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Search Results (18)

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Keywords = Geobacter sulfurreducens

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20 pages, 1982 KiB  
Article
Hydrogen Production from Winery Wastewater Through a Dual-Chamber Microbial Electrolysis Cell
by Ana Baía, Alonso I. Arroyo-Escoto, Nuno Ramos, Bilel Abdelkarim, Marta Pereira, Maria C. Fernandes, Yifeng Zhang and Annabel Fernandes
Energies 2025, 18(12), 3043; https://doi.org/10.3390/en18123043 - 9 Jun 2025
Viewed by 532
Abstract
This study explores the feasibility of producing biohydrogen from winery wastewater using a dual-chamber microbial electrolysis cell (MEC). A mixed microbial consortium pre-adapted to heavy-metal environments and enriched with Geobacter sulfurreducens was anaerobically cultivated from diverse waste streams. Over 5000 h of development, [...] Read more.
This study explores the feasibility of producing biohydrogen from winery wastewater using a dual-chamber microbial electrolysis cell (MEC). A mixed microbial consortium pre-adapted to heavy-metal environments and enriched with Geobacter sulfurreducens was anaerobically cultivated from diverse waste streams. Over 5000 h of development, the MEC system was progressively adapted to winery wastewater, enabling long-term electrochemical stability and high organic matter degradation. Upon winery wastewater addition (5% v/v), the system achieved a sustained hydrogen production rate of (0.7 ± 0.3) L H2 L−1 d−1, with an average current density of (60 ± 4) A m−3, and COD removal efficiency exceeding 55%, highlighting the system’s resilience despite the presence of inhibitory compounds. Coulombic efficiency and cathodic hydrogen recovery reached (75 ± 4)% and (87 ± 5)%, respectively. Electrochemical impedance spectroscopy provided mechanistic insight into charge transfer and biofilm development, correlating resistive parameters with biological adaptation. These findings demonstrate the potential of MECs to simultaneously treat agro-industrial wastewaters and recover energy in the form of hydrogen, supporting circular resource management strategies. Full article
(This article belongs to the Special Issue Advanced Materials and Technologies for Hydrogen Evolution)
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16 pages, 2072 KiB  
Article
Metagenomic Insights into the Abundance of Iron-Reducing Microorganisms in a Petroleum-Contaminated Iron-Rich Aquifer
by He Di, Min Zhang, Zhuo Ning, Changli Liu, Ze He, Shuaiwei Wang, Siyu Kong, Shuang Gan, Weichao Sun, Zhe Xu and Jinjin Ti
Microorganisms 2025, 13(2), 433; https://doi.org/10.3390/microorganisms13020433 - 17 Feb 2025
Cited by 1 | Viewed by 556
Abstract
In petroleum-contaminated aquifers, iron (III) serves as an electron acceptor, enabling microbial degradation of organic matter. While previous studies have focused on iron reduction and organic matter degradation under laboratory conditions, research on iron-associated microorganisms in petroleum-contaminated aquifers is limited. To explore the [...] Read more.
In petroleum-contaminated aquifers, iron (III) serves as an electron acceptor, enabling microbial degradation of organic matter. While previous studies have focused on iron reduction and organic matter degradation under laboratory conditions, research on iron-associated microorganisms in petroleum-contaminated aquifers is limited. To explore the diversity and distribution of such microorganisms in natural settings, this study used metagenomic analysis of an iron-rich, petroleum-contaminated aquifer. Sixteen groundwater samples from both pollution source and background areas were collected for species annotation and functional gene identification. Results show more than 7000 species were identified as iron-reducing microorganisms (IRMs), including several previously well-characterized iron-reducing species (e.g., Geobacter luticola and Geobacter sulfurreducens). However, the majority of IRMs were not found in existing iron-reducing microbial databases. Some of them, such as Sulfurospirillum sp. and Extensimonas perlucida, could be taxonomically classified at the species level, while most were only annotated as unclassified bacteria. In the contamination source zone, these microorganisms proliferated extensively, which led to hydrocarbon degradation predominantly driven by iron reduction in the aquifer. This study enhances our understanding of hydrocarbon-degrading microorganisms and supports the management of petroleum-contaminated sites. Full article
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17 pages, 3307 KiB  
Article
Defying Gravity to Enhance Power Output and Conversion Efficiency in a Vertically Oriented Four-Electrode Microfluidic Microbial Fuel Cell
by Linlin Liu, Haleh Baghernavehsi and Jesse Greener
Micromachines 2024, 15(8), 961; https://doi.org/10.3390/mi15080961 - 27 Jul 2024
Cited by 2 | Viewed by 1578
Abstract
High power output and high conversion efficiency are crucial parameters for microbial fuel cells (MFCs). In our previous work, we worked with microfluidic MFCs to study fundamentals related to the power density of the MFCs, but nutrient consumption was limited to one side [...] Read more.
