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Lin T, Ding W, Zhang D, You Z, Yang Y, Li F, Xu D, Lovley DR, Song H. Expression of filaments of the Geobacter extracellular cytochrome OmcS in Shewanella oneidensis. Biotechnol Bioeng 2024; 121:2002-2012. [PMID: 38555482 DOI: 10.1002/bit.28702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 03/01/2024] [Accepted: 03/11/2024] [Indexed: 04/02/2024]
Abstract
The physiological role of Geobacter sulfurreducens extracellular cytochrome filaments is a matter of debate and the development of proposed electronic device applications of cytochrome filaments awaits methods for large-scale cytochrome nanowire production. Functional studies in G. sulfurreducens are stymied by the broad diversity of redox-active proteins on the outer cell surface and the redundancy and plasticity of extracellular electron transport routes. G. sulfurreducens is a poor chassis for producing cytochrome nanowires for electronics because of its slow, low-yield, anaerobic growth. Here we report that filaments of the G. sulfurreducens cytochrome OmcS can be heterologously expressed in Shewanella oneidensis. Multiple lines of evidence demonstrated that a strain of S. oneidensis, expressing the G. sulfurreducens OmcS gene on a plasmid, localized OmcS on the outer cell surface. Atomic force microscopy revealed filaments with the unique morphology of OmcS filaments emanating from cells. Electron transfer to OmcS appeared to require a functional outer-membrane porin-cytochrome conduit. The results suggest that S. oneidensis, which grows rapidly to high culture densities under aerobic conditions, may be suitable for the development of a chassis for producing cytochrome nanowires for electronics applications and may also be a good model microbe for elucidating cytochrome filament function in anaerobic extracellular electron transfer.
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Affiliation(s)
- Tong Lin
- Frontiers Science Centre for Synthetic Biology (Ministry of Education), and Key Laboratory of Systems Bioengineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
- College of Life Science, Langfang Normal University, Langfang, Hebei, China
| | - Wenqi Ding
- Frontiers Science Centre for Synthetic Biology (Ministry of Education), and Key Laboratory of Systems Bioengineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
| | - Danni Zhang
- Shenyang National Laboratory for Materials Science, Northeastern University, Shenyang, China
- Electrobiomaterials Institute, Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang, China
| | - Zixuan You
- Frontiers Science Centre for Synthetic Biology (Ministry of Education), and Key Laboratory of Systems Bioengineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
| | - Yun Yang
- Beijing Advanced Innovation Centre for Biomedical Engineering, Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Engineering Medicine, Beihang University, Beijing, China
| | - Feng Li
- Frontiers Science Centre for Synthetic Biology (Ministry of Education), and Key Laboratory of Systems Bioengineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
| | - Dake Xu
- Shenyang National Laboratory for Materials Science, Northeastern University, Shenyang, China
- Electrobiomaterials Institute, Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang, China
| | - Derek R Lovley
- Shenyang National Laboratory for Materials Science, Northeastern University, Shenyang, China
- Electrobiomaterials Institute, Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang, China
| | - Hao Song
- Frontiers Science Centre for Synthetic Biology (Ministry of Education), and Key Laboratory of Systems Bioengineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
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2
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Jaramillo-Rodríguez JB, Vega-Alvarado L, Rodríguez-Torres LM, Huerta-Miranda GA, Hernández-Eligio A, Juarez K. Global transcriptional analysis of Geobacter sulfurreducens gsu1771 mutant biofilm grown on two different support structures. PLoS One 2023; 18:e0293359. [PMID: 37878651 PMCID: PMC10599522 DOI: 10.1371/journal.pone.0293359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Accepted: 09/28/2023] [Indexed: 10/27/2023] Open
Abstract
Electroactive biofilms formation by the metal-reducing bacterium Geobacter sulfurreducens is a step crucial for bioelectricity generation and bioremediation. The transcriptional regulator GSU1771 controls the expression of essential genes involved in electron transfer and biofilm formation in G. sulfurreducens, with GSU1771-deficient producing thicker and more electroactive biofilms. Here, RNA-seq analyses were conducted to compare the global gene expression patterns of wild-type and Δgsu1771 mutant biofilms grown on non-conductive (glass) and conductive (graphite electrode) materials. The Δgsu1771 biofilm grown on the glass surface exhibited 467 differentially expressed (DE) genes (167 upregulated and 300 downregulated) versus the wild-type biofilm. In contrast, the Δgsu1771 biofilm grown on the graphite electrode exhibited 119 DE genes (79 upregulated and 40 downregulated) versus the wild-type biofilm. Among these DE genes, 67 were also differentially expressed in the Δgsu1771 biofilm grown on glass (56 with the same regulation and 11 exhibiting counter-regulation). Among the upregulated genes in the Δgsu1771 biofilms, we identified potential target genes involved in exopolysaccharide synthesis (gsu1961-63, gsu1959, gsu1972-73, gsu1976-77). RT-qPCR analyses were then conducted to confirm the differential expression of a selection of genes of interest. DNA-protein binding assays demonstrated the direct binding of the GSU1771 regulator to the promoter region of pgcA, pulF, relA, and gsu3356. Furthermore, heme-staining and western blotting revealed an increase in c-type cytochromes including OmcS and OmcZ in Δgsu1771 biofilms. Collectively, our findings demonstrated that GSU1771 is a global regulator that controls extracellular electron transfer and exopolysaccharide synthesis in G. sulfurreducens, which is crucial for electroconductive biofilm development.
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Affiliation(s)
- Juan B. Jaramillo-Rodríguez
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
| | - Leticia Vega-Alvarado
- Instituto de Ciencias Aplicadas y Tecnología, Universidad Nacional Autónoma de México, Ciudad Universitaria, Ciudad de México, México
| | - Luis M. Rodríguez-Torres
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
| | - Guillermo A. Huerta-Miranda
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
| | - Alberto Hernández-Eligio
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
- Investigador por México, Consejo Nacional de Ciencia y Tecnología, Ciudad de México, México
| | - Katy Juarez
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
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Gu Y, Qi X, Yang X, Jiang Y, Liu P, Quan X, Liang P. Extracellular electron transfer and the conductivity in microbial aggregates during biochemical wastewater treatment: A bottom-up analysis of existing knowledge. WATER RESEARCH 2023; 231:119630. [PMID: 36689883 DOI: 10.1016/j.watres.2023.119630] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 12/14/2022] [Accepted: 01/15/2023] [Indexed: 06/17/2023]
Abstract
Microbial extracellular electron transfer (EET) plays a crucial role in bioenergy production and resource recovery from wastewater. Interdisciplinary efforts have been made to unveil EET processes at various spatial scales, from nanowires to microbial aggregates. Electrical conductivity has been frequently measured as an indicator of EET efficiency. In this review, the conductivity of nanowires, biofilms, and granular sludge was summarized, and factors including subjects, measurement methods, and conducting conditions that affect the conductivity difference were discussed in detail. The high conductivity of nanowires does not necessarily result in efficient EET in microbial aggregates due to the existence of non-conductive substances and contact resistance. Improving the conductivity measurement of microbial aggregates is important because it enables the calculation of an EET flux from conductivity and a comparison of the flux with mass transfer coefficients. This review provides new insight into the significance, characterization, and optimization of EET in microbial aggregates during a wastewater treatment process.
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Affiliation(s)
- Yuyi Gu
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, PR China
| | - Xiang Qi
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, PR China
| | - Xufei Yang
- Department of Agricultural and Biosystems Engineering, South Dakota State University, Brookings, SD 57007 USA
| | - Yong Jiang
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, Fujian 350002, China
| | - Panpan Liu
- School of Ecology and Environment, Zhengzhou University, Zhengzhou 450001, PR China
| | - Xiangchun Quan
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Beijing Normal University, Beijing 100875, China
| | - Peng Liang
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, PR China.
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Hoang AT, Nižetić S, Ng KH, Papadopoulos AM, Le AT, Kumar S, Hadiyanto H, Pham VV. Microbial fuel cells for bioelectricity production from waste as sustainable prospect of future energy sector. CHEMOSPHERE 2022; 287:132285. [PMID: 34563769 DOI: 10.1016/j.chemosphere.2021.132285] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 08/23/2021] [Accepted: 09/16/2021] [Indexed: 06/13/2023]
Abstract
Microbial fuel cell (MFC) is lauded for its potentials to solve both energy crisis and environmental pollution. Technologically, it offers the capability to harness electricity from the chemical energy stored in the organic substrate with no intermediate steps, thereby minimizes the entropic loss due to the inter-conversion of energy. The sciences underneath such MFCs include the electron and proton generation from the metabolic decomposition of the substrate by microbes at the anode, followed by the shuttling of these charges to cathode for electricity generation. While its promising prospects were mutually evinced in the past investigations, the upscaling of MFC in sustaining global energy demands and waste treatments is yet to be put into practice. In this context, the current review summarizes the important knowledge and applications of MFCs, concurrently identifies the technological bottlenecks that restricted its vast implementation. In addition, economic analysis was also performed to provide multiangle perspectives to readers. Succinctly, MFCs are mainly hindered by the slow metabolic kinetics, sluggish transfer of charged particles, and low economic competitiveness when compared to conventional technologies. From these hindering factors, insightful strategies for improved practicality of MFCs were formulated, with potential future research direction being identified too. With proper planning, we are delighted to see the industrialization of MFCs in the near future, which would benefit the entire human race with cleaner energy and the environment.
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Affiliation(s)
- Anh Tuan Hoang
- Institute of Engineering, Ho Chi Minh City University of Technology (HUTECH), Ho Chi Minh City, Viet Nam.
| | - Sandro Nižetić
- University of Split, FESB, Rudjera Boskovica 32, 21000, Split, Croatia
| | - Kim Hoong Ng
- Department of Chemical Engineering, Ming Chi University of Technology, New Taipei City, 24301, Taiwan.
| | - Agis M Papadopoulos
- Process Equipment Design Laboratory, Department of Mechanical Engineering, Aristotle University of Thessaloniki, Postal Address: GR-54124, Thessaloniki, Greece
| | - Anh Tuan Le
- School of Transportation Engineering, Hanoi University of Science and Technology, Hanoi, Viet Nam.
| | - Sunil Kumar
- Waste Reprocessing Division, CSIR-National Environmental Engineering Research Institute, Nagpur, 440 020, India
| | - H Hadiyanto
- Center of Biomass and Renewable Energy (CBIORE), Department of Chemical Engineering, Diponegoro University, Jl. Prof. Soedarto SH, Tembalang, Semarang, 50271, Indonesia; School of Postgraduate Studies, Diponegoro University, Jl. Imam Bardjo, SH Semarang, 50241, Indonesia.
| | - Van Viet Pham
- PATET Research Group, Ho Chi Minh City University of Transport, Ho Chi Minh City, Viet Nam.
