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Chong GW, Karbelkar AA, El-Naggar MY. Nature's conductors: what can microbial multi-heme cytochromes teach us about electron transport and biological energy conversion? Curr Opin Chem Biol 2018; 47:7-17. [PMID: 30015234 DOI: 10.1016/j.cbpa.2018.06.007] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 06/04/2018] [Indexed: 10/28/2022]
Abstract
Microorganisms can acquire energy from the environment by extending their electron transport chains to external solid electron donors or acceptors. This process, known as extracellular electron transfer (EET), is now being heavily pursued for wiring microbes to electrodes in bioelectrochemical renewable energy technologies. Recent studies highlight the crucial role of multi-heme cytochromes in facilitating biotic-abiotic EET both for cellular electron export and uptake. Here we explore progress in understanding the range and function of these biological electron conduits in the context of fuel-to-electricity and electricity-to-bioproduct conversion. We also highlight emerging topics, including the role of multi-heme cytochromes in inter-species electron transfer and in inspiring the design and synthesis of a new generation of protein-based bioelectronic components.
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Affiliation(s)
- Grace W Chong
- Molecular and Computational Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-2910, USA
| | - Amruta A Karbelkar
- Department of Chemistry, University of Southern California, Los Angeles, CA 90089-1062, USA
| | - Mohamed Y El-Naggar
- Molecular and Computational Biology Section, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-2910, USA; Department of Chemistry, University of Southern California, Los Angeles, CA 90089-1062, USA; Department of Physics and Astronomy, University of Southern California, Los Angeles, CA 90089-0484, USA.
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102
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Nanowires under the microscope. Nat Rev Microbiol 2018; 16:330. [DOI: 10.1038/s41579-018-0012-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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103
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Reguera G. Harnessing the power of microbial nanowires. Microb Biotechnol 2018; 11:979-994. [PMID: 29806247 PMCID: PMC6201914 DOI: 10.1111/1751-7915.13280] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 04/13/2018] [Accepted: 04/22/2018] [Indexed: 12/13/2022] Open
Abstract
The reduction of iron oxide minerals and uranium in model metal reducers in the genus Geobacter is mediated by conductive pili composed primarily of a structurally divergent pilin peptide that is otherwise recognized, processed and assembled in the inner membrane by a conserved Type IVa pilus apparatus. Electronic coupling among the peptides is promoted upon assembly, allowing the discharge of respiratory electrons at rates that greatly exceed the rates of cellular respiration. Harnessing the unique properties of these conductive appendages and their peptide building blocks in metal bioremediation will require understanding of how the pilins assemble to form a protein nanowire with specialized sites for metal immobilization. Also important are insights into how cells assemble the pili to make an electroactive matrix and grow on electrodes as biofilms that harvest electrical currents from the oxidation of waste organic substrates. Genetic engineering shows promise to modulate the properties of the peptide building blocks, protein nanowires and current‐harvesting biofilms for various applications. This minireview discusses what is known about the pilus material properties and reactions they catalyse and how this information can be harnessed in nanotechnology, bioremediation and bioenergy applications.
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Affiliation(s)
- Gemma Reguera
- Department of Microbiology and Molecular Genetics, Michigan State University, 567 Wilson Rd., Rm. 6190, East Lansing, MI, 48824, USA
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104
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105
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Barrozo A, El-Naggar MY, Krylov AI. Distinct Electron Conductance Regimes in Bacterial Decaheme Cytochromes. Angew Chem Int Ed Engl 2018; 57:6805-6809. [PMID: 29663609 DOI: 10.1002/anie.201800294] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 03/28/2018] [Indexed: 12/12/2022]
Abstract
Shewanella oneidensis MR-1 gains energy by extracellular electron transfer to solid surfaces. They employ c-type cytochromes in two Mtr transmembrane complexes, forming a multiheme wire for electron transport across the cellular outer membrane. We investigated electron- and hole-transfer mechanisms in the external terminal of the two complexes, MtrC and MtrF. Comparison of computed redox potentials with previous voltammetry experiments in distinct environments (isolated and electrode-bound conditions of PFV or in vivo) suggests that these systems function in different regimes depending on the environment. Analysis of redox potential shifts in different regimes indicates strong coupling between the hemes via an interplay between direct Coulomb and indirect interactions through local structural reorganization. The latter results in the screening of Coulomb interactions and explains poor correlation of the strength of the heme-to-heme interactions with the distance between the hemes.
