953953 DOI: 10.3390/microorganisms10030510] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 02/09/2022] [Accepted: 02/11/2022] [Indexed: 01/04/2023] Open
Abstract
Here, we examine the geobiological response to a whole-lake alum (aluminum sulfate) treatment (2016) of Base Mine Lake (BML), the first pilot-scale pit lake established in the Alberta oil sands region. The rationale for trialing this management amendment was based on its successful use to reduce internal phosphorus loading to eutrophying lakes. Modest increases in water cap epilimnetic oxygen concentrations, associated with increased Secchi depths and chlorophyll-a concentrations, were co-incident with anoxic waters immediately above the fluid fine tailings (FFT) layer post alum. Decreased water cap nitrate and detectable sulfide concentrations, as well as increased hypolimnetic phospholipid fatty acid abundances, signaled greater anaerobic heterotrophic activity. Shifts in microbial community to groups associated with greater organic carbon degradation (i.e., SAR11-LD12 subclade) and the SRB group Desulfuromonodales emerged post alum and the loss of specialist groups associated with carbon-limited, ammonia-rich restricted niches (i.e., MBAE14) also occurred. Alum treatment resulted in additional oxygen consumption associated with increased autochthonous carbon production, watercap anoxia and sulfide generation, which further exacerbate oxygen consumption associated with on-going FFT mobilized reductants. The results illustrate the importance of understanding the broader biogeochemical implications of adaptive management interventions to avoid unanticipated outcomes that pose greater risks and improve tailings reclamation for oil sands operations and, more broadly, the global mining sector.
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Affiliation(s)
- Gerdhard L. Jessen
- Instituto de Ciencias Marinas y Limnológicas, Universidad Austral de Chile, Valdivia 5090000, Chile
- Department of Civil and Mineral Engineering, University of Toronto, Toronto, ON M5S 1A4, Canada; (J.F.M.); (T.E.C.N.)
- Correspondence: (G.L.J.); (L.A.W.)
| | - Lin-Xing Chen
- Department of Earth and Planetary Science, University of California, Berkeley, CA 94706, USA; (L.-X.C.); (J.F.B.)
| | - Jiro F. Mori
- Department of Civil and Mineral Engineering, University of Toronto, Toronto, ON M5S 1A4, Canada; (J.F.M.); (T.E.C.N.)
- Graduate School of Nanobioscience, Yokohama City University, Yokohama 236-0027, Japan
| | - Tara E. Colenbrander Nelson
- Department of Civil and Mineral Engineering, University of Toronto, Toronto, ON M5S 1A4, Canada; (J.F.M.); (T.E.C.N.)
- School of Earth, Environment and Society, McMaster University, Hamilton, ON L8S 4L8, Canada;
| | - Gregory F. Slater
- School of Earth, Environment and Society, McMaster University, Hamilton, ON L8S 4L8, Canada;
| | - Matthew B. J. Lindsay
- Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK S7N 5E2, Canada;
| | - Jillian F. Banfield
- Department of Earth and Planetary Science, University of California, Berkeley, CA 94706, USA; (L.-X.C.); (J.F.B.)
| | - Lesley A. Warren
- Department of Civil and Mineral Engineering, University of Toronto, Toronto, ON M5S 1A4, Canada; (J.F.M.); (T.E.C.N.)
- School of Earth, Environment and Society, McMaster University, Hamilton, ON L8S 4L8, Canada;
- Correspondence: (G.L.J.); (L.A.W.)
