1
|
Guberman-Pfeffer MJ. Structural Determinants of Redox Conduction Favor Robustness over Tunability in Microbial Cytochrome Nanowires. J Phys Chem B 2023; 127:7148-7161. [PMID: 37552847 DOI: 10.1021/acs.jpcb.3c02912] [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] [Indexed: 08/10/2023]
Abstract
Structural determinants of a 103-fold variation in electrical conductivity for helical homopolymers of tetra-, hexa-, and octa-heme cytochromes (named Omc- E, S, and Z, respectively) from Geobacter sulfurreducens are investigated with the Pathways model for electron tunneling, classical molecular dynamics, and hybrid quantum/classical molecular mechanics. Thermally averaged electronic couplings for through-space heme-to-heme electron transfer in the "nanowires" computed with density functional theory are ≤0.015 eV. Pathways analyses also indicate that couplings match within a factor of 5 for all "nanowires", but some alternative tunneling routes are found involving covalent protein backbone bonds (Omc- S and Z) or propionic acid-ligating His H-bonds on adjacent hemes (OmcZ). Reorganization energies computed from electrostatic vertical energy gaps or a version of the Marcus continuum expression parameterized on the total (donor + acceptor) solvent-accessible surface area typically agree within 20% and fall within the range 0.48-0.98 eV. Reaction free energies in all three "nanowires" are ≤|0.28| eV, even though Coulombic interactions primarily tune the site redox energies by 0.7-1.2 eV. Given the conserved energetic parameters, redox conductivity differs by < 103-fold among the cytochrome "nanowires". Redox currents do not exceed 3.0 × 10-3 pA at a physiologically relevant 0.1 V bias, with the slowest electron transfers being on a (μs) timescale much faster than typical (ms) enzymatic turnovers. Thus, the "nanowires" are proposed to be functionally robust to variations in structure that provide a habitat-customized protein interface. The 30 pA to 30 nA variation in conductivity previously reported from atomic force microscopy experiments is not intrinsic to the structures and/or does not result from the physiologically relevant redox conduction mechanism.
Collapse
Affiliation(s)
- Matthew J Guberman-Pfeffer
- Department of Molecular Biophysics and Biochemistry, Yale University, 333 Cedar Street, New Haven, Connecticut 06510, United States
- Microbial Sciences Institute, Yale University, 840 West Campus Drive, West Haven, Connecticut 06516, United States
| |
Collapse
|
2
|
Song B, Wang Z, Wang L, Wang Q, Li J, Song M, Ali J, Wang Y, Glebov EM, Zhuang X. In Situ Enhanced Yields of Microbial Nanowires: The Key Role of Environmental Stress. ACS Biomater Sci Eng 2023. [PMID: 37146257 DOI: 10.1021/acsbiomaterials.3c00313] [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: 05/07/2023]
Abstract
The conductive microbial nanowires of Geobacter sulfurreducens serve as a model for long-range extracellular electron transfer (EET), which is considered a revolutionary "green" nanomaterial in the fields of bioelectronics, renewable energy, and bioremediation. However, there is no efficient pathway to induce microorganisms to express a large amount of microbial nanowires. Here, several strategies have been used to successfully induce the expression of microbial nanowires. Microbial nanowire expression was closely related to the concentration of electron acceptors. The microbial nanowire was around 17.02 μm in length, more than 3 times compared to its own length. The graphite electrode was used as an alternative electron acceptor by G. sulfurreducens, which obtained a fast start-up time of 44 h in microbial fuel cells (MFCs). Meanwhile, Fe(III) citrate-coated sugarcane carbon and biochar were prepared to test the applicability of these strategies in the actual microbial community. The unsatisfied EET efficiency between c-type cytochrome and extracellular insoluble electron receptors promoted the expression of microbial nanowires. Hence, microbial nanowires were proposed to be an effective survival strategy for G. sulfurreducens to cope with various environmental stresses. Based on this top-down strategy of artificially constructed microbial environmental stress, this study is of great significance for exploring more efficient methods to induce microbial nanowires expression.