High power output and high conversion efficiency are crucial parameters for microbial fuel cells (MFCs). In our previous work, we worked with microfluidic MFCs to study fundamentals related to the power density of the MFCs, but nutrient consumption was limited to one side of the microchannel (the electrode layer) due to diffusion limitations. In this work, long-term experiments were conducted on a new four-electrode microfluidic MFC design, which grew Geobacter sulfurreducens biofilms on upward- and downward-facing electrodes in the microchannel. To our knowledge, this is the first study comparing electroactive biofilm (EAB) growth experiencing the influence of opposing gravitational fields. It was discovered that inoculation and growth of the EAB did not proceed as fast at the downward-facing anode, which we hypothesize to be due to gravity effects that negatively impacted bacterial settling on that surface. Rotating the device during the growth phase resulted in uniform and strong outputs from both sides, yielding individual power densities of 4.03 and 4.13 W m−2, which increased to nearly double when the top- and bottom-side electrodes were operated in parallel as a single four-electrode MFC. Similarly, acetate consumption could be doubled with the four electrodes operated in parallel. Full article
(This article belongs to the Section E:Engineering and Technology)
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17 pages, 3561 KiB  
Article
The Performance of a Modified Anode Using a Combination of Kaolin and Graphite Nanoparticles in Microbial Fuel Cells
by Lea Ouaknin Hirsch, Bharath Gandu, Abhishiktha Chiliveru, Irina Amar Dubrovin, Shmuel Rozenfeld, Alex Schechter and Rivka Cahan
Microorganisms 2024, 12(3), 604; https://doi.org/10.3390/microorganisms12030604 - 18 Mar 2024
Cited by 5 | Viewed by 2179
Abstract
The bacterial anode in microbial fuel cells was modified by increasing the biofilm’s adhesion to the anode material using kaolin and graphite nanoparticles. The MFCs were inoculated with G. sulfurreducens, kaolin (12.5 g·L−1), and three different concentrations of graphite (0.25, [...] Read more.
The bacterial anode in microbial fuel cells was modified by increasing the biofilm’s adhesion to the anode material using kaolin and graphite nanoparticles. The MFCs were inoculated with G. sulfurreducens, kaolin (12.5 g·L−1), and three different concentrations of graphite (0.25, 1.25, and 2.5 g·L−1). The modified anode with the graphite nanoparticles (1.25 g·L−1) showed the highest electroactivity and biofilm viability. A potential of 0.59, 0.45, and 0.23 V and a power density of 0.54 W·m−2, 0.3 W·m−2, and 0.2 W·m−2 were obtained by the MFCs based on kaolin–graphite nanoparticles, kaolin, and bare anodes, respectively. The kaolin–graphite anode exhibited the highest Coulombic efficiency (21%) compared with the kaolin (17%) and the bare (14%) anodes. Scanning electron microscopy and confocal laser scanning microscopy revealed a large amount of biofilm on the kaolin–graphite anode. We assume that the graphite nanoparticles increased the charge transfer between the bacteria that are in the biofilm and are far from the anode material. The addition of kaolin and graphite nanoparticles increased the attachment of several bacteria. Thus, for MFCs that are fed with wastewater, the modified anode should be prepared with a pure culture of G. sulfurreducens before adding wastewater that includes non-exoelectrogenic bacteria. Full article
(This article belongs to the Special Issue Microbial Fuel Cells: An Update)
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14 pages, 1898 KiB  
Communication
Geobacter grbiciae—A New Electron Donor in the Formation of Co-Cultures via Direct Interspecies Electron Transfer
by Panbo Deng, Lulu Wang, Xia Li, Jinshan Zhang and Haiming Jiang
Microbiol. Res. 2023, 14(4), 1774-1787; https://doi.org/10.3390/microbiolres14040122 - 2 Nov 2023
Cited by 5 | Viewed by 1989
Abstract
Geobacter grbiciae can grow via coupling oxidation of ethanol to the reduction of various forms of soluble Fe(III) and poorly crystalline Fe(III) oxide, suggesting that G. grbiciae can act as an electron-donor microbe for forming co-cultures through direct interspecies electron transfer (DIET). In [...] Read more.
