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Hu N, Xiao F, Zhang D, Hu R, Xiong R, Lv W, Yang Z, Tan W, Yu H, Ding D, Yan Q, He Z. Organophosphorus mineralizing-Streptomyces species underpins uranate immobilization and phosphorus availability in uranium tailings. JOURNAL OF HAZARDOUS MATERIALS 2024; 476:134975. [PMID: 38908177 DOI: 10.1016/j.jhazmat.2024.134975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/22/2024] [Revised: 06/11/2024] [Accepted: 06/18/2024] [Indexed: 06/24/2024]
Abstract
Phosphate-solubilizing bacteria (PSB) are important but often overlooked regulators of uranium (U) cycling in soil. However, the impact of PSB on uranate fixation coupled with the decomposition of recalcitrant phosphorus (P) in mining land remains poorly understood. Here, we combined gene amplicon sequencing, metagenome and metatranscriptome sequencing analysis and strain isolation to explore the effects of PSB on the stabilization of uranate and P availability in U mining areas. We found that the content of available phosphorus (AP), carbonate-U and Fe-Mn-U oxides in tailings was significantly (P < 0.05) higher than their adjacent soils. Also, organic phosphate mineralizing (PhoD) bacteria (e.g., Streptomyces) and inorganic phosphate solubilizing (gcd) bacteria (e.g., Rhodococcus) were enriched in tailings and soils, but only organic phosphate mineralizing-bacteria substantially contributed to the AP. Notably, most genes involved in organophosphorus mineralization and uranate resistance were widely present in tailings rather than soil. Comparative genomics analyses supported that organophosphorus mineralizing-Streptomyces species could increase soil AP content and immobilize U(VI) through organophosphorus mineralization (e.g., PhoD, ugpBAEC) and U resistance related genes (e.g., petA). We further demonstrated that the isolated Streptomyces sp. PSBY1 could enhance the U(VI) immobilization mediated by the NADH-dependent ubiquinol-cytochrome c reductase (petA) through decomposing organophosphorous compounds. This study advances our understanding of the roles of PSB in regulating the fixation of uranate and P availability in U tailings.
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Affiliation(s)
- Nan Hu
- Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang 421001, China
| | - Fangfang Xiao
- Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang 421001, China
| | - Dandan Zhang
- Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), School of Marine Science, State Key Laboratory for Biocontrol, Sun Yat-sen University, Zhuhai 519080, China
| | - Ruiwen Hu
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Rui Xiong
- Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang 421001, China
| | - Wenpan Lv
- Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang 421001, China
| | - Zhaolan Yang
- Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang 421001, China
| | - Wenfa Tan
- Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang 421001, China
| | - Huang Yu
- Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang 421001, China.
| | - Dexin Ding
- Key Discipline Laboratory for National Defense for Biotechnology in Uranium Mining and Hydrometallurgy, University of South China, Hengyang 421001, China
| | - Qingyun Yan
- Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), School of Marine Science, State Key Laboratory for Biocontrol, Sun Yat-sen University, Zhuhai 519080, China
| | - Zhili He
- Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), School of Marine Science, State Key Laboratory for Biocontrol, Sun Yat-sen University, Zhuhai 519080, China
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D'Ermo G, Audebert S, Camoin L, Planer-Friedrich B, Casiot-Marouani C, Delpoux S, Lebrun R, Guiral M, Schoepp-Cothenet B. Quantitative proteomics reveals the Sox system's role in sulphur and arsenic metabolism of phototroph Halorhodospira halophila. Environ Microbiol 2024; 26:e16655. [PMID: 38897608 DOI: 10.1111/1462-2920.16655] [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: 02/08/2024] [Accepted: 05/07/2024] [Indexed: 06/21/2024]
Abstract
The metabolic process of purple sulphur bacteria's anoxygenic photosynthesis has been primarily studied in Allochromatium vinosum, a member of the Chromatiaceae family. However, the metabolic processes of purple sulphur bacteria from the Ectothiorhodospiraceae and Halorhodospiraceae families remain unexplored. We have analysed the proteome of Halorhodospira halophila, a member of the Halorhodospiraceae family, which was cultivated with various sulphur compounds. This analysis allowed us to reconstruct the first comprehensive sulphur-oxidative photosynthetic network for this family. Some members of the Ectothiorhodospiraceae family have been shown to use arsenite as a photosynthetic electron donor. Therefore, we analysed the proteome response of Halorhodospira halophila when grown under arsenite and sulphide conditions. Our analyses using ion chromatography-inductively coupled plasma mass spectrometry showed that thioarsenates are chemically formed under these conditions. However, they are more extensively generated and converted in the presence of bacteria, suggesting a biological process. Our quantitative proteomics revealed that the SoxAXYZB system, typically dedicated to thiosulphate oxidation, is overproduced under these growth conditions. Additionally, two electron carriers, cytochrome c551/c5 and HiPIP III, are also overproduced. Electron paramagnetic resonance spectroscopy suggested that these transporters participate in the reduction of the photosynthetic Reaction Centre. These results support the idea of a chemically and biologically formed thioarsenate being oxidized by the Sox system, with cytochrome c551/c5 and HiPIP III directing electrons towards the Reaction Centre.
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Affiliation(s)
- Giulia D'Ermo
- Aix-Marseille Université, CNRS, BIP-UMR 7281, Marseille, France
| | - Stéphane Audebert
- Aix-Marseille Université, Inserm, CNRS, Institut Paoli-Calmettes, CRCM, Marseille Protéomique, Marseille, France
| | - Luc Camoin
- Aix-Marseille Université, Inserm, CNRS, Institut Paoli-Calmettes, CRCM, Marseille Protéomique, Marseille, France
| | - Britta Planer-Friedrich
- Environmental Geochemistry, Bayreuth Centre for Ecology and Environmental Research (BAYCEER), University of Bayreuth, Bayreuth, Germany
| | | | - Sophie Delpoux
- Laboratoire HydroSciences Montpellier, Univ. Montpellier, CNRS, IRD, Montpellier, France
| | - Régine Lebrun
- Aix-Marseille Université, CNRS, IMM-FR3479, Marseille Protéomique, Marseille, France
| | - Marianne Guiral
- Aix-Marseille Université, CNRS, BIP-UMR 7281, Marseille, France
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Liang ZH, Sun H, Li Y, Hu A, Tang Q, Yu HQ. Enforcing energy consumption promotes microbial extracellular respiration for xenobiotic bioconversion. Environ Microbiol 2023; 25:2943-2957. [PMID: 37602917 DOI: 10.1111/1462-2920.16484] [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: 12/15/2022] [Accepted: 08/08/2023] [Indexed: 08/22/2023]
Abstract
Extracellular electron transfer (EET) empowers electrogens to catalyse the bioconversion of a wide range of xenobiotics in the environment. Synthetic bioengineering has proven effective in promoting EET output. However, conventional strategies mainly focus on modifications of EET-related genes or pathways, which leads to a bottleneck due to the intricate nature of electrogenic metabolic properties and intricate pathway regulation that remain unelucidated. Herein, we propose a novel EET pathway-independent approach, from an energy manipulation perspective, to enhance microbial EET output. The Controlled Hydrolyzation of ATP to Enhance Extracellular Respiration (CHEER) strategy promotes energy utilization and persistently reduces the intracellular ATP level in Shewanella oneidensis, a representative electrogenic microbe. This approach leads to the accelerated consumption of carbon substrate, increased biomass accumulation and an expanded intracellular NADH pool. Both microbial electrolysis cell and microbial fuel cell tests exhibit that the CHEER strain substantially enhances EET capability. Analysis of transcriptome profiles reveals that the CHEER strain considerably bolsters biomass synthesis and metabolic activity. When applied to the bioconversion of model xenobiotics including methyl orange, Cr(VI) and U(VI), the CHEER strain consistently exhibits enhanced removal efficiencies. This work provides a new perspective and a feasible strategy to enhance microbial EET for efficient xenobiotic conversion.
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Affiliation(s)
- Zi-Han Liang
- Department of Environmental Science and Technology, University of Science and Technology of China, Hefei, China
| | - Hong Sun
- CAS Key Laboratory of Urban Pollutant Conversion, School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Yang Li
- CAS Key Laboratory of Urban Pollutant Conversion, School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Anyi Hu
- CAS Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, China
| | - Qiang Tang
- Department of Environmental Science and Technology, University of Science and Technology of China, Hefei, China
| | - Han-Qing Yu
- Department of Environmental Science and Technology, University of Science and Technology of China, Hefei, China
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Klein EM, Knoll MT, Gescher J. Microbe-Anode Interactions: Comparing the impact of genetic and material engineering approaches to improve the performance of microbial electrochemical systems (MES). Microb Biotechnol 2023; 16:1179-1202. [PMID: 36808480 PMCID: PMC10221544 DOI: 10.1111/1751-7915.14236] [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: 08/09/2022] [Revised: 01/30/2023] [Accepted: 02/02/2023] [Indexed: 02/20/2023] Open
Abstract
Microbial electrochemical systems (MESs) are a highly versatile platform technology with a particular focus on power or energy production. Often, they are used in combination with substrate conversion (e.g., wastewater treatment) and production of value-added compounds via electrode-assisted fermentation. This rapidly evolving field has seen great improvements both technically and biologically, but this interdisciplinarity sometimes hampers overseeing strategies to increase process efficiency. In this review, we first briefly summarize the terminology of the technology and outline the biological background that is essential for understanding and thus improving MES technology. Thereafter, recent research on improvements at the biofilm-electrode interface will be summarized and discussed, distinguishing between biotic and abiotic approaches. The two approaches are then compared, and resulting future directions are discussed. This mini-review therefore provides basic knowledge of MES technology and the underlying microbiology in general and reviews recent improvements at the bacteria-electrode interface.
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Affiliation(s)
- Edina M. Klein
- Institute of Technical MicrobiologyUniversity of Technology HamburgHamburgGermany
| | - Melanie T. Knoll
- Institute of Technical MicrobiologyUniversity of Technology HamburgHamburgGermany
| | - Johannes Gescher
- Institute of Technical MicrobiologyUniversity of Technology HamburgHamburgGermany
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Jia Y, Liu D, Chen Y, Hu Y. Evidence for the feasibility of transmembrane proton gradient regulating oxytetracycline extracellular biodegradation mediated by biosynthesized palladium nanoparticles. JOURNAL OF HAZARDOUS MATERIALS 2023; 455:131544. [PMID: 37196438 DOI: 10.1016/j.jhazmat.2023.131544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Revised: 04/16/2023] [Accepted: 04/29/2023] [Indexed: 05/19/2023]
Abstract
Extracellular biodegradation is a promising technology for removing antibiotics and repressing the spread of resistance genes, but the strategy is limited by the low extracellular electron transfer (EET) efficiency of microorganisms. In this work, biogenic Pd0 nanoparticles (bio-Pd0) were introduced in cells in situ to enhance oxytetracycline (OTC) extracellular degradation and the effects of transmembrane proton gradient (TPG) on EET and energy metabolism mediated by bio-Pd0 were investigated. The results indicated that the intracellular OTC concentration gradually decreased with increase in pH due to the simultaneous decreases of OTC adsorption and TPG-dependent OTC uptake. On the contrary, the efficiency of OTC biodegradation mediated by bio-Pd0@B. megaterium showed a pH-dependent increase. The negligible intracellular OTC degradation, the high dependence of OTC biodegradation on respiration chain and the results on enzyme activity and respiratory chain inhibition experiments showed that NADH-dependent (rather than FADH2-dependent) EET process mediated by substrate-level phosphorylation modulated OTC biodegradation due to high energy storage and proton translocation capacity. Moreover, the results showed that altering TPG is an efficient approach to improve EET efficiency, which can be attributed to the increased NADH generation by the TCA cycle, enhanced transmembrane electron output efficiency (as evidenced by increased intracellular electron transfer system (IETS) activity, the negative shift of onset potential, and enhanced one-electron transfer through bound flavin) and stimulation of substrate-level phosphorylation energy metabolism catalyzed by succinic thiokinase (STH) under low TPG conditions. The results of structural equation model that OTC biodegradation was directly and positively modulated by the net outward proton flux as well as STH activity, and indirectly regulated by TPG through NADH level and IETS activity confirmed the previous findings. This study provides a new perspective for engineering microbial EET and application of bioelectrochemistry processes in bioremediation.