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Structure of Geobacter pili reveals secretory rather than nanowire behaviour. Nature 2021; 597:430-434. [PMID: 34471289 PMCID: PMC9127704 DOI: 10.1038/s41586-021-03857-w] [Citation(s) in RCA: 86] [Impact Index Per Article: 28.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Accepted: 07/28/2021] [Indexed: 02/07/2023]
Abstract
Extracellular electron transfer by Geobacter species through surface appendages known as microbial nanowires1 is important in a range of globally important environmental phenomena2, as well as for applications in bio-remediation, bioenergy, biofuels and bioelectronics. Since 2005, these nanowires have been thought to be type 4 pili composed solely of the PilA-N protein1. However, previous structural analyses have demonstrated that, during extracellular electron transfer, cells do not produce pili but rather nanowires made up of the cytochromes OmcS2,3 and OmcZ4. Here we show that Geobacter sulfurreducens binds PilA-N to PilA-C to assemble heterodimeric pili, which remain periplasmic under nanowire-producing conditions that require extracellular electron transfer5. Cryo-electron microscopy revealed that C-terminal residues of PilA-N stabilize its copolymerization with PilA-C (to form PilA-N-C) through electrostatic and hydrophobic interactions that position PilA-C along the outer surface of the filament. PilA-N-C filaments lack π-stacking of aromatic side chains and show a conductivity that is 20,000-fold lower than that of OmcZ nanowires. In contrast with surface-displayed type 4 pili, PilA-N-C filaments show structure, function and localization akin to those of type 2 secretion pseudopili6. The secretion of OmcS and OmcZ nanowires is lost when pilA-N is deleted and restored when PilA-N-C filaments are reconstituted. The substitution of pilA-N with the type 4 pili of other microorganisms also causes a loss of secretion of OmcZ nanowires. As all major phyla of prokaryotes use systems similar to type 4 pili, this nanowire translocation machinery may have a widespread effect in identifying the evolution and prevalence of diverse electron-transferring microorganisms and in determining nanowire assembly architecture for designing synthetic protein nanowires.
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Cologgi DL, Otwell AE, Speers AM, Rotondo JA, Reguera G. Genetic analysis of electroactive biofilms. Int Microbiol 2021; 24:631-648. [PMID: 33907940 DOI: 10.1007/s10123-021-00176-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 04/01/2021] [Accepted: 04/08/2021] [Indexed: 12/17/2022]
Abstract
Geobacter biofilms synthesize an electroactive exopolysaccharide matrix with conductive pili and c-cytochromes that spatially organizes cells optimally for growth and electron transport to iron oxide substrates, soluble metal contaminants, and current-harvesting electrodes. Despite its relevance to bioremediation and bioenergy applications, little is known about the developmental stages leading to the formation of mature (>20 μm thick) electroactive biofilms. Thus, we developed a transposon mutagenesis method and a high-throughput screening assay and identified mutants of Geobacter sulfurreducens PCA interrupted in the initial stages of surface colonization (attachment and monolayer formation) and the vertical growth and maturation of multilayered biofilms. The molecular dissection of biofilm formation demonstrated that cells undergo a regulated developmental program to first colonize the surface to saturation and then synthesize an electroactive matrix to support optimal cell growth within structured communities. Transitioning from a monolayer to a multilayered, mature biofilm required the expression of conductive pili, consistent with the essential role of these extracellular protein appendages as electronic conduits across all layers of the biofilms. The genetic screening also identified cell envelope processes, regulatory pathways, and electron transport components not previously linked to biofilm formation. These genes provide much-needed understanding of the cellular reprogramming needed to build electroactive biofilms. Importantly, they serve as predictive markers of the physiology and reductive capacity of Geobacter biofilms during the bioremediation of toxic metals and radionuclides and current harvesting in bioelectrochemical systems.
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Affiliation(s)
- Dena L Cologgi
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, 48824, USA
| | - Anne E Otwell
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, 48824, USA.,Present address: Department of Civil and Environmental Engineering, University of Washington, Seattle, WA, 98195, USA
| | - Allison M Speers
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, 48824, USA
| | - John A Rotondo
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, 48824, USA
| | - Gemma Reguera
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, 48824, USA.
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Abstract
Extracellular electron transfer (EET) is an important biological process in microbial physiology as found in dissimilatory metal oxidation/reduction and interspecies electron transfer in syntrophy in natural environments. EET also plays a critical role in microorganisms relevant to environmental biotechnology in metal-contaminated areas, metal corrosion, bioelectrochemical systems, and anaerobic digesters. Geobacter species exist in a diversity of natural and artificial environments. One of the outstanding features of Geobacter species is the capability of direct EET with solid electron donors and acceptors, including metals, electrodes, and other cells. Therefore, Geobacter species are pivotal in environmental biogeochemical cycles and biotechnology applications. Geobacter sulfurreducens, a representative Geobacter species, has been studied for direct EET as a model microorganism. G. sulfurreducens employs electrically conductive pili (e-pili) and c-type cytochromes for the direct EET. The biological function and electronics applications of the e-pili have been reviewed recently, and this review focuses on the cytochromes. Geobacter species have an unusually large number of cytochromes encoded in their genomes. Unlike most other microorganisms, Geobacter species localize multiple cytochromes in each subcellular fraction, outer membrane, periplasm, and inner membrane, as well as in the extracellular space, and differentially utilize these cytochromes for EET with various electron donors and acceptors. Some of the cytochromes are functionally redundant. Thus, the EET in Geobacter is complicated. Geobacter coordinates the cytochromes with other cellular components in the elaborate EET system to flourish in the environment.
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Affiliation(s)
- Toshiyuki Ueki
- Department of Microbiology, University of Massachusetts, Amherst, Massachusetts, USA
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Lovley DR, Yao J. Intrinsically Conductive Microbial Nanowires for 'Green' Electronics with Novel Functions. Trends Biotechnol 2021; 39:940-952. [PMID: 33419586 DOI: 10.1016/j.tibtech.2020.12.005] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2020] [Revised: 12/04/2020] [Accepted: 12/07/2020] [Indexed: 10/22/2022]
Abstract
Intrinsically conductive protein nanowires, microbially produced from inexpensive, renewable feedstocks, are a sustainable alternative to traditional nanowire electronic materials, which require high energy inputs and hazardous conditions/chemicals for fabrication and can be highly toxic. Pilin-based nanowires can be tailored for specific functions via the design of synthetic pilin genes to tune wire conductivity or introduce novel functionalities. Other microbially produced nanowire options for electronics may include cytochrome wires, curli fibers, and the conductive fibers of cable bacteria. Proof-of-concept protein nanowire electronics that have been successfully demonstrated include biomedical sensors, neuromorphic devices, and a device that generates electricity from ambient humidity. Further development of applications will require interdisciplinary teams of engineers, biophysicists, and synthetic biologists.
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Affiliation(s)
- Derek R Lovley
- Electrobiomaterials Institute, Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110819, China; Department of Microbiology, University of Massachusetts, Amherst, MA, USA; Institute for Applied Life Sciences (IALS), University of Massachusetts, Amherst, MA, USA.
| | - Jun Yao
- Institute for Applied Life Sciences (IALS), University of Massachusetts, Amherst, MA, USA; Department of Electrical and Computer Engineering, University of Massachusetts, Amherst, MA, USA; Department of Biomedical Engineering, University of Massachusetts, Amherst, MA, USA
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9
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Bray MS, Wu J, Padilla CC, Stewart FJ, Fowle DA, Henny C, Simister RL, Thompson KJ, Crowe SA, Glass JB. Phylogenetic and structural diversity of aromatically dense pili from environmental metagenomes. ENVIRONMENTAL MICROBIOLOGY REPORTS 2020; 12:49-57. [PMID: 31701641 PMCID: PMC7779115 DOI: 10.1111/1758-2229.12809] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 10/14/2019] [Accepted: 11/03/2019] [Indexed: 06/10/2023]
Abstract
Electroactive type IV pili, or e-pili, are used by some microbial species for extracellular electron transfer. Recent studies suggest that e-pili may be more phylogenetically and structurally diverse than previously assumed. Here, we used updated aromatic density thresholds (≥9.8% aromatic amino acids, ≤22-aa aromatic gaps and aromatic amino acids at residues 1, 24, 27, 50 and/or 51, and 32 and/or 57) to search for putative e-pilin genes in metagenomes from diverse ecosystems with active microbial metal cycling. Environmental putative e-pilins were diverse in length and phylogeny, and included truncated e-pilins in Geobacter spp., as well as longer putative e-pilins in Fe(II)-oxidizing Betaproteobacteria and Zetaproteobacteria.
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Affiliation(s)
- Marcus S. Bray
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Jieying Wu
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Cory C. Padilla
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Frank J. Stewart
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - David A. Fowle
- Department of Geology, University of Kansas, Lawrence, KS, USA
| | - Cynthia Henny
- Research Center for Limnology, Indonesian Institute of Sciences, Cibinong, Indonesia
| | - Rachel L. Simister
- Department of Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, BC, Canada
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| | - Katharine J. Thompson
- Department of Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, BC, Canada
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| | - Sean A. Crowe
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- Department of Earth, Ocean, and Atmospheric Sciences, University of British Columbia, Vancouver, BC, Canada
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
- Division of Earth and Planetary Sciences, School of Biological Sciences, and Swire Institute of Marine Science, The University of Hong Kong, Hong Kong
| | - Jennifer B. Glass
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
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Abstract
The study of electrically conductive protein nanowires in Geobacter sulfurreducens has led to new concepts for long-range extracellular electron transport, as well as for the development of sustainable conductive materials and electronic devices with novel functions. Until recently, electrically conductive pili (e-pili), assembled from the PilA pilin monomer, were the only known Geobacter protein nanowires. However, filaments comprised of the multi-heme c-type cytochrome, OmcS, are present in some preparations of G. sulfurreducens outer-surface proteins. The purpose of this review is to evaluate the available evidence on the in vivo expression of e-pili and OmcS filaments and their biological function. Abundant literature demonstrates that G. sulfurreducens expresses e-pili, which are required for long-range electron transport to Fe (III) oxides and through conductive biofilms. In contrast, there is no definitive evidence yet that wild-type G. sulfurreducens express long filaments of OmcS extending from the cells, and deleting the gene for OmcS actually increases biofilm conductivity. The literature does not support the concern that many previous studies on e-pili were mistakenly studying OmcS filaments. For example, heterologous expression of the aromatic-rich pilin monomer of Geobacter metallireducens in G. sulfurreducens increases the conductivity of individual nanowires more than 5,000-fold, whereas expression of an aromatic-poor pilin reduced conductivity more than 1,000-fold. This more than million-fold range in nanowire conductivity was achieved while maintaining the 3-nm diameter characteristic of e-pili. Purification methods that eliminate all traces of OmcS yield highly conductive e-pili, as does heterologous expression of the e-pilin monomer in microbes that do not produce OmcS or any other outer-surface cytochromes. Future studies of G. sulfurreducens expression of protein nanowires need to be cognizant of the importance of maintaining environmentally relevant growth conditions because artificial laboratory culture conditions can rapidly select against e-pili expression. Principles derived from the study of e-pili have enabled identification of non-cytochrome protein nanowires in diverse bacteria and archaea. A similar search for cytochrome appendages is warranted. Both e-pili and OmcS filaments offer design options for the synthesis of protein-based "green" electronics, which may be the primary driving force for the study of these structures in the near future.