Geobacter grbiciae can grow via coupling oxidation of ethanol to the reduction of various forms of soluble Fe(III) and poorly crystalline Fe(III) oxide, suggesting that G. grbiciae can act as an electron-donor microbe for forming co-cultures through direct interspecies electron transfer (DIET). In this report, potential co-cultures through DIET of G. grbiciae and Methanosarcina barkeri 800, G. sulfurreducens Δhyb, or Methanospirillum hungatei, as electron-acceptor microbes, were examined. Co-cultures of G. grbiciae and G. sulfurreducens Δhyb were performed with ethanol as the sole electron-donor substance and fumarate as the electron-acceptor substance in the presence of granular activated carbon (GAC), magnetite, or polyester felt. The conditions for co-culturing G. grbiciae and M. barkeri 800 (or M. hungatei) were the same as those for G. grbiciae and G. sulfurreducens Δhyb, except fumarate was absent and different cultivation temperatures were used. All co-cultures were anaerobically cultivated. Samples were regularly withdrawn from the co-cultures to monitor methane, fumarate, and succinate via gas or high-performance liquid chromatography. G. grbiciae formed functional co-cultures with M. barkeri 800 in the presence of GAC or magnetite. No co-culture of G. grbiciae with the H2/formate-utilizing methanogen M. hungatei was observed. Additionally, G. grbiciae formed functional co-cultures with H2/formate-un-utilizing G. sulfurreducens Δhyb without the GAC or magnetite supplement. These findings indicate electron transfer between G. grbiciae and M. barkeri 800/G. sulfurreducens Δhyb is via DIET rather than H2/formate, confirming that G. grbiciae acts as an electron-donor microbe. Although the co-cultures of G. grbiciae and M. barkeri 800 syntrophically converted ethanol to methane through DIET, the conversion of propionate or butyrate to methane was not observed. These findings expand the range of microbes that can act as electron donors for interaction with other microbes through DIET. However, propionate and butyrate metabolism through DIET in mixed microbial communities with methane as a product requires further analysis. This study provides a framework for finding new electron-donor microbes. Full article
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16 pages, 4999 KiB  
Article
A Biochemical Deconstruction-Based Strategy to Assist the Characterization of Bacterial Electric Conductive Filaments
by Marta A. Silva, Ana P. Fernandes, David L. Turner and Carlos A. Salgueiro
Int. J. Mol. Sci. 2023, 24(8), 7032; https://doi.org/10.3390/ijms24087032 - 11 Apr 2023
Cited by 3 | Viewed by 1865
Abstract
Periplasmic nanowires and electric conductive filaments made of the polymeric assembly of c-type cytochromes from Geobacter sulfurreducens bacterium are crucial for electron storage and/or extracellular electron transfer. The elucidation of the redox properties of each heme is fundamental to the understanding of [...] Read more.