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Affiliation(s)
- Yating Jia
- School of Environment and Safety Engineering, North University of China, Taiyuan 030051, China; Ministry of Education Key Laboratory of Pollution Control and Ecological Remediation for Industrial Agglomeration Area, School of Environment and Energy, South China University of Technology, Guangzhou 510006, China
| | - Dejin Liu
- Ministry of Education Key Laboratory of Pollution Control and Ecological Remediation for Industrial Agglomeration Area, School of Environment and Energy, South China University of Technology, Guangzhou 510006, China
| | - Yuancai Chen
- Ministry of Education Key Laboratory of Pollution Control and Ecological Remediation for Industrial Agglomeration Area, School of Environment and Energy, South China University of Technology, Guangzhou 510006, China.
| | - Yongyou Hu
- Ministry of Education Key Laboratory of Pollution Control and Ecological Remediation for Industrial Agglomeration Area, School of Environment and Energy, South China University of Technology, Guangzhou 510006, China
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Li J, Han H, Chang Y, Wang B. The material-microorganism interface in microbial hybrid electrocatalysis systems. NANOSCALE 2023; 15:6009-6024. [PMID: 36912348 DOI: 10.1039/d3nr00742a] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
This review presents a comprehensive summary of the material-microorganism interface in microbial hybrid electrocatalysis systems. Microbial hybrid electrocatalysis has been developed to combine the advantages of inorganic electrocatalysis and microbial catalysis. However, electron transfer at the interfaces between microorganisms and materials is a very critical issue that affects the efficiency of the system. Therefore, this review focuses on the electron transfer at the material-microorganism interface and the strategies for building efficient microorganism and material interfaces. We begin with a brief introduction of the electron transfer mechanism in both the bioanode and biocathode of bioelectrochemical systems to understand the material-microorganism interface. Next, we summarise the strategies for constructing efficient material-microorganism interfaces including material design and modification and bacterial engineering. We also discuss emerging studies on the bio-inorganic hybrid electrocatalysis system. Understanding the interface between electrode/active materials and the microorganisms, especially the electron transfer processes, could help to drive the evolution of material-microorganism hybrid electrocatalysis systems towards maturity.
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Affiliation(s)
- Jiyao Li
- Department of Environmental Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China.
- Beijing Key Laboratory of Resource-oriented Treatment of Industrial Pollutants, Beijing 100083, China
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology (NCNST), Beijing 100190, China.
| | - Hexing Han
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology (NCNST), Beijing 100190, China.
| | - Yanhong Chang
- Department of Environmental Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China.
- Beijing Key Laboratory of Resource-oriented Treatment of Industrial Pollutants, Beijing 100083, China
| | - Bin Wang
- CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology (NCNST), Beijing 100190, China.
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A Cysteine Pair Controls Flavin Reduction by Extracellular Cytochromes during Anoxic/Oxic Environmental Transitions. mBio 2023; 14:e0258922. [PMID: 36645302 PMCID: PMC9973256 DOI: 10.1128/mbio.02589-22] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Many bacteria of the genus Shewanella are facultative anaerobes able to reduce a broad range of soluble and insoluble substrates, including Fe(III) mineral oxides. Under anoxic conditions, the bacterium Shewanella oneidensis MR-1 uses a porin-cytochrome complex (Mtr) to mediate extracellular electron transfer (EET) across the outer membrane to extracellular substrates. However, it is unclear how EET prevents generating harmful reactive oxygen species (ROS) when exposed to oxic environments. The Mtr complex is expressed under anoxic and oxygen-limited conditions and contains an extracellular MtrC subunit. This has a conserved CX8C motif that inhibits aerobic growth when removed. This inhibition is caused by an increase in ROS that kills the majority of S. oneidensis cells in culture. To better understand this effect, soluble MtrC isoforms with modified CX8C were isolated. These isoforms produced increased concentrations of H2O2 in the presence of flavin mononucleotide (FMN) and greatly increased the affinity between MtrC and FMN. X-ray crystallography revealed that the molecular structure of MtrC isoforms was largely unchanged, while small-angle X-ray scattering suggested that a change in flexibility was responsible for controlling FMN binding. Together, these results reveal that FMN reduction in S. oneidensis MR-1 is controlled by the redox-active disulfide on the cytochrome surface. In the presence of oxygen, the disulfide forms, lowering the affinity for FMN and decreasing the rate of peroxide formation. This cysteine pair consequently allows the cell to respond to changes in oxygen level and survive in a rapidly transitioning environment. IMPORTANCE Bacteria that live at the oxic/anoxic interface have to rapidly adapt to changes in oxygen levels within their environment. The facultative anaerobe Shewanella oneidensis MR-1 can use EET to respire in the absence of oxygen, but on exposure to oxygen, EET could directly reduce extracellular oxygen and generate harmful reactive oxygen species that damage the bacterium. By modifying an extracellular cytochrome called MtrC, we show how preventing a redox-active disulfide from forming causes the production of cytotoxic concentrations of peroxide. The disulfide affects the affinity of MtrC for the redox-active flavin mononucleotide, which is part of the EET pathway. Our results demonstrate how a cysteine pair exposed on the surface controls the path of electron transfer, allowing facultative anaerobic bacteria to rapidly adapt to changes in oxygen concentration at the oxic/anoxic interface.
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Lack of Specificity in Geobacter Periplasmic Electron Transfer. J Bacteriol 2022; 204:e0032222. [PMID: 36383007 PMCID: PMC9765071 DOI: 10.1128/jb.00322-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Reduction of extracellular acceptors requires electron transfer across the periplasm. In Geobacter sulfurreducens, three separate cytoplasmic membrane cytochromes are utilized depending on redox potential, and at least five cytochrome conduits span the outer membrane. Because G. sulfurreducens produces 5 structurally similar triheme periplasmic cytochromes (PpcABCDE) that differ in expression level, midpoint potential, and heme biochemistry, many hypotheses propose distinct periplasmic carriers could be used for specific redox potentials, terminal acceptors, or growth conditions. Using a panel of marker-free single, quadruple, and quintuple mutants, little support for these models could be found. Three quadruple mutants containing only one paralog (PpcA, PpcB, and PpcD) reduced Fe(III) citrate and Fe(III) oxide at the same rate and extent, even though PpcB and PpcD were at much lower periplasmic levels than PpcA. Mutants containing only PpcC and PpcE showed defects, but these cytochromes were nearly undetectable in the periplasm. When expressed sufficiently, PpcC and PpcE supported wild-type Fe(III) reduction. PpcA and PpcE from G. metallireducens similarly restored metal respiration in G. sulfurreducens. PgcA, an unrelated extracellular triheme c-type cytochrome, also participated in periplasmic electron transfer. While triheme cytochromes were important for metal reduction, sextuple ΔppcABCDE ΔpgcA mutants grew near wild-type rates with normal cyclic voltammetry profiles when using anodes as electron acceptors. These results reveal broad promiscuity in the periplasmic electron transfer network of metal-reducing Geobacter and suggest that an as-yet-undiscovered periplasmic mechanism supports electron transfer to electrodes. IMPORTANCE Many inner and outer membrane cytochromes used by Geobacter for electron transfer to extracellular acceptors have specific functions. How these are connected by periplasmic carriers remains poorly understood. G. sulfurreducens contains multiple triheme periplasmic cytochromes with unique biochemical properties and expression profiles. It is hypothesized that each could be involved in a different respiratory pathway, depending on redox potential or energy needs. Here, we show that Geobacter periplasmic cytochromes instead show evidence of being highly promiscuous. Any of 6 triheme cytochromes supported similar growth with soluble or insoluble metals, but none were required when cells utilized electrodes. These findings fail to support many models of Geobacter electron transfer, and question why these organisms produce such an array of periplasmic cytochromes.
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Hao X, Tang J, Yi X, Gao K, Yao Q, Feng C, Huang W, Dang Z. Extracellular polymeric substance induces biogenesis of vivianite under inorganic phosphate-free conditions. J Environ Sci (China) 2022; 120:115-124. [PMID: 35623765 DOI: 10.1016/j.jes.2021.08.043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 08/16/2021] [Accepted: 08/17/2021] [Indexed: 06/15/2023]
Abstract
Vivianite is often found in reducing environments rich in iron and phosphorus from organic debris degradation or phosphorus mineral dissolution. The formation of vivianite is essential to the geochemical cycling of phosphorus and iron elements in natural environments. In this study, extracellular polymeric substances (EPS) were selected as the source of phosphorus. Microcosm experiments were conducted to test the evolution of mineralogy during the reduction of polyferric sulfate flocs (PFS) by Shewanella oneidensis MR-1 (S. oneidensis MR-1) at EPS concentrations of 0, 0.03, and 0.3 g/L. Vivianite was found to be the secondary mineral in EPS treatment when there was no phosphate in the media. The EPS DNA served as the phosphorus source and DNA-supplied phosphate could induce the formation of vivianite. EPS impedes PFS aggregation, contains redox proteins and stores electron shuttle, and thus greatly promotes the formation of minerals and enhances the reduction of Fe(III). At EPS concentration of 0, 0.03, and 0.3 g/L, the produced HCl-extractable Fe(II) was 107.9, 111.0, and 115.2 mg/L, respectively. However, when the microcosms remained unstirred, vivianite can be formed without the addition of EPS. In unstirred systems, the EPS secreted by S. oneidensis MR-1 could agglomerate at some areas, resulting in the formation of vivianite in the proximity of microbial cells. It was found that vivianite can be generated biogenetically by S. oneidensis MR-1 strain and EPS may play a key role in iron reduction and concentrating phosphorus in the oligotrophic ecosystems where quiescent conditions prevail.
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Affiliation(s)
- Xinrui Hao
- School of Environment and Energy, South China University of Technology, Guangzhou 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, South China University of Technology, Guangzhou 510006, China
| | - Jie Tang
- School of Environment and Energy, South China University of Technology, Guangzhou 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, South China University of Technology, Guangzhou 510006, China
| | - Xiaoyun Yi
- School of Environment and Energy, South China University of Technology, Guangzhou 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, South China University of Technology, Guangzhou 510006, China.
| | - Kun Gao
- School of Environment and Energy, South China University of Technology, Guangzhou 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, South China University of Technology, Guangzhou 510006, China
| | - Qian Yao
- School of Environment and Energy, South China University of Technology, Guangzhou 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, South China University of Technology, Guangzhou 510006, China
| | - Chunhua Feng
- School of Environment and Energy, South China University of Technology, Guangzhou 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, South China University of Technology, Guangzhou 510006, China
| | - Weilin Huang
- Department of Environmental Science, Rutgers University, New Brunswick, NJ 08901, USA
| | - Zhi Dang
- School of Environment and Energy, South China University of Technology, Guangzhou 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, South China University of Technology, Guangzhou 510006, China
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10
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Single molecule tracking of bacterial cell surface cytochromes reveals dynamics that impact long-distance electron transport. Proc Natl Acad Sci U S A 2022; 119:e2119964119. [PMID: 35503913 PMCID: PMC9171617 DOI: 10.1073/pnas.2119964119] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Multiheme cytochromes in Shewanella oneidensis MR-1 transport electrons across the cell wall, in a process called extracellular electron transfer. These electron conduits can also enable electron transport along and between cells. While the underlying mechanism is thought to involve a combination of electron hopping and lateral diffusion of cytochromes along membranes, these diffusive dynamics have never been observed in vivo. Here, we observe the mobility of quantum dot-labeled cytochromes on living cell surfaces and membrane nanowires, quantify their diffusion with single-particle tracking techniques, and simulate the contribution of these dynamics to electron transport. This work reveals the impact of redox molecule dynamics on bacterial electron transport, with implications for understanding and harnessing this process in the environment and bioelectronics. Using a series of multiheme cytochromes, the metal-reducing bacterium Shewanella oneidensis MR-1 can perform extracellular electron transfer (EET) to respire redox-active surfaces, including minerals and electrodes outside the cell. While the role of multiheme cytochromes in transporting electrons across the cell wall is well established, these cytochromes were also recently found to facilitate long-distance (micrometer-scale) redox conduction along outer membranes and across multiple cells bridging electrodes. Recent studies proposed that long-distance conduction arises from the interplay of electron hopping and cytochrome diffusion, which allows collisions and electron exchange between cytochromes along membranes. However, the diffusive dynamics of the multiheme cytochromes have never been observed or quantified in vivo, making it difficult to assess their hypothesized contribution to the collision-exchange mechanism. Here, we use quantum dot labeling, total internal reflection fluorescence microscopy, and single-particle tracking to quantify the lateral diffusive dynamics of the outer membrane-associated decaheme cytochromes MtrC and OmcA, two key components of EET in S. oneidensis. We observe confined diffusion behavior for both quantum dot-labeled MtrC and OmcA along cell surfaces (diffusion coefficients DMtrC = 0.0192 ± 0.0018 µm2/s, DOmcA = 0.0125 ± 0.0024 µm2/s) and the membrane extensions thought to function as bacterial nanowires. We find that these dynamics can trace a path for electron transport via overlap of cytochrome trajectories, consistent with the long-distance conduction mechanism. The measured dynamics inform kinetic Monte Carlo simulations that combine direct electron hopping and redox molecule diffusion, revealing significant electron transport rates along cells and membrane nanowires.