Collapse
Affiliation(s)
- Bo Song
- Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhibin Wang
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Lei Wang
- Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Qi Wang
- Henan Institute of Advanced Technology, Zhengzhou University, Zhengzhou 450003, China
| | - Jiaxin Li
- Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110819, China
| | - Manjiao Song
- Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Jafar Ali
- Jilin Provincial Key Laboratory of Water Resources and Environment, Jilin University, Changchun 130021, China
| | - Yaxin Wang
- Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Evgeni M Glebov
- Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch of the Russian Academy of Sciences, 3 Institutskaya Str., Novosibirsk 630090, Russian Federation
- Novosibirsk State University, 2 Pirogova Str., Novosibirsk 630090, Russian Federation
| | - Xuliang Zhuang
- Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
- State Key Laboratory of Tibetan Plateau Earth System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China
| |
Collapse
|
3
|
Guberman-Pfeffer MJ. Structural Determinants of Redox Conduction Favor Robustness over Tunability in Microbial Cytochrome Nanowires. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.21.525004. [PMID: 36712098 PMCID: PMC9882360 DOI: 10.1101/2023.01.21.525004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Helical homopolymers of multiheme cytochromes catalyze biogeochemically significant electron transfers with a reported 10 3 -fold variation in conductivity. Herein, classical molecular dynamics and hybrid quantum/classical molecular mechanics are used to elucidate the structural determinants of the redox potentials and conductivities of the tetra-, hexa-, and octaheme outer-membrane cytochromes E, S, and Z, respectively, from Geobacter sulfurreducens . Second-sphere electrostatic interactions acting on minimally polarized heme centers are found to regulate redox potentials over a computed 0.5-V range. However, the energetics of redox conduction are largely robust to the structural diversity: Single-step electronic couplings (⟨H mn ⟩), reaction free energies , and reorganization energies (λ mn ) are always respectively <|0.026|, <|0.26|, and between 0.5 - 1.0 eV. With these conserved parameter ranges, redox conductivity differed by less than a factor of 10 among the 'nanowires' and is sufficient to meet the demands of cellular respiration if 10 2 - 10 3 'nanowires' are expressed. The 'nanowires' are proposed to be differentiated by the protein packaging to interface with a great variety of environments, and not by conductivity, because the rate-limiting electron transfers are elsewhere in the respiratory process. Conducting-probe atomic force microscopy measurements that find conductivities 10 3 -10 6 -fold more than cellular demands are suggested to report on functionality that is either not used or not accessible under physiological conditions. The experimentally measured difference in conductivity between Omc- S and Z is suggested to not be an intrinsic feature of the CryoEM-resolved structures.
Collapse
Affiliation(s)
- Matthew J. Guberman-Pfeffer
- Department of Molecular Biophysics and Biochemistry, Yale University, 333 Cedar St., New Haven, CT, 06510
- Microbial Sciences Institute, Yale University, 840 West Campus Drive, West Haven, CT, 06516
| |
Collapse
|
4
|
Guberman-Pfeffer MJ. Assessing Thermal Response of Redox Conduction for Anti-Arrhenius Kinetics in a Microbial Cytochrome Nanowire. J Phys Chem B 2022; 126:10083-10097. [PMID: 36417757 PMCID: PMC9743091 DOI: 10.1021/acs.jpcb.2c06822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
A micrometers-long helical homopolymer of the outer-membrane cytochrome type S (OmcS) from Geobacter sulfurreducens is proposed to transport electrons to extracellular acceptors in an ancient respiratory strategy of biogeochemical and technological significance. OmcS surprisingly exhibits higher conductivity upon cooling (anti-Arrhenius kinetics), an effect previously attributed to H-bond restructuring and heme redox potential shifts. Herein, the temperature sensitivity of redox conductivity is more thoroughly examined with conventional and constant-redox and -pH molecular dynamics and quantum mechanics/molecular mechanics. A 30 K drop in temperature constituted a weak perturbation to electron transfer energetics, changing electronic couplings (⟨Hmn⟩), reaction free energies (ΔGmn), reorganization energies (λmn), and activation energies (Ea) by at most |0.002|, |0.050|, |0.120|, and |0.045| eV, respectively. Changes in ΔGmn reflected -0.07 ± 0.03 V shifts in redox potentials that were caused in roughly equal measure by altered electrostatic interactions with the solvent and protein. Changes in intraprotein H-bonding reproduced the earlier observations. Single-particle diffusion and multiparticle steady-state flux models, parametrized with Marcus theory rates, showed that biologically relevant incoherent hopping cannot qualitatively or quantitatively describe electrical conductivity measured by atomic force microscopy in filamentous OmcS. The discrepancy is attributed to differences between solution-phase simulations and solid-state measurements and the need to model intra- and intermolecular vibrations explicitly.