Periplasmic nanowires and electric conductive filaments made of the polymeric assembly of c-type cytochromes from Geobacter sulfurreducens bacterium are crucial for electron storage and/or extracellular electron transfer. The elucidation of the redox properties of each heme is fundamental to the understanding of the electron transfer mechanisms in these systems, which first requires the specific assignment of the heme NMR signals. The high number of hemes and the molecular weight of the nanowires dramatically decrease the spectral resolution and make this assignment extremely complex or unattainable. The nanowire cytochrome GSU1996 (~42 kDa) is composed of four domains (A to D) each containing three c-type heme groups. In this work, the individual domains (A to D), bi-domains (AB, CD) and full-length nanowire were separately produced at natural abundance. Sufficient protein expression was obtained for domains C (~11 kDa/three hemes) and D (~10 kDa/three hemes), as well as for bi-domain CD (~21 kDa/six hemes). Using 2D-NMR experiments, the assignment of the heme proton NMR signals for domains C and D was obtained and then used to guide the assignment of the corresponding signals in the hexaheme bi-domain CD. This new biochemical deconstruction-based procedure, using nanowire GSU1996 as a model, establishes a new strategy to functionally characterize large multiheme cytochromes. Full article
(This article belongs to the Special Issue Transition Metal Ions in Biology)
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12 pages, 2259 KiB  
Article
Facet Dependence of Biosynthesis of Vivianite from Iron Oxides by Geobacter sulfurreducens
by Xiaoshan Luo, Liumei Wen, Lihua Zhou and Yong Yuan
Int. J. Environ. Res. Public Health 2023, 20(5), 4247; https://doi.org/10.3390/ijerph20054247 - 27 Feb 2023
Cited by 6 | Viewed by 2078
Abstract
Vivianite plays an important role in alleviating the phosphorus crisis and phosphorus pollution. The dissimilatory iron reduction has been found to trigger the biosynthesis of vivianite in soil environments, but the mechanism behind this remains largely unexplored. Herein, by regulating the crystal surfaces [...] Read more.
Vivianite plays an important role in alleviating the phosphorus crisis and phosphorus pollution. The dissimilatory iron reduction has been found to trigger the biosynthesis of vivianite in soil environments, but the mechanism behind this remains largely unexplored. Herein, by regulating the crystal surfaces of iron oxides, we explored the influence of different crystal surface structures on the synthesis of vivianite driven by microbial dissimilatory iron reduction. The results showed that different crystal faces significantly affect the reduction and dissolution of iron oxides by microorganisms and the subsequent formation of vivianite. In general, goethite is more easily reduced by Geobacter sulfurreducens than hematite. Compared with Hem_{100} and Goe_L{110}, Hem_{001} and Goe_H{110} have higher initial reduction rates (approximately 2.25 and 1.5 times, respectively) and final Fe(II) content (approximately 1.56 and 1.20 times, respectively). In addition, in the presence of sufficient PO43−, Fe(II) combined to produce phosphorus crystal products. The final phosphorus recoveries of Hem_{001} and Goe_H{110} systems were about 5.2 and 13.6%, which were 1.3 and 1.6 times of those of Hem_{100} and Goe_L{110}, respectively. Material characterization analyses indicated that these phosphorous crystal products are vivianite and that different iron oxide crystal surfaces significantly affected the size of the vivianite crystals. This study demonstrates that different crystal faces can affect the biological reduction dissolution of iron oxides and the secondary biological mineralization process driven by dissimilatory iron reduction. Full article
(This article belongs to the Special Issue Analytical Chemistry on Environmental Detection and Remediation)
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16 pages, 2100 KiB  
Article
The Signaling Pathway That cGAMP Riboswitches Found: Analysis and Application of Riboswitches to Study cGAMP Signaling in Geobacter sulfurreducens
by Zhesen Tan, Chi Ho Chan, Michael Maleska, Bryan Banuelos Jara, Brian K. Lohman, Nathan J. Ricks, Daniel R. Bond and Ming C. Hammond
Int. J. Mol. Sci. 2022, 23(3), 1183; https://doi.org/10.3390/ijms23031183 - 21 Jan 2022
Cited by 2 | Viewed by 3685
Abstract
The Hypr cGAMP signaling pathway was discovered via the function of the riboswitch. In this study, we show the development of a method for affinity capture followed by sequencing to identify non-coding RNA regions that bind nucleotide signals such as cGAMP. The RNAseq [...] Read more.