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Morgado L, Salgueiro CA. Elucidation of complex respiratory chains: a straightforward strategy to monitor electron transfer between cytochromes. Metallomics 2022; 14:6539350. [DOI: 10.1093/mtomcs/mfac012] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 02/17/2022] [Indexed: 11/12/2022]
Abstract
Abstract
Cytochromes are electron transfer proteins essential in various biological systems, playing crucial roles in the respiratory chains of bacteria. These proteins are particularly abundant in electrogenic microorganisms and are responsible for the efficient delivery of electrons to the cells’ exterior. The capability of sending electron outside the cells open new avenues to be explored for emerging biotechnological applications in bioremediation, microbial electrosynthesis and bioenergy fields. To develop these applications, it is critical to identify the different redox partners and elucidate the stepwise electron transfer along the respiratory paths. However, investigating direct electron transfer events between proteins with identical features in nearly all spectroscopic techniques is extremely challenging. NMR spectroscopy offers the possibility to overcome this difficulty by analysing the alterations of the spectral signatures of each protein caused by electron exchange events. The uncrowded NMR spectral regions containing the heme resonances of the cytochromes display unique and distinct signatures in the reduced and oxidized states, which can be explored to monitor electron transfer within the redox complex. In this study, we present a strategy for a fast and straightforward monitorization of electron transfer between c-type cytochromes, using as model a triheme periplasmic cytochrome (PpcA) and a membrane associated monoheme cytochrome (OmcF) from the electrogenic bacterium Geobacter sulfurreducens. The comparison between the 1D 1H NMR spectra obtained for samples containing the two cytochromes and for samples containing the individual proteins clearly demonstrated a unidirectional electron transfer within the redox complex. This strategy provides a simple and straightforward means to elucidate complex biologic respiratory electron transfer chains.
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Affiliation(s)
- Leonor Morgado
- Associate Laboratory i4HB—Institute for Health and Bioeconomy, NOVA School of Science and Technology, NOVA University Lisbon, 2819-516 Caparica, Portugal
- UCIBIO—Applied Molecular Biosciences Unit, Department of Chemistry, NOVA School of Science and Technology, NOVA University Lisbon, 2819-516 Caparica, Portugal
| | - Carlos A Salgueiro
- Associate Laboratory i4HB—Institute for Health and Bioeconomy, NOVA School of Science and Technology, NOVA University Lisbon, 2819-516 Caparica, Portugal
- UCIBIO—Applied Molecular Biosciences Unit, Department of Chemistry, NOVA School of Science and Technology, NOVA University Lisbon, 2819-516 Caparica, Portugal
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Partipilo G, Graham AJ, Belardi B, Keitz BK. Extracellular Electron Transfer Enables Cellular Control of Cu(I)-Catalyzed Alkyne-Azide Cycloaddition. ACS CENTRAL SCIENCE 2022; 8:246-257. [PMID: 35233456 PMCID: PMC8875427 DOI: 10.1021/acscentsci.1c01208] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Indexed: 05/03/2023]
Abstract
Extracellular electron transfer (EET) is an anaerobic respiration process that couples carbon oxidation to the reduction of metal species. In the presence of a suitable metal catalyst, EET allows for cellular metabolism to control a variety of synthetic transformations. Here, we report the use of EET from the electroactive bacterium Shewanella oneidensis for metabolic and genetic control over Cu(I)-catalyzed alkyne-azide cycloaddition (CuAAC). CuAAC conversion under anaerobic and aerobic conditions was dependent on live, actively respiring S. oneidensis cells. The reaction progress and kinetics were manipulated by tailoring the central carbon metabolism. Similarly, EET-CuAAC activity was dependent on specific EET pathways that could be regulated via inducible expression of EET-relevant proteins: MtrC, MtrA, and CymA. EET-driven CuAAC exhibited modularity and robustness in the ligand and substrate scope. Furthermore, the living nature of this system could be exploited to perform multiple reaction cycles without regeneration, something inaccessible to traditional chemical reductants. Finally, S. oneidensis enabled bioorthogonal CuAAC membrane labeling on live mammalian cells without affecting cell viability, suggesting that S. oneidensis can act as a dynamically tunable biocatalyst in complex environments. In summary, our results demonstrate how EET can expand the reaction scope available to living systems by enabling cellular control of CuAAC.
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Affiliation(s)
- Gina Partipilo
- McKetta
Department of Chemical Engineering, University
of Texas at Austin, Austin, Texas 78712, United States
- Center
for Dynamics and Control of Materials, University
of Texas at Austin, Austin, Texas 78712, United States
| | - Austin J. Graham
- McKetta
Department of Chemical Engineering, University
of Texas at Austin, Austin, Texas 78712, United States
- Center
for Dynamics and Control of Materials, University
of Texas at Austin, Austin, Texas 78712, United States
| | - Brian Belardi
- McKetta
Department of Chemical Engineering, University
of Texas at Austin, Austin, Texas 78712, United States
| | - Benjamin K. Keitz
- McKetta
Department of Chemical Engineering, University
of Texas at Austin, Austin, Texas 78712, United States
- Center
for Dynamics and Control of Materials, University
of Texas at Austin, Austin, Texas 78712, United States
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Xiao Y, Lu H, Tan W, Tang J, Wang Y, Shi J, Yu T, Yuan Y. Effects of compost-derived humic acid on the bio-dechlorination of pentachlorophenol in high iron content paddy soil. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2021; 227:112900. [PMID: 34673405 DOI: 10.1016/j.ecoenv.2021.112900] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Revised: 10/08/2021] [Accepted: 10/11/2021] [Indexed: 06/13/2023]
Abstract
Pentachlorophenol (PCP) is a common residual organic pollutant in paddy soil, and its harmful effects on soil ecosystems have been confirmed. Humic acid (HA) could act as an electron shuttle to promote the reductive dechlorination of PCP under anaerobic conditions. Humic-like substances produced by composting of kitchen waste were able to facilitate the reductive dechlorination of PCP during Fe(III) oxide reduction by iron-reducing bacteria. However, the effects of compost-derived HAs on reductive dechlorination of PCP in a paddy soil system with a high iron content have not been fully confirmed. The characteristics of HAs from different stages of composting during bio-dechlorination of PCP were still unclear. The functional components of compost-derived HAs, which are responsible for reductive dechlorination of PCP in different stages of composting, also need further investigation. In this study, we conducted a series of experiments on the Guangdong paddy soil system with high iron content (17.5 mg kg-1) to investigate the reductive dechlorination of PCP by HA in the early, middle, and later stages of food waste composting. The results showed that the middle- and late-stages of compost-derived HAs all promoted reductive dechlorination of PCP in the paddy system, but it was opposite in the early-stage. Significant differences were also presented in the components of HAs from different stages of composting. The early-stage compost-derived HAs contain numerous easy degradable components, it would inhibit the dechlorination of PCP by the changes of microbial metabolism in paddy soil. Compost-derived HAs in the middle composting stage showed the best reductive dechlorination effects on PCP. The reason might be that the compost-derived HAs in the middle composting stage could act both as electron donors and transfers. The electron transfer capacities (ETC) of middle-stage compost-derived HAs were significantly higher than those in the early and later composting stages. Compared with the natural HAs in the soil system, compost-derived HAs contained more chlorinated products with lower toxicities after the PCP degradation. This result mainly contributed to the detoxification and mineralization of PCP in the soil. These findings clarified the effects of compost-derived HAs on PCP bio-dechlorination in paddy soil with high iron content, identifying the optimal phase of compost-derived HA and providing a theoretical basis for the utilization of kitchen waste composting as a resource of HA.
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Affiliation(s)
- Yu Xiao
- College of Energy and Environment Shenyang Aerospace University, No.37 Daoyi southstreet, Shenbei new district, Shenyang 110122, China
| | - Haojie Lu
- State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
| | - Wenbing Tan
- State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
| | - Jun Tang
- State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
| | - Yang Wang
- State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
| | - Junxiang Shi
- State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
| | - Tingqiao Yu
- International Education College, Beijing Vocational College of Agriculture, Beijing 102442, China
| | - Ying Yuan
- State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
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Pyruvate accelerates palladium reduction by regulating catabolism and electron transfer pathway in Shewanella oneidensis. Appl Environ Microbiol 2021; 87:AEM.02716-20. [PMID: 33514518 PMCID: PMC8091111 DOI: 10.1128/aem.02716-20] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Shewanella oneidensis is a model strain of the electrochemical active bacteria (EAB) because of its strong capability of extracellular electron transfer (EET) and genetic tractability. In this study, we investigated the effect of carbon sources on EET in S. oneidensis by using reduction of palladium ions (Pd(II)) as a model and found that pyruvate greatly accelerated the Pd(II) reduction compared with lactate by resting cells. Both Mtr pathway and hydrogenases played a role in Pd(II) reduction when pyruvate was used as a carbon source. Furthermore, in comparison with lactate-feeding S. oneidensis, the transcriptional levels of formate dehydrogenases involving in pyruvate catabolism, Mtr pathway, and hydrogenases in pyruvate-feeding S. oneidensis were up-regulated. Mechanistically, the enhancement of electron generation from pyruvate catabolism and electron transfer to Pd(II) explains the pyruvate effect on Pd(II) reduction. Interestingly, a 2-h time window is required for pyruvate to regulate transcription of these genes and profoundly improve Pd(II) reduction capability, suggesting a hierarchical regulation for pyruvate sensing and response in S. oneidensis IMPORTANCE The unique respiration of EET is crucial for the biogeochemical cycling of metal elements and diverse applications of EAB. Although a carbon source is a determinant factor of bacterial metabolism, the research into the regulation of carbon source on EET is rare. In this work, we reported the pyruvate-specific regulation and improvement of EET in S. oneidensis and revealed the underlying mechanism, which suggests potential targets to engineer and improve the EET efficiency of this bacterium. This study sheds light on the regulatory role of carbon sources in anaerobic respiration in EAB, providing a way to regulate EET for diverse applications from a novel perspective.
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Yuan Q, Wang S, Wang X, Li N. Biosynthesis of vivianite from microbial extracellular electron transfer and environmental application. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 762:143076. [PMID: 33129535 DOI: 10.1016/j.scitotenv.2020.143076] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Revised: 10/01/2020] [Accepted: 10/11/2020] [Indexed: 06/11/2023]
Abstract
Vivianite (Fe3(PO4)2·8H2O) is a common hydrous ferrous phosphate mineral which often occurs in reductive conditions, especially anoxic non-sulfide environment containing high concentrations of ferrous iron (Fe2+) and orthophosphate (PO43-). Vivianite is an important product of dissimilatory iron reduction and a promising route for phosphorus recovery from wastewater. Its formation is closely related to the extracellular electron transfer (EET), a key mechanism for microbial respiration and a crucial explanation for the reduction of metal oxides in soil and sediments. Despite of the natural ubiquity, easy accessibility and attractive economic value, the application value of vivianite has not received much attention. This review introduces the characteristics, occurrence and biosynthesis of vivianite from microbial EET, and systematically analyzes the application value of vivianite in the environmental field, including immobilization of heavy metals (HMs), dechlorination of carbon tetrachloride (CT), sedimentary phosphorus sequestration and eutrophication alleviation. Additionally, its potential functions as a slow-release fertilizer are discussed as well. In general, vivianite is expected to make more contributions to the future scientific research, especially the solution of environmental problems. Overcoming the lack of understanding and some technical limitations will be beneficial to the further application of vivianite in environmental field.
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Affiliation(s)
- Qing Yuan
- Tianjin Key Lab of Indoor Air Environmental Quality Control, School of Environmental Science and Engineering, Tianjin University, No. 92 Weijin Road, Nankai District, Tianjin 300072, China
| | - Shu Wang
- Tianjin Key Lab of Indoor Air Environmental Quality Control, School of Environmental Science and Engineering, Tianjin University, No. 92 Weijin Road, Nankai District, Tianjin 300072, China
| | - Xin Wang
- MOE Key Laboratory of Pollution Processes and Environmental Criteria, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, Nankai University, No. 38 Tongyan Road, Jinnan District, Tianjin 300350, China
| | - Nan Li
- Tianjin Key Lab of Indoor Air Environmental Quality Control, School of Environmental Science and Engineering, Tianjin University, No. 92 Weijin Road, Nankai District, Tianjin 300072, China.