Collapse
Affiliation(s)
- Matthew J. Guberman-Pfeffer
- Department
of Molecular Biophysics and Biochemistry, Yale University, 333 Cedar St., New Haven, Connecticut06510, United States,Microbial
Sciences Institute, Yale University, 840 West Campus Drive, West Haven, Connecticut06516, United States,
| |
Collapse
|
5
|
Chen Z, Zhang J, Lyu Q, Wang H, Ji X, Yan Z, Chen F, Dahlgren RA, Zhang M. Modular configurations of living biomaterials incorporating nano-based artificial mediators and synthetic biology to improve bioelectrocatalytic performance: A review. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 824:153857. [PMID: 35176368 DOI: 10.1016/j.scitotenv.2022.153857] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 01/24/2022] [Accepted: 02/09/2022] [Indexed: 06/14/2023]
Abstract
Currently, the industrial application of bioelectrochemical systems (BESs) that are incubated with natural electrochemically active microbes (EABs) is limited due to inefficient extracellular electron transfer (EET) by natural EABs. Notably, recent studies have identified several novel living biomaterials comprising highly efficient electron transfer systems allowing unparalleled proficiency of energy conversion. Introduction of these biomaterials into BESs could fundamentally increase their utilization for a wide range of applications. This review provides a comprehensive assessment of recent advancements in the design of living biomaterials that can be exploited to enhance bioelectrocatalytic performance. Further, modular configurations of abiotic and biotic components promise a powerful enhancement through integration of nano-based artificial mediators and synthetic biology. Herein, recent advancements in BESs are synthesized and assessed, including heterojunctions between conductive nanomaterials and EABs, in-situ hybrid self-assembly of EABs and nano-sized semiconductors, cytoprotection in biohybrids, synthetic biological modifications of EABs and electroactive biofilms. Since living biomaterials comprise a broad range of disciplines, such as molecular biology, electrochemistry and material sciences, full integration of technological advances applied in an interdisciplinary framework will greatly enhance/advance the utility and novelty of BESs. Overall, emerging fundamental knowledge concerning living biomaterials provides a powerful opportunity to markedly boost EET efficiency and facilitate the industrial application of BESs to meet global sustainability challenges/goals.
Collapse
Affiliation(s)
- Zheng Chen
- School of Public Health and Management, Wenzhou Medical University, Wenzhou 325035, People's Republic of China; School of Environmental Science & Engineering, Tan Kah Kee College, Xiamen University, Zhangzhou 363105, People's Republic of China; Fujian Provincial Key Lab of Coastal Basin Environment, Fujian Polytechnic Normal University, Fuqing 350300, People's Republic of China.