The Hypr cGAMP signaling pathway was discovered via the function of the riboswitch. In this study, we show the development of a method for affinity capture followed by sequencing to identify non-coding RNA regions that bind nucleotide signals such as cGAMP. The RNAseq of affinity-captured cGAMP riboswitches from the Geobacter sulfurreducens transcriptome highlights general challenges that remain for this technique. Furthermore, by applying riboswitch reporters in vivo, we identify new growth conditions and transposon mutations that affect cGAMP levels in G. sulfurreducens. This work reveals an extensive regulatory network and supports a second functional cGAMP synthase gene in G. sulfurreducens. The activity of the second synthase was validated using riboswitch-based fluorescent biosensors, and is the first known example of an active enzyme with a variant GGDDF motif. Full article
(This article belongs to the Special Issue Bacterial Non-coding RNA)
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15 pages, 4601 KiB  
Article
Algae-Assisted Microbial Desalination Cell: Analysis of Cathode Performance and Desalination Efficiency Assessment
by David Ewusi-Mensah, Jingyu Huang, Laura Katherin Chaparro, Pau Rodenas, Marina Ramírez-Moreno, Juan Manuel Ortiz and Abraham Esteve-Núñez
Processes 2021, 9(11), 2011; https://doi.org/10.3390/pr9112011 - 10 Nov 2021
Cited by 18 | Viewed by 4062
Abstract
Algae-assisted microbial desalination cells represent a sustainable technology for low-energy fresh water production in which microalgae culture is integrated into the system to enhance oxygen reduction reaction in the cathode chamber. However, the water production (desalination rate) is low compared to conventional technologies [...] Read more.
Algae-assisted microbial desalination cells represent a sustainable technology for low-energy fresh water production in which microalgae culture is integrated into the system to enhance oxygen reduction reaction in the cathode chamber. However, the water production (desalination rate) is low compared to conventional technologies (i.e., reverse osmosis and/or electrodialysis), as biocathodes provide low current generation to sustain the desalination process. In this sense, more research efforts on this topic are necessary to address this bottleneck. Thus, this study provides analysis, from the electrochemical point of view, on the cathode performance of an algae-assisted microbial desalination cell (MDC) using Chlorella vulgaris. Firstly, the system was run with a pure culture of Chlorella vulgaris suspension in the cathode under conditions of an abiotic anode to assess the cathodic behavior (i.e., cathode polarization curves in light-dark conditions and oxygen depletion). Secondly, Geobacter sulfurreducens was inoculated in the anode compartment of the MDC, and the desalination cycle was carried out. The results showed that microalgae could generate an average of 9–11.5 mg/L of dissolved oxygen during the light phase, providing enough dissolved oxygen to drive the migration of ions (i.e., desalination) in the MDC system. Moreover, during the dark phase, a residual concentration of oxygen (ca. 5.5–8 mg/L) was measured, indicating that oxygen was not wholly depleted under our experimental conditions. Interestingly, the oxygen concentration was restored (after complete depletion of dissolved oxygen by flushing with N2) as soon as microalgae were exposed to the light phase again. After a 31 h desalination cycle, the cell generated a current density of 0.12 mA/cm2 at an efficiency of 60.15%, 77.37% salt was removed at a nominal desalination rate of 0.63 L/m2/h, coulombic efficiency was 9%, and 0.11 kWh/m3 of electric power was generated. The microalgae-assisted biocathode has an advantage over the air diffusion and bubbling as it can self-sustain a steady and higher concentration of oxygen, cost-effectively regenerate or recover from loss and sustainably retain the system’s performance under naturally occurring conditions. Thus, our study provides insights into implementing the algae-assisted cathode for sustainable desalination using MDC technology and subsequent optimization. Full article
(This article belongs to the Special Issue Advances of Microbial Processes in Bioelectrochemical Systems)
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26 pages, 6097 KiB  
Review
Multistep Signaling in Nature: A Close-Up of Geobacter Chemotaxis Sensing
by Marta A. Silva and Carlos A. Salgueiro
Int. J. Mol. Sci. 2021, 22(16), 9034; https://doi.org/10.3390/ijms22169034 - 21 Aug 2021
Cited by 4 | Viewed by 3868
Abstract
Environmental changes trigger the continuous adaptation of bacteria to ensure their survival. This is possible through a variety of signal transduction pathways involving chemoreceptors known as methyl-accepting chemotaxis proteins (MCP) that allow the microorganisms to redirect their mobility towards favorable environments. MCP are [...] Read more.