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7
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A noncanonical cytochrome c stimulates calcium binding by PilY1 for type IVa pili formation. Proc Natl Acad Sci U S A 2022; 119:2115061119. [PMID: 35121662 PMCID: PMC8833165 DOI: 10.1073/pnas.2115061119] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/28/2021] [Indexed: 12/23/2022] Open
Abstract
Type IVa pili (T4aP) are versatile bacterial cell surface structures that undergo extension/adhesion/retraction cycles powered by the cell envelope-spanning T4aP machine. In this machine, a complex composed of four minor pilins and PilY1 primes T4aP extension and is also present at the pilus tip mediating adhesion. Similar to many several other bacteria, Myxococcus xanthus contains multiple minor pilins/PilY1 sets that are incompletely understood. Here, we report that minor pilins and PilY1 (PilY1.1) of cluster_1 form priming and tip complexes contingent on calcium and a noncanonical cytochrome c (TfcP) with an unusual His/Cys heme ligation. We provide evidence that TfcP is unlikely to participate in electron transport and instead stimulates calcium binding by PilY1.1 at low-calcium concentrations, thereby stabilizing PilY1.1 and enabling T4aP function in a broader range of calcium concentrations. These results not only identify a previously undescribed function of cytochromes c but also illustrate how incorporation of an accessory factor expands the environmental range under which the T4aP system functions.
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8
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Scarabotti F, Bühler K, Schmidt M, Harnisch F. Thickness and roughness of transparent gold-palladium anodes have no impact on growth kinetics and yield coefficients of early-stage Geobacter sulfurreducens biofilms. Bioelectrochemistry 2021; 144:108043. [PMID: 34959027 DOI: 10.1016/j.bioelechem.2021.108043] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 11/24/2021] [Accepted: 12/13/2021] [Indexed: 01/05/2023]
Abstract
Geobacter sulfurreducens is the model organism for electroactive microorganisms performing direct extracellular electron transfer and forming thick mature biofilm electrodes. Although numerous physiological properties of mature biofilm electrodes are deciphered, there is an extensive gap of knowledge on the early-stage biofilm formation. We have shown recently that transparent gold-palladium (AuPd) electrodes allow for analysis of early-stage biofilm formation using confocal laser scanning microscopy. Here we analysed the influence of thickness (ranging from 12.5 to 200 nm) and roughness of AuPd electrodes on physiological parameters of G. sulfurreducens early-stage biofilms. We show that when grown potentiostatically at -200 mV vs. Ag/ AgCl sat. KCl neither maximum current density (jmax of ∼ 80-150 µA cm-2) nor lag time (lag t of ∼ 0.2-0.4 days) or single cell yield coefficients (YNe of 1.43 × 1012 cells mole--1) of the biofilms are influenced by the electrode preparation. This confirms the robustness of the experimental approach, which is an inevitable prerequisite for obtaining reliable results in follow-up experiments.
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Affiliation(s)
- Francesco Scarabotti
- Department of Environmental Microbiology, Helmholtz-Centre for Environmental Research - UFZ, Leipzig, Germany
| | - Katja Bühler
- Department Solar Materials, Helmholtz-Centre for Environmental Research - UFZ, Leipzig, Germany
| | - Matthias Schmidt
- Department of Isotope Biogeochemistry, Helmholtz-Centre for Environmental Research - UFZ, Leipzig, Germany
| | - Falk Harnisch
- Department of Environmental Microbiology, Helmholtz-Centre for Environmental Research - UFZ, Leipzig, Germany.
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9
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Zhang S, Schuster J, Frühauf-Wyllie H, Arat S, Yadav S, Schneider JJ, Stöckl M, Ukrainczyk N, Koenders E. Conductive Geopolymers as Low-Cost Electrode Materials for Microbial Fuel Cells. ACS OMEGA 2021; 6:28859-28870. [PMID: 34746578 PMCID: PMC8567353 DOI: 10.1021/acsomega.1c03805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/17/2021] [Accepted: 09/27/2021] [Indexed: 06/13/2023]
Abstract
Geopolymer (GP) inorganic binders have a superior acid resistance compared to conventional cement (e.g., Portland cement, PC) binders, have better microbial compatibility, and are suitable for introducing electrically conductive additives to improve electron and ion transfer properties. In this study, GP-graphite (GPG) composites and PC-graphite (PCG) composites with a graphite content of 1-10 vol % were prepared and characterized. The electrical conductivity percolation threshold of the GPG and PCG composites was around 7 and 8 vol %, respectively. GPG and PCG composites with a graphite content of 8 to 10 vol % were selected as anode electrodes for the electrochemical analysis in two-chamber polarized microbial fuel cells (MFCs). Graphite electrodes were used as the positive control reference material. Geobacter sulfurreducens was used as a biofilm-forming and electroactive model organism for MFC experiments. Compared to the conventional graphite anodes, the anode-respiring biofilms resulted in equal current production on GPG composite anodes, whereas the PCG composites showed a very poor performance. The largest mean value of the measured current densities of a GPG composite used as anodes in MFCs was 380.4 μA cm-2 with a standard deviation of 129.5 μA cm-2. Overall, the best results were obtained with electrodes having a relatively low Ohmic resistance, that is, GPG composites and graphite. The very first approach employing sustainable GPs as a low-cost electrode binder material in an MFC showed promising results with the potential to greatly reduce the production costs of MFCs, which would also increase the feasibility of MFC large-scale applications.
