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Abstract
Extracellular electron transfer (EET) is the physiological process that enables the reduction or oxidation of molecules and minerals beyond the surface of a microbial cell. The first bacteria characterized with this capability were Shewanella and Geobacter, both reported to couple their growth to the reduction of iron or manganese oxide minerals located extracellularly. A key difference between EET and nearly every other respiratory activity on Earth is the need to transfer electrons beyond the cell membrane. The past decade has resolved how well-conserved strategies conduct electrons from the inner membrane to the outer surface. However, recent data suggest a much wider and less well understood collection of mechanisms enabling electron transfer to distant acceptors. This review reflects the current state of knowledge from Shewanella and Geobacter, specifically focusing on transfer across the outer membrane and beyond-an activity that enables reduction of highly variable minerals, electrodes, and even other organisms.
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Affiliation(s)
- J A Gralnick
- BioTechnology Institute and Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA; ,
| | - D R Bond
- BioTechnology Institute and Department of Plant and Microbial Biology, University of Minnesota, St. Paul, Minnesota, USA; ,
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Zhang B, Shi S, Tang R, Qiao C, Yang M, You Z, Shao S, Wu D, Yu H, Zhang J, Cao Y, Li F, Song H. Recent advances in enrichment, isolation, and bio-electrochemical activity evaluation of exoelectrogenic microorganisms. Biotechnol Adv 2023; 66:108175. [PMID: 37187358 DOI: 10.1016/j.biotechadv.2023.108175] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Revised: 05/10/2023] [Accepted: 05/10/2023] [Indexed: 05/17/2023]
Abstract
Exoelectrogenic microorganisms (EEMs) catalyzed the conversion of chemical energy to electrical energy via extracellular electron transfer (EET) mechanisms, which underlay diverse bio-electrochemical systems (BES) applications in clean energy development, environment and health monitoring, wearable/implantable devices powering, and sustainable chemicals production, thereby attracting increasing attentions from academic and industrial communities in the recent decades. However, knowledge of EEMs is still in its infancy as only ~100 EEMs of bacteria, archaea, and eukaryotes have been identified, motivating the screening and capture of new EEMs. This review presents a systematic summarization on EEM screening technologies in terms of enrichment, isolation, and bio-electrochemical activity evaluation. We first generalize the distribution characteristics of known EEMs, which provide a basis for EEM screening. Then, we summarize EET mechanisms and the principles underlying various technological approaches to the enrichment, isolation, and bio-electrochemical activity of EEMs, in which a comprehensive analysis of the applicability, accuracy, and efficiency of each technology is reviewed. Finally, we provide a future perspective on EEM screening and bio-electrochemical activity evaluation by focusing on (i) novel EET mechanisms for developing the next-generation EEM screening technologies, and (ii) integration of meta-omics approaches and bioinformatics analyses to explore nonculturable EEMs. This review promotes the development of advanced technologies to capture new EEMs.
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Affiliation(s)
- Baocai Zhang
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, China; Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Sicheng Shi
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, China; Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Rui Tang
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, China; Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Chunxiao Qiao
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, China; Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Meiyi Yang
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, China; Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Zixuan You
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, China; Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Shulin Shao
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, China; Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Deguang Wu
- Department of Brewing Engineering, Moutai Institute, Luban Ave, Renhuai 564507, Guizhou, PR China
| | - Huan Yu
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, China; Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Junqi Zhang
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, China; Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Yingxiu Cao
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, China; Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Feng Li
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, China; Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.
| | - Hao Song
- Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, China; Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.
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Wang F, Craig L, Liu X, Rensing C, Egelman EH. Microbial nanowires: type IV pili or cytochrome filaments? Trends Microbiol 2023; 31:384-392. [PMID: 36446702 PMCID: PMC10033339 DOI: 10.1016/j.tim.2022.11.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2022] [Revised: 11/08/2022] [Accepted: 11/09/2022] [Indexed: 11/27/2022]
Abstract
A dynamic field of study has emerged involving long-range electron transport by extracellular filaments in anaerobic bacteria, with Geobacter sulfurreducens being used as a model system. The interest in this topic stems from the potential uses of such systems in bioremediation, energy generation, and new bio-based nanotechnology for electronic devices. These conductive extracellular filaments were originally thought, based upon low-resolution observations of dried samples, to be type IV pili (T4P). However, the recently published atomic structure for the T4P from G. sulfurreducens, obtained by cryo-electron microscopy (cryo-EM), is incompatible with the numerous models that have been put forward for electron conduction. As with all high-resolution structures of T4P, the G. sulfurreducens T4P structure shows a partial melting of the α-helix that substantially impacts the aromatic residue positions such that they are incompatible with conductivity. Furthermore, new work using high-resolution cryo-EM shows that conductive filaments thought to be T4P are actually polymerized cytochromes, with stacked heme groups forming a continuous conductive wire, or extracellular DNA. Recent atomic structures of three different cytochrome filaments from G. sulfurreducens suggest that such polymers evolved independently on multiple occasions. The expectation is that such polymerized cytochromes may be found emanating from other anaerobic organisms.
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Affiliation(s)
- Fengbin Wang
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22903, USA
| | - Lisa Craig
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Xing Liu
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Christopher Rensing
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Edward H Egelman
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22903, USA.
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Conners EM, Rengasamy K, Bose A. "Electroactive biofilms: how microbial electron transfer enables bioelectrochemical applications". J Ind Microbiol Biotechnol 2022; 49:6563884. [PMID: 35381088 PMCID: PMC9338886 DOI: 10.1093/jimb/kuac012] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 03/30/2022] [Indexed: 11/22/2022]
Abstract
Microbial biofilms are ubiquitous. In marine and freshwater ecosystems, microbe–mineral interactions sustain biogeochemical cycles, while biofilms found on plants and animals can range from pathogens to commensals. Moreover, biofouling and biocorrosion represent significant challenges to industry. Bioprocessing is an opportunity to take advantage of biofilms and harness their utility as a chassis for biocommodity production. Electrochemical bioreactors have numerous potential applications, including wastewater treatment and commodity production. The literature examining these applications has demonstrated that the cell–surface interface is vital to facilitating these processes. Therefore, it is necessary to understand the state of knowledge regarding biofilms’ role in bioprocessing. This mini-review discusses bacterial biofilm formation, cell–surface redox interactions, and the role of microbial electron transfer in bioprocesses. It also highlights some current goals and challenges with respect to microbe-mediated bioprocessing and future perspectives.