Environmental changes trigger the continuous adaptation of bacteria to ensure their survival. This is possible through a variety of signal transduction pathways involving chemoreceptors known as methyl-accepting chemotaxis proteins (MCP) that allow the microorganisms to redirect their mobility towards favorable environments. MCP are two-component regulatory (or signal transduction) systems (TCS) formed by a sensor and a response regulator domain. These domains synchronize transient protein phosphorylation and dephosphorylation events to convert the stimuli into an appropriate cellular response. In this review, the variability of TCS domains and the most common signaling mechanisms are highlighted. This is followed by the description of the overall cellular topology, classification and mechanisms of MCP. Finally, the structural and functional properties of a new family of MCP found in Geobacter sulfurreducens are revisited. This bacterium has a diverse repertoire of chemosensory systems, which represents a striking example of a survival mechanism in challenging environments. Two G. sulfurreducens MCP—GSU0582 and GSU0935—are members of a new family of chemotaxis sensor proteins containing a periplasmic PAS-like sensor domain with a c-type heme. Interestingly, the cellular location of this domain opens new routes to the understanding of the redox potential sensing signaling transduction pathways. Full article
(This article belongs to the Special Issue Bacterial Chemoreceptors and Chemosensory Pathways)
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15 pages, 3832 KiB  
Article
Improvement of Microbial Electrolysis Cell Activity by Using Anode Based on Combined Plasma-Pretreated Carbon Cloth and Stainless Steel
by Shmuel Rozenfeld, Lea Ouaknin Hirsch, Bharath Gandu, Ravit Farber, Alex Schechter and Rivka Cahan
Energies 2019, 12(10), 1968; https://doi.org/10.3390/en12101968 - 23 May 2019
Cited by 24 | Viewed by 5220
Abstract
The anode activity in a microbial electrolysis cell (MEC) is known to be a limiting factor in hydrogen production. In this study, the MEC was constructed using different anode materials and a platinum-coated carbon-cloth cathode (CC). The anodes were comprised of CC, stainless [...] Read more.
The anode activity in a microbial electrolysis cell (MEC) is known to be a limiting factor in hydrogen production. In this study, the MEC was constructed using different anode materials and a platinum-coated carbon-cloth cathode (CC). The anodes were comprised of CC, stainless steel (SS), and a combination of the two (COMB). The CC and SS anodes were also treated with plasma to improve their surface morphology and hydrophilic properties (CCP and SSP, respectively). A combined version of CCP attached to SS was also applied (COMBP). After construction of the MEC using the different anodes, we conducted electrochemical measurements and examination of biofilm viability. Under an applied voltage of 0.6 V (Ag/AgCl), the currents of a MEC based on CCP and COMBP were 11.66 ± 0.1331 and 16.36 ± 0.3172 A m−2, respectively, which are about three times higher compared to the untreated CC and COMB. A MEC utilizing an untreated SS anode exhibited current of only 0.3712 ± 0.0108 A m−2. The highest biofilm viability of 0.92 OD540 ± 0.07 and hydrogen production rate of 0.0736 ± 0.0022 m3 d−1 m−2 at 0.8 V were obtained in MECs based on the COMBP anode. To our knowledge, this is the first study that evaluated the effect of plasma-treated anodes and the use of a combined anode composed of SS and CC for hydrogen evolution in a MEC. Full article
(This article belongs to the Section A4: Bio-Energy)
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14 pages, 6932 KiB  
Article
On-Line Raman Spectroscopic Study of Cytochromes’ Redox State of Biofilms in Microbial Fuel Cells
by Adolf Krige, Magnus Sjöblom, Kerstin Ramser, Paul Christakopoulos and Ulrika Rova
Molecules 2019, 24(3), 646; https://doi.org/10.3390/molecules24030646 - 12 Feb 2019
Cited by 24 | Viewed by 4971
Abstract
Bio-electrochemical systems such as microbial fuel cells and microbial electrosynthesis cells depend on efficient electron transfer between the microorganisms and the electrodes. Understanding the mechanisms and dynamics of the electron transfer is important in order to design more efficient reactors, as well as [...] Read more.