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Affiliation(s)
- Derek R. Lovley
- Department of Microbiology, Institute for Applied Life Sciences, University of Massachusetts, Amherst, MA, United States
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11
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Sun D, Wan X, Liu W, Xia X, Huang F, Wang A, Smith JA, Dang Y, Holmes DE. Characterization of the genome from Geobacter anodireducens, a strain with enhanced current production in bioelectrochemical systems. RSC Adv 2019; 9:25890-25899. [PMID: 35530078 PMCID: PMC9070056 DOI: 10.1039/c9ra02343g] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Accepted: 07/20/2019] [Indexed: 11/21/2022] Open
Abstract
Geobacter anodireducens is unique in that it can generate high current densities in bioelectrochemical systems (BES) operating under high salt conditions. This ability is important for the development of BES treating high salt wastewater and microbial desalination cells. Therefore, the genome of G. anodireducens was characterized to identify proteins that might allow this strain to survive in high salt BES. Comparison to other Geobacter species revealed that 81 of its 87 c-type cytochromes had homologs in G. soli and G. sulfurreducens. Genes coding for many extracellular electron transfer proteins were also detected, including the outer membrane c-type cytochromes OmcS and OmcZ and the soluble c-type cytochrome PgcA. G. anodireducens also appears to have numerous membrane complexes involved in the translocation of protons and sodium ions and channels that provide protection against osmotic shock. In addition, it has more DNA repair genes than most Geobacter species, suggesting that it might be able to more rapidly repair DNA damage caused in high salt and low pH anode environments. Although this genomic analysis provides invaluable insight into mechanisms used by G. anodireducens to survive in high salt BES, genetic, transcriptomic, and proteomic studies will need to be done to validate their roles.
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Affiliation(s)
- Dan Sun
- Ocean College, Zhejiang University Zhoushan 316021 P. R. China
| | - Xinyuan Wan
- Ocean College, Zhejiang University Zhoushan 316021 P. R. China
| | - Wenzong Liu
- Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, China Academy of Sciences Beijing 100084 P. R. China
| | - Xue Xia
- Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, China Academy of Sciences Beijing 100084 P. R. China
| | - Fangliang Huang
- College of Life Sciences, Zhejiang University Hangzhou 310058 P. R. China
| | - Aijie Wang
- Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, China Academy of Sciences Beijing 100084 P. R. China
| | - Jessica A Smith
- Department of Biomolecular Sciences, Central Connecticut State University 1615 Stanley Street New Britain CT 06050 USA
| | - Yan Dang
- Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, College of Environmental Science & Engineering, Beijing Forestry University 35 Tsinghua East Road Beijing 100083 China
| | - Dawn E Holmes
- Department of Physical and Biological Sciences, Western New England University 1215 Wilbraham Rd Springfield MA 01190 USA
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Li D, Li J, Liu D, Ma X, Cheng L, Li W, Qian C, Mu Y, Yu H. Potential regulates metabolism and extracellular respiration of electroactiveGeobacterbiofilm. Biotechnol Bioeng 2019; 116:961-971. [DOI: 10.1002/bit.26928] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2018] [Revised: 11/26/2018] [Accepted: 01/17/2019] [Indexed: 01/02/2023]
Affiliation(s)
- Dao‐Bo Li
- Department of Applied ChemistryUniversity of Science and Technology of ChinaHefei China
| | - Jie Li
- Department of Applied ChemistryUniversity of Science and Technology of ChinaHefei China
| | - Dong‐Feng Liu
- Department of Applied ChemistryUniversity of Science and Technology of ChinaHefei China
| | - Xin Ma
- School of Life Sciences, University of Science and Technology of ChinaHefei China
| | - Lei Cheng
- School of Life Sciences, University of Science and Technology of ChinaHefei China
| | - Wen‐Wei Li
- Department of Applied ChemistryUniversity of Science and Technology of ChinaHefei China
| | - Chen Qian
- Department of Applied ChemistryUniversity of Science and Technology of ChinaHefei China
| | - Yang Mu
- Department of Applied ChemistryUniversity of Science and Technology of ChinaHefei China
| | - Han‐Qing Yu
- Department of Applied ChemistryUniversity of Science and Technology of ChinaHefei China
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13
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Wilmoth JL, Moran MA, Thompson A. Transient O 2 pulses direct Fe crystallinity and Fe(III)-reducer gene expression within a soil microbiome. MICROBIOME 2018; 6:189. [PMID: 30352628 PMCID: PMC6199725 DOI: 10.1186/s40168-018-0574-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 10/09/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND Many environments contain redox transition zones, where transient oxygenation events can modulate anaerobic reactions that influence the cycling of iron (Fe) and carbon (C) on a global scale. In predominantly anoxic soils, this biogeochemical cycling depends on Fe mineral composition and the activity of mixed Fe(III)-reducer populations that may be altered by periodic pulses of molecular oxygen (O2). METHODS We repeatedly exposed anoxic (4% H2:96% N2) suspensions of soil from the Luquillo Critical Zone Observatory to 1.05 × 102, 1.05 × 103, and 1.05 × 104 mmol O2 kg-1 soil h-1 during pulsed oxygenation treatments. Metatranscriptomic analysis and 57Fe Mössbauer spectroscopy were used to investigate changes in Fe(III)-reducer gene expression and Fe(III) crystallinity, respectively. RESULTS Slow oxygenation resulted in soil Fe-(oxyhydr)oxides of higher crystallinity (38.1 ± 1.1% of total Fe) compared to fast oxygenation (30.6 ± 1.5%, P < 0.001). Transcripts binning to the genomes of Fe(III)-reducers Anaeromyxobacter, Geobacter, and Pelosinus indicated significant differences in extracellular electron transport (e.g., multiheme cytochrome c, multicopper oxidase, and type-IV pilin gene expression), adhesion/contact (e.g., S-layer, adhesin, and flagellin gene expression), and selective microbial competition (e.g., bacteriocin gene expression) between the slow and fast oxygenation treatments during microbial Fe(III) reduction. These data also suggest that diverse Fe(III)-reducer functions, including cytochrome-dependent extracellular electron transport, are associated with type-III fibronectin domains. Additionally, the metatranscriptomic data indicate that Methanobacterium was significantly more active in the reduction of CO2 to CH4 and in the expression of class(III) signal peptide/type-IV pilin genes following repeated fast oxygenation compared to slow oxygenation. CONCLUSIONS This study demonstrates that specific Fe(III)-reduction mechanisms in mixed Fe(III)-reducer populations are uniquely sensitive to the rate of O2 influx, likely mediated by shifts in soil Fe(III)-(oxyhydr)oxide crystallinity. Overall, we provide evidence that transient oxygenation events play an important role in directing anaerobic pathways within soil microbiomes, which is expected to alter Fe and C cycling in redox-dynamic environments.
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Affiliation(s)
- Jared Lee Wilmoth
- Department of Crop and Soil Sciences, University of Georgia, Athens, 30602, GA, USA
| | - Mary Ann Moran
- Department of Marine Sciences, University of Georgia, Athens, GA, USA
| | - Aaron Thompson
- Department of Crop and Soil Sciences, University of Georgia, Athens, 30602, GA, USA.
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14
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Cai X, Huang L, Yang G, Yu Z, Wen J, Zhou S. Transcriptomic, Proteomic, and Bioelectrochemical Characterization of an Exoelectrogen Geobacter soli Grown With Different Electron Acceptors. Front Microbiol 2018; 9:1075. [PMID: 29963016 PMCID: PMC6013743 DOI: 10.3389/fmicb.2018.01075] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Accepted: 05/07/2018] [Indexed: 01/10/2023] Open
Abstract
The ability of Geobacter species to transfer electrons outside cells enables them to play an important role in biogeochemical and bioenergy processes. Our knowledge of the extracellular electron transfer (EET) process in the genus Geobacter is mainly from the study of G. sulfurreducens, and in order to fully investigate the EET mechanisms in the genus Geobacter, other Geobacter species should also be considered. This study focused on the EET of Geobacter soli GSS01, which exhibited a capability of reducing insoluble Fe(III) oxides and generating electrical current comparable with G. sulfurreducens PCA. Electrochemical characterization, including cyclic voltammetry, differential pulse voltammetry, and electrochemical in situ FTIR spectra, revealed that different redox proteins contributed to the electrochemical behaviors of G. soli and G. sulfurreducens. Based on comparative transcriptomic and proteomic analyses, OmcS was the most upregulated protein in both G. soli and G. sulfurreducens cells grown with insoluble Fe(III) oxides vs. soluble electron acceptor. However, the proteins including OmcE and PilA that were previously reported as being important for EET in G. sulfurreducens were downregulated or unchanged in G. soli cells grown with insoluble electron acceptors vs. soluble electron acceptor, and many proteins that were upregulated in G. soli cells grown with insoluble electron acceptors vs. soluble electron acceptor, such as OmcN, are not important for EET in G. sulfurreducens. We also identified 30 differentially expressed small RNAs (sRNAs) in G. soli cells grown with different acceptors. Taken together, these findings help to understand the versatile EET mechanisms that exist in the genus Geobacter and point to the possibility of sRNA in modulating EET gene expression.
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Affiliation(s)
- Xixi Cai
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Lingyan Huang
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Guiqin Yang
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Zhen Yu
- Guangdong Key Laboratory of Integrated Agro-Environmental Pollution Control and Management, Guangdong Institute of Eco-Environmental Science and Technology, Guangzhou, China
| | - Junlin Wen
- Guangdong Key Laboratory of Integrated Agro-Environmental Pollution Control and Management, Guangdong Institute of Eco-Environmental Science and Technology, Guangzhou, China
| | - Shungui Zhou
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou, China
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15
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Costa NL, Clarke TA, Philipp LA, Gescher J, Louro RO, Paquete CM. Electron transfer process in microbial electrochemical technologies: The role of cell-surface exposed conductive proteins. BIORESOURCE TECHNOLOGY 2018; 255:308-317. [PMID: 29444758 DOI: 10.1016/j.biortech.2018.01.133] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 01/26/2018] [Accepted: 01/27/2018] [Indexed: 06/08/2023]
Abstract
Electroactive microorganisms have attracted significant interest for the development of novel biotechnological systems of low ecological footprint. These can be used for the sustainable production of energy, bioremediation of metal-contaminated environments and production of added-value products. Currently, almost 100 microorganisms from the Bacterial and Archaeal domains are considered electroactive, given their ability to efficiently interact with electrodes in microbial electrochemical technologies. Cell-surface exposed conductive proteins are key players in the electron transfer between cells and electrodes. Interestingly, it seems that among the electroactive organisms identified so far, these cell-surface proteins fall into one of four groups. In this review, the different types of cell-surface conductive proteins found in electroactive organisms will be overviewed, focusing on their structural and functional properties.