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Affiliation(s)
- Eric M Conners
- Department of Biology. One Brookings Drive, Washington University in St. Louis, Missouri, 63105, USA
| | - Karthikeyan Rengasamy
- Department of Biology. One Brookings Drive, Washington University in St. Louis, Missouri, 63105, USA
| | - Arpita Bose
- Department of Biology. One Brookings Drive, Washington University in St. Louis, Missouri, 63105, USA
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Abram S, Fromm KM. Handling (Nano)Silver as Antimicrobial Agent: Therapeutic Window, Dissolution Dynamics, Detection Methods and Molecular Interactions. Chemistry 2020; 26:10948-10971. [DOI: 10.1002/chem.202002143] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Indexed: 12/27/2022]
Affiliation(s)
- Sarah‐Luise Abram
- Department of Chemistry University of Fribourg Chemin du Musée 9 1700 Fribourg Switzerland
| | - Katharina M. Fromm
- Department of Chemistry University of Fribourg Chemin du Musée 9 1700 Fribourg Switzerland
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6
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Strategies for improving the electroactivity and specific metabolic functionality of microorganisms for various microbial electrochemical technologies. Biotechnol Adv 2019; 39:107468. [PMID: 31707076 DOI: 10.1016/j.biotechadv.2019.107468] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2019] [Revised: 11/02/2019] [Accepted: 11/04/2019] [Indexed: 01/31/2023]
Abstract
Electroactive microorganisms, which possess extracellular electron transfer (EET) capabilities, are the basis of microbial electrochemical technologies (METs) such as microbial fuel and electrolysis cells. These are considered for several applications ranging from the energy-efficient treatment of waste streams to the production of value-added chemicals and fuels, bioremediation, and biosensing. Various aspects related to the microorganisms, electrodes, separators, reactor design, and operational or process parameters influence the overall functioning of METs. The most fundamental and critical performance-determining factor is, however, the microorganism-electrode interactions. Modification of the electrode surfaces and microorganisms for optimizing their interactions has therefore been the major MET research focus area over the last decade. In the case of microorganisms, primarily their EET mechanisms and efficiencies along with the biofilm formation capabilities, collectively considered as microbial electroactivity, affect their interactions with the electrodes. In addition to electroactivity, the specific metabolic or biochemical functionality of microorganisms is equally crucial to the target MET application. In this article, we present the major strategies that are used to enhance the electroactivity and specific functionality of microorganisms pertaining to both anodic and cathodic processes of METs. These include simple physical methods based on the use of heat and magnetic field along with chemical, electrochemical, and growth media amendment approaches to the complex procedure-based microbial bioaugmentation, co-culture, and cell immobilization or entrapment, and advanced toolkit-based biofilm engineering, genetic modifications, and synthetic biology strategies. We further discuss the applicability and limitations of these strategies and possible future research directions for advancing the highly promising microbial electrochemistry-driven biotechnology.
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7
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Newsome L, Lopez Adams R, Downie HF, Moore KL, Lloyd JR. NanoSIMS imaging of extracellular electron transport processes during microbial iron(III) reduction. FEMS Microbiol Ecol 2019; 94:5033680. [PMID: 29878195 PMCID: PMC6041951 DOI: 10.1093/femsec/fiy104] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 06/05/2018] [Indexed: 01/25/2023] Open
Abstract
Microbial iron(III) reduction can have a profound effect on the fate of contaminants in natural and engineered environments. Different mechanisms of extracellular electron transport are used by Geobacter and Shewanella spp. to reduce insoluble Fe(III) minerals. Here we prepared a thin film of iron(III)-(oxyhydr)oxide doped with arsenic, and allowed the mineral coating to be colonised by Geobacter sulfurreducens or Shewanella ANA3 labelled with 13C from organic electron donors. This preserved the spatial relationship between metabolically active Fe(III)-reducing bacteria and the iron(III)-(oxyhydr)oxide that they were respiring. NanoSIMS imaging showed cells of G. sulfurreducens were co-located with the iron(III)-(oxyhydr)oxide surface and were significantly more 13C-enriched compared to cells located away from the mineral, consistent with Geobacter species requiring direct contact with an extracellular electron acceptor to support growth. There was no such intimate relationship between 13C-enriched S. ANA3 and the iron(III)-(oxyhydr)oxide surface, consistent with Shewanella species being able to reduce Fe(III) indirectly using a secreted endogenous mediator. Some differences were observed in the amount of As relative to Fe in the local environment of G. sulfurreducens compared to the bulk mineral, highlighting the usefulness of this type of analysis for probing interactions between microbial cells and Fe-trace metal distributions in biogeochemical experiments.
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Affiliation(s)
- Laura Newsome
- Williamson Research Centre, School of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK
| | - Rebeca Lopez Adams
- Williamson Research Centre, School of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK
| | - Helen F Downie
- Williamson Research Centre, School of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK
| | - Katie L Moore
- School of Materials, University of Manchester, Manchester, M13 9PL, UK.,Photon Science Institute, University of Manchester, Manchester, M13 9PL, UK
| | - Jonathan R Lloyd
- Williamson Research Centre, School of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK
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Zhao J, Wang L, Tang L, Ren R, You W, Farooq R, Wang Z, Zhang Y. Changes in bacterial community structure and humic acid composition in response to enhanced extracellular electron transfer process in coastal sediment. Arch Microbiol 2019; 201:897-906. [DOI: 10.1007/s00203-019-01659-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 02/25/2019] [Accepted: 04/10/2019] [Indexed: 12/24/2022]
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9
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Electro-Microbiology as a Promising Approach Towards Renewable Energy and Environmental Sustainability. ENERGIES 2018. [DOI: 10.3390/en11071822] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Microbial electrochemical technologies provide sustainable wastewater treatment and energy production. Despite significant improvements in the power output of microbial fuel cells (MFCs), this technology is still far from practical applications. Extracting electrical energy and harvesting valuable products by electroactive bacteria (EAB) in bioelectrochemical systems (BESs) has emerged as an innovative approach to address energy and environmental challenges. Thus, maximizing power output and resource recovery is highly desirable for sustainable systems. Insights into the electrode-microbe interactions may help to optimize the performance of BESs for envisioned applications, and further validation by bioelectrochemical techniques is a prerequisite to completely understand the electro-microbiology. This review summarizes various extracellular electron transfer mechanisms involved in BESs. The significant role of characterization techniques in the advancement of the electro-microbiology field is discussed. Finally, diverse applications of BESs, such as resource recovery, and contributions to the pursuit of a more sustainable society are also highlighted.