| | - Jing Zhang
- School of Environmental Science & Engineering, Tan Kah Kee College, Xiamen University, Zhangzhou 363105, People's Republic of China
| | - Qingyang Lyu
- CAS Key Laboratory of Environmental and Applied Microbiology, Environmental Microbiology Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, People's Republic of China
| | - Honghui Wang
- School of Environmental Science & Engineering, Tan Kah Kee College, Xiamen University, Zhangzhou 363105, People's Republic of China
| | - Xiaoliang Ji
- School of Public Health and Management, Wenzhou Medical University, Wenzhou 325035, People's Republic of China
| | - Zhiying Yan
- CAS Key Laboratory of Environmental and Applied Microbiology, Environmental Microbiology Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, People's Republic of China
| | - Fang Chen
- Fujian Provincial Key Lab of Coastal Basin Environment, Fujian Polytechnic Normal University, Fuqing 350300, People's Republic of China
| | - Randy A Dahlgren
- School of Public Health and Management, Wenzhou Medical University, Wenzhou 325035, People's Republic of China; Department of Land, Air and Water Resources, University of California, Davis, CA 95616, USA
| | - Minghua Zhang
- School of Public Health and Management, Wenzhou Medical University, Wenzhou 325035, People's Republic of China; Department of Land, Air and Water Resources, University of California, Davis, CA 95616, USA
| |
Collapse
|
6
|
Shi R, Zhang J, Yang J, Xu Y, Li C, Chen S, Xu F. Direct-Ink-Write Printing and Electrospinning of Cellulose Derivatives for Conductive Composite Materials. MATERIALS 2022; 15:ma15082840. [PMID: 35454533 PMCID: PMC9028373 DOI: 10.3390/ma15082840] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/12/2022] [Revised: 04/03/2022] [Accepted: 04/08/2022] [Indexed: 02/04/2023]
Abstract
The aim of this study is to realize the controlled construction and modulation of micro-/nanostructures of conductive composite materials (CCMs) in a facile way. Herein, interdigital electrodes are prepared by direct-ink-write printing co-blended inks made of ethyl cellulose and carbon nanotubes on cellulose paper. The cellulose nanofibers (CFs) are prepared by electrospinning cellulose acetate on to an aluminum foil, followed by deacetylation in NaOH/ethanol. All co-blended inks exhibit a typical non-Newtonian shear thinning behavior, enabling smooth extrusion and printing. The above electrodes and the conductive CF films with excellent thermal stability are assembled into a pressure sensor, which has a high sensitivity (0.0584 KPa−1) to detect the change in external loading pressure. The obtained porous CFs film is further endowed with conductivity by in situ polymerization of polypyrrole (PPy), which are uniformly distributed on the CFs surface as particles; a triboelectric nanogenerator is constructed by using the CF@PPy film as a tribo-positive friction layer to achieve efficient energy harvesting (output voltage = 29.78 V, output current = 2.12 μA). Therefore, the construction of CCMs with micro-/nanostructures based on cellulose derivatives have essential application prospects in emerging high-tech fields, such as green electronics for sensing and energy harvesting.
Collapse
Affiliation(s)
- Runfeng Shi
- Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing 100083, China; (R.S.); (J.Z.); (J.Y.); (Y.X.); (C.L.)
| | - Jiankang Zhang
- Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing 100083, China; (R.S.); (J.Z.); (J.Y.); (Y.X.); (C.L.)
| | - Jinheng Yang
- Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing 100083, China; (R.S.); (J.Z.); (J.Y.); (Y.X.); (C.L.)
| | - Yanglei Xu
- Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing 100083, China; (R.S.); (J.Z.); (J.Y.); (Y.X.); (C.L.)
| | - Cuihuan Li
- Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing 100083, China; (R.S.); (J.Z.); (J.Y.); (Y.X.); (C.L.)
| | - Sheng Chen
- Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing 100083, China; (R.S.); (J.Z.); (J.Y.); (Y.X.); (C.L.)
- Correspondence: (S.C.); (F.X.)
| | - Feng Xu
- State Key Laboratory of Biobased Material and Green Papermaking, Qilu University of Technology, Shandong Academy of Sciences, Jinan 250353, China
- Correspondence: (S.C.); (F.X.)