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Affiliation(s)
- Shifan Zhang
- Department
of Materials in Civil Engineering at the Technical University of Darmstadt, Franziska-Braun-Straße 3, 64287 Darmstadt, Germany
| | - Jürgen Schuster
- Department
of Electrochemistry, DECHEMA-Research Institute, Theodor-Heuss-Allee 25, 60486 Frankfurt a. M., Germany
| | - Hanna Frühauf-Wyllie
- Department
of Industrial Biotechnology, DECHEMA-Research
Institute, Theodor-Heuss-Allee 25, 60486 Frankfurt a. M., Germany
| | - Serkan Arat
- Department
of Corrosion, DECHEMA-Research Institute, Theodor-Heuss-Allee 25, 60486 Frankfurt a. M., Germany
| | - Sandeep Yadav
- Department
of Chemistry at the Technical University of Darmstadt, Alarich-Weiss-Straße 4, 64287 Darmstadt, Germany
| | - Jörg J. Schneider
- Department
of Chemistry at the Technical University of Darmstadt, Alarich-Weiss-Straße 4, 64287 Darmstadt, Germany
| | - Markus Stöckl
- Department
of Electrochemistry, DECHEMA-Research Institute, Theodor-Heuss-Allee 25, 60486 Frankfurt a. M., Germany
| | - Neven Ukrainczyk
- Department
of Materials in Civil Engineering at the Technical University of Darmstadt, Franziska-Braun-Straße 3, 64287 Darmstadt, Germany
| | - Eddie Koenders
- Department
of Materials in Civil Engineering at the Technical University of Darmstadt, Franziska-Braun-Straße 3, 64287 Darmstadt, Germany
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10
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Garber AI, Cohen AB, Nealson KH, Ramírez GA, Barco RA, Enzingmüller-Bleyl TC, Gehringer MM, Merino N. Metagenomic Insights Into the Microbial Iron Cycle of Subseafloor Habitats. Front Microbiol 2021; 12:667944. [PMID: 34539592 PMCID: PMC8446621 DOI: 10.3389/fmicb.2021.667944] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 07/30/2021] [Indexed: 11/13/2022] Open
Abstract
Microbial iron cycling influences the flux of major nutrients in the environment (e.g., through the adsorptive capacity of iron oxides) and includes biotically induced iron oxidation and reduction processes. The ecological extent of microbial iron cycling is not well understood, even with increased sequencing efforts, in part due to limitations in gene annotation pipelines and limitations in experimental studies linking phenotype to genotype. This is particularly true for the marine subseafloor, which remains undersampled, but represents the largest contiguous habitat on Earth. To address this limitation, we used FeGenie, a database and bioinformatics tool that identifies microbial iron cycling genes and enables the development of testable hypotheses on the biogeochemical cycling of iron. Herein, we survey the microbial iron cycle in diverse subseafloor habitats, including sediment-buried crustal aquifers, as well as surficial and deep sediments. We inferred the genetic potential for iron redox cycling in 32 of the 46 metagenomes included in our analysis, demonstrating the prevalence of these activities across underexplored subseafloor ecosystems. We show that while some processes (e.g., iron uptake and storage, siderophore transport potential, and iron gene regulation) are near-universal, others (e.g., iron reduction/oxidation, siderophore synthesis, and magnetosome formation) are dependent on local redox and nutrient status. Additionally, we detected niche-specific differences in strategies used for dissimilatory iron reduction, suggesting that geochemical constraints likely play an important role in dictating the dominant mechanisms for iron cycling. Overall, our survey advances the known distribution, magnitude, and potential ecological impact of microbe-mediated iron cycling and utilization in sub-benthic ecosystems.