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Katuri KP, Kalathil S, Ragab A, Bian B, Alqahtani MF, Pant D, Saikaly PE. Dual-Function Electrocatalytic and Macroporous Hollow-Fiber Cathode for Converting Waste Streams to Valuable Resources Using Microbial Electrochemical Systems. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1707072. [PMID: 29707854 DOI: 10.1002/adma.201707072] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2017] [Indexed: 06/08/2023]
Abstract
Dual-function electrocatalytic and macroporous hollow-fiber cathodes are recently proposed as promising advanced material for maximizing the conversion of waste streams such as wastewater and waste CO2 to valuable resources (e.g., clean freshwater, energy, value-added chemicals) in microbial electrochemical systems. The first part of this progress report reviews recent developments in this type of cathode architecture for the simultaneous recovery of clean freshwater and energy from wastewater. Critical insights are provided on suitable materials for fabricating these cathodes, as well as addressing some challenges in the fabrication process with proposed strategies to overcome them. The second and complementary part of the progress report highlights how the unique features of this cathode architecture can solve one of the intrinsic bottlenecks (gas-liquid mass transfer limitation) in the application of microbial electrochemical systems for CO2 reduction to value-added products. Strategies to further improve the availability of CO2 to microbial catalysts on the cathode are proposed. The importance of understanding microbe-cathode interactions, as well as electron transfer mechanisms at the cathode-cell and cell-cell interface to better design dual-function macroporous hollow-fiber cathodes, is critically discussed with insights on how the choice of material is important in facilitating direct electron transfer versus mediated electron transfer.
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Affiliation(s)
- Krishna P Katuri
- Biological and Environmental Sciences and Engineering (BESE) Division, Water Desalination and Reuse Center (WDRC), King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia
| | - Shafeer Kalathil
- Biological and Environmental Sciences and Engineering (BESE) Division, Water Desalination and Reuse Center (WDRC), King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia
| | - Ala'a Ragab
- Biological and Environmental Sciences and Engineering (BESE) Division, Water Desalination and Reuse Center (WDRC), King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia
| | - Bin Bian
- Biological and Environmental Sciences and Engineering (BESE) Division, Water Desalination and Reuse Center (WDRC), King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia
| | - Manal F Alqahtani
- Biological and Environmental Sciences and Engineering (BESE) Division, Water Desalination and Reuse Center (WDRC), King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia
| | - Deepak Pant
- Separation and Conversion Technology, Flemish Institute for Technological Research (VITO), Boeretang 200, Mol, 2400, Belgium
| | - Pascal E Saikaly
- Biological and Environmental Sciences and Engineering (BESE) Division, Water Desalination and Reuse Center (WDRC), King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia
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11
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Danchin A, Sekowska A, Noria S. Functional Requirements in the Program and the Cell Chassis for Next-Generation Synthetic Biology. Synth Biol (Oxf) 2018. [DOI: 10.1002/9783527688104.ch5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Antoine Danchin
- Institute of Cardiometabolism and Nutrition; 47 boulevard de l'Hôpital Paris 75013 France
| | - Agnieszka Sekowska
- Institute of Cardiometabolism and Nutrition; 47 boulevard de l'Hôpital Paris 75013 France
| | - Stanislas Noria
- Fondation Fourmentin-Guilbert; 2 avenue du Pavé Neuf Noisy le Grand 93160 France
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Huang B, Gao S, Xu Z, He H, Pan X. The Functional Mechanisms and Application of Electron Shuttles in Extracellular Electron Transfer. Curr Microbiol 2017; 75:99-106. [PMID: 29127455 DOI: 10.1007/s00284-017-1386-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2017] [Accepted: 10/30/2017] [Indexed: 12/01/2022]
Abstract
Electron shuttles extensively exist in various environments. Some kinds of organic substances can be applied by microorganisms to produce electrons, and then the electrons can be transferred to other substances or microorganisms through electron shuttles, resulting in coexistence and interaction of diverse species of microbes. In this review, the functional mechanisms of extracellular electron transfer mediated by different electron shuttles are described. And different subtypes as well as the application of electron shuttles in microbial degradation of pollutants, microbial electricity, and the promotion of energy generation are also discussed. Summary results show that extracellular electron transfer is based on the electrogenesis microorganism with the structure of cytochromes or pili. Materials were usually used in long-distance electron transfer because of their widespread presence and abundance. Therefore, the review is beneficial to perceive the pathways of extracellular electron transfer mediated by electron shuttles and explore the contribution of different electron shuttles in extracellular electron transfer.
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Affiliation(s)
- Bin Huang
- Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, Yunnan, People's Republic of China
| | - Shumei Gao
- Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, Yunnan, People's Republic of China
| | - Zhixiang Xu
- Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, Yunnan, People's Republic of China
| | - Huan He
- Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, Yunnan, People's Republic of China
| | - Xuejun Pan
- Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming, 650500, Yunnan, People's Republic of China.