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Evidence for Horizontal and Vertical Transmission of Mtr-Mediated Extracellular Electron Transfer among the Bacteria. mBio 2021; 13:e0290421. [PMID: 35100867 PMCID: PMC8805035 DOI: 10.1128/mbio.02904-21] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Some bacteria and archaea have evolved the means to use extracellular electron donors and acceptors for energy metabolism, a phenomenon broadly known as extracellular electron transfer (EET). One such EET mechanism is the transmembrane electron conduit MtrCAB, which has been shown to transfer electrons derived from metabolic substrates to electron acceptors, like Fe(III) and Mn(IV) oxides, outside the cell. Although most studies of MtrCAB-mediated EET have been conducted in Shewanella oneidensis MR-1, recent investigations in Vibrio and Aeromonas species have revealed that the electron-donating proteins that support MtrCAB in Shewanella are not as representative as previously thought. This begs the question of how widespread the capacity for MtrCAB-mediated EET is, the changes it has accrued in different lineages, and where these lineages persist today. Here, we employed a phylogenetic and comparative genomics approach to identify the MtrCAB system across all domains of life. We found mtrCAB in the genomes of numerous diverse Bacteria from a wide range of environments, and the patterns therein strongly suggest that mtrCAB was distributed through both horizontal and subsequent vertical transmission, and with some cases indicating downstream modular diversification of both its core and accessory components. Our data point to an emerging evolutionary story about metal-oxidizing and -reducing metabolism, demonstrates that this capacity for EET has broad relevance to a diversity of taxa and the biogeochemical cycles they drive, and lays the foundation for further studies to shed light on how this mechanism may have coevolved with Earth's redox landscape. IMPORTANCE While many metabolisms make use of soluble, cell-permeable substrates like oxygen or hydrogen, there are other substrates, like iron or manganese, that cannot be brought into the cell. Some bacteria and archaea have evolved the means to directly "plug in" to such environmental electron reservoirs in a process known as extracellular electron transfer (EET), making them powerful agents of biogeochemical change and promising vehicles for bioremediation and alternative energy. Yet the diversity, distribution, and evolution of EET mechanisms are poorly constrained. Here, we present findings showing that the genes encoding one such EET system (mtrCAB) are present in a broad diversity of bacteria found in a wide range of environments, emphasizing the ubiquity and potential impact of EET in our biosphere. Our results suggest that these genes have been disseminated largely through horizontal transfer, and the changes they have accrued in these lineages potentially reflect adaptations to changing environments.
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Engineering S. oneidensis for Performance Improvement of Microbial Fuel Cell-a Mini Review. Appl Biochem Biotechnol 2020; 193:1170-1186. [PMID: 33200267 DOI: 10.1007/s12010-020-03469-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Accepted: 11/09/2020] [Indexed: 02/02/2023]
Abstract
Microbial fuel cell (MFC) is a promising technology that utilizes exoelectrogens cultivated in the form of biofilm to generate power from various types of sources supplied. A metal-reducing pathway is utilized by these organisms to transfer electrons obtained from the metabolism of substrate from anaerobic respiration extracellularly. A widely established model organism that is capable of extracellular electron transfer (EET) is Shewanella oneidensis. This review highlights the strategies used in the transformation of S. oneidensis and the recent development of MFC in terms of intervention through genetic modifications. S. oneidensis was genetically engineered for several aims including the study on the underlying mechanisms of EET, and the enhancement of power generation and wastewater treating potential when used in an MFC. Through engineering S. oneidensis, genes responsible for EET are identified and strategies on enhancing the EET efficiency are studied. Overexpressing genes related to EET to enhance biofilm formation, mediator biosynthesis, and respiration appears as one of the common approaches.
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Dundas CM, Walker DJ, Keitz BK. Tuning Extracellular Electron Transfer by Shewanella oneidensis Using Transcriptional Logic Gates. ACS Synth Biol 2020; 9:2301-2315. [PMID: 32786362 DOI: 10.1021/acssynbio.9b00517] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Extracellular electron transfer (EET) pathways, such as those in the bacterium Shewanella oneidensis, interface cellular metabolism with a variety of redox-driven applications. However, designer control over EET flux in S. oneidensis has proven challenging because a functional understanding of its EET pathway proteins and their effect on engineering parametrizations (e.g., response curves, dynamic range) is generally lacking. To address this, we systematically altered transcription and translation of single genes encoding parts of the primary EET pathway of S. oneidensis, CymA/MtrCAB, and examined how expression differences affected model-fitted parameters for Fe(III) reduction kinetics. Using a suite of plasmid-based inducible circuits maintained by appropriate S. oneidensis knockout strains, we pinpointed construct/strain pairings that expressed cymA, mtrA, and mtrC with maximal dynamic range of Fe(III) reduction rate. These optimized EET gene constructs were employed to create Buffer and NOT gate architectures that predictably turn on and turn off EET flux, respectively, in response to isopropyl β-D-1-thiogalactopyranoside (IPTG). Furthermore, we found that response functions generated by these logic gates (i.e., EET activity vs inducer concentration) were comparable to those generated by conventional synthetic biology circuits, where fluorescent reporters are the output. Our results provide insight on programming EET activity with transcriptional logic gates and suggest that previously developed transcriptional circuitry can be adapted to predictably control EET flux.
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Affiliation(s)
- Christopher M. Dundas
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, United States
| | - David J.F. Walker
- Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas 78712, United States
| | - Benjamin K. Keitz
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, United States
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A Hybrid Extracellular Electron Transfer Pathway Enhances the Survival of Vibrio natriegens. Appl Environ Microbiol 2020; 86:AEM.01253-20. [PMID: 32737131 DOI: 10.1128/aem.01253-20] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 07/28/2020] [Indexed: 02/06/2023] Open
Abstract
Vibrio natriegens is the fastest-growing microorganism discovered to date, making it a useful model for biotechnology and basic research. While it is recognized for its rapid aerobic metabolism, less is known about anaerobic adaptations in V. natriegens or how the organism survives when oxygen is limited. Here, we describe and characterize extracellular electron transfer (EET) in V. natriegens, a metabolism that requires movement of electrons across protective cellular barriers to reach the extracellular space. V. natriegens performs extracellular electron transfer under fermentative conditions with gluconate, glucosamine, and pyruvate. We characterized a pathway in V. natriegens that requires CymA, PdsA, and MtrCAB for Fe(III) citrate and Fe(III) oxide reduction, which represents a hybrid of strategies previously discovered in Shewanella and Aeromonas Expression of these V. natriegens genes functionally complemented Shewanella oneidensis mutants. Phylogenetic analysis of the inner membrane quinol dehydrogenases CymA and NapC in gammaproteobacteria suggests that CymA from Shewanella diverged from Vibrionaceae CymA and NapC. Analysis of sequenced Vibrionaceae revealed that the genetic potential to perform EET is conserved in some members of the Harveyi and Vulnificus clades but is more variable in other clades. We provide evidence that EET enhances anaerobic survival of V. natriegens, which may be the primary physiological function for EET in Vibrionaceae IMPORTANCE Bacteria from the genus Vibrio occupy a variety of marine and brackish niches with fluctuating nutrient and energy sources. When oxygen is limited, fermentation or alternative respiration pathways must be used to conserve energy. In sedimentary environments, insoluble oxide minerals (primarily iron and manganese) are able to serve as electron acceptors for anaerobic respiration by microorganisms capable of extracellular electron transfer, a metabolism that enables the use of these insoluble substrates. Here, we identify the mechanism for extracellular electron transfer in Vibrio natriegens, which uses a combination of strategies previously identified in Shewanella and Aeromonas We show that extracellular electron transfer enhanced survival of V. natriegens under fermentative conditions, which may be a generalized strategy among Vibrio spp. predicted to have this metabolism.
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Liu T, Luo X, Wu Y, Reinfelder JR, Yuan X, Li X, Chen D, Li F. Extracellular Electron Shuttling Mediated by Soluble c-Type Cytochromes Produced by Shewanella oneidensis MR-1. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:10577-10587. [PMID: 32692167 DOI: 10.1021/acs.est.9b06868] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
How metal-reducing bacteria transfer electrons during dissimilatory energy generation under electron acceptor-limited conditions is poorly understood. Here, we incubated the iron and manganese-reducing bacterium Shewanella oneidensis MR-1 without electron acceptors. Removal of soluble extracellular organic compounds (EOCs) dramatically retarded transfer of electrons to an experimental electron acceptor, Cr(VI), by MR-1. However, the return of either high MW (>3000 Da) or low MW (<3000 Da) soluble EOCs produced by MR-1 to washed cells restored Cr(VI) reduction though Cr(VI) reduction was fastest when both size fractions were added together. Spectral and electrochemical characterization of EOCs indicated the presence of flavins and c-type cytochromes (c-Cyts). A model of the kinetics of individual elementary reactions between cells, flavins, released c-Cyts, and Cr(VI), including the direct reduction of flavins, released c-Cyts, and Cr(VI) by cells and the indirect reduction of Cr(VI) by reduced forms of flavins and released c-Cyts, was developed. Model results suggest that released c-Cyts could act as electron mediators to accelerate electron transfer from cells to Cr(VI), and the relative contribution of this pathway was higher than that mediated by flavins. Hence, extracellular c-Cyts produced by MR-1 likely play a role in extracellular electron transfer under electron acceptor-limited conditions. These findings provide new insights into extracellular electron shuttling and the metabolic strategy of metal-reducing bacteria under electron acceptor-limited conditions.
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Affiliation(s)
- Tongxu Liu
- Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental Science & Technology, Guangzhou 510650, PR China
- National-Regional Joint Engineering Research Center for Soil Pollution Control and Remediation in South China, Guangzhou 510650, China
| | - Xiaobo Luo
- Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China
| | - Yundang Wu
- Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental Science & Technology, Guangzhou 510650, PR China
| | - John R Reinfelder
- Department of Environmental Sciences, Rutgers University, 14 College Farm Road, New Brunswick, New Jersey 08901, United States
| | - Xiu Yuan
- Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental Science & Technology, Guangzhou 510650, PR China
| | - Xiaomin Li
- SCNU Environmental Research Institute, Guangdong Provincial Key Laboratory of Chemical Pollution and Environmental Safety & MOE Key Laboratory of Environmental Theoretical Chemistry, South China Normal University, Guangzhou 510006, China
| | - Dandan Chen
- Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental Science & Technology, Guangzhou 510650, PR China
| | - Fangbai Li
- Guangdong Key Laboratory of Agricultural Environment Pollution Integrated Control, Guangdong Institute of Eco-Environmental Science & Technology, Guangzhou 510650, PR China
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Romero-Cedillo L, Poggi-Varaldo HM, Santoyo-Salazar J, Escamilla-Alvarado C, Matsumoto-Kuwabara Y, Ponce-Noyola MT, Bretón-Deval L, García-Rocha M. Biological synthesis of iron nanoparticles using hydrolysates from a waste-based biorefinery. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2020; 27:28649-28669. [PMID: 32347480 DOI: 10.1007/s11356-020-08729-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Accepted: 04/02/2020] [Indexed: 06/11/2023]
Abstract
The purpose of this work was to produce iron nanoparticles (Fe-NP) by microbial pathway from anaerobic bacteria grown in anaerobic fluidized bed reactors (AnFBRs) that constitute a new stage of a waste-based biorefinery. Bioparticles from biological fluidized bed reactors from a biorefinery of organic fraction of municipal solid wastes (that produces hydrolysates rich in reducing sugars) were nanodecorated (embedded nanobioparticle or nanodecorated bioparticle, ENBP) by biological reduction of iron salts. Factors "origin of bioparticles" (either from hydrogenogenic or methanogenic fluidized bed reactor) and "type of iron precursor salt" (iron chloride or iron citrate) were explored. SEM and high-resolution transmission electron microscopy (HRTEM) showed amorphous distribution of nanoparticles (NP) on the bioparticles surface, although small structures that are nanoparticle-like could be seen in the SEM micrographs. Some agglomeration of NPs was confirmed by DLS. Average NP size was lower in general for NP in ENBP-M than ENBP-H according to HRTEM. The factors did not have a significant influence on the specific surface area of NPs, which was high and in the range 490 to 650 m2 g-1. Analysis by EDS displayed consistent iron concentration 60-65% iron in nanoparticles present in ENBP-M (bioparticles previously grown in methanogenic bioreactor), whereas the iron concentration in NPs present in ENBP-H (bioparticles previously grown in hydrogenogenic bioreactor) was more variable in a range from 8.5 to 62%, depending on the iron salt. X-ray diffraction patterns showed the typical peaks for magnetite at 35° (3 1 1), 43° (4 0 0), and 62° (4 0 0); moreover, siderite diffraction pattern was found at 26° (0 1 2), 38° (1 1 0), and 42° (1 1 3). Results of infrared analysis of ENBP in our work were congruent with presence of magnetite and occasionally siderite determined by XRD analysis as well as presence of both Fe+2 and F+3 (and selected satellite signal peaks) observed by XPS. Our results on the ENBPs hold promise for water treatment, since iron NPs are commonly used in wastewater technologies that treat a wide variety of pollutants. Finally, the biological production of ENBP coupled to a biorefinery could become an environmentally friendly platform for nanomaterial biosynthesis as well as an additional source of revenues for a waste-based biorefinery.