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Affiliation(s)
- Nazua L Costa
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Av. da República-EAN, 2780-157, Oeiras, Portugal
| | - Thomas A Clarke
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom
| | - Laura-Alina Philipp
- Department of Applied Biology, Institute for Applied Biosciences, Karlsruhe Institute of Technology (CS), Karlsruhe, Germany
| | - Johannes Gescher
- Department of Applied Biology, Institute for Applied Biosciences, Karlsruhe Institute of Technology (CS), Karlsruhe, Germany; Institute for Biological Interfaces, Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, Germany
| | - Ricardo O Louro
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Av. da República-EAN, 2780-157, Oeiras, Portugal
| | - Catarina M Paquete
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Av. da República-EAN, 2780-157, Oeiras, Portugal.
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16
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He S, Barco RA, Emerson D, Roden EE. Comparative Genomic Analysis of Neutrophilic Iron(II) Oxidizer Genomes for Candidate Genes in Extracellular Electron Transfer. Front Microbiol 2017; 8:1584. [PMID: 28871245 PMCID: PMC5566968 DOI: 10.3389/fmicb.2017.01584] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 08/04/2017] [Indexed: 11/13/2022] Open
Abstract
Extracellular electron transfer (EET) is recognized as a key biochemical process in circumneutral pH Fe(II)-oxidizing bacteria (FeOB). In this study, we searched for candidate EET genes in 73 neutrophilic FeOB genomes, among which 43 genomes are complete or close-to-complete and the rest have estimated genome completeness ranging from 5 to 91%. These neutrophilic FeOB span members of the microaerophilic, anaerobic phototrophic, and anaerobic nitrate-reducing FeOB groups. We found that many microaerophilic and several anaerobic FeOB possess homologs of Cyc2, an outer membrane cytochrome c originally identified in Acidithiobacillus ferrooxidans. The "porin-cytochrome c complex" (PCC) gene clusters homologous to MtoAB/PioAB are present in eight FeOB, accounting for 19% of complete and close-to-complete genomes examined, whereas PCC genes homologous to OmbB-OmaB-OmcB in Geobacter sulfurreducens are absent. Further, we discovered gene clusters that may potentially encode two novel PCC types. First, a cluster (tentatively named "PCC3") encodes a porin, an extracellular and a periplasmic cytochrome c with remarkably large numbers of heme-binding motifs. Second, a cluster (tentatively named "PCC4") encodes a porin and three periplasmic multiheme cytochromes c. A conserved inner membrane protein (IMP) encoded in PCC3 and PCC4 gene clusters might be responsible for translocating electrons across the inner membrane. Other bacteria possessing PCC3 and PCC4 are mostly Proteobacteria isolated from environments with a potential niche for Fe(II) oxidation. In addition to cytochrome c, multicopper oxidase (MCO) genes potentially involved in Fe(II) oxidation were also identified. Notably, candidate EET genes were not found in some FeOB, especially the anaerobic ones, probably suggesting EET genes or Fe(II) oxidation mechanisms are different from the searched models. Overall, based on current EET models, the search extends our understanding of bacterial EET and provides candidate genes for future research.
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Affiliation(s)
- Shaomei He
- Department of Geoscience, University of Wisconsin-MadisonMadison, WI, United States.,NASA Astrobiology Institute, University of WisconsinMadison, WI, United States.,Department of Bacteriology, University of Wisconsin-MadisonMadison, WI, United States
| | - Roman A Barco
- Bigelow Laboratory for Ocean SciencesEast Boothbay Harbor, ME, United States.,Department of Earth Sciences, University of Southern CaliforniaLos Angeles, CA, United States
| | - David Emerson
- Bigelow Laboratory for Ocean SciencesEast Boothbay Harbor, ME, United States
| | - Eric E Roden
- Department of Geoscience, University of Wisconsin-MadisonMadison, WI, United States.,NASA Astrobiology Institute, University of WisconsinMadison, WI, United States
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17
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Saratale GD, Saratale RG, Shahid MK, Zhen G, Kumar G, Shin HS, Choi YG, Kim SH. A comprehensive overview on electro-active biofilms, role of exo-electrogens and their microbial niches in microbial fuel cells (MFCs). CHEMOSPHERE 2017; 178:534-547. [PMID: 28351012 DOI: 10.1016/j.chemosphere.2017.03.066] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Revised: 03/14/2017] [Accepted: 03/16/2017] [Indexed: 06/06/2023]
Abstract
Microbial fuel cells (MFCs) are biocatalyzed systems which can drive electrical energy by directly converting chemical energy using microbial biocatalyst and are considered as one of the important propitious technologies for sustainable energy production. Much research on MFCs experiments is under way with great potential to become an alternative to produce clean energy from renewable waste. MFCs have been one of the most promising technologies for generating clean energy industry in the future. This article summarizes the important findings in electro-active biofilm formation and the role of exo-electrogens in electron transfer in MFCs. This study provides and brings special attention on the effects of various operating and biological parameters on the biofilm formation in MFCs. In addition, it also highlights the significance of different molecular techniques used in the microbial community analysis of electro-active biofilm. It reviews the challenges as well as the emerging opportunities required to develop MFCs at commercial level, electro-active biofilms and to understand potential application of microbiological niches are also depicted. Thus, this review is believed to widen the efforts towards the development of electro-active biofilm and will provide the research directions to overcome energy and environmental challenges.
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Affiliation(s)
- Ganesh Dattatraya Saratale
- Department of Food Science and Biotechnology, Dongguk University-Seoul, Ilsandong-gu, Goyang-si, Gyeonggi-do, 10326, Republic of Korea
| | - Rijuta Ganesh Saratale
- Research Institute of Biotechnology and Medical Converged Science, Dongguk University-Seoul, Ilsandong-gu, Goyang-si, Gyeonggi-do, 10326, Republic of Korea
| | | | - Guangyin Zhen
- Shanghai Key Lab for Urban Ecological Processes and Eco-Restoration, School of Ecological and Environmental Sciences, East China Normal University, Dongchuan Rd. 500, Shanghai 200241, China
| | - Gopalakrishnan Kumar
- Sustainable Management of Natural Resources and Environment Research Group, Faculty of Environment and Labour Safety, Ton Duc Thang University, Ho Chi Minh City, Vietnam.
| | - Han-Seung Shin
- Department of Food Science and Biotechnology, Dongguk University-Seoul, Ilsandong-gu, Goyang-si, Gyeonggi-do, 10326, Republic of Korea
| | - Young-Gyun Choi
- Department of Environmental Engineering, Daegu university, Gyeongsan, Republic of Korea
| | - Sang-Hyoun Kim
- Department of Environmental Engineering, Daegu university, Gyeongsan, Republic of Korea
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18
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Choudhury P, Prasad Uday US, Bandyopadhyay TK, Ray RN, Bhunia B. Performance improvement of microbial fuel cell (MFC) using suitable electrode and Bioengineered organisms: A review. Bioengineered 2017; 8:471-487. [PMID: 28453385 DOI: 10.1080/21655979.2016.1267883] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Abstract
There is an urgent need to find an environment friendly and sustainable technology for alternative energy due to rapid depletion of fossil fuel and industrialization. Microbial Fuel Cells (MFCs) have operational and functional advantages over the current technologies for energy generation from organic matter as it directly converts electricity from substrate at ambient temperature. However, MFCs are still unsuitable for high energy demands due to practical limitations. The overall performance of an MFC depends on microorganism, appropriate electrode materials, suitable MFC designs, and optimizing process parameters which would accelerate commercialization of this technology in near future. In this review, we put forth the recent developments on microorganism and electrode material that are critical for the generation of bioelectricity generation. This would give a comprehensive insight into the characteristics, options, modifications, and evaluations of these parameters and their effects on process development of MFCs.
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Affiliation(s)
- Payel Choudhury
- a Department of Electrical Engineering , National Institute of Technology , Agartala , India
| | | | | | - Rup Narayan Ray
- a Department of Electrical Engineering , National Institute of Technology , Agartala , India
| | - Biswanath Bhunia
- c Department of Bio Engineering , National Institute of Technology , Agartala , India
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19
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Abstract
Type II secretion (T2S) is one means by which Gram-negative pathogens secrete proteins into the extracellular milieu and/or host organisms. Based upon recent genome sequencing, it is clear that T2S is largely restricted to the Proteobacteria, occurring in many, but not all, genera in the Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Deltaproteobacteria classes. Prominent human and/or animal pathogens that express a T2S system(s) include Acinetobacter baumannii, Burkholderia pseudomallei, Chlamydia trachomatis, Escherichia coli, Klebsiella pneumoniae, Legionella pneumophila, Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Vibrio cholerae, and Yersinia enterocolitica T2S-expressing plant pathogens include Dickeya dadantii, Erwinia amylovora, Pectobacterium carotovorum, Ralstonia solanacearum, Xanthomonas campestris, Xanthomonas oryzae, and Xylella fastidiosa T2S also occurs in nonpathogenic bacteria, facilitating symbioses, among other things. The output of a T2S system can range from only one to dozens of secreted proteins, encompassing a diverse array of toxins, degradative enzymes, and other effectors, including novel proteins. Pathogenic processes mediated by T2S include the death of host cells, degradation of tissue, suppression of innate immunity, adherence to host surfaces, biofilm formation, invasion into and growth within host cells, nutrient assimilation, and alterations in host ion flux. The reach of T2S is perhaps best illustrated by those bacteria that clearly use it for both environmental survival and virulence; e.g., L. pneumophila employs T2S for infection of amoebae, growth within lung cells, dampening of cytokines, and tissue destruction. This minireview provides an update on the types of bacteria that have T2S, the kinds of proteins that are secreted via T2S, and how T2S substrates promote infection.