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13
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Affiliation(s)
- Derek R. Lovley
- Department of Microbiology, University of Massachusetts, Amherst, Massachusetts 01003
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14
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Ha PT, Lindemann SR, Shi L, Dohnalkova AC, Fredrickson JK, Madigan MT, Beyenal H. Syntrophic anaerobic photosynthesis via direct interspecies electron transfer. Nat Commun 2017; 8:13924. [PMID: 28067226 PMCID: PMC5227917 DOI: 10.1038/ncomms13924] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 11/11/2016] [Indexed: 11/29/2022] Open
Abstract
Microbial phototrophs, key primary producers on Earth, use H2O, H2, H2S and other reduced inorganic compounds as electron donors. Here we describe a form of metabolism linking anoxygenic photosynthesis to anaerobic respiration that we call ‘syntrophic anaerobic photosynthesis'. We show that photoautotrophy in the green sulfur bacterium Prosthecochloris aestaurii can be driven by either electrons from a solid electrode or acetate oxidation via direct interspecies electron transfer from a heterotrophic partner bacterium, Geobacter sulfurreducens. Photosynthetic growth of P. aestuarii using reductant provided by either an electrode or syntrophy is robust and light-dependent. In contrast, P. aestuarii does not grow in co-culture with a G. sulfurreducens mutant lacking a trans-outer membrane porin-cytochrome protein complex required for direct intercellular electron transfer. Syntrophic anaerobic photosynthesis is therefore a carbon cycling process that could take place in anoxic environments. This process could be exploited for biotechnological applications, such as waste treatment and bioenergy production, using engineered phototrophic microbial communities. Direct interspecies electron transfer has been shown in methane-producing communities, but it is unknown how widespread this mechanism is. Here, Ha et al. show that anoxygenic photosynthesis can be driven by direct electron transfer from a heterotrophic partner bacterium.
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Affiliation(s)
- Phuc T Ha
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99164, USA
| | - Stephen R Lindemann
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99354, USA
| | - Liang Shi
- Department of Biological Sciences and Technology, School of Environmental Studies, China University of Geoscience, Wuhan, Hubei 430074, China
| | - Alice C Dohnalkova
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99354, USA
| | - James K Fredrickson
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99354, USA
| | - Michael T Madigan
- Department of Microbiology, Southern Illinois University, Carbondale, Illinois 62901, USA
| | - Haluk Beyenal
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99164, USA
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15
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Extracellular Electron Transfer and Biosensors. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2017; 167:15-38. [PMID: 29071406 DOI: 10.1007/10_2017_34] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
This chapter summarizes in the beginning our current understanding of extracellular electron transport processes in organisms belonging to the genera Shewanella and Geobacter. Organisms belonging to these genera developed strategies to transport respiratory electrons to the cell surface that are defined by modules of which some seem to be rather unique for one or the other genus while others are similar. We use this overview regarding our current knowledge of extracellular electron transfer to explain the physiological interaction of microorganisms in direct interspecies electron transfer, a process in which one organism basically comprises the electron acceptor for another microbe and that depends also on extended electron transport chains. This analysis of mechanisms for the transport of respiratory electrons to insoluble electron acceptors ends with an overview of questions that remain so far unanswered. Moreover, we use the description of the biochemistry of extracellular electron transport to explain the fundamentals of biosensors based on this process and give an overview regarding their status of development and applicability. Graphical Abstract.
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16
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Shu C, Xiao K, Yan Q, Sun X. Comparative Analysis of Type IV Pilin in Desulfuromonadales. Front Microbiol 2016; 7:2080. [PMID: 28066394 PMCID: PMC5174107 DOI: 10.3389/fmicb.2016.02080] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 12/08/2016] [Indexed: 12/24/2022] Open
Abstract
During anaerobic respiration, the bacteria Geobacter sulfurreducens can transfer electrons to extracellular electron accepters through its pilus. G. sulfurreducens pili have been reported to have metallic-like conductivity that is similar to doped organic semiconductors. To study the characteristics and origin of conductive pilin proteins found in the pilus structure, their genetic, structural, and phylogenetic properties were analyzed. The genetic relationships, and conserved structures and sequences that were obtained were used to predict the evolution of the pilins. Homologous genes that encode conductive pilin were found using PilFind and Cluster. Sequence characteristics and protein tertiary structures were analyzed with MAFFT and QUARK, respectively. The origin of conductive pilins was explored by building a phylogenetic tree. Truncation is a characteristic of conductive pilin. The structures of truncated pilins and their accompanying proteins were found to be similar to the N-terminal and C-terminal ends of full-length pilins respectively. The emergence of the truncated pilins can probably be ascribed to the evolutionary pressure of their extracellular electron transporting function. Genes encoding truncated pilins and proteins similar to the C-terminal of full-length pilins, which contain a group of consecutive anti-parallel beta-sheets, are adjacent in bacterial genomes. According to the genetic, structure, and phylogenetic analyses performed in this study, we inferred that the truncated pilins and their accompanying proteins probably evolved from full-length pilins by gene fission through duplication, degeneration, and separation. These findings provide new insights about the molecular mechanisms involved in long-range electron transport along the conductive pili of Geobacter species.