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Affiliation(s)
- Alexandre Barrozo
- Department of Chemistry, University of Southern California, Los Angeles, CA, 90089, USA
| | - Mohamed Y El-Naggar
- Department of Physics, University of Southern California, Los Angeles, CA, 90089, USA.,Department of Chemistry, University of Southern California, Los Angeles, CA, 90089, USA.,Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA
| | - Anna I Krylov
- Department of Chemistry, University of Southern California, Los Angeles, CA, 90089, USA
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106
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Motovilov KA, Savinov M, Zhukova ES, Pronin AA, Gagkaeva ZV, Grinenko V, Sidoruk KV, Voeikova TA, Barzilovich PY, Grebenko AK, Lisovskii SV, Torgashev VI, Bednyakov P, Pokorný J, Dressel M, Gorshunov BP. Observation of dielectric universalities in albumin, cytochrome C and Shewanella oneidensis MR-1 extracellular matrix. Sci Rep 2017; 7:15731. [PMID: 29147016 PMCID: PMC5691187 DOI: 10.1038/s41598-017-15693-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Accepted: 10/31/2017] [Indexed: 11/09/2022] Open
Abstract
The electrodynamics of metals is well understood within the Drude conductivity model; properties of insulators and semiconductors are governed by a gap in the electronic states. But there is a great variety of disordered materials that do not fall in these categories and still respond to external field in an amazingly uniform manner. At radiofrequencies delocalized charges yield a frequency-independent conductivity σ 1(ν) whose magnitude exponentially decreases while cooling. With increasing frequency, dispersionless conductivity starts to reveal a power-law dependence σ 1(ν)∝ν s with s < 1 caused by hopping charge carriers. At low temperatures, such Universal Dielectric Response can cross over to another universal regime with nearly constant loss ε″∝σ1/ν = const. The powerful research potential based on such universalities is widely used in condensed matter physics. Here we study the broad-band (1-1012 Hz) dielectric response of Shewanella oneidensis MR-1 extracellular matrix, cytochrome C and serum albumin. Applying concepts of condensed matter physics, we identify transport mechanisms and a number of energy, time, frequency, spatial and temperature scales in these biological objects, which can provide us with deeper insight into the protein dynamics.
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Affiliation(s)
- K A Motovilov
- Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia.
| | - M Savinov
- Institute of Physics AS CR, Praha 8, Czech Republic
| | - E S Zhukova
- Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia
- A.M. Prokhorov General Physics Institute, RAS, Moscow, Russia
- 1. Physikalisches Institut, Universität Stuttgart, Stuttgart, Germany
| | - A A Pronin
- A.M. Prokhorov General Physics Institute, RAS, Moscow, Russia
| | - Z V Gagkaeva
- Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia
| | - V Grinenko
- Institute for Metallic Materials, IFW Dresden, Dresden, Germany
| | - K V Sidoruk
- Scientific Center of Russian Federation Research Institute for Genetics and Selection of Industrial Microorganisms, Moscow, Russia
| | - T A Voeikova
- Scientific Center of Russian Federation Research Institute for Genetics and Selection of Industrial Microorganisms, Moscow, Russia
| | - P Yu Barzilovich
- Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia
| | - A K Grebenko
- Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia
| | - S V Lisovskii
- Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia
| | | | - P Bednyakov
- Institute of Physics AS CR, Praha 8, Czech Republic
| | - J Pokorný
- Institute of Physics AS CR, Praha 8, Czech Republic
| | - M Dressel
- 1. Physikalisches Institut, Universität Stuttgart, Stuttgart, Germany
- Moscow Institute of Physics and Technology, Institutsky lane 9, Dolgoprudny, Moscow, 141701, Russia
| | - B P Gorshunov
- Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia.
- A.M. Prokhorov General Physics Institute, RAS, Moscow, Russia.
- 1. Physikalisches Institut, Universität Stuttgart, Stuttgart, Germany.
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107
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Abstract
Descriptions of the changeable, striking colors associated with secreted natural products date back well over a century. These molecules can serve as extracellular electron shuttles (EESs) that permit microbes to access substrates at a distance. In this review, we argue that the colorful world of EESs has been too long neglected. Rather than simply serving as a diagnostic attribute of a particular microbial strain, redox-active natural products likely play fundamental, underappreciated roles in the biology of their producers, particularly those that inhabit biofilms. Here, we describe the chemical diversity and potential distribution of EES producers and users, discuss the costs associated with their biosynthesis, and critically evaluate strategies for their economical usage. We hope this review will inspire efforts to identify and explore the importance of EES cycling by a wide range of microorganisms so that their contributions to shaping microbial communities can be better assessed and exploited.
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Affiliation(s)
- Nathaniel R Glasser
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125; , ,
| | - Scott H Saunders
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125; , ,
| | - Dianne K Newman
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, California 91125; , , .,Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125
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108
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Abstract
The growing ubiquity of electronic devices is increasingly consuming substantial energy and rare resources for materials fabrication, as well as creating expansive volumes of toxic waste. This is not sustainable. Electronic biological materials (e-biologics) that are produced with microbes, or designed with microbial components as the guide for synthesis, are a potential green solution. Some e-biologics can be fabricated from renewable feedstocks with relatively low energy inputs, often while avoiding the harsh chemicals used for synthesizing more traditional electronic materials. Several are completely free of toxic components, can be readily recycled, and offer unique features not found in traditional electronic materials in terms of size, performance, and opportunities for diverse functionalization. An appropriate investment in the concerted multidisciplinary collaborative research required to identify and characterize e-biologics and to engineer materials and devices based on e-biologics could be rewarded with a new "green age" of sustainable electronic materials and devices.
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Affiliation(s)
- Derek R Lovley
- Department of Microbiology, University of Massachusetts, Amherst, Massachusetts, USA
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