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20
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Kavanagh P, Botting CH, Jana PS, Leech D, Abram F. Comparative Proteomics Implicates a Role for Multiple Secretion Systems in Electrode-Respiring Geobacter sulfurreducens Biofilms. J Proteome Res 2016; 15:4135-4145. [DOI: 10.1021/acs.jproteome.5b01019] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Paul Kavanagh
- School
of Chemistry, National University of Ireland Galway, University Road, Galway, Ireland
| | - Catherine H. Botting
- Biomedical
Sciences Research Complex, University of St. Andrews, North Haugh, Fife KY16 9ST, United Kingdom
| | - Partha S. Jana
- School
of Chemistry, National University of Ireland Galway, University Road, Galway, Ireland
| | - Dónal Leech
- School
of Chemistry, National University of Ireland Galway, University Road, Galway, Ireland
| | - Florence Abram
- Functional
Environmental Microbiology, School of Natural Sciences, National University of Ireland Galway, University Road, Galway, Ireland
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21
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Metagenomic Analyses of the Autotrophic Fe(II)-Oxidizing, Nitrate-Reducing Enrichment Culture KS. Appl Environ Microbiol 2016; 82:2656-2668. [PMID: 26896135 DOI: 10.1128/aem.03493-15] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 02/16/2016] [Indexed: 01/22/2023] Open
Abstract
Nitrate-dependent ferrous iron [Fe(II)] oxidation (NDFO) is a well-recognized chemolithotrophic pathway in anoxic sediments. The neutrophilic chemolithoautotrophic enrichment culture KS originally obtained from a freshwater sediment (K. L. Straub, M. Benz, B. Schink, and F. Widdel, Appl Environ Microbiol 62:1458-1460, 1996) has been used as a model system to study NDFO. However, the primary Fe(II) oxidizer in this culture has not been isolated, despite extensive efforts to do so. Here, we present a metagenomic analysis of this enrichment culture in order to gain insight into electron transfer pathways and the roles of different bacteria in the culture. We obtained a near-complete genome of the primary Fe(II) oxidizer, a species in the family Gallionellaceae, and draft genomes from its flanking community members. A search of the putative extracellular electron transfer pathways in these genomes led to the identification of a homolog of the MtoAB complex [a porin-multiheme cytochromec system identified in neutrophilic microaerobic Fe(II)-oxidizing Sideroxydans lithotrophicus ES-1] in a Gallionellaceae sp., and findings of other putative genes involving cytochromecand multicopper oxidases, such as Cyc2 and OmpB. Genome-enabled metabolic reconstruction revealed that this Gallionellaceae sp. lacks nitric oxide and nitrous oxide reductase genes and may partner with flanking populations capable of complete denitrification to avoid toxic metabolite accumulation, which may explain its resistance to growth in pure culture. This and other revealed interspecies interactions and metabolic interdependencies in nitrogen and carbon metabolisms may allow these organisms to cooperate effectively to achieve robust chemolithoautotrophic NDFO. Overall, the results significantly expand our knowledge of NDFO and suggest a range of genetic targets for further exploration.
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Martins LO, Durão P, Brissos V, Lindley PF. Laccases of prokaryotic origin: enzymes at the interface of protein science and protein technology. Cell Mol Life Sci 2015; 72:911-22. [PMID: 25572294 PMCID: PMC11113980 DOI: 10.1007/s00018-014-1822-x] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Accepted: 12/30/2014] [Indexed: 10/24/2022]
Abstract
The ubiquitous members of the multicopper oxidase family of enzymes oxidize a range of aromatic substrates such as polyphenols, methoxy-substituted phenols, amines and inorganic compounds, concomitantly with the reduction of molecular dioxygen to water. This family of enzymes can be broadly divided into two functional classes: metalloxidases and laccases. Several prokaryotic metalloxidases have been described in the last decade showing a robust activity towards metals, such as Cu(I), Fe(II) or Mn(II) and have been implicated in the metal metabolism of the corresponding microorganisms. Many laccases, with a superior efficiency for oxidation of organic compounds when compared with metals, have also been identified and characterized from prokaryotes, playing roles that more closely conform to those of intermediary metabolism. This review aims to present an update of current knowledge on prokaryotic multicopper oxidases, with a special emphasis on laccases, anticipating their enormous potential for industrial and environmental applications.
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Affiliation(s)
- Lígia O Martins
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República, 2781-901, Oeiras, Portugal,
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23
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Smith JA, Nevin KP, Lovley DR. Syntrophic growth via quinone-mediated interspecies electron transfer. Front Microbiol 2015; 6:121. [PMID: 25741332 PMCID: PMC4330893 DOI: 10.3389/fmicb.2015.00121] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Accepted: 01/30/2015] [Indexed: 11/16/2022] Open
Abstract
The mechanisms by which microbial species exchange electrons are of interest because interspecies electron transfer can expand the metabolic capabilities of microbial communities. Previous studies with the humic substance analog anthraquinone-2,6-disulfonate (AQDS) suggested that quinone-mediated interspecies electron transfer (QUIET) is feasible, but it was not determined if sufficient energy is available from QUIET to support the growth of both species. Furthermore, there have been no previous studies on the mechanisms for the oxidation of anthrahydroquinone-2,6-disulfonate (AHQDS). A co-culture of Geobacter metallireducens and G. sulfurreducens metabolized ethanol with the reduction of fumarate much faster in the presence of AQDS, and there was an increase in cell protein. G. sulfurreducens was more abundant, consistent with G. sulfurreducens obtaining electrons from acetate that G. metallireducens produced from ethanol, as well as from AHQDS. Co-cultures initiated with a citrate synthase-deficient strain of G. sulfurreducens that was unable to use acetate as an electron donor also metabolized ethanol with the reduction of fumarate and cell growth, but acetate accumulated over time. G. sulfurreducens and G. metallireducens were equally abundant in these co-cultures reflecting the inability of the citrate synthase-deficient strain of G. sulfurreducens to metabolize acetate. Evaluation of the mechanisms by which G. sulfurreducens accepts electrons from AHQDS demonstrated that a strain deficient in outer-surface c-type cytochromes that are required for AQDS reduction was as effective at QUIET as the wild-type strain. Deletion of additional genes previously implicated in extracellular electron transfer also had no impact on QUIET. These results demonstrate that QUIET can yield sufficient energy to support the growth of both syntrophic partners, but that the mechanisms by which electrons are derived from extracellular hydroquinones require further investigation.
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Affiliation(s)
- Jessica A Smith
- Department of Microbiology, University of Massachusetts Amherst Amherst, MA, USA
| | - Kelly P Nevin
- Department of Microbiology, University of Massachusetts Amherst Amherst, MA, USA
| | - Derek R Lovley
- Department of Microbiology, University of Massachusetts Amherst Amherst, MA, USA
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24
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Liu Y, Wang Z, Liu J, Levar C, Edwards MJ, Babauta JT, Kennedy DW, Shi Z, Beyenal H, Bond DR, Clarke TA, Butt JN, Richardson DJ, Rosso KM, Zachara JM, Fredrickson JK, Shi L. A trans-outer membrane porin-cytochrome protein complex for extracellular electron transfer by Geobacter sulfurreducens PCA. ENVIRONMENTAL MICROBIOLOGY REPORTS 2014; 6:776-85. [PMID: 25139405 PMCID: PMC4282303 DOI: 10.1111/1758-2229.12204] [Citation(s) in RCA: 115] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Accepted: 08/14/2014] [Indexed: 05/19/2023]
Abstract
The multi-heme, outer membrane c-type cytochrome (c-Cyt) OmcB of Geobacter sulfurreducens was previously proposed to mediate electron transfer across the outer membrane. However, the underlying mechanism has remained uncharacterized. In G. sulfurreducens, the omcB gene is part of two tandem four-gene clusters, each is predicted to encode a transcriptional factor (OrfR/OrfS), a porin-like outer membrane protein (OmbB/OmbC), a periplasmic c-type cytochrome (OmaB/OmaC) and an outer membrane c-Cyt (OmcB/OmcC) respectively. Here, we showed that OmbB/OmbC, OmaB/OmaC and OmcB/OmcC of G. sulfurreducens PCA formed the porin-cytochrome (Pcc) protein complexes, which were involved in transferring electrons across the outer membrane. The isolated Pcc protein complexes reconstituted in proteoliposomes transferred electrons from reduced methyl viologen across the lipid bilayer of liposomes to Fe(III)-citrate and ferrihydrite. The pcc clusters were found in all eight sequenced Geobacter and 11 other bacterial genomes from six different phyla, demonstrating a widespread distribution of Pcc protein complexes in phylogenetically diverse bacteria. Deletion of ombB-omaB-omcB-orfS-ombC-omaC-omcC gene clusters had no impact on the growth of G. sulfurreducens PCA with fumarate but diminished the ability of G. sulfurreducens PCA to reduce Fe(III)-citrate and ferrihydrite. Complementation with the ombB-omaB-omcB gene cluster restored the ability of G. sulfurreducens PCA to reduce Fe(III)-citrate and ferrihydrite.
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Affiliation(s)
- Yimo Liu
- Fundamental & Computational Sciences Directorate, Pacific Northwest National LaboratoryRichland, WA, 99352, USA
| | - Zheming Wang
- Fundamental & Computational Sciences Directorate, Pacific Northwest National LaboratoryRichland, WA, 99352, USA
| | - Juan Liu
- Fundamental & Computational Sciences Directorate, Pacific Northwest National LaboratoryRichland, WA, 99352, USA
- † College of Environmental Sciences and Engineering, Peking University, China
| | - Caleb Levar
- Department of Microbiology, University of MinnesotaSt. Paul, MN, 55108, USA
| | - Marcus J Edwards
- Center for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East AngliaNorwich, NR4 7TJ, UK
| | - Jerome T Babauta
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State UniversityPullman, WA, 99164, USA
| | - David W Kennedy
- Fundamental & Computational Sciences Directorate, Pacific Northwest National LaboratoryRichland, WA, 99352, USA
| | - Zhi Shi
- Fundamental & Computational Sciences Directorate, Pacific Northwest National LaboratoryRichland, WA, 99352, USA
- ‡ Analytical Technology Center, The Dow Chemical Company, Freeport, TX, 77541, USA
| | - Haluk Beyenal
- The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State UniversityPullman, WA, 99164, USA
| | - Daniel R Bond
- Department of Microbiology, University of MinnesotaSt. Paul, MN, 55108, USA
| | - Thomas A Clarke
- Center for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East AngliaNorwich, NR4 7TJ, UK
| | - Julea N Butt
- Center for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East AngliaNorwich, NR4 7TJ, UK
| | - David J Richardson
- Center for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East AngliaNorwich, NR4 7TJ, UK
| | - Kevin M Rosso
- Fundamental & Computational Sciences Directorate, Pacific Northwest National LaboratoryRichland, WA, 99352, USA
| | - John M Zachara
- Fundamental & Computational Sciences Directorate, Pacific Northwest National LaboratoryRichland, WA, 99352, USA
| | - James K Fredrickson
- Fundamental & Computational Sciences Directorate, Pacific Northwest National LaboratoryRichland, WA, 99352, USA
| | - Liang Shi
- Fundamental & Computational Sciences Directorate, Pacific Northwest National LaboratoryRichland, WA, 99352, USA
- * For correspondence. E-mail ; Tel. 509 371 6967; Fax 509 376 1632
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Orellana R, Hixson KK, Murphy S, Mester T, Sharma ML, Lipton MS, Lovley DR. Proteome of Geobacter sulfurreducens in the presence of U(VI). Microbiology (Reading) 2014; 160:2607-2617. [DOI: 10.1099/mic.0.081398-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Geobacter species often play an important role in the in situ bioremediation of uranium-contaminated groundwater, but little is known about how these microbes avoid uranium toxicity. To evaluate this further, the proteome of Geobacter sulfurreducens exposed to 100 µM U(VI) acetate was compared to control cells not exposed to U(VI). Of the 1363 proteins detected from these cultures, 203 proteins had higher abundance during exposure to U(VI) compared with the control cells and 148 proteins had lower abundance. U(VI)-exposed cultures expressed lower levels of proteins involved in growth, protein and amino acid biosynthesis, as well as key central metabolism enzymes as a result of the deleterious effect of U(VI) on the growth of G. sulfurreducens. In contrast, proteins involved in detoxification, such as several efflux pumps belonging to the RND (resistance–nodulation–cell division) family, and membrane protection, and other proteins, such as chaperones and proteins involved in secretion systems, were found in higher abundance in cells exposed to U(VI). Exposing G. sulfurreducens to U(VI) resulted in a higher abundance of many proteins associated with the oxidative stress response, such as superoxide dismutase and superoxide reductase. A strain in which the gene for superoxide dismutase was deleted grew more slowly than the WT strain in the presence of U(VI), but not in its absence. The results suggested that there is no specific mechanism for uranium detoxification. Rather, multiple general stress responses are induced, which presumably enable Geobacter species to tolerate high uranium concentrations.