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Affiliation(s)
| | | | | | - Xiao Sun
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast UniversityNanjing, China
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17
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Casalini S, Berto M, Kovtun A, Operamolla A, Di Rocco G, Facci P, Liscio A, Farinola GM, Borsari M, Bortolotti CA. Surface Immobilized His-tagged Azurin as a Model Interface for the Investigation of Vectorial Electron Transfer in Biological Systems. Electrochim Acta 2015. [DOI: 10.1016/j.electacta.2015.07.156] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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18
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Iron management and production of electricity by microorganisms. Appl Microbiol Biotechnol 2015; 99:8329-36. [DOI: 10.1007/s00253-015-6897-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 07/27/2015] [Accepted: 07/30/2015] [Indexed: 10/23/2022]
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19
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The Confluence of Heavy Metal Biooxidation and Heavy Metal Resistance: Implications for Bioleaching by Extreme Thermoacidophiles. MINERALS 2015. [DOI: 10.3390/min5030397] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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20
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Functional environmental proteomics: elucidating the role of a c-type cytochrome abundant during uranium bioremediation. ISME JOURNAL 2015; 10:310-20. [PMID: 26140532 DOI: 10.1038/ismej.2015.113] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Revised: 05/27/2015] [Accepted: 06/04/2015] [Indexed: 01/29/2023]
Abstract
Studies with pure cultures of dissimilatory metal-reducing microorganisms have demonstrated that outer-surface c-type cytochromes are important electron transfer agents for the reduction of metals, but previous environmental proteomic studies have typically not recovered cytochrome sequences from subsurface environments in which metal reduction is important. Gel-separation, heme-staining and mass spectrometry of proteins in groundwater from in situ uranium bioremediation experiments identified a putative c-type cytochrome, designated Geobacter subsurface c-type cytochrome A (GscA), encoded within the genome of strain M18, a Geobacter isolate previously recovered from the site. Homologs of GscA were identified in the genomes of other Geobacter isolates in the phylogenetic cluster known as subsurface clade 1, which predominates in a diversity of Fe(III)-reducing subsurface environments. Most of the gscA sequences recovered from groundwater genomic DNA clustered in a tight phylogenetic group closely related to strain M18. GscA was most abundant in groundwater samples in which Geobacter sp. predominated. Expression of gscA in a strain of Geobacter sulfurreducens that lacked the gene for the c-type cytochrome OmcS, thought to facilitate electron transfer from conductive pili to Fe(III) oxide, restored the capacity for Fe(III) oxide reduction. Atomic force microscopy provided evidence that GscA was associated with the pili. These results demonstrate that a c-type cytochrome with an apparent function similar to that of OmcS is abundant when Geobacter sp. are abundant in the subsurface, providing insight into the mechanisms for the growth of subsurface Geobacter sp. on Fe(III) oxide and suggesting an approach for functional analysis of other Geobacter proteins found in the subsurface.
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21
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Pohlschroder M, Esquivel RN. Archaeal type IV pili and their involvement in biofilm formation. Front Microbiol 2015; 6:190. [PMID: 25852657 PMCID: PMC4371748 DOI: 10.3389/fmicb.2015.00190] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Accepted: 02/20/2015] [Indexed: 12/13/2022] Open
Abstract
Type IV pili are ancient proteinaceous structures present on the cell surface of species in nearly all bacterial and archaeal phyla. These filaments, which are required for a diverse array of important cellular processes, are assembled employing a conserved set of core components. While type IV pilins, the structural subunits of pili, share little sequence homology, their signal peptides are structurally conserved allowing for in silico prediction. Recently, in vivo studies in model archaea representing the euryarchaeal and crenarchaeal kingdoms confirmed that several of these pilins are incorporated into type IV adhesion pili. In addition to facilitating surface adhesion, these in vivo studies also showed that several predicted pilins are required for additional functions that are critical to biofilm formation. Examples include the subunits of Sulfolobus acidocaldarius Ups pili, which are induced by exposure to UV light and promote cell aggregation and conjugation, and a subset of the Haloferax volcanii adhesion pilins, which play a critical role in microcolony formation while other pilins inhibit this process. The recent discovery of novel pilin functions such as the ability of haloarchaeal adhesion pilins to regulate swimming motility may point to novel regulatory pathways conserved across prokaryotic domains. In this review, we will discuss recent advances in our understanding of the functional roles played by archaeal type IV adhesion pili and their subunits, with particular emphasis on their involvement in biofilm formation.
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Affiliation(s)
| | - Rianne N Esquivel
- Department of Biology, University of Pennsylvania Philadelphia, PA, USA
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22
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Tikhonova TV, Popov VO. Structural and functional studies of multiheme cytochromes c involved in extracellular electron transport in bacterial dissimilatory metal reduction. BIOCHEMISTRY (MOSCOW) 2015; 79:1584-601. [DOI: 10.1134/s0006297914130094] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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23
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Semenec L, E Franks A. Delving through electrogenic biofilms: from anodes to cathodes to microbes. AIMS BIOENGINEERING 2015. [DOI: 10.3934/bioeng.2015.3.222] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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24
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Zhang E, Cai Y, Luo Y, Piao Z. Riboflavin-shuttled extracellular electron transfer from Enterococcus faecalis to electrodes in microbial fuel cells. Can J Microbiol 2014; 60:753-9. [PMID: 25345758 DOI: 10.1139/cjm-2014-0389] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Great attention has been focused on Gram-negative bacteria in the application of microbial fuel cells. In this study, the Gram-positive bacterium Enterococcus faecalis was employed in microbial fuel cells. Bacterial biofilms formed by E. faecalis ZER6 were investigated with respect to electricity production through the riboflavin-shuttled extracellular electron transfer. Trace riboflavin was shown to be essential for transferring electrons derived from the oxidation of glucose outside the peptidoglycan layer in the cell wall of E. faecalis biofilms formed on the surface of electrodes, in the absence of other potential electron mediators (e.g., yeast extract).