Bio-electrochemical systems such as microbial fuel cells and microbial electrosynthesis cells depend on efficient electron transfer between the microorganisms and the electrodes. Understanding the mechanisms and dynamics of the electron transfer is important in order to design more efficient reactors, as well as modifying microorganisms for enhanced electricity production. Geobacter are well known for their ability to form thick biofilms and transfer electrons to the surfaces of electrodes. Currently, there are not many “on-line” systems for monitoring the activity of the biofilm and the electron transfer process without harming the biofilm. Raman microscopy was shown to be capable of providing biochemical information, i.e., the redox state of C-type cytochromes, which is integral to external electron transfer, without harming the biofilm. In the current study, a custom 3D printed flow-through cuvette was used in order to analyze the oxidation state of the C-type cytochromes of suspended cultures of three Geobacter sulfurreducens strains (PCA, KN400 and ΔpilA). It was found that the oxidation state is a good indicator of the metabolic state of the cells. Furthermore, an anaerobic fluidic system enabling in situ Raman measurements was designed and applied successfully to monitor and characterize G. sulfurreducens biofilms during electricity generation, for both a wild strain, PCA, and a mutant, ΔS. The cytochrome redox state, monitored by the Raman peak areas, could be modulated by applying different poise voltages to the electrodes. This also correlated with the modulation of current transferred from the cytochromes to the electrode. The Raman peak area changed in a predictable and reversible manner, indicating that the system could be used for analyzing the oxidation state of the proteins responsible for the electron transfer process and the kinetics thereof in-situ. Full article
(This article belongs to the Special Issue Raman Spectroscopy: A Spectroscopic 'Swiss-Army Knife')
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20 pages, 2197 KiB  
Article
Characterization of a Novel Porin-Like Protein, ExtI, from Geobacter sulfurreducens and Its Implication in the Reduction of Selenite and Tellurite
by Mst. Ishrat Jahan, Ryuta Tobe and Hisaaki Mihara
Int. J. Mol. Sci. 2018, 19(3), 809; https://doi.org/10.3390/ijms19030809 - 11 Mar 2018
Cited by 14 | Viewed by 7238
Abstract
The extI gene in Geobacter sulfurreducens encodes a putative outer membrane channel porin, which resides within a cluster of extHIJKLMNOPQS genes. This cluster is highly conserved across the Geobacteraceae and includes multiple putative c-type cytochromes. In silico analyses of the ExtI sequence, [...] Read more.