| |
Collapse
|
7
|
Lu S, Jayaraman A. Effect of Nanorod Physical Roughness on the Aggregation and Percolation of Nanorods in Polymer Nanocomposites. ACS Macro Lett 2021; 10:1416-1422. [PMID: 35549008 DOI: 10.1021/acsmacrolett.1c00503] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Using molecular dynamics simulations, we elucidate the effect of nanorod roughness on nanorod aggregation, dispersion, and percolation in polymer nanocomposites (PNCs). By choosing coarse-grained models that enable systematic variation of the nanorod roughness and by selecting purely repulsive pairwise interactions for nanorods and polymer chains, we show how nanorod roughness affects the entropic driving forces for various PNC morphologies. At this entropically driven limit, we find that increasing nanorod roughness hinders nanorod aggregation and promotes nanorod percolation in the polymer melt. As nanorod roughness increases, the nanorod volume fraction needed to induce nanorod aggregation also increases. Increasing nanorod roughness increases the configurational entropy of the polymer chains and lowers the entropically induced depletion attraction between nanorods.
Collapse
Affiliation(s)
- Shizhao Lu
- Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy Street, Newark, Delaware 19716, United States
| | - Arthi Jayaraman
- Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy Street, Newark, Delaware 19716, United States.,Department of Materials Science and Engineering, University of Delaware, 201 DuPont Hall, Newark, Delaware 19716, United States
| |
Collapse
|
8
|
Wei Y, Jiang S, Li X, Li J, Dong Y, Shi SQ, Li J, Fang Z. "Green" Flexible Electronics: Biodegradable and Mechanically Strong Soy Protein-Based Nanocomposite Films for Human Motion Monitoring. ACS APPLIED MATERIALS & INTERFACES 2021; 13:37617-37627. [PMID: 34313436 DOI: 10.1021/acsami.1c09209] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Soy protein isolate (SPI) is envisioned as a promising alternative to fabricate "green" flexible electronics, showing great potential in the field of flexible wearable electronics. However, it is challenging to simultaneously achieve conductive film-based human motion-monitoring strain sensors with reliable fatigue resistance, robust mechanical property, environmental degradability, and sensing capability of human motions. Herein, we prepared a series of SPI-based nanocomposite films by embedding a surface-hydroxylated high-dielectric constant inorganic filler, BaTiO3, (HBT) as interspersed nanoparticles into a biodegradable SPI substrate. In particular, the fabricated film comprising 0.5 wt % HBT and glycerin (GL), namely, SPI-HBT0.5-GL0.5, presents multifunctional properties, including a combination of excellent toughness, tensile strength, conductivity, translucence, recyclability, and excellent thermal stability. Meanwhile, this multifunctional film could be simply degraded in phosphate buffered saline solution and does not cause any pollution to the environment. Attractively, wearable sensors prepared with this particular material (SPI-HBT0.5-GL0.5) displayed excellent biocompatibility, prevented the occurrence of an immune response, and could accurately monitor various types of human joint motions and successfully remain operable after 10,000 cycles. These properties make the developed SPI-based film a great candidate in formulating biobased and multifunctional wearable electronics.
Collapse
Affiliation(s)
- Yanqiang Wei
- College of Materials Science and Engineering, Nanjing Forestry University, Nanjing, Jiangsu 210037, China
| | - Shuaicheng Jiang
- College of Materials Science and Engineering, Nanjing Forestry University, Nanjing, Jiangsu 210037, China
| | - Xiaona Li
- College of Materials Science and Engineering, Nanjing Forestry University, Nanjing, Jiangsu 210037, China
| | - Jiongjiong Li
- College of Materials Science and Engineering, Nanjing Forestry University, Nanjing, Jiangsu 210037, China
| | - Youming Dong
- College of Materials Science and Engineering, Nanjing Forestry University, Nanjing, Jiangsu 210037, China
| | - Sheldon Q Shi
- Department of Mechanical Engineering, University of North Texas, Denton 76203, United States
| | - Jianzhang Li
- College of Materials Science and Engineering, Nanjing Forestry University, Nanjing, Jiangsu 210037, China
- College of Materials Science and Engineering, Beijing Forestry University, Beijing 100083, China
| | - Zhen Fang