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Affiliation(s)
- Enren Zhang
- a Department of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou City 225002, People's Republic of China
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25
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Sharma M, Bajracharya S, Gildemyn S, Patil SA, Alvarez-Gallego Y, Pant D, Rabaey K, Dominguez-Benetton X. A critical revisit of the key parameters used to describe microbial electrochemical systems. Electrochim Acta 2014. [DOI: 10.1016/j.electacta.2014.02.111] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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26
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Melton ED, Stief P, Behrens S, Kappler A, Schmidt C. High spatial resolution of distribution and interconnections between Fe- and N-redox processes in profundal lake sediments. Environ Microbiol 2014; 16:3287-303. [DOI: 10.1111/1462-2920.12566] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 07/05/2014] [Indexed: 11/29/2022]
Affiliation(s)
- Emily D. Melton
- Geomicrobiology; Center for Applied Geosciences; University of Tübingen; Tübingen 72076 Germany
| | - Peter Stief
- Microsensor Research Group; Max Planck Institute for Marine Microbiology; Bremen Germany
| | - Sebastian Behrens
- Geomicrobiology; Center for Applied Geosciences; University of Tübingen; Tübingen 72076 Germany
| | - Andreas Kappler
- Geomicrobiology; Center for Applied Geosciences; University of Tübingen; Tübingen 72076 Germany
| | - Caroline Schmidt
- Geomicrobiology; Center for Applied Geosciences; University of Tübingen; Tübingen 72076 Germany
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27
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Daidone I, Paltrinieri L, Amadei A, Battistuzzi G, Sola M, Borsari M, Bortolotti CA. Unambiguous Assignment of Reduction Potentials in Diheme Cytochromes. J Phys Chem B 2014; 118:7554-7560. [DOI: 10.1021/jp506017a] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Isabella Daidone
- Department
of Physical and Chemical Sciences, University of L’Aquila, via
Vetoio (Coppito 1), 67010 L’Aquila, Italy
| | - Licia Paltrinieri
- Department
of Chemical and Geological Sciences, University of Modena and Reggio Emilia, via Campi 183, 41125 Modena, Italy
| | - Andrea Amadei
- Department
of Chemical Sciences and Technologies, University of Rome “Tor Vergata”, via della Ricerca Scientifica 1, 00133 Rome, Italy
| | - Gianantonio Battistuzzi
- Department
of Chemical and Geological Sciences, University of Modena and Reggio Emilia, via Campi 183, 41125 Modena, Italy
| | - Marco Sola
- Department
of Life Sciences, University of Modena and Reggio Emilia, via Campi
183, 41125 Modena, Italy
- CNR-Nano Institute
of Nanoscience, via Campi 213/A, 41125 Modena, Italy
| | - Marco Borsari
- Department
of Chemical and Geological Sciences, University of Modena and Reggio Emilia, via Campi 183, 41125 Modena, Italy
| | - Carlo Augusto Bortolotti
- Department
of Life Sciences, University of Modena and Reggio Emilia, via Campi
183, 41125 Modena, Italy
- CNR-Nano Institute
of Nanoscience, via Campi 213/A, 41125 Modena, Italy
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28
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Shrestha PM, Rotaru AE. Plugging in or going wireless: strategies for interspecies electron transfer. Front Microbiol 2014; 5:237. [PMID: 24904551 PMCID: PMC4032928 DOI: 10.3389/fmicb.2014.00237] [Citation(s) in RCA: 119] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Accepted: 04/30/2014] [Indexed: 11/13/2022] Open
Abstract
Interspecies exchange of electrons enables a diversity of microbial communities to gain energy from reactions that no one microbe can catalyze. The first recognized strategies for interspecies electron transfer were those that relied on chemical intermediates that are recycled through oxidized and reduced forms. Well-studied examples are interspecies H2 transfer and the cycling of sulfur intermediates in anaerobic photosynthetic communities. Direct interspecies electron transfer (DIET) in which two species establish electrical contact is an alternative. Electrical contacts documented to date include electrically conductive pili, as well as conductive iron minerals and conductive carbon moieties such as activated carbon and biochar. Interspecies electron transfer is central to the functioning of methane-producing microbial communities. The importance of interspecies H2 transfer in many methanogenic communities is clear, but under some circumstances DIET predominates. It is expected that further mechanistic studies and broadening investigations to a wider range of environments will help elucidate the factors that favor specific forms of interspecies electron exchange under different environmental conditions.
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Affiliation(s)
- Pravin Malla Shrestha
- Department of Microbiology, University of MassachusettsAmherst, MA, USA
- Energy Biosciences Institute, University of CaliforniaBerkeley, CA, USA
| | - Amelia-Elena Rotaru
- Nordic Center for Earth Evolution, University of Southern DenmarkOdense, Denmark
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29
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Going wireless: Fe(III) oxide reduction without pili by Geobacter sulfurreducens strain JS-1. Appl Environ Microbiol 2014; 80:4331-40. [PMID: 24814783 DOI: 10.1128/aem.01122-14] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previous studies have suggested that the conductive pili of Geobacter sulfurreducens are essential for extracellular electron transfer to Fe(III) oxides and for optimal long-range electron transport through current-producing biofilms. The KN400 strain of G. sulfurreducens reduces poorly crystalline Fe(III) oxide more rapidly than the more extensively studied DL-1 strain. Deletion of the gene encoding PilA, the structural pilin protein, in strain KN400 inhibited Fe(III) oxide reduction. However, low rates of Fe(III) reduction were detected after extended incubation (>30 days) in the presence of Fe(III) oxide. After seven consecutive transfers, the PilA-deficient strain adapted to reduce Fe(III) oxide as fast as the wild type. Microarray, whole-genome resequencing, proteomic, and gene deletion studies indicated that this adaptation was associated with the production of larger amounts of the c-type cytochrome PgcA, which was released into the culture medium. It is proposed that the extracellular cytochrome acts as an electron shuttle, promoting electron transfer from the outer cell surface to Fe(III) oxides. The adapted PilA-deficient strain competed well with the wild-type strain when both were grown together on Fe(III) oxide. However, when 50% of the culture medium was replaced with fresh medium every 3 days, the wild-type strain outcompeted the adapted strain. A possible explanation for this is that the necessity to produce additional PgcA, to replace the PgcA being continually removed, put the adapted strain at a competitive disadvantage, similar to the apparent selection against electron shuttle-producing Fe(III) reducers in many anaerobic soils and sediments. Despite increased extracellular cytochrome production, the adapted PilA-deficient strain produced low levels of current, consistent with the concept that long-range electron transport through G. sulfurreducens biofilms is more effective via pili.