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Affiliation(s)
- Arkadiy I Garber
- School of Life Sciences, Arizona State University, Tempe, AZ, United States
| | - Ashley B Cohen
- School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY, United States
| | - Kenneth H Nealson
- Department of Earth Sciences, University of Southern California, Los Angeles, CA, United States
| | - Gustavo A Ramírez
- Department of Marine Biology, Leon H. Charney School of Marine Sciences, University of Haifa, Haifa, Israel.,College of Veterinary Medicine, Western University of Health Sciences, Pomona, CA, United States
| | - Roman A Barco
- Department of Earth Sciences, University of Southern California, Los Angeles, CA, United States
| | | | - Michelle M Gehringer
- Department of Microbiology, Technical University of Kaiserslautern, Kaiserslautern, Germany
| | - Nancy Merino
- Biosciences & Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, CA, United States
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11
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Speers AM, Reguera G. Competitive advantage of oxygen-tolerant bioanodes of Geobacter sulfurreducens in bioelectrochemical systems. Biofilm 2021; 3:100052. [PMID: 34222855 PMCID: PMC8242959 DOI: 10.1016/j.bioflm.2021.100052] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 05/18/2021] [Accepted: 05/19/2021] [Indexed: 10/31/2022] Open
Abstract
Oxidative stress greatly limits current harvesting from anode biofilms in bioelectrochemical systems yet insufficient knowledge of the antioxidant responses of electricigens prevents optimization. Using Geobacter sulfurreducens PCA as a model electricigen, we demonstrated enhanced oxygen tolerance and reduced electron losses as the biofilms grew in height on the anode. To investigate the molecular basis of biofilm tolerance, we developed a genetic screening and isolated 11 oxygen-tolerant (oxt) strains from a library of transposon-insertion mutants. The aggregative properties of the oxt mutants promoted biofilm formation and oxygen tolerance. Yet, unlike the wild type, none of the mutants diverted respiratory electrons to oxygen. Most of the oxt mutations inactivated pathways for the detoxification of reactive oxygen species that could have triggered compensatory chronic responses to oxidative stress and inhibit aerobic respiration. One of the mutants (oxt10) also had a growth advantage with Fe(III) oxides and during the colonization of the anode electrode. The enhanced antioxidant response in this mutant reduced the system's start-up and promoted current harvesting from bioanodes even in the presence of oxygen. These results highlight a hitherto unknown role of oxidative stress responses in the stability and performance of current-harvesting biofilms of G. sulfurreducens and identify biological and engineering approaches to grow electroactive biofilms with the resilience needed for practical applications.