The extI gene in Geobacter sulfurreducens encodes a putative outer membrane channel porin, which resides within a cluster of extHIJKLMNOPQS genes. This cluster is highly conserved across the Geobacteraceae and includes multiple putative c-type cytochromes. In silico analyses of the ExtI sequence, together with Western blot analysis and proteinase protection assays, showed that it is an outer membrane protein. The expression level of ExtI did not respond to changes in osmolality and phosphate starvation. An extI-deficient mutant did not show any significant impact on fumarate or Fe(III) citrate reduction or sensitivity to β-lactam antibiotics, as compared with those of the wild-type strain. However, extI deficiency resulted in a decreased ability to reduce selenite and tellurite. Heme staining analysis revealed that extI deficiency affects certain heme-containing proteins in the outer and inner membranes, which may cause a decrease in the ability to reduce selenite and tellurite. Based on these observations, we discuss possible roles for ExtI in selenite and tellurite reduction in G. sulfurreducens. Full article
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21 pages, 71714 KiB  
Article
Structural Basis for the Influence of A1, 5A, and W51W57 Mutations on the Conductivity of the Geobacter sulfurreducens Pili
by Chuanjun Shu, Ke Xiao and Xiao Sun
Crystals 2018, 8(1), 10; https://doi.org/10.3390/cryst8010010 - 25 Dec 2017
Cited by 6 | Viewed by 4480
Abstract
The metallic-like conductivity of the Geobacter sulfurreducens pilus and higher conductivity of its mutants reflected that biological synthesis can be utilized to improve the properties of electrically conductive pili. However, the structural basis for diverse conductivities of nanowires remains uncertain. Here, the impacts [...] Read more.
The metallic-like conductivity of the Geobacter sulfurreducens pilus and higher conductivity of its mutants reflected that biological synthesis can be utilized to improve the properties of electrically conductive pili. However, the structural basis for diverse conductivities of nanowires remains uncertain. Here, the impacts of point mutations on the flexibility and stability of pilins were investigated based on molecular dynamics simulations. Structures of the G. sulfurreducens pilus and its mutants were constructed by Rosetta. Details of the structure (i.e., electrostatic properties, helical parameters, residue interaction network, distances between amino acids, and salt bridges) were analyzed by PDB2PQR, Rosetta, RING, PyMOL, and VMD, respectively. Changes in stability, flexibility, residue interaction, and electrostatic properties of subunits directly caused wild-type pilin and its mutants assemble different structures of G. sulfurreducens pili. By comparing the structures of pili with different conductivities, the mechanism by which the G. sulfurreducens pilus transfers electron along pili was attributed, at least in part, to the density of aromatic rings, the distances between neighboring aromatic rings, and the local electrostatic environment around aromatic contacts. These results provide new insight into the potential for the biological synthesis of highly electrically conductive, nontoxic nanowires. Full article
(This article belongs to the Special Issue Crystal Structures of Amino Acids and Peptides)
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4 pages, 722 KiB  
Proceeding Paper
Vertical 3D GaN Nanoarchitectures towards an Integrated Optoelectronic Biosensing Platform in Microbial Fuel Cells
by Heidi Boht, Hilke Wichmann, Gregor Scholz, Feng Yu, Klaas Strempel, Shinta Mariana, Muhammad Fahlesa Fatahilah, Irene Manglano Clavero, Joan Daniel Prades, Uwe Schröder, Hutomo Suryo Wasisto and Andreas Waag
Proceedings 2017, 1(4), 508; https://doi.org/10.3390/proceedings1040508 - 4 Aug 2017
Cited by 1 | Viewed by 2200
Abstract
An integrated nano-optoelectronic biological sensor system is developed to obtain insights of the biochemical and physical processes of Geobacter sulfurreducens-based biofilm growth inside a miniaturized microbial fuel cell (MFC) reactor. Gallium nitride (GaN), which was used as a novel electrode material, has [...] Read more.
An integrated nano-optoelectronic biological sensor system is developed to obtain insights of the biochemical and physical processes of Geobacter sulfurreducens-based biofilm growth inside a miniaturized microbial fuel cell (MFC) reactor. Gallium nitride (GaN), which was used as a novel electrode material, has been investigated in terms of its biocompatibility and performance to transport the electrons delivered by the microorganisms. Moreover, in order to enhance the produced current density, vertical 3D GaN nanoarchitectures (i.e., arrays of nanowires and nanofins) with larger surface-to-volume ratios were fabricated using a top-down nanomachining method involving nanolithography and hybrid etching technique. Full article
(This article belongs to the Proceedings of Proceedings of Eurosensors 2017, Paris, France, 3–6 September 2017)
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