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30
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Liu F, Rotaru AE, Shrestha PM, Malvankar NS, Nevin KP, Lovley DR. Magnetite compensates for the lack of a pilin-associatedc-type cytochrome in extracellular electron exchange. Environ Microbiol 2014; 17:648-55. [DOI: 10.1111/1462-2920.12485] [Citation(s) in RCA: 238] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2013] [Accepted: 04/04/2014] [Indexed: 11/28/2022]
Affiliation(s)
- Fanghua Liu
- Department of Microbiology; University of Massachusetts; Amherst MA 01003 USA
- Key Laboratory of Coastal Biology and Utilization; Yantai Institute of Coastal Zone Research; Chinese Academy of Sciences; Yantai Shandong 264003 China
| | - Amelia-Elena Rotaru
- Department of Microbiology; University of Massachusetts; Amherst MA 01003 USA
| | - Pravin M. Shrestha
- Department of Microbiology; University of Massachusetts; Amherst MA 01003 USA
| | - Nikhil S. Malvankar
- Department of Microbiology; University of Massachusetts; Amherst MA 01003 USA
| | - Kelly P. Nevin
- Department of Microbiology; University of Massachusetts; Amherst MA 01003 USA
| | - Derek R. Lovley
- Department of Microbiology; University of Massachusetts; Amherst MA 01003 USA
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31
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A Geobacter sulfurreducens strain expressing pseudomonas aeruginosa type IV pili localizes OmcS on pili but is deficient in Fe(III) oxide reduction and current production. Appl Environ Microbiol 2013; 80:1219-24. [PMID: 24296506 DOI: 10.1128/aem.02938-13] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The conductive pili of Geobacter species play an important role in electron transfer to Fe(III) oxides, in long-range electron transport through current-producing biofilms, and in direct interspecies electron transfer. Although multiple lines of evidence have indicated that the pili of Geobacter sulfurreducens have a metal-like conductivity, independent of the presence of c-type cytochromes, this claim is still controversial. In order to further investigate this phenomenon, a strain of G. sulfurreducens, designated strain PA, was constructed in which the gene for the native PilA, the structural pilin protein, was replaced with the PilA gene of Pseudomonas aeruginosa PAO1. Strain PA expressed and properly assembled P. aeruginosa PilA subunits into pili and exhibited a profile of outer surface c-type cytochromes similar to that of a control strain expressing the G. sulfurreducens PilA. Surprisingly, the strain PA pili were decorated with the c-type cytochrome OmcS in a manner similar to the control strain. However, the strain PA pili were 14-fold less conductive than the pili of the control strain, and strain PA was severely impaired in Fe(III) oxide reduction and current production. These results demonstrate that the presence of OmcS on pili is not sufficient to confer conductivity to pili and suggest that there are unique structural features of the G. sulfurreducens PilA that are necessary for conductivity.
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32
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Reconstitution of supramolecular organization involved in energy metabolism at electrochemical interfaces for biosensing and bioenergy production. Anal Bioanal Chem 2013; 406:1011-27. [DOI: 10.1007/s00216-013-7465-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 10/01/2013] [Accepted: 10/25/2013] [Indexed: 12/26/2022]
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33
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Shrestha PM, Rotaru AE, Aklujkar M, Liu F, Shrestha M, Summers ZM, Malvankar N, Flores DC, Lovley DR. Syntrophic growth with direct interspecies electron transfer as the primary mechanism for energy exchange. ENVIRONMENTAL MICROBIOLOGY REPORTS 2013; 5:904-10. [PMID: 24249299 DOI: 10.1111/1758-2229.12093] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 08/07/2013] [Indexed: 05/26/2023]
Abstract
Direct interspecies electron transfer (DIET) through biological electrical connections is an alternative to interspecies H2 transfer as a mechanism for electron exchange in syntrophic cultures. However, it has not previously been determined whether electrons received via DIET yield energy to support cell growth. In order to investigate this, co-cultures of Geobacter metallireducens, which can transfer electrons to wild-type G. sulfurreducens via DIET, were established with a citrate synthase-deficient G. sulfurreducens strain that can receive electrons for respiration through DIET only. In a medium with ethanol as the electron donor and fumarate as the electron acceptor, co-cultures with the citrate synthase-deficient G. sulfurreducens strain metabolized ethanol as fast as co-cultures with wild-type, but the acetate that G. metallireducens generated from ethanol oxidation accumulated. The lack of acetate metabolism resulted in less fumarate reduction and lower cell abundance of G. sulfurreducens. RNAseq analysis of transcript abundance was consistent with a lack of acetate metabolism in G. sulfurreducens and revealed gene expression levels for the uptake hydrogenase, formate dehydrogenase, the pilus-associated c-type cytochrome OmcS and pili consistent with electron transfer via DIET. These results suggest that electrons transferred via DIET can serve as the sole energy source to support anaerobic respiration.
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34
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Reardon PN, Mueller KT. Structure of the type IVa major pilin from the electrically conductive bacterial nanowires of Geobacter sulfurreducens. J Biol Chem 2013; 288:29260-6. [PMID: 23965997 DOI: 10.1074/jbc.m113.498527] [Citation(s) in RCA: 91] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Several species of δ proteobacteria are capable of reducing insoluble metal oxides as well as other extracellular electron acceptors. These bacteria play a critical role in the cycling of minerals in subsurface environments, sediments, and groundwater. In some species of bacteria such as Geobacter sulfurreducens, the transport of electrons is proposed to be facilitated by filamentous fibers that are referred to as bacterial nanowires. These nanowires are polymeric assemblies of proteins belonging to the type IVa family of pilin proteins and are mainly comprised of one subunit protein, PilA. Here, we report the high resolution solution NMR structure of the PilA protein from G. sulfurreducens determined in detergent micelles. The protein is >85% α-helical and exhibits similar architecture to the N-terminal regions of other non-conductive type IVa pilins. The detergent micelle interacts with the first 21 amino acids of the protein, indicating that this region likely associates with the bacterial inner membrane prior to fiber formation. A model of the G. sulfurreducens pilus fiber is proposed based on docking of this structure into the fiber model of the type IVa pilin from Neisseria gonorrhoeae. This model provides insight into the organization of aromatic amino acids that are important for electrical conduction.