- College of Materials Science and Engineering, Nanjing Forestry University, Nanjing, Jiangsu 210037, China
- Department of Biochemistry & Molecular Biology, Michigan State University, 603 Wilson Road, East Lansing, Michigan 48824, United States
- Great Lakes Bioenergy Research Center, Michigan State University, 1129 Farm Lane, East Lansing, Michigan 48824, United States
| |
Collapse
|
9
|
Lovley DR, Holmes DE. Electromicrobiology: the ecophysiology of phylogenetically diverse electroactive microorganisms. Nat Rev Microbiol 2021; 20:5-19. [PMID: 34316046 DOI: 10.1038/s41579-021-00597-6] [Citation(s) in RCA: 156] [Impact Index Per Article: 52.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/16/2021] [Indexed: 02/03/2023]
Abstract
Electroactive microorganisms markedly affect many environments in which they establish outer-surface electrical contacts with other cells and minerals or reduce soluble extracellular redox-active molecules such as flavins and humic substances. A growing body of research emphasizes their broad phylogenetic diversity and shows that these microorganisms have key roles in multiple biogeochemical cycles, as well as the microbiome of the gut, anaerobic waste digesters and metal corrosion. Diverse bacteria and archaea have independently evolved cytochrome-based strategies for electron exchange between the outer cell surface and the cell interior, but cytochrome-free mechanisms are also prevalent. Electrically conductive protein filaments, soluble electron shuttles and non-biological conductive materials can substantially extend the electronic reach of microorganisms beyond the surface of the cell. The growing appreciation of the diversity of electroactive microorganisms and their unique electronic capabilities is leading to a broad range of applications.
Collapse
Affiliation(s)
- Derek R Lovley
- Electrobiomaterials Institute, Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang, China. .,Department of Microbiology, University of Massachusetts, Amherst, MA, USA. .,Institute for Applied Life Sciences (IALS), University of Massachusetts, Amherst, MA, USA.
| | - Dawn E Holmes
- Department of Microbiology, University of Massachusetts, Amherst, MA, USA.,Institute for Applied Life Sciences (IALS), University of Massachusetts, Amherst, MA, USA.,Department of Physical and Biological Sciences, Western New England University, Springfield, MA, USA
| |
Collapse
|
10
|
Lu S, Wu Z, Jayaraman A. Molecular Modeling and Simulation of Polymer Nanocomposites with Nanorod Fillers. J Phys Chem B 2021; 125:2435-2449. [PMID: 33646794 DOI: 10.1021/acs.jpcb.1c00097] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We present a coarse-grained (CG) molecular dynamics (MD) simulation study of polymer nanocomposites (PNCs) containing nanorods with homogeneous and patchy surface chemistry/functionalization, modeled with isotropic and directional nanorod-nanorod attraction, respectively. We show how the PNC morphology is impacted by the nanorod design (i.e., aspect ratio, homogeneous or patchy surface chemistry/functionalization) for nanorods with a diameter equal to the Kuhn length of the polymer in the matrix. For PNCs with 10 vol % nanorods that have an aspect ratio ≤5, we observe percolated morphology with directional nanorod-nanorod attraction and phase-separated (i.e., nanorod aggregation) morphology with isotropic nanorod-nanorod attraction. In contrast, for nanorods with higher aspect ratios, both types of attractions result in aggregated nanorods morphology due to the dominance of entropic driving forces that cause long nanorods to form orientationally ordered aggregates. For most PNCs with isotropic or directional nanorod-nanorod attractions, the average matrix polymer conformation is not perturbed by the inclusion of up to 20 vol % nanorods. The polymer chains in contact with nanorods (i.e., interfacial chains) are on average extended and statistically different from the conformations the matrix chains adopt in the pure melt state (with no nanorods); in contrast, the polymer chains far from nanorods (i.e., bulk chains) adopt the same conformations as the matrix chains adopt in the pure melt state. We also study the effect of other parameters, such as attraction strength, nanorod volume fraction, and matrix chain length, for PNCs with isotropic or directional nanorod-nanorod attractions. Collectively, our results provide valuable design rules to achieve specific PNC morphologies (i.