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Affiliation(s)
- Roberto Orellana
- Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA
| | - Kim K. Hixson
- Environmental Molecular Sciences Laboratory and Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Sean Murphy
- Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA
| | - Tünde Mester
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Kellogg Eye Center, Ann Arbor, MI 48105, USA
| | - Manju L. Sharma
- Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA
| | - Mary S. Lipton
- Environmental Molecular Sciences Laboratory and Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Derek R. Lovley
- Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA
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Dantas JM, Morgado L, Marques AC, Salgueiro CA. Probing the effect of ionic strength on the functional robustness of the triheme cytochrome PpcA from Geobacter sulfurreducens: a contribution for optimizing biofuel cell's power density. J Phys Chem B 2014; 118:12416-25. [PMID: 25275217 DOI: 10.1021/jp507898x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The increase of conductivity of electrolytes favors the current production in microbial fuel cells (MFCs). Adaptation of cell cultures to higher ionic strength is a promising strategy to increase electricity production. The bacterium Geobacter sulfurreducens is considered a leading candidate for MFCs. Therefore, it is important to evaluate the impact of the ionic strength on the functional properties of key periplasmic proteins that warrants electron transfer to cell exterior. The effect of the ionic strength on the functional properties of triheme cytochrome PpcA, the most abundant periplasmic cytochrome in G. sulfurreducens, was investigated by NMR and potentiometric methods. The redox properties of heme IV are the most affected ones. Chemical shift perturbation measurements on the backbone NMR signals, at increasing ionic strength, also showed that the region close to heme IV is the most affected due to the large number of positively charged residues, which confer a highly positive electrostatic surface around this heme. The shielding of these positive charges at high ionic strength explain the observed decrease in the reduction potential of heme IV and shows that PpcA was designed to maintain its functional mechanistic features even at high ionic strength.
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Affiliation(s)
- Joana M Dantas
- Requimte-CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa , Campus Caparica, 2829-516 Caparica, Portugal
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Type II secretion system: A magic beanstalk or a protein escalator. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:1568-77. [DOI: 10.1016/j.bbamcr.2013.12.020] [Citation(s) in RCA: 129] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Revised: 12/13/2013] [Accepted: 12/23/2013] [Indexed: 12/12/2022]
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Comparative c-type cytochrome expression analysis in Shewanella oneidensis strain MR-1 and Anaeromyxobacter dehalogenans strain 2CP-C grown with soluble and insoluble oxidized metal electron acceptors. Biochem Soc Trans 2013; 40:1204-10. [PMID: 23176455 DOI: 10.1042/bst20120182] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The genomes of Shewanella oneidensis strain MR-1 and Anaeromyxobacter dehalogenans strain 2CP-C encode 40 and 69 putative c-type cytochrome genes respectively. Deletion mutant and biochemical studies have assigned specific functions to a few c-type cytochromes involved in electron transfer to oxidized metals in S. oneidensis strain MR-1. Although promising, the genetic approach is limited to gene deletions that produce a distinct phenotype and to an organism for which a genetic system is available. To investigate and compare c-type cytochrome expression in S. oneidensis strain MR-1 and Anaeromyxobacter dehalogenans strain 2CP-C more comprehensively, proteomic measurements were used to characterize lysates of cells grown with soluble Fe(III) (as ferric citrate) and insoluble Mn(IV) (as MnO2) as electron acceptors. Strain MR-1 expressed 19 and 20, and strain 2CP-C expressed 27 and 25, c-type cytochromes when grown with Fe(III) and Mn(IV) respectively. The majority of c-type cytochromes (77% for strain MR-1 and 63% for strain 2CP-C) were expressed under both growth conditions; however, the analysis also revealed unique c-type cytochromes that were specifically expressed in cells grown with soluble Fe(III) or insoluble Mn(IV). Proteomic characterization proved to be a promising approach for determining the c-type cytochrome complement expressed under different growth conditions, and will help to elucidate the specific functions of more c-type cytochromes that are the basis for Shewanella and Anaeromyxobacter respiratory versatility.
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Rondelet A, Condemine G. Type II secretion: the substrates that won't go away. Res Microbiol 2013; 164:556-61. [PMID: 23538405 DOI: 10.1016/j.resmic.2013.03.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Accepted: 02/05/2013] [Indexed: 02/06/2023]
Abstract
Type II secretion systems (T2SSs) generally release their substrates into the culture medium. A few T2SS substrates remain anchored to or bound at the surface of the bacteria after secretion. Since they handle already folded proteins, T2SSs are the best way for bacteria to target, at their surface, proteins containing a cofactor, proteins that have to be folded in the cytoplasm or in the periplasm, or multimeric proteins. However, how a T2SS deals with membrane-anchored proteins is not yet understood. While this type of protein has until now been overlooked, new proteomic approaches will facilitate its identification.
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Affiliation(s)
- Arnaud Rondelet
- Université de Lyon, F69003, Université Lyon 1, F69622, INSA-Lyon, F69621, CNRS UMR5240, Microbiologie Adaptation et Pathogénie, 10 rue Dubois, Bât. Lwoff, 69622 Villeurbanne, France
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Aklujkar M, Coppi MV, Leang C, Kim BC, Chavan MA, Perpetua LA, Giloteaux L, Liu A, Holmes DE. Proteins involved in electron transfer to Fe(III) and Mn(IV) oxides by Geobacter sulfurreducens and Geobacter uraniireducens. MICROBIOLOGY-SGM 2013; 159:515-535. [PMID: 23306674 DOI: 10.1099/mic.0.064089-0] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Whole-genome microarray analysis of Geobacter sulfurreducens grown on insoluble Fe(III) oxide or Mn(IV) oxide versus soluble Fe(III) citrate revealed significantly different expression patterns. The most upregulated genes, omcS and omcT, encode cell-surface c-type cytochromes, OmcS being required for Fe(III) and Mn(IV) oxide reduction. Other electron transport genes upregulated on both metal oxides included genes encoding putative menaquinol : ferricytochrome c oxidoreductase complexes Cbc4 and Cbc5, periplasmic c-type cytochromes Dhc2 and PccF, outer membrane c-type cytochromes OmcC, OmcG and OmcV, multicopper oxidase OmpB, the structural components of electrically conductive pili, PilA-N and PilA-C, and enzymes that detoxify reactive oxygen/nitrogen species. Genes upregulated on Fe(III) oxide encode putative menaquinol : ferricytochrome c oxidoreductase complexes Cbc3 and Cbc6, periplasmic c-type cytochromes, including PccG and PccJ, and outer membrane c-type cytochromes, including OmcA, OmcE, OmcH, OmcL, OmcN, OmcO and OmcP. Electron transport genes upregulated on Mn(IV) oxide encode periplasmic c-type cytochromes PccR, PgcA, PpcA and PpcD, outer membrane c-type cytochromes OmaB/OmaC, OmcB and OmcZ, multicopper oxidase OmpC and menaquinone-reducing enzymes. Genetic studies indicated that MacA, OmcB, OmcF, OmcG, OmcH, OmcI, OmcJ, OmcM, OmcV and PccH, the putative Cbc5 complex subunit CbcC and the putative Cbc3 complex subunit CbcV are important for reduction of Fe(III) oxide but not essential for Mn(IV) oxide reduction. Gene expression patterns for Geobacter uraniireducens were similar. These results demonstrate that the physiology of Fe(III)-reducing bacteria differs significantly during growth on different insoluble and soluble electron acceptors and emphasize the importance of c-type cytochromes for extracellular electron transfer in G. sulfurreducens.
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Affiliation(s)
- M Aklujkar
- Department of Microbiology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - M V Coppi
- Department of Microbiology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - C Leang
- Department of Microbiology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - B C Kim
- Department of Microbiology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - M A Chavan
- Department of Microbiology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - L A Perpetua
- Department of Microbiology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - L Giloteaux
- Department of Microbiology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - A Liu
- Department of Mathematics and Statistics, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - D E Holmes
- Department of Physical and Biological Sciences, Western New England University, Springfield, MA 01119, USA
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Aklujkar M, Haveman SA, DiDonato R, Chertkov O, Han CS, Land ML, Brown P, Lovley DR. The genome of Pelobacter carbinolicus reveals surprising metabolic capabilities and physiological features. BMC Genomics 2012; 13:690. [PMID: 23227809 PMCID: PMC3543383 DOI: 10.1186/1471-2164-13-690] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Accepted: 11/22/2012] [Indexed: 11/24/2022] Open
Abstract
Background The bacterium Pelobacter carbinolicus is able to grow by fermentation, syntrophic hydrogen/formate transfer, or electron transfer to sulfur from short-chain alcohols, hydrogen or formate; it does not oxidize acetate and is not known to ferment any sugars or grow autotrophically. The genome of P. carbinolicus was sequenced in order to understand its metabolic capabilities and physiological features in comparison with its relatives, acetate-oxidizing Geobacter species. Results Pathways were predicted for catabolism of known substrates: 2,3-butanediol, acetoin, glycerol, 1,2-ethanediol, ethanolamine, choline and ethanol. Multiple isozymes of 2,3-butanediol dehydrogenase, ATP synthase and [FeFe]-hydrogenase were differentiated and assigned roles according to their structural properties and genomic contexts. The absence of asparagine synthetase and the presence of a mutant tRNA for asparagine encoded among RNA-active enzymes suggest that P. carbinolicus may make asparaginyl-tRNA in a novel way. Catabolic glutamate dehydrogenases were discovered, implying that the tricarboxylic acid (TCA) cycle can function catabolically. A phosphotransferase system for uptake of sugars was discovered, along with enzymes that function in 2,3-butanediol production. Pyruvate:ferredoxin/flavodoxin oxidoreductase was identified as a potential bottleneck in both the supply of oxaloacetate for oxidation of acetate by the TCA cycle and the connection of glycolysis to production of ethanol. The P. carbinolicus genome was found to encode autotransporters and various appendages, including three proteins with similarity to the geopilin of electroconductive nanowires. Conclusions Several surprising metabolic capabilities and physiological features were predicted from the genome of P. carbinolicus, suggesting that it is more versatile than anticipated.