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Affiliation(s)
- Leticia Romero-Cedillo
- Programa de Doctorado en Nanociencias y Nanotecnología, CINVESTAV del IPN, P.O. Box 17-740, 07000, Mexico City, Mexico
- Environmental Biotechnology and Renewable Energies Group, CINVESTAV del IPN, P.O. Box 14-740, 07000, Mexico City, Mexico
| | - Héctor M Poggi-Varaldo
- Programa de Doctorado en Nanociencias y Nanotecnología, CINVESTAV del IPN, P.O. Box 17-740, 07000, Mexico City, Mexico.
- Environmental Biotechnology and Renewable Energies Group, CINVESTAV del IPN, P.O. Box 14-740, 07000, Mexico City, Mexico.
| | - Jaime Santoyo-Salazar
- Programa de Doctorado en Nanociencias y Nanotecnología, CINVESTAV del IPN, P.O. Box 17-740, 07000, Mexico City, Mexico
| | - Carlos Escamilla-Alvarado
- Centre for Research on Biotechnology and Nanotechnology (CIByN), Faculty of Chemical Sciences, Engineering and Sustainable Bioprocesses Group, UANL, Parque de Investigación e Innovación Tecnológica, km 10 Autopista al Aeropuerto Internacional Mariano Escobedo, 66629, Apodaca, Nuevo León, Mexico
| | - Yasuhiro Matsumoto-Kuwabara
- Programa de Doctorado en Nanociencias y Nanotecnología, CINVESTAV del IPN, P.O. Box 17-740, 07000, Mexico City, Mexico
| | - M Teresa Ponce-Noyola
- Departamento de Biotecnología y Bioingeniería, CINVESTAV del IPN, Mexico City, Mexico
| | - Luz Bretón-Deval
- Cátedras Conacyt - Instituto de Biotecnología, UNAM, Av. Universidad 2001, Chamilpa, 62210, Cuernavaca, Morelos, Mexico
| | - Miguel García-Rocha
- Programa de Doctorado en Nanociencias y Nanotecnología, CINVESTAV del IPN, P.O. Box 17-740, 07000, Mexico City, Mexico
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Tefft NM, TerAvest MA. Reversing an Extracellular Electron Transfer Pathway for Electrode-Driven Acetoin Reduction. ACS Synth Biol 2019; 8:1590-1600. [PMID: 31243980 DOI: 10.1021/acssynbio.8b00498] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Microbial electrosynthesis is an emerging technology with the potential to simultaneously store renewably generated energy, fix carbon dioxide, and produce high-value organic compounds. However, limited understanding of the route of electrons into the cell remains an obstacle to developing a robust microbial electrosynthesis platform. To address this challenge, we leveraged the native extracellular electron transfer pathway in Shewanella oneidensis MR-1 to connect an extracellular electrode with an intracellular reduction reaction. The system uses native Mtr proteins to transfer electrons from an electrode to the inner membrane quinone pool. Subsequently, electrons are transferred from quinones to NAD+ by native NADH dehydrogenases. This reverse functioning of NADH dehydrogenases is thermodynamically unfavorable; therefore, we added a light-driven proton pump (proteorhodopsin) to generate proton-motive force to drive this activity. Finally, we use reduction of acetoin to 2,3-butanediol via a heterologous butanediol dehydrogenase (Bdh) as an electron sink. Bdh is an NADH-dependent enzyme; therefore, observation of acetoin reduction supports our hypothesis that cathodic electrons are transferred to intracellular NAD+. Multiple lines of evidence indicate proper functioning of the engineered electrosynthesis system: electron flux from the cathode is influenced by both light and acetoin availability, and 2,3-butanediol production is highest when both light and a poised electrode are present. Using a hydrogenase-deficient S. oneidensis background strain resulted in a stronger correlation between electron transfer and 2,3-butanediol production, suggesting that hydrogen production is an off-target electron sink in the wild-type background. This system represents a promising step toward a genetically engineered microbial electrosynthesis platform and will enable a new focus on synthesis of specific compounds using electrical energy.
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Affiliation(s)
- Nicholas M. Tefft
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, United States
| | - Michaela A. TerAvest
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, United States
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Astudillo-García C, Hermans SM, Stevenson B, Buckley HL, Lear G. Microbial assemblages and bioindicators as proxies for ecosystem health status: potential and limitations. Appl Microbiol Biotechnol 2019; 103:6407-6421. [DOI: 10.1007/s00253-019-09963-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 06/03/2019] [Accepted: 06/04/2019] [Indexed: 01/04/2023]
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24
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Zhao G, Li E, Li J, Liu F, Liu F, Xu M. Goethite Hinders Azo Dye Bioreduction by Blocking Terminal Reductive Sites on the Outer Membrane of Shewanella decolorationis S12. Front Microbiol 2019; 10:1452. [PMID: 31293561 PMCID: PMC6604703 DOI: 10.3389/fmicb.2019.01452] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Accepted: 06/11/2019] [Indexed: 01/21/2023] Open
Abstract
Iron (hydr)oxides are the most ubiquitous Fe(III)-containing minerals in the near-surface environments and can regulate organic pollutant biotransformation by participating in bacterial extracellular electron transfer under anaerobic conditions. Mechanisms described so far are based on their redox properties in bacterial extracellular respiration. Here, we find that goethite, a typical iron (hydr)oxide, inhibits the bioreduction of different polar azo dyes by Shewanella decolorationis S12 not through electron competition, but by the contact of its surface Fe(III) with the bacterial outer surface. Through the combined results of attenuated total reflectance (ATR) Fourier transform infrared spectroscopy, two-dimensional correlation spectroscopy, and confocal laser scanning microscope, we found that the outer membrane proteins MtrC and OmcA of strain S12 are key binding sites for goethite surface. Meanwhile, they were identified as the important reductive terminals for azo dyes. These results suggest that goethite may block the terminal reductive sites of azo dyes on the bacterial outer membrane to inhibit their bioreduction. This discovered role of goethite in bioreduction provides new insight into the microbial transformation processes of organic pollutants in iron (hydr)oxide-containing environments.
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Affiliation(s)
- Gang Zhao
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Institute of Microbiology, Guangdong Academy of Sciences, Guangzhou, China.,State Key Laboratory of Applied Microbiology Southern China, Guangzhou, China
| | - Enze Li
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Institute of Microbiology, Guangdong Academy of Sciences, Guangzhou, China.,State Key Laboratory of Applied Microbiology Southern China, Guangzhou, China
| | - Jianjun Li
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Institute of Microbiology, Guangdong Academy of Sciences, Guangzhou, China.,State Key Laboratory of Applied Microbiology Southern China, Guangzhou, China
| | - Feifei Liu
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Institute of Microbiology, Guangdong Academy of Sciences, Guangzhou, China.,State Key Laboratory of Applied Microbiology Southern China, Guangzhou, China
| | - Fei Liu
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Institute of Microbiology, Guangdong Academy of Sciences, Guangzhou, China.,State Key Laboratory of Applied Microbiology Southern China, Guangzhou, China
| | - Meiying Xu
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Institute of Microbiology, Guangdong Academy of Sciences, Guangzhou, China.,State Key Laboratory of Applied Microbiology Southern China, Guangzhou, China
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25
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Liu X, Zhan J, Jing X, Zhou S, Lovley DR. A pilin chaperone required for the expression of electrically conductive
Geobacter sulfurreducens
pili. Environ Microbiol 2019; 21:2511-2522. [DOI: 10.1111/1462-2920.14638] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 04/15/2019] [Accepted: 04/21/2019] [Indexed: 11/30/2022]
Affiliation(s)
- Xing Liu
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and EnvironmentFujian Agriculture and Forestry University Fuzhou China
| | - Ji Zhan
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and EnvironmentFujian Agriculture and Forestry University Fuzhou China
| | - Xianyue Jing
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and EnvironmentFujian Agriculture and Forestry University Fuzhou China
| | - Shungui Zhou
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and EnvironmentFujian Agriculture and Forestry University Fuzhou China
| | - Derek R. Lovley
- Department of MicrobiologyUniversity of Massachusetts Amherst Amherst MA USA
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Wu Z, Wang J, Liu J, Wang Y, Bi C, Zhang X. Engineering an electroactive Escherichia coli for the microbial electrosynthesis of succinate from glucose and CO 2. Microb Cell Fact 2019; 18:15. [PMID: 30691454 PMCID: PMC6348651 DOI: 10.1186/s12934-019-1067-3] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 01/20/2019] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Electrochemical energy is a key factor of biosynthesis, and is necessary for the reduction or assimilation of substrates such as CO2. Previous microbial electrosynthesis (MES) research mainly utilized naturally electroactive microbes to generate non-specific products. RESULTS In this research, an electroactive succinate-producing cell factory was engineered in E. coli T110(pMtrABC, pFccA-CymA) by expressing mtrABC, fccA and cymA from Shewanella oneidensis MR-1, which can utilize electricity to reduce fumarate. The electroactive T110 strain was further improved by incorporating a carbon concentration mechanism (CCM). This strain was fermented in an MES system with neutral red as the electron carrier and supplemented with HCO3+, which produced a succinate yield of 1.10 mol/mol glucose-a 1.6-fold improvement over the parent strain T110. CONCLUSIONS The strain T110(pMtrABC, pFccA-CymA, pBTCA) is to our best knowledge the first electroactive microbial cell factory engineered to directly utilize electricity for the production of a specific product. Due to the versatility of the E. coli platform, this pioneering research opens the possibility of engineering various other cell factories to utilize electricity for bioproduction.
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Affiliation(s)
- Zaiqiang Wu
- Center for Molecular Metabolism, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China
| | - Junsong Wang
- Center for Molecular Metabolism, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China.
| | - Jun Liu
- Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, 32 West 7th Ave, Tianjin Airport Economic Park, Tianjin, 300308, China
| | - Yan Wang
- Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, 32 West 7th Ave, Tianjin Airport Economic Park, Tianjin, 300308, China
| | - Changhao Bi
- Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, 32 West 7th Ave, Tianjin Airport Economic Park, Tianjin, 300308, China.
| | - Xueli Zhang
- Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, 32 West 7th Ave, Tianjin Airport Economic Park, Tianjin, 300308, China.
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Metal Reduction and Protein Secretion Genes Required for Iodate Reduction by Shewanella oneidensis. Appl Environ Microbiol 2019; 85:AEM.02115-18. [PMID: 30446562 DOI: 10.1128/aem.02115-18] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Accepted: 11/07/2018] [Indexed: 01/28/2023] Open
Abstract
The metal-reducing gammaproteobacterium Shewanella oneidensis reduces iodate (IO3 -) as an anaerobic terminal electron acceptor. Microbial IO3 - electron transport pathways are postulated to terminate with nitrate (NO3 -) reductase, which reduces IO3 - as an alternative electron acceptor. Recent studies with S. oneidensis, however, have demonstrated that NO3 - reductase is not involved in IO3 - reduction. The main objective of the present study was to determine the metal reduction and protein secretion genes required for IO3 - reduction by Shewanella oneidensis with lactate, formate, or H2 as the electron donor. With all electron donors, the type I and type V protein secretion mutants retained wild-type IO3 - reduction activity, while the type II protein secretion mutant lacking the outer membrane secretin GspD was impaired in IO3 - reduction. Deletion mutants lacking the cyclic AMP receptor protein (CRP), cytochrome maturation permease CcmB, and inner membrane-tethered c-type cytochrome CymA were impaired in IO3 - reduction with all electron donors, while deletion mutants lacking c-type cytochrome MtrA and outer membrane β-barrel protein MtrB of the outer membrane MtrAB module were impaired in IO3 - reduction with only lactate as an electron donor. With all electron donors, mutants lacking the c-type cytochromes OmcA and MtrC of the metal-reducing extracellular electron conduit MtrCAB retained wild-type IO3 - reduction activity. These findings indicate that IO3 - reduction by S. oneidensis involves electron donor-dependent metal reduction and protein secretion pathway components, including the outer membrane MtrAB module and type II protein secretion of an unidentified IO3 - reductase to the S. oneidensis outer membrane.IMPORTANCE Microbial iodate (IO3 -) reduction is a major component in the biogeochemical cycling of iodine and the bioremediation of iodine-contaminated environments; however, the molecular mechanism of microbial IO3 - reduction is poorly understood. Results of the present study indicate that outer membrane (type II) protein secretion and metal reduction genes encoding the outer membrane MtrAB module of the extracellular electron conduit MtrCAB are required for IO3 - reduction by S. oneidensis On the other hand, the metal-reducing c-type cytochrome MtrC of the extracellular electron conduit is not required for IO3 - reduction by S. oneidensis These findings indicate that the IO3 - electron transport pathway terminates with an as yet unidentified IO3 - reductase that associates with the outer membrane MtrAB module to deliver electrons extracellularly to IO3.