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Affiliation(s)
- Allison M Speers
- Department of Microbiology and Molecular Genetics, Michigan State University, USA
| | - Gemma Reguera
- Department of Microbiology and Molecular Genetics, Michigan State University, USA
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Cheng Q, Call DF. Developing microbial communities containing a high abundance of exoelectrogenic microorganisms using activated carbon granules. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 768:144361. [PMID: 33736328 DOI: 10.1016/j.scitotenv.2020.144361] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2020] [Revised: 11/30/2020] [Accepted: 12/01/2020] [Indexed: 06/12/2023]
Abstract
Microorganisms that can transfer electrons outside their cells are useful in a range of wastewater treatment and remediation technologies. Conventional methods of enriching exoelectrogens are cost-prohibitive (e.g., controlled-potential electrodes) or lack specificity (e.g., soluble electron acceptors). In this study a low-cost and simple approach to enrich exoelectrogens from a mixed microbial inoculum was investigated. After the method was validated using the exoelectrogen Geobacter sulfurreducens, microorganisms from a pilot-scale biological activated carbon (BAC) filter were subjected to incubations in which acetate was provided as the electron donor and granular activated carbon (GAC) as the electron acceptor. The BAC-derived community oxidized acetate and reduced GAC at a capacity of 1.0 mmol e- (g GAC)-1. After three transfers to new bottles, acetate oxidation rates increased 4.3-fold, and microbial morphologies and GAC surface coverage became homogenous. Although present at <0.01% in the inoculum, Geobacter species were significantly enriched in the incubations (up to 96% abundance), suggesting they were responsible for reducing the GAC. The ability to quickly and effectively develop an exoelectrogenic microbial community using GAC may help initiate and/or maintain environmental systems that benefit from the unique metabolic capabilities of these microorganisms.
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Affiliation(s)
- Qiwen Cheng
- Department of Civil, Construction, and Environmental Engineering, North Carolina State University, 2501 Stinson Drive, Raleigh, NC 27695-7908, United States
| | - Douglas F Call
- Department of Civil, Construction, and Environmental Engineering, North Carolina State University, 2501 Stinson Drive, Raleigh, NC 27695-7908, United States.
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Scarabotti F, Rago L, Bühler K, Harnisch F. The electrode potential determines the yield coefficients of early-stage Geobacter sulfurreducens biofilm anodes. Bioelectrochemistry 2021; 140:107752. [PMID: 33618189 DOI: 10.1016/j.bioelechem.2021.107752] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 01/29/2021] [Accepted: 01/30/2021] [Indexed: 01/05/2023]
Abstract
Geobacter sulfurreducens is the model for electroactive microorganisms (EAM). EAM can use solid state terminal electron acceptors (TEA) including anodes via extracellular electron transfer (EET). Yield coefficients relate the produced cell number or biomass to the oxidized substrate or the reduced TEA. These data are not yet sufficiently available for EAM growing at anodes. Thus, this study provides information about kinetics as well as yield coefficients of early-stage G. sulfurreducens biofilms using anodes as TEA at the potentials of -200 mV, 0 mV and +200 mV (vs. Ag/AgCl sat. KCl). The selected microorganism was therefore cultivated in single and double chamber batch reactors on graphite or AuPd anodes. Interestingly, whereas the lag time and maximum current density within 12 days of growth differed, the anode potential does not influence the coulombic efficiency and the formal potential of the EET, which remains constant for all the experiments at ~ -300 to -350 mV. We demonstrated for the first time that the anode potential has a strong influence on single cell yield coefficients which ranged from 2.69 × 1012 cells mole--1 at -200 mV and 1.48 × 1012 cells mole--1 at 0 mV to 2.58 × 1011 cells mole--1 at +200 mV in single chamber reactors and from 1.15 × 1012 cells mole--1 at -200 mV to 8.98× 1011 cells mole--1 at 0 mV in double chamber reactors. This data can be useful for optimization and scaling-up of primary microbial electrochemical technologies.
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Affiliation(s)
- Francesco Scarabotti
- Department of Environmental Microbiology, Helmholtz-Centre for Environmental Research - UFZ, Leipzig, Germany
| | - Laura Rago
- Department of Environmental Microbiology, Helmholtz-Centre for Environmental Research - UFZ, Leipzig, Germany
| | - Katja Bühler
- Department Solar Materials, Helmholtz-Centre for Environmental Research - UFZ, Leipzig, Germany
| | - Falk Harnisch
- Department of Environmental Microbiology, Helmholtz-Centre for Environmental Research - UFZ, Leipzig, Germany.
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Viefhues M. Analytics in Microfluidic Systems. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2020; 179:191-209. [DOI: 10.1007/10_2020_131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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