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Affiliation(s)
- Muktak Aklujkar
- University of Massachusetts Amherst, Amherst, MA 01003, USA.
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Abstract
The in situ stimulation of Fe(III) oxide reduction in the subsurface stimulates the growth of Geobacter spp. and the precipitation of U(VI) from groundwater. As with Fe(III) oxide reduction, the reduction of uranium by Geobacter spp. requires the expression of their conductive pili. The pili bind the soluble uranium and catalyse its extracellular reductive precipitation along the pili filaments as a mononuclear U(IV) complexed by carbon-containing ligands. Although most of the uranium is immobilized by the pili, some uranium deposits are also observed in discreet regions of the outer membrane, consistent with the participation of redox-active foci, presumably c-type cytochromes, in the extracellular reduction of uranium. It is unlikely that cytochromes released from the outer membrane could associate with the pili and contribute to the catalysis, because scanning tunnelling microscopy spectroscopy did not reveal any haem-specific electronic features in the pili, but, rather, showed topographic and electronic features intrinsic to the pilus shaft. Pili not only enhance the rate and extent of uranium reduction per cell, but also prevent the uranium from traversing the outer membrane and mineralizing the cell envelope. As a result, pili expression preserves the essential respiratory activities of the cell envelope and the cell's viability. Hence the results support a model in which the conductive pili function as the primary mechanism for the reduction of uranium and cellular protection in Geobacter spp.
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Butler JE, Young ND, Aklujkar M, Lovley DR. Comparative genomic analysis of Geobacter sulfurreducens KN400, a strain with enhanced capacity for extracellular electron transfer and electricity production. BMC Genomics 2012; 13:471. [PMID: 22967216 PMCID: PMC3495685 DOI: 10.1186/1471-2164-13-471] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Accepted: 08/06/2012] [Indexed: 11/22/2022] Open
Abstract
Background A new strain of Geobacter sulfurreducens, strain KN400, produces more electrical current in microbial fuel cells and reduces insoluble Fe(III) oxides much faster than the wildtype strain, PCA. The genome of KN400 was compared to wildtype with the goal of discovering how the network for extracellular electron transfer has changed and how these two strains evolved. Results Both genomes were re-annotated, resulting in 14 fewer genes (net) in the PCA genome; 28 fewer (net) in the KN400 genome; and ca. 400 gene start and stop sites moved. 96% of genes in KN400 had clear orthologs with conserved synteny in PCA. Most of the remaining genes were in regions of genomic mobility and were strain-specific or conserved in other Geobacteraceae, indicating that the changes occurred post-divergence. There were 27,270 single nucleotide polymorphisms (SNP) between the genomes. There was significant enrichment for SNP locations in non-coding or synonymous amino acid sites, indicating significant selective pressure since the divergence. 25% of orthologs had sequence differences, and this set was enriched in phosphorylation and ATP-dependent enzymes. Substantial sequence differences (at least 12 non-synonymous SNP/kb) were found in 3.6% of the orthologs, and this set was enriched in cytochromes and integral membrane proteins. Genes known to be involved in electron transport, those used in the metabolic cell model, and those that exhibit changes in expression during growth in microbial fuel cells were examined in detail. Conclusions The improvement in external electron transfer in the KN400 strain does not appear to be due to novel gene acquisition, but rather to changes in the common metabolic network. The increase in electron transfer rate and yield in KN400 may be due to changes in carbon flux towards oxidation pathways and to changes in ATP metabolism, both of which indicate that the overall energy state of the cell may be different. The electrically conductive pili appear to be unchanged, but cytochrome folding, localization, and redox potentials may all be affected, which would alter the electrical connection between the cell and the substrate.
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Affiliation(s)
- Jessica E Butler
- Department of Microbiology, 203 Morrill Science Center IVN, University of Massachusetts, 639 North Pleasant Street, Amherst, MA 01003, USA.
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Abstract
Electromicrobiology deals with the interactions between microorganisms and electronic devices and with the novel electrical properties of microorganisms. A diversity of microorganisms can donate electrons to, or accept electrons from, electrodes without the addition of artificial electron shuttles. However, the mechanisms for microbe-electrode electron exchange have been seriously studied in only a few microorganisms. Shewanella oneidensis interacts with electrodes primarily via flavins that function as soluble electron shuttles. Geobacter sulfurreducens makes direct electrical contacts with electrodes via outer-surface, c-type cytochromes. G. sulfurreducens is also capable of long-range electron transport along pili, known as microbial nanowires, that have metallic-like conductivity similar to that previously described in synthetic conducting polymers. Pili networks confer conductivity to G. sulfurreducens biofilms, which function as a conducting polymer, with supercapacitor and transistor functionalities. Conductive microorganisms and/or their nanowires have a number of potential practical applications, but additional basic research will be necessary for rational optimization.
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Affiliation(s)
- Derek R Lovley
- Department of Microbiology, University of Massachusetts, Amherst, 01003, USA.
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Tremblay PL, Aklujkar M, Leang C, Nevin KP, Lovley D. A genetic system for Geobacter metallireducens: role of the flagellin and pilin in the reduction of Fe(III) oxide. ENVIRONMENTAL MICROBIOLOGY REPORTS 2012; 4:82-88. [PMID: 23757233 DOI: 10.1111/j.1758-2229.2011.00305.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Geobacter metallireducens is an important model organism for many novel aspects of extracellular electron exchange and the anaerobic degradation of aromatic compounds, but studies of its physiology have been limited by a lack of techniques for gene deletion and replacement. Therefore, a genetic system was developed for G. metallireducens by making a number of modifications in the previously described approach for homologous recombination in Geobacter sulfurreducens. Critical modifications included, among others, a 3.5-fold increased in the quantity of electrotransformed linear DNA and the harvesting of cells at early-log. The Cre-lox recombination system was used to remove an antibiotic resistance cassette from the G. metallireducens chromosome permitting the generation of multiple mutations in the same strain. Deletion of the gene fliC, which encodes the flagellin protein, resulted in a strain that did not produce flagella, was non-motile, and was defective for the reduction of insoluble Fe(III). Deletion of pilA, which encodes the structural protein of the type IV pili, inhibited the production of lateral pili as well as Fe(III) oxide reduction and electron transfer to an electrode. These results demonstrate the importance of flagella and pili in the reduction of insoluble Fe(III) by G. metallireducens and provide methods for additional genetic-based approaches for the study of G. metallireducens.
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Affiliation(s)
- Pier-Luc Tremblay
- Department of Microbiology, University of Massachusetts, Amherst, MA, USA
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MATSUDA S, LIU H, HASHIMOTO K, NAKANISHI S. Potential and Cell Density Dependences of Extracellular Electron Transfer of Anode-Respiring Geobacter sulfurreducens Cells. ELECTROCHEMISTRY 2012. [DOI: 10.5796/electrochemistry.80.330] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Dissimilatory reduction of extracellular electron acceptors in anaerobic respiration. Appl Environ Microbiol 2011; 78:913-21. [PMID: 22179232 DOI: 10.1128/aem.06803-11] [Citation(s) in RCA: 166] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
An extension of the respiratory chain to the cell surface is necessary to reduce extracellular electron acceptors like ferric iron or manganese oxides. In the past few years, more and more compounds were revealed to be reduced at the surface of the outer membrane of Gram-negative bacteria, and the list does not seem to have an end so far. Shewanella as well as Geobacter strains are model organisms to discover the biochemistry that enables the dissimilatory reduction of extracellular electron acceptors. In both cases, c-type cytochromes are essential electron-transferring proteins. They make the journey of respiratory electrons from the cytoplasmic membrane through periplasm and over the outer membrane possible. Outer membrane cytochromes have the ability to catalyze the last step of the respiratory chains. Still, recent discoveries provided evidence that they are accompanied by further factors that allow or at least facilitate extracellular reduction. This review gives a condensed overview of our current knowledge of extracellular respiration, highlights recent discoveries, and discusses critically the influence of different strategies for terminal electron transfer reactions.
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Arends JBA, Verstraete W. 100 years of microbial electricity production: three concepts for the future. Microb Biotechnol 2011; 5:333-46. [PMID: 21958308 PMCID: PMC3821677 DOI: 10.1111/j.1751-7915.2011.00302.x] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Bioelectrochemical systems (BES) have been explored according to three main concepts: to produce energy from organic substrates, to generate products and to provide specific environmental services. In this work, by using an engineering approach, biological conversion rates are calculated for BES resp. anaerobic digestion. These rates are compared with currents produced by chemical batteries and chemical fuel cells in order to position BES in the 'energy'-market. To evaluate the potential of generating various products, the biochemistry behind the biological conversion rates is examined in relation to terminal electron transfer molecules. By comparing kinetics rather than thermodynamics, more insight is gained in the biological bottlenecks that hamper a BES. The short-term future for BES research and its possible application is situated in smart niches in sustainable environmental development, i.e. in processes where no large currents or investment cost intensive reactors are needed to obtain the desired results. Some specific examples are identified.
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Extracellular reduction of uranium via Geobacter conductive pili as a protective cellular mechanism. Proc Natl Acad Sci U S A 2011; 108:15248-52. [PMID: 21896750 DOI: 10.1073/pnas.1108616108] [Citation(s) in RCA: 149] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The in situ stimulation of Fe(III) oxide reduction by Geobacter bacteria leads to the concomitant precipitation of hexavalent uranium [U(VI)] from groundwater. Despite its promise for the bioremediation of uranium contaminants, the biological mechanism behind this reaction remains elusive. Because Fe(III) oxide reduction requires the expression of Geobacter's conductive pili, we evaluated their contribution to uranium reduction in Geobacter sulfurreducens grown under pili-inducing or noninducing conditions. A pilin-deficient mutant and a genetically complemented strain with reduced outer membrane c-cytochrome content were used as controls. Pili expression significantly enhanced the rate and extent of uranium immobilization per cell and prevented periplasmic mineralization. As a result, pili expression also preserved the vital respiratory activities of the cell envelope and the cell's viability. Uranium preferentially precipitated along the pili and, to a lesser extent, on outer membrane redox-active foci. In contrast, the pilus-defective strains had different degrees of periplasmic mineralization matching well with their outer membrane c-cytochrome content. X-ray absorption spectroscopy analyses demonstrated the extracellular reduction of U(VI) by the pili to mononuclear tetravalent uranium U(IV) complexed by carbon-containing ligands, consistent with a biological reduction. In contrast, the U(IV) in the pilin-deficient mutant cells also required an additional phosphorous ligand, in agreement with the predominantly periplasmic mineralization of uranium observed in this strain. These findings demonstrate a previously unrecognized role for Geobacter conductive pili in the extracellular reduction of uranium, and highlight its essential function as a catalytic and protective cellular mechanism that is of interest for the bioremediation of uranium-contaminated groundwater.