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The Widely Conserved ebo Cluster Is Involved in Precursor Transport to the Periplasm during Scytonemin Synthesis in Nostoc punctiforme. mBio 2018; 9:mBio.02266-18. [PMID: 30482833 PMCID: PMC6282210 DOI: 10.1128/mbio.02266-18] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Scytonemin is a dimeric indole-phenol sunscreen synthesized by some cyanobacteria under conditions of exposure to UVA radiation. While its biosynthetic pathway has been elucidated only partially, comparative genomics reveals that the scytonemin operon often contains a cluster of five highly conserved genes (ebo cluster) of unknown function that is widespread and conserved among several bacterial and algal phyla. We sought to elucidate the function of the ebo cluster in the cyanobacterium Nostoc punctiforme by constructing and analyzing in-frame deletion mutants (one for each ebo gene and one for the entire cluster). Under conditions of UVA induction, all ebo mutants were scytoneminless, and all accumulated a single compound, the scytonemin monomer, clearly implicating all ebo genes in scytonemin production. We showed that the scytonemin monomer also accumulated in an induced deletion mutant of scyE, a non-ebo scytonemin gene whose product is demonstrably targeted to the periplasm. Confocal autofluorescence microscopy revealed that the accumulation was confined to the cytoplasm in all ebo mutants but that that was not the case in the scyE deletion, with an intact ebo cluster, where the scytonemin monomer was also excreted to the periplasm. The results implicate the ebo cluster in the export of the scytonemin monomer to the periplasm for final oxidative dimerization by ScyE. By extension, the ebo gene cluster may play similar roles in metabolite translocation across many bacterial phyla. We discuss potential mechanisms for such a role on the basis of structural and phylogenetic considerations of the ebo proteins.IMPORTANCE Elucidating the biochemical and genetic basis of scytonemin constitutes an interesting challenge because of its unique structure and the unusual fact that it is partially synthesized in the periplasmic space. Our work points to the ebo gene cluster, associated with the scytonemin operon of cyanobacteria, as being responsible for the excretion of scytonemin intermediates from the cytoplasm into the periplasm during biosynthesis. Few conserved systems have been described that facilitate the membrane translocation of small molecules. Because the ebo cluster is well conserved among a large diversity of bacteria and algae and yet insights into its potential function are lacking, our findings suggest that translocation of small molecules across the plasma membrane may be its generic role across microbes.
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29
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Divergent Nrf Family Proteins and MtrCAB Homologs Facilitate Extracellular Electron Transfer in Aeromonas hydrophila. Appl Environ Microbiol 2018; 84:AEM.02134-18. [PMID: 30266730 DOI: 10.1128/aem.02134-18] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 09/26/2018] [Indexed: 01/05/2023] Open
Abstract
Extracellular electron transfer (EET) is a strategy for respiration in which electrons generated from metabolism are moved outside the cell to a terminal electron acceptor, such as iron or manganese oxide. EET has primarily been studied in two model systems, Shewanella oneidensis and Geobacter sulfurreducens Metal reduction has also been reported in numerous microorganisms, including Aeromonas spp., which are ubiquitous Gammaproteobacteria found in aquatic ecosystems, with some species capable of pathogenesis in humans and fish. Genomic comparisons of Aeromonas spp. revealed a potential outer membrane conduit homologous to S. oneidensis MtrCAB. While the ability to respire metals and mineral oxides is not widespread in the genus Aeromonas, 90% of the sequenced Aeromonas hydrophila isolates contain MtrCAB homologs. A. hydrophila ATCC 7966 mutants lacking mtrA are unable to reduce metals. Expression of A. hydrophila mtrCAB in an S. oneidensis mutant lacking homologous components restored metal reduction. Although the outer membrane conduits for metal reduction were similar, homologs of the S. oneidensis inner membrane and periplasmic EET components CymA, FccA, and CctA were not found in A. hydrophila We characterized a cluster of genes predicted to encode components related to a formate-dependent nitrite reductase (NrfBCD), here named NetBCD (for Nrf-like electron transfer), and a predicted diheme periplasmic cytochrome, PdsA (periplasmic diheme shuttle). We present genetic evidence that proteins encoded by this cluster facilitate electron transfer from the cytoplasmic membrane across the periplasm to the MtrCAB conduit and function independently from an authentic NrfABCD system. A. hydrophila mutants lacking pdsA and netBCD were unable to reduce metals, while heterologous expression of these genes could restore metal reduction in an S. oneidensis mutant background. EET may therefore allow A. hydrophila and other species of Aeromonas to persist and thrive in iron- or manganese-rich oxygen-limited environments.IMPORTANCE Metal-reducing microorganisms are used for electricity production, bioremediation of toxic compounds, wastewater treatment, and production of valuable compounds. Despite numerous microorganisms being reported to reduce metals, the molecular mechanism has primarily been studied in two model systems, Shewanella oneidensis and Geobacter sulfurreducens We have characterized the mechanism of extracellular electron transfer in Aeromonas hydrophila, which uses the well-studied Shewanella system, MtrCAB, to move electrons across the outer membrane; however, most Aeromonas spp. appear to use a novel mechanism to transfer electrons from the inner membrane through the periplasm and to the outer membrane. The conserved use of MtrCAB in Shewanella spp. and Aeromonas spp. for metal reduction and conserved genomic architecture of metal reduction genes in Aeromonas spp. may serve as genomic markers for identifying metal-reducing microorganisms from genomic or transcriptomic sequencing. Understanding the variety of pathways used to reduce metals can allow for optimization and more efficient design of microorganisms used for practical applications.
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30
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Morrison C, Heitmann E, Armiger W, Dodds D, Koffas M. Electrochemical Bioreactor Technology for Biocatalysis and Microbial Electrosynthesis. ADVANCES IN APPLIED MICROBIOLOGY 2018; 105:51-86. [PMID: 30342723 DOI: 10.1016/bs.aambs.2018.07.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Two seemingly distinct fields, industrial biocatalysis and microbial electrosynthesis, can be viewed together through the lens of electrochemical bioreactor technology in order to highlight the challenges that exist in creating a versatile platform technology for use in chemical and biological applications. Industrial biocatalysis applications requiring NAD(P)H to perform redox transformations often necessitate convoluted coupled-enzyme regeneration systems to regenerate reduced cofactor, NAD(P)H from oxidized cofactor, NAD(P). Renewed interest in continuously recycling the cofactor via electrochemical reduction is motivated by the low cost of performing electrochemical reactions, easy monitoring of the reaction progress, and straightforward product recovery. However, electrochemical cofactor regeneration methods invariably produce adventitious reduced cofactor side products which result in unproductive loss of input NAD(P). Microbial electrosynthesis is a form of microbially driven catalysis in which electricity is supplied to living microorganisms for the production of industrially relevant chemical products at higher carbon efficiencies and yields compared with traditional, nonelectrically driven, fermentations. The fundamental biochemistry of these organisms as related to selected biochemical redox processes will be explored in order to highlight opportunities to devise strategies for taking advantage of these biochemical processes in engineered systems.
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Affiliation(s)
- Clifford Morrison
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, NY, United States
| | - Elizabeth Heitmann
- Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY, United States
| | | | - David Dodds
- BioChemInsights, Inc., Malvern, PA, United States
| | - Mattheos Koffas
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, NY, United States; Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY, United States
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31
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Binnenkade L, Kreienbaum M, Thormann KM. Characterization of ExeM, an Extracellular Nuclease of Shewanella oneidensis MR-1. Front Microbiol 2018; 9:1761. [PMID: 30123203 PMCID: PMC6085458 DOI: 10.3389/fmicb.2018.01761] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Accepted: 07/13/2018] [Indexed: 01/08/2023] Open
Abstract
Bacterial extracellular nucleases have multiple functions in processes as diverse as nutrient acquisition, natural transformation, biofilm formation, or defense against neutrophil extracellular traps (NETs). Here we explored the properties of ExeM in Shewanella oneidensis MR-1, an extracellular nuclease, which is widely conserved among species of Shewanella, Vibrio, Aeromonas, and others. In S. oneidensis, ExeM is crucial for normal biofilm formation. In vitro activity measurements on heterologously produced ExeM revealed that this enzyme is a sugar-unspecific endonuclease, which requires Ca2+ and Mg2+/Mn2+ as co-factors for full activity. ExeM was almost exclusively localized to the cytoplasmic membrane fraction, even when a putative C-terminal membrane anchor was deleted. In contrast, ExeM was not detected in medium supernatants. Based on the results we hypothesize that ExeM predominantly interacts with DNA in close proximity to the cell, e.g., to promote biofilm formation and defense against NETs, or to control uptake of DNA.
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Affiliation(s)
- Lucas Binnenkade
- Institute for Microbiology and Molecular Biology, Justus Liebig University Giessen, Giessen, Germany
| | - Maximilian Kreienbaum
- Institute for Microbiology and Molecular Biology, Justus Liebig University Giessen, Giessen, Germany
| | - Kai M Thormann
- Institute for Microbiology and Molecular Biology, Justus Liebig University Giessen, Giessen, Germany
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32
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Beblawy S, Bursac T, Paquete C, Louro R, Clarke TA, Gescher J. Extracellular reduction of solid electron acceptors by Shewanella oneidensis. Mol Microbiol 2018; 109:571-583. [PMID: 29995975 DOI: 10.1111/mmi.14067] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/26/2018] [Indexed: 12/11/2022]
Abstract
Shewanella oneidensis is the best understood model organism for the study of dissimilatory iron reduction. This review focuses on the current state of our knowledge regarding this extracellular respiratory process and highlights its physiologic, regulatory and biochemical requirements. It seems that we have widely understood how respiratory electrons can reach the cell surface and what the minimal set of electron transport proteins to the cell surface is. Nevertheless, even after decades of work in different research groups around the globe there are still several important questions that were not answered yet. In particular, the physiology of this organism, the possible evolutionary benefit of some responses to anoxic conditions, as well as the exact mechanism of electron transfer onto solid electron acceptors are yet to be addressed. The elucidation of these questions will be a great challenge for future work and important for the application of extracellular respiration in biotechnological processes.
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Affiliation(s)
- Sebastian Beblawy
- Department of Applied Biology, Institute for Applied Biosciences, Karlsruhe Institute of Technology (CS), Karlsruhe, Germany
| | - Thea Bursac
- Department of Applied Biology, Institute for Applied Biosciences, Karlsruhe Institute of Technology (CS), Karlsruhe, Germany
| | - Catarina Paquete
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Av. da República-EAN, Oeiras, 2780-157, Portugal
| | - Ricardo Louro
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Av. da República-EAN, Oeiras, 2780-157, 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, UK
| | - 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
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33
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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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34
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Edwards MJ, White GF, Lockwood CW, Lawes MC, Martel A, Harris G, Scott DJ, Richardson DJ, Butt JN, Clarke TA. Structural modeling of an outer membrane electron conduit from a metal-reducing bacterium suggests electron transfer via periplasmic redox partners. J Biol Chem 2018; 293:8103-8112. [PMID: 29636412 PMCID: PMC5971433 DOI: 10.1074/jbc.ra118.001850] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Revised: 03/19/2018] [Indexed: 11/06/2022] Open
Abstract
Many subsurface microorganisms couple their metabolism to the reduction or oxidation of extracellular substrates. For example, anaerobic mineral-respiring bacteria can use external metal oxides as terminal electron acceptors during respiration. Porin-cytochrome complexes facilitate the movement of electrons generated through intracellular catabolic processes across the bacterial outer membrane to these terminal electron acceptors. In the mineral-reducing model bacterium Shewanella oneidensis MR-1, this complex is composed of two decaheme cytochromes (MtrA and MtrC) and an outer-membrane β-barrel (MtrB). However, the structures and mechanisms by which porin-cytochrome complexes transfer electrons are unknown. Here, we used small-angle neutron scattering (SANS) to study the molecular structure of the transmembrane complexes MtrAB and MtrCAB. Ab initio modeling of the scattering data yielded a molecular envelope with dimensions of ∼105 × 60 × 35 Å for MtrAB and ∼170 × 60 × 45 Å for MtrCAB. The shapes of these molecular envelopes suggested that MtrC interacts with the surface of MtrAB, extending ∼70 Å from the membrane surface and allowing the terminal hemes to interact with both MtrAB and an extracellular acceptor. The data also reveal that MtrA fully extends through the length of MtrB, with ∼30 Å being exposed into the periplasm. Proteoliposome models containing membrane-associated MtrCAB and internalized small tetraheme cytochrome (STC) indicate that MtrCAB could reduce Fe(III) citrate with STC as an electron donor, disclosing a direct interaction between MtrCAB and STC. Taken together, both structural and proteoliposome experiments support porin-cytochrome-mediated electron transfer via periplasmic cytochromes such as STC.