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Affiliation(s)
- Patrick N Reardon
- From the Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99354 and
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35
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U(VI) reduction by diverse outer surface c-type cytochromes of Geobacter sulfurreducens. Appl Environ Microbiol 2013; 79:6369-74. [PMID: 23934497 DOI: 10.1128/aem.02551-13] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Early studies with Geobacter sulfurreducens suggested that outer-surface c-type cytochromes might play a role in U(VI) reduction, but it has recently been suggested that there is substantial U(VI) reduction at the surface of the electrically conductive pili known as microbial nanowires. This phenomenon was further investigated. A strain of G. sulfurreducens, known as Aro-5, which produces pili with substantially reduced conductivity reduced U(VI) nearly as well as the wild type, as did a strain in which the gene for PilA, the structural pilin protein, was deleted. In order to reduce rates of U(VI) reduction to levels less than 20% of the wild-type rates, it was necessary to delete the genes for the five most abundant outer surface c-type cytochromes of G. sulfurreducens. X-ray absorption near-edge structure spectroscopy demonstrated that whereas 83% ± 10% of the uranium associated with wild-type cells correspond to U(IV) after 4 h of incubation, with the quintuple mutant, 89% ± 10% of uranium was U(VI). Transmission electron microscopy and X-ray energy dispersion spectroscopy revealed that wild-type cells did not precipitate uranium along pili as previously reported, but U(IV) was precipitated at the outer cell surface. These findings are consistent with those of previous studies, which have suggested that G. sulfurreducens requires outer-surface c-type cytochromes but not pili for the reduction of soluble extracellular electron acceptors.
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36
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Electron transport at the microbe-mineral interface: a synthesis of current research challenges. Biochem Soc Trans 2013; 40:1163-6. [PMID: 23176448 DOI: 10.1042/bst20120242] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Many bacterial and archaeal species can couple growth to the respiratory reduction or oxidation of insoluble mineral oxides of transition metals. These solid substrates are abundant electron sinks and sources for life on Earth, but, since they are insoluble in water, they cannot enter the bacterial cells. So, to exploit these electron sinks and sources, specific respiratory electron-transfer mechanisms must overcome the physical limitations associated with electron transfer between a microbe and extracellular metal oxides. Recent microbiological, geochemical, biochemical, spectroscopic and structural work is beginning to shed light on the molecular mechanism and impacts of electron transfer at the microbe-mineral interface from a nanometre to kilometre scale. The research field is attracting attention in applied quarters from those with interests in nanowires, microbial fuel cells, bioremediation and microbial cell factories.
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Aromatic amino acids required for pili conductivity and long-range extracellular electron transport in Geobacter sulfurreducens. mBio 2013; 4:e00105-13. [PMID: 23481602 PMCID: PMC3604773 DOI: 10.1128/mbio.00105-13] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
It has been proposed that Geobacter sulfurreducens requires conductive pili for long-range electron transport to Fe(III) oxides and for high-density current production in microbial fuel cells. In order to investigate this further, we constructed a strain of G. sulfurreducens, designated Aro-5, which produced pili with diminished conductivity. This was accomplished by modifying the amino acid sequence of PilA, the structural pilin protein. An alanine was substituted for each of the five aromatic amino acids in the carboxyl terminus of PilA, the region in which G. sulfurreducens PilA differs most significantly from the PilAs of microorganisms incapable of long-range extracellular electron transport. Strain Aro-5 produced pili that were properly decorated with the multiheme c-type cytochrome OmcS, which is essential for Fe(III) oxide reduction. However, pili preparations of the Aro-5 strain had greatly diminished conductivity and Aro-5 cultures were severely limited in their capacity to reduce Fe(III) compared to the control strain. Current production of the Aro-5 strain, with a graphite anode serving as the electron acceptor, was less than 10% of that of the control strain. The conductivity of the Aro-5 biofilms was 10-fold lower than the control strain’s. These results demonstrate that the pili of G. sulfurreducens must be conductive in order for the cells to be effective in extracellular long-range electron transport. Extracellular electron transfer by Geobacter species plays an important role in the biogeochemistry of soils and sediments and has a number of bioenergy applications. For example, microbial reduction of Fe(III) oxide is one of the most geochemically significant processes in anaerobic soils, aquatic sediments, and aquifers, and Geobacter organisms are often abundant in such environments. Geobacter sulfurreducens produces the highest current densities of any known pure culture, and close relatives are often the most abundant organisms colonizing anodes in microbial fuel cells that harvest electricity from wastewater or aquatic sediments. The finding that a strain of G. sulfurreducens that produces pili with low conductivity is limited in these extracellular electron transport functions provides further insight into these environmentally significant processes.
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Bonanni PS, Massazza D, Busalmen JP. Stepping stones in the electron transport from cells to electrodes in Geobacter sulfurreducens biofilms. Phys Chem Chem Phys 2013; 15:10300-6. [DOI: 10.1039/c3cp50411e] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Outer cell surface components essential for Fe(III) oxide reduction by Geobacter metallireducens. Appl Environ Microbiol 2012. [PMID: 23183974 DOI: 10.1128/aem.02954-12] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Geobacter species are important Fe(III) reducers in a diversity of soils and sediments. Mechanisms for Fe(III) oxide reduction have been studied in detail in Geobacter sulfurreducens, but a number of the most thoroughly studied outer surface components of G. sulfurreducens, particularly c-type cytochromes, are not well conserved among Geobacter species. In order to identify cellular components potentially important for Fe(III) oxide reduction in Geobacter metallireducens, gene transcript abundance was compared in cells grown on Fe(III) oxide or soluble Fe(III) citrate with whole-genome microarrays. Outer-surface cytochromes were also identified. Deletion of genes for c-type cytochromes that had higher transcript abundance during growth on Fe(III) oxides and/or were detected in the outer-surface protein fraction identified six c-type cytochrome genes, that when deleted removed the capacity for Fe(III) oxide reduction. Several of the c-type cytochromes which were essential for Fe(III) oxide reduction in G. metallireducens have homologs in G. sulfurreducens that are not important for Fe(III) oxide reduction. Other genes essential for Fe(III) oxide reduction included a gene predicted to encode an NHL (Ncl-1-HT2A-Lin-41) repeat-containing protein and a gene potentially involved in pili glycosylation. Genes associated with flagellum-based motility, chemotaxis, and pili had higher transcript abundance during growth on Fe(III) oxide, consistent with the previously proposed importance of these components in Fe(III) oxide reduction. These results demonstrate that there are similarities in extracellular electron transfer between G. metallireducens and G. sulfurreducens but the outer-surface c-type cytochromes involved in Fe(III) oxide reduction are different.
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