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Liu Y, Kim H, Franklin RR, Bond DR. Linking Spectral and Electrochemical Analysis to Monitor c-type Cytochrome Redox Status in Living Geobacter sulfurreducens Biofilms. Chemphyschem 2011; 12:2235-41. [DOI: 10.1002/cphc.201100246] [Citation(s) in RCA: 153] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Indexed: 01/05/2023]
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Tremblay PL, Summers ZM, Glaven RH, Nevin KP, Zengler K, Barrett CL, Qiu Y, Palsson BO, Lovley DR. A c-type cytochrome and a transcriptional regulator responsible for enhanced extracellular electron transfer in Geobacter sulfurreducens revealed by adaptive evolution. Environ Microbiol 2011; 13:13-23. [PMID: 20636372 DOI: 10.1111/j.1462-2920.2010.02302.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The stimulation of subsurface microbial metabolism often associated with engineered bioremediation of groundwater contaminants presents subsurface microorganisms, which are adapted for slow growth and metabolism in the subsurface, with new selective pressures. In order to better understand how Geobacter species might adapt to selective pressure for faster metal reduction in the subsurface, Geobacter sulfurreducens was put under selective pressure for rapid Fe(III) oxide reduction. The genomes of two resultant strains with rates of Fe(III) oxide reduction that were 10-fold higher than those of the parent strain were resequenced. Both strains contain either a single base-pair change or a 1 nucleotide insertion in a GEMM riboswitch upstream of GSU1761, a gene coding for the periplasmic c-type cytochrome designated PgcA. GSU1771, a gene coding for a SARP regulator, was also mutated in both strains. Introduction of either of the GEMM riboswitch mutations upstream of pgcA in the wild-type increased the abundance of pgcA transcripts, consistent with increased expression of pgcA in the adapted strains. One of the mutations doubled the rate of Fe(III) oxide reduction. Interruption of GSU1771 doubled the Fe(III) oxide reduction rate. This was associated with an increased in expression of pilA, the gene encoding the structural protein for the pili thought to function as microbial nanowires. The combination of the GSU1771 interruption with either of the pgcA mutations resulted in a strain that reduced Fe(III) as fast as the comparable adapted strain. These results suggest that the accumulation of a small number of beneficial mutations under selective pressure, similar to that potentially present during bioremediation, can greatly enhance the capacity for Fe(III) oxide reduction in G. sulfurreducens. Furthermore, the results emphasize the importance of the c-type cytochrome PgcA and pili in Fe(III) oxide reduction and demonstrate how adaptive evolution studies can aid in the elucidation of complex mechanisms, such as extracellular electron transfer.
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Affiliation(s)
- Pier-Luc Tremblay
- Department of Microbiology, University of Massachusetts, Amherst, MA, USACenter for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC, USADepartment of Bioengineering, University of California, San Diego, La Jolla, CA, USA
| | - Zarath M Summers
- Department of Microbiology, University of Massachusetts, Amherst, MA, USACenter for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC, USADepartment of Bioengineering, University of California, San Diego, La Jolla, CA, USA
| | - Richard H Glaven
- Department of Microbiology, University of Massachusetts, Amherst, MA, USACenter for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC, USADepartment of Bioengineering, University of California, San Diego, La Jolla, CA, USA
| | - Kelly P Nevin
- Department of Microbiology, University of Massachusetts, Amherst, MA, USACenter for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC, USADepartment of Bioengineering, University of California, San Diego, La Jolla, CA, USA
| | - Karsten Zengler
- Department of Microbiology, University of Massachusetts, Amherst, MA, USACenter for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC, USADepartment of Bioengineering, University of California, San Diego, La Jolla, CA, USA
| | - Christian L Barrett
- Department of Microbiology, University of Massachusetts, Amherst, MA, USACenter for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC, USADepartment of Bioengineering, University of California, San Diego, La Jolla, CA, USA
| | - Yu Qiu
- Department of Microbiology, University of Massachusetts, Amherst, MA, USACenter for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC, USADepartment of Bioengineering, University of California, San Diego, La Jolla, CA, USA
| | - Bernhard O Palsson
- Department of Microbiology, University of Massachusetts, Amherst, MA, USACenter for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC, USADepartment of Bioengineering, University of California, San Diego, La Jolla, CA, USA
| | - Derek R Lovley
- Department of Microbiology, University of Massachusetts, Amherst, MA, USACenter for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC, USADepartment of Bioengineering, University of California, San Diego, La Jolla, CA, USA
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Lovley DR, Ueki T, Zhang T, Malvankar NS, Shrestha PM, Flanagan KA, Aklujkar M, Butler JE, Giloteaux L, Rotaru AE, Holmes DE, Franks AE, Orellana R, Risso C, Nevin KP. Geobacter: the microbe electric's physiology, ecology, and practical applications. Adv Microb Physiol 2011; 59:1-100. [PMID: 22114840 DOI: 10.1016/b978-0-12-387661-4.00004-5] [Citation(s) in RCA: 384] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Geobacter species specialize in making electrical contacts with extracellular electron acceptors and other organisms. This permits Geobacter species to fill important niches in a diversity of anaerobic environments. Geobacter species appear to be the primary agents for coupling the oxidation of organic compounds to the reduction of insoluble Fe(III) and Mn(IV) oxides in many soils and sediments, a process of global biogeochemical significance. Some Geobacter species can anaerobically oxidize aromatic hydrocarbons and play an important role in aromatic hydrocarbon removal from contaminated aquifers. The ability of Geobacter species to reductively precipitate uranium and related contaminants has led to the development of bioremediation strategies for contaminated environments. Geobacter species produce higher current densities than any other known organism in microbial fuel cells and are common colonizers of electrodes harvesting electricity from organic wastes and aquatic sediments. Direct interspecies electron exchange between Geobacter species and syntrophic partners appears to be an important process in anaerobic wastewater digesters. Functional and comparative genomic studies have begun to reveal important aspects of Geobacter physiology and regulation, but much remains unexplored. Quantifying key gene transcripts and proteins of subsurface Geobacter communities has proven to be a powerful approach to diagnose the in situ physiological status of Geobacter species during groundwater bioremediation. The growth and activity of Geobacter species in the subsurface and their biogeochemical impact under different environmental conditions can be predicted with a systems biology approach in which genome-scale metabolic models are coupled with appropriate physical/chemical models. The proficiency of Geobacter species in transferring electrons to insoluble minerals, electrodes, and possibly other microorganisms can be attributed to their unique "microbial nanowires," pili that conduct electrons along their length with metallic-like conductivity. Surprisingly, the abundant c-type cytochromes of Geobacter species do not contribute to this long-range electron transport, but cytochromes are important for making the terminal electrical connections with Fe(III) oxides and electrodes and also function as capacitors, storing charge to permit continued respiration when extracellular electron acceptors are temporarily unavailable. The high conductivity of Geobacter pili and biofilms and the ability of biofilms to function as supercapacitors are novel properties that might contribute to the field of bioelectronics. The study of Geobacter species has revealed a remarkable number of microbial physiological properties that had not previously been described in any microorganism. Further investigation of these environmentally relevant and physiologically unique organisms is warranted.
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Affiliation(s)
- Derek R Lovley
- Department of Microbiology and Environmental Biotechnology Center, University of Massachusetts, Amherst, Massachusetts, USA
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Genome-wide survey for PilR recognition sites of the metal-reducing prokaryote Geobacter sulfurreducens. Gene 2010; 469:31-44. [DOI: 10.1016/j.gene.2010.08.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2010] [Revised: 08/03/2010] [Accepted: 08/05/2010] [Indexed: 11/20/2022]
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Klimes A, Franks AE, Glaven RH, Tran H, Barrett CL, Qiu Y, Zengler K, Lovley DR. Production of pilus-like filaments in Geobacter sulfurreducens in the absence of the type IV pilin protein PilA. FEMS Microbiol Lett 2010; 310:62-8. [PMID: 20629752 DOI: 10.1111/j.1574-6968.2010.02046.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The pili of Geobacter sulfurreducens are of interest because of the apparent importance of the type IV pili in extracellular electron transfer. A strain of G. sulfurreducens, designated strain MA, produced many more pili than the previously studied DL-1 strain even though genome resequencing indicated that the MA and DL-1 genome sequences were identical. Filaments that looked similar to type IV pili in transmission electron micrographs were abundant even after the gene encoding PilA, the structural pilin protein, was deleted. The results of proteinase K treatment indicated that the filaments were proteinaceous. The simultaneous deletion of several genes encoding homologues of type II pseudopilins was required before the filaments were significantly depleted. The pilA-deficient MA strain attached to glass as well as the wild-type MA did, but strains in which three or four pseudopilin genes were deleted in addition to pilA had impaired attachment capabilities. These results demonstrate that there are several proteins that can yield pilin-like filaments in G. sulfurreducens and that some means other than microscopic observation is required before the composition of filaments can be unambiguously specified.
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Affiliation(s)
- Anna Klimes
- Department of Microbiology, University of Massachusetts Amherst, Amherst, MA 01003, USA.
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Marshall MJ, Beliaev AS, Fredrickson JK. Microbial Transformations of Radionuclides in the Subsurface. Environ Microbiol 2010. [DOI: 10.1002/9780470495117.ch4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Alignment of the c-type cytochrome OmcS along pili of Geobacter sulfurreducens. Appl Environ Microbiol 2010; 76:4080-4. [PMID: 20400557 DOI: 10.1128/aem.00023-10] [Citation(s) in RCA: 271] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Immunogold localization revealed that OmcS, a cytochrome that is required for Fe(III) oxide reduction by Geobacter sulfurreducens, was localized along the pili. The apparent spacing between OmcS molecules suggests that OmcS facilitates electron transfer from pili to Fe(III) oxides rather than promoting electron conduction along the length of the pili.
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Marsili E, Sun J, Bond D. Voltammetry and Growth Physiology of Geobacter sulfurreducens Biofilms as a Function of Growth Stage and Imposed Electrode Potential. ELECTROANAL 2010. [DOI: 10.1002/elan.200800007] [Citation(s) in RCA: 212] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Bouhenni R, Vora G, Biffinger J, Shirodkar S, Brockman K, Ray R, Wu P, Johnson B, Biddle E, Marshall M, Fitzgerald L, Little B, Fredrickson J, Beliaev A, Ringeisen B, Saffarini D. The Role of Shewanella oneidensis MR-1 Outer Surface Structures in Extracellular Electron Transfer. ELECTROANAL 2010. [DOI: 10.1002/elan.200880006] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Role of Geobacter sulfurreducens outer surface c-type cytochromes in reduction of soil humic acid and anthraquinone-2,6-disulfonate. Appl Environ Microbiol 2010; 76:2371-5. [PMID: 20154112 DOI: 10.1128/aem.02250-09] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Deleting individual genes for outer surface c-type cytochromes in Geobacter sulfurreducens partially inhibited the reduction of humic substances and anthraquinone-2,6,-disulfonate. Complete inhibition was obtained only when five of these genes were simultaneously deleted, suggesting that diverse outer surface cytochromes can contribute to the reduction of humic substances and other extracellular quinones.
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