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Affiliation(s)
- Marcus J Edwards
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom
| | - Gaye F White
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom
| | - Colin W Lockwood
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom
| | - Matthew C Lawes
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom
| | - Anne Martel
- Institut Laue-Langevin, 38042 Grenoble, France
| | - Gemma Harris
- Research Complex at Harwell, Rutherford Appleton Laboratory, Oxfordshire OX11 0FA, United Kingdom
| | - David J Scott
- Research Complex at Harwell, Rutherford Appleton Laboratory, Oxfordshire OX11 0FA, United Kingdom; ISIS Spallation Neutron and Muon Source, Rutherford Appleton Laboratory, Oxfordshire OX11 0QX, United Kingdom; School of Biosciences, University of Nottingham, Sutton Bonington Campus, Leicestershire LE12 5RD, United Kingdom
| | - David J Richardson
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom
| | - Julea N Butt
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom
| | - 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.
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Ultrastructure of Shewanella oneidensis MR-1 nanowires revealed by electron cryotomography. Proc Natl Acad Sci U S A 2018; 115:E3246-E3255. [PMID: 29555764 DOI: 10.1073/pnas.1718810115] [Citation(s) in RCA: 108] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bacterial nanowires have garnered recent interest as a proposed extracellular electron transfer (EET) pathway that links the bacterial electron transport chain to solid-phase electron acceptors away from the cell. Recent studies showed that Shewanella oneidensis MR-1 produces outer membrane (OM) and periplasmic extensions that contain EET components and hinted at their possible role as bacterial nanowires. However, their fine structure and distribution of cytochrome electron carriers under native conditions remained unclear, making it difficult to evaluate the potential electron transport (ET) mechanism along OM extensions. Here, we report high-resolution images of S. oneidensis OM extensions, using electron cryotomography (ECT). We developed a robust method for fluorescence light microscopy imaging of OM extension growth on electron microscopy grids and used correlative light and electron microscopy to identify and image the same structures by ECT. Our results reveal that S. oneidensis OM extensions are dynamic chains of interconnected outer membrane vesicles (OMVs) with variable dimensions, curvature, and extent of tubulation. Junction densities that potentially stabilize OMV chains are seen between neighboring vesicles in cryotomograms. By comparing wild type and a cytochrome gene deletion mutant, our ECT results provide the likely positions and packing of periplasmic and outer membrane proteins consistent with cytochromes. Based on the observed cytochrome packing density, we propose a plausible ET path along the OM extensions involving a combination of direct hopping and cytochrome diffusion. A mean-field calculation, informed by the observed ECT cytochrome density, supports this proposal by revealing ET rates on par with a fully packed cytochrome network.
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Hwang ET, Orchard KL, Hojo D, Beton J, Lockwood CWJ, Adschiri T, Butt JN, Reisner E, Jeuken LJC. Exploring Step-by-Step Assembly of Nanoparticle:Cytochrome Biohybrid Photoanodes. ChemElectroChem 2017; 4:1959-1968. [PMID: 28920010 PMCID: PMC5573906 DOI: 10.1002/celc.201700030] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Indexed: 11/07/2022]
Abstract
Coupling light-harvesting semiconducting nanoparticles (NPs) with redox enzymes has been shown to create artificial photosynthetic systems that hold promise for the synthesis of solar fuels. High quantum yields require efficient electron transfer from the nanoparticle to the redox protein, a property that can be difficult to control. Here, we have compared binding and electron transfer between dye-sensitized TiO2 nanocrystals or CdS quantum dots and two decaheme cytochromes on photoanodes. The effect of NP surface chemistry was assessed by preparing NPs capped with amine or carboxylic acid functionalities. For the TiO2 nanocrystals, binding to the cytochromes was optimal when capped with a carboxylic acid ligand, whereas for the CdS QDs, better adhesion was observed for amine capped ligand shells. When using TiO2 nanocrystals, dye-sensitized with a phosphonated bipyridine Ru(II) dye, photocurrents are observed that are dependent on the redox state of the decaheme, confirming that electrons are transferred from the TiO2 nanocrystals to the surface via the decaheme conduit. In contrast, when CdS NPs are used, photocurrents are not dependent on the redox state of the decaheme, consistent with a model in which electron transfer from CdS to the photoanode bypasses the decaheme protein. These results illustrate that although the organic shell of NPs nanoparticles crucially affects coupling with proteinaceous material, the coupling can be difficult to predict or engineer.
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Affiliation(s)
- Ee Taek Hwang
- School of Biomedical Sciences, and The Astbury Centre for Structural Molecular BiologyUniversity of LeedsLeedsLS2 9JTU.K
| | - Katherine L. Orchard
- Department of ChemistryUniversity of CambridgeLensfield RoadCambridgeCB2 1EWU.K.
- Advanced Institute for Materials ResearchTohoku University2-1-1 Katahira Aoba-ku SendaiMiyagi980-8577Japan
| | - Daisuke Hojo
- Advanced Institute for Materials ResearchTohoku University2-1-1 Katahira Aoba-ku SendaiMiyagi980-8577Japan
| | - Joseph Beton
- School of Biomedical Sciences, and The Astbury Centre for Structural Molecular BiologyUniversity of LeedsLeedsLS2 9JTU.K
| | - Colin W. J. Lockwood
- Centre for Molecular and Structural BiochemistrySchool of Chemistry, and School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJUnited Kingdom
| | - Tadafumi Adschiri
- Advanced Institute for Materials ResearchTohoku University2-1-1 Katahira Aoba-ku SendaiMiyagi980-8577Japan
| | - Julea N. Butt
- Centre for Molecular and Structural BiochemistrySchool of Chemistry, and School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJUnited Kingdom
| | - Erwin Reisner
- Department of ChemistryUniversity of CambridgeLensfield RoadCambridgeCB2 1EWU.K.
| | - Lars J. C. Jeuken
- School of Biomedical Sciences, and The Astbury Centre for Structural Molecular BiologyUniversity of LeedsLeedsLS2 9JTU.K
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Outer membrane cytochromes/flavin interactions in Shewanella spp.-A molecular perspective. Biointerphases 2017; 12:021004. [PMID: 28565913 DOI: 10.1116/1.4984007] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Extracellular electron transfer (EET) is intrinsically associated with the core phenomena of energy harvesting/energy conversion in natural ecosystems and biotechnology applications. However, the mechanisms associated with EET are complex and involve molecular interactions that take place at the "bionano interface" where biotic/abiotic interactions are usually explored. This work provides molecular perspective on the electron transfer mechanism(s) employed by Shewanella oneidensis MR-1. Molecular docking simulations were used to explain the interfacial relationships between two outer-membrane cytochromes (OMC) OmcA and MtrC and riboflavin (RF) and flavin mononucleotide (FMN), respectively. OMC-flavin interactions were analyzed by studying the electrostatic potential, the hydrophilic/hydrophobic surface properties, and the van der Waals surface of the OMC proteins. As a result, it was proposed that the interactions between flavins and OMCs are based on geometrical recognition event. The possible docking positions of RF and FMN to OmcA and MtrC were also shown.
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Bursac T, Gralnick JA, Gescher J. Acetoin production via unbalanced fermentation in Shewanella oneidensis. Biotechnol Bioeng 2017; 114:1283-1289. [DOI: 10.1002/bit.26243] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Revised: 12/27/2016] [Accepted: 01/03/2017] [Indexed: 12/17/2022]
Affiliation(s)
- Thea Bursac
- Department of Applied Biology; Institute for Applied Biosciences; Karlsruhe Institute of Technology; Karlsruhe Germany
| | - Jeffrey A. Gralnick
- BioTechnology Institute and Department of Microbiology; University of Minnesota; Twin Cities St. Paul, Minnesota
| | - Johannes Gescher
- Department of Applied Biology; Institute for Applied Biosciences; Karlsruhe Institute of Technology; Karlsruhe Germany
- Department of Microbiology of Natural and Technical Interfaces; Institute of Functional Interfaces; Karlsruhe Institute of Technology; Eggenstein-Leopoldshafen Germany
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Vilajeliu-Pons A, Bañeras L, Puig S, Molognoni D, Vilà-Rovira A, Hernández-del Amo E, Balaguer MD, Colprim J. External Resistances Applied to MFC Affect Core Microbiome and Swine Manure Treatment Efficiencies. PLoS One 2016; 11:e0164044. [PMID: 27701451 PMCID: PMC5049776 DOI: 10.1371/journal.pone.0164044] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Accepted: 09/19/2016] [Indexed: 11/19/2022] Open
Abstract
Microbial fuel cells (MFCs) can be designed to combine water treatment with concomitant electricity production. Animal manure treatment has been poorly explored using MFCs, and its implementation at full-scale primarily relies on the bacterial distribution and activity within the treatment cell. This study reports the bacterial community changes at four positions within the anode of two almost identically operated MFCs fed swine manure. Changes in the microbiome structure are described according to the MFC fluid dynamics and the application of a maximum power point tracking system (MPPT) compared to a fixed resistance system (Ref-MFC). Both external resistance and cell hydrodynamics are thought to heavily influence MFC performance. The microbiome was characterised both quantitatively (qPCR) and qualitatively (454-pyrosequencing) by targeting bacterial 16S rRNA genes. The diversity of the microbial community in the MFC biofilm was reduced and differed from the influent swine manure. The adopted electric condition (MPPT vs fixed resistance) was more relevant than the fluid dynamics in shaping the MFC microbiome. MPPT control positively affected bacterial abundance and promoted the selection of putatively exoelectrogenic bacteria in the MFC core microbiome (Sedimentibacter sp. and gammaproteobacteria). These differences in the microbiome may be responsible for the two-fold increase in power production achieved by the MPPT-MFC compared to the Ref-MFC.
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Affiliation(s)
| | - Lluis Bañeras
- Molecular Microbial Ecology Group, Institute of Aquatic Ecology, University of Girona, Girona, Spain
- * E-mail:
| | - Sebastià Puig
- LEQUiA, Institute of the Environment, University of Girona, Girona, Spain
| | - Daniele Molognoni
- Department of Civil Engineering and Architecture (D.I.C.Ar.), University of Pavia, Pavia, Italy
| | - Albert Vilà-Rovira
- LEQUiA, Institute of the Environment, University of Girona, Girona, Spain
| | - Elena Hernández-del Amo
- Molecular Microbial Ecology Group, Institute of Aquatic Ecology, University of Girona, Girona, Spain
| | - Maria D. Balaguer
- LEQUiA, Institute of the Environment, University of Girona, Girona, Spain
| | - Jesús Colprim
- LEQUiA, Institute of the Environment, University of Girona, Girona, Spain
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40
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Extracellular electron transfer mechanisms between microorganisms and minerals. Nat Rev Microbiol 2016; 14:651-62. [DOI: 10.1038/nrmicro.2016.93] [Citation(s) in RCA: 850] [Impact Index Per Article: 106.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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41
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Larsen Ø, Karlsen OA. Transcriptomic profiling of Methylococcus capsulatus (Bath) during growth with two different methane monooxygenases. Microbiologyopen 2016; 5:254-67. [PMID: 26687591 PMCID: PMC4831470 DOI: 10.1002/mbo3.324] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Revised: 11/04/2015] [Accepted: 11/06/2015] [Indexed: 11/23/2022] Open
Abstract
Methylococcus capsulatus (Bath) is a methanotroph that possesses both a membrane-embedded (pMMO) and a soluble methane monooxygenase (sMMO). The expression of these two MMO's is tightly controlled by the availability of copper in the growth medium, but the underlying mechanisms and the number of genes involved in this switch in methane oxidation is not yet fully elucidated. Microarray analyses were used to assess the transcriptome in cells producing either pMMO or sMMO. A total of 137 genes were differentially expressed, with 87 genes showing a significant up-regulation during sMMO production. The majority of the differentially expressed genes could be assigned to functional roles in the energy metabolism and transport. Furthermore, three copper responding gene clusters were discovered, including an extended cluster that also harbors the genes for sMMO. Our data also indicates that major changes takes place in the respiratory chain between pMMO- and sMMO-producing cells, and that quinone are predominantly used as the electron donors for methane oxidation by pMMO. Intriguingly, a large proportion of the differentially expressed genes between pMMO- and sMMO-producing cells encode c-type cytochromes. By combining microarray- and mass spectrometry data, a total of 35 c-type cytochromes are apparently expressed in M. capsulatus when grown in nitrate mineral salt medium with methane as sole energy and carbon source, and the expression of 21 of these respond to the availability of copper. Interestingly, several of these c-type cytochromes are recovered from the cell surface, suggesting that extracellular electron transfers may occur in M. capsulatus.
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Affiliation(s)
- Øivind Larsen
- Uni Research EnvironmentThormøhlensgate 49bBergen5006Norway
| | - Odd A. Karlsen
- Department of Molecular BiologyUniversity of BergenBergenNorway
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42
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White GF, Edwards MJ, Gomez-Perez L, Richardson DJ, Butt JN, Clarke TA. Mechanisms of Bacterial Extracellular Electron Exchange. Adv Microb Physiol 2016; 68:87-138. [PMID: 27134022 DOI: 10.1016/bs.ampbs.2016.02.002] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The biochemical mechanisms by which microbes interact with extracellular soluble metal ions and insoluble redox-active minerals have been the focus of intense research over the last three decades. The process presents two challenges to the microorganism. Firstly, electrons have to be transported at the cell surface, which in Gram-negative bacteria presents an additional problem of electron transfer across the ~6nm of the outer membrane. Secondly, the electrons must be transferred to or from the terminal electron acceptors or donors. This review covers the known mechanisms that bacteria use to transport electrons across the cell envelope to external electron donors/acceptors. In Gram-negative bacteria, electron transfer across the outer membrane involves the use of an outer membrane β-barrel and cytochrome. These can be in the form of a porin-cytochrome protein, such as Cyc2 of Acidithiobacillus ferrooxidans, or a multiprotein porin-cytochrome complex like MtrCAB of Shewanella oneidensis MR-1. For mineral-respiring organisms, there is the additional challenge of transferring the electrons from the cell to mineral surface. For the strict anaerobe Geobacter sulfurreducens this requires electron transfer through conductive pili to associated cytochrome OmcS that directly reduces Fe(III)oxides, while the facultative anaerobe S. oneidensis MR-1 accomplishes mineral reduction through direct membrane contact, contact through filamentous extensions and soluble flavin shuttles, all of which require the outer membrane cytochromes MtrC and OmcA in addition to secreted flavin.
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Affiliation(s)
- G F White
- School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich, United Kingdom
| | - M J Edwards
- School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich, United Kingdom
| | - L Gomez-Perez
- School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich, United Kingdom
| | - D J Richardson
- School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich, United Kingdom
| | - J N Butt
- School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich, United Kingdom
| | - T A Clarke
- School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich, United Kingdom.
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43
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Heath GR, Li M, Polignano IL, Richens JL, Catucci G, O’Shea P, Sadeghi SJ, Gilardi G, Butt JN, Jeuken LJC. Layer-by-Layer Assembly of Supported Lipid Bilayer Poly-l-Lysine Multilayers. Biomacromolecules 2015; 17:324-35. [DOI: 10.1021/acs.biomac.5b01434] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- George R. Heath
- School
of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Mengqiu Li
- School
of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
| | | | - Joanna L. Richens
- Cell
Biophysics Group, Institute of Biophysics, Imaging and Optical Science,
School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - Gianluca Catucci
- Life
Sciences and Systems Biology, University of Torino, 10123, Turin, Italy
| | - Paul O’Shea
- Cell
Biophysics Group, Institute of Biophysics, Imaging and Optical Science,
School of Life Sciences, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - Sheila J. Sadeghi
- Life
Sciences and Systems Biology, University of Torino, 10123, Turin, Italy
| | - Gianfranco Gilardi
- Life
Sciences and Systems Biology, University of Torino, 10123, Turin, Italy
| | - Julea N. Butt
- Centre
for Molecular and Structural Biochemistry, School of Biological Sciences,
and School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom
| | - Lars J. C. Jeuken
- School
of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
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44
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Kim B, An J, Fapyane D, Chang IS. Bioelectronic platforms for optimal bio-anode of bio-electrochemical systems: From nano- to macro scopes. BIORESOURCE TECHNOLOGY 2015; 195:2-13. [PMID: 26122091 DOI: 10.1016/j.biortech.2015.06.061] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 06/12/2015] [Accepted: 06/13/2015] [Indexed: 06/04/2023]
Abstract
The current trend of bio-electrochemical systems is to improve strategies related to their applicability and potential for scaling-up. To date, literature has suggested strategies, but the proposal of correlations between each research field remains insufficient. This review paper provides a correlation based on platform techniques, referred to as bio-electronics platforms (BEPs). These BEPs consist of three platforms divided by scope scale: nano-, micro-, and macro-BEPs. In the nano-BEP, several types of electron transfer mechanisms used by electrochemically active bacteria are discussed. In the micro-BEP, factors affecting the formation of conductive biofilms and transport of electrons in the conductive biofilm are investigated. In the macro-BEP, electrodes and separators in bio-anode are debated in terms of real applications, and a scale-up strategy is discussed. Overall, the challenges of each BEP are highlighted, and potential solutions are suggested. In addition, future research directions are provided and research ideas proposed to develop research interest.
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Affiliation(s)
- Bongkyu Kim
- School of Environmental Science and Engineering, Gwangju Institute of Science and Technology, Republic of Korea
| | - Junyeong An
- School of Environmental Science and Engineering, Gwangju Institute of Science and Technology, Republic of Korea
| | - Deby Fapyane
- School of Environmental Science and Engineering, Gwangju Institute of Science and Technology, Republic of Korea; Interdisciplinary Nanoscience Center, Aarhus University, Denmark
| | - In Seop Chang
- School of Environmental Science and Engineering, Gwangju Institute of Science and Technology, Republic of Korea.
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45
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Breuer M, Rosso KM, Blumberger J, Butt JN. Multi-haem cytochromes in Shewanella oneidensis MR-1: structures, functions and opportunities. J R Soc Interface 2015; 12:20141117. [PMID: 25411412 DOI: 10.1098/rsif.2014.1117] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Multi-haem cytochromes are employed by a range of microorganisms to transport electrons over distances of up to tens of nanometres. Perhaps the most spectacular utilization of these proteins is in the reduction of extracellular solid substrates, including electrodes and insoluble mineral oxides of Fe(III) and Mn(III/IV), by species of Shewanella and Geobacter. However, multi-haem cytochromes are found in numerous and phylogenetically diverse prokaryotes where they participate in electron transfer and redox catalysis that contributes to biogeochemical cycling of N, S and Fe on the global scale. These properties of multi-haem cytochromes have attracted much interest and contributed to advances in bioenergy applications and bioremediation of contaminated soils. Looking forward, there are opportunities to engage multi-haem cytochromes for biological photovoltaic cells, microbial electrosynthesis and developing bespoke molecular devices. As a consequence, it is timely to review our present understanding of these proteins and we do this here with a focus on the multitude of functionally diverse multi-haem cytochromes in Shewanella oneidensis MR-1. We draw on findings from experimental and computational approaches which ideally complement each other in the study of these systems: computational methods can interpret experimentally determined properties in terms of molecular structure to cast light on the relation between structure and function. We show how this synergy has contributed to our understanding of multi-haem cytochromes and can be expected to continue to do so for greater insight into natural processes and their informed exploitation in biotechnologies.
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Affiliation(s)
- Marian Breuer
- Department of Physics and Astronomy, University College London, London WC1E 6BT, UK
| | - Kevin M Rosso
- Pacific Northwest National Laboratory, Richland, WA, USA
| | - Jochen Blumberger
- Department of Physics and Astronomy, University College London, London WC1E 6BT, UK
| | - Julea N Butt
- School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich NR4 7TJ, UK
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46
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Kouzuma A, Kasai T, Hirose A, Watanabe K. Catabolic and regulatory systems in Shewanella oneidensis MR-1 involved in electricity generation in microbial fuel cells. Front Microbiol 2015; 6:609. [PMID: 26136738 PMCID: PMC4468914 DOI: 10.3389/fmicb.2015.00609] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 06/02/2015] [Indexed: 12/12/2022] Open
Abstract
Shewanella oneidensis MR-1 is a facultative anaerobe that respires using a variety of inorganic and organic compounds. MR-1 is also capable of utilizing extracellular solid materials, including anodes in microbial fuel cells (MFCs), as electron acceptors, thereby enabling electricity generation. As MFCs have the potential to generate electricity from biomass waste and wastewater, MR-1 has been extensively studied to identify the molecular systems that are involved in electricity generation in MFCs. These studies have demonstrated the importance of extracellular electron-transfer (EET) pathways that electrically connect the quinone pool in the cytoplasmic membrane to extracellular electron acceptors. Electricity generation is also dependent on intracellular catabolic pathways that oxidize electron donors, such as lactate, and regulatory systems that control the expression of genes encoding the components of catabolic and electron-transfer pathways. In addition, recent findings suggest that cell-surface polymers, e.g., exopolysaccharides, and secreted chemicals, which function as electron shuttles, are also involved in electricity generation. Despite these advances in our knowledge on the EET processes in MR-1, further efforts are necessary to fully understand the underlying intra- and extracellular molecular systems for electricity generation in MFCs. We suggest that investigating how MR-1 coordinates these systems to efficiently transfer electrons to electrodes and conserve electrochemical energy for cell proliferation is important for establishing the biological basis for MFCs.
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Affiliation(s)
- Atsushi Kouzuma
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences , Hachioji, Japan
| | - Takuya Kasai
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences , Hachioji, Japan
| | - Atsumi Hirose
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences , Hachioji, Japan
| | - Kazuya Watanabe
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences , Hachioji, Japan
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47
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Gorgel M, Ulstrup JJ, Bøggild A, Jones NC, Hoffmann SV, Nissen P, Boesen T. High-resolution structure of a type IV pilin from the metal-reducing bacterium Shewanella oneidensis. BMC STRUCTURAL BIOLOGY 2015; 15:4. [PMID: 25886849 PMCID: PMC4376143 DOI: 10.1186/s12900-015-0031-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Accepted: 02/02/2015] [Indexed: 11/10/2022]
Abstract
Background Type IV pili are widely expressed among Gram-negative bacteria, where they are involved in biofilm formation, serve in the transfer of DNA, motility and in the bacterial attachment to various surfaces. Type IV pili in Shewanella oneidensis are also supposed to play an important role in extracellular electron transfer by the attachment to sediments containing electron acceptors and potentially forming conductive nanowires. Results The potential nanowire type IV pilin PilBac1 from S. oneidensis was characterized by a combination of complementary structural methods and the atomic structure was determined at a resolution of 1.67 Å by X-ray crystallography. PilBac1 consists of one long N-terminal α-helix packed against four antiparallel β-strands, thus revealing the core fold of type IV pilins. In the crystal, PilBac1 forms a parallel dimer with a sodium ion bound to one of the monomers. Interestingly, our PilBac1 crystal structure reveals two unusual features compared to other type IVa pilins: an unusual position of the disulfide bridge and a straight α-helical section, which usually exhibits a pronounced kink. This straight helix leads to a distinct packing in a filament model of PilBac1 based on an EM model of a Neisseria pilus. Conclusions In this study we have described the first structure of a pilin from Shewanella oneidensis. The structure possesses features of the common type IV pilin core, but also exhibits significant variations in the α-helical part and the D-region. Electronic supplementary material The online version of this article (doi:10.1186/s12900-015-0031-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Manuela Gorgel
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10c, Aarhus C, 8000, Denmark.
| | - Jakob Jensen Ulstrup
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10c, Aarhus C, 8000, Denmark.
| | - Andreas Bøggild
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10c, Aarhus C, 8000, Denmark.
| | - Nykola C Jones
- ISA, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, building 1525, Aarhus C, 8000, Denmark.
| | - Søren V Hoffmann
- ISA, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, building 1525, Aarhus C, 8000, Denmark.
| | - Poul Nissen
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10c, Aarhus C, 8000, Denmark.
| | - Thomas Boesen
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10c, Aarhus C, 8000, Denmark.
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48
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A dynamic periplasmic electron transfer network enables respiratory flexibility beyond a thermodynamic regulatory regime. ISME JOURNAL 2015; 9:1802-11. [PMID: 25635641 DOI: 10.1038/ismej.2014.264] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 11/24/2014] [Accepted: 12/05/2014] [Indexed: 11/09/2022]
Abstract
Microorganisms show an astonishing versatility in energy metabolism. They can use a variety of different catabolic electron acceptors, but they use them according to a thermodynamic hierarchy, which is determined by the redox potential of the available electron acceptors. This hierarchy is reflected by a regulatory machinery that leads to the production of respiratory chains in dependence of the availability of the corresponding electron acceptors. In this study, we showed that the γ-proteobacterium Shewanella oneidensis produces several functional electron transfer chains simultaneously. Furthermore, these chains are interconnected, most likely with the aid of c-type cytochromes. The cytochrome pool of a single S. oneidensis cell consists of ca. 700 000 hemes, which are reduced in the absence on an electron acceptor, but can be reoxidized in the presence of a variety of electron acceptors, irrespective of prior growth conditions. The small tetraheme cytochrome (STC) and the soluble heme and flavin containing fumarate reductase FccA have overlapping activity and appear to be important for this electron transfer network. Double deletion mutants showed either delayed growth or no growth with ferric iron, nitrate, dimethyl sulfoxide or fumarate as electron acceptor. We propose that an electron transfer machinery that is produced irrespective of a thermodynamic hierarchy not only enables the organism to quickly release catabolic electrons to a variety of environmental electron acceptors, but also offers a fitness benefit in redox-stratified environments.
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Tikhonova TV, Popov VO. Structural and functional studies of multiheme cytochromes c involved in extracellular electron transport in bacterial dissimilatory metal reduction. BIOCHEMISTRY (MOSCOW) 2015; 79:1584-601. [DOI: 10.1134/s0006297914130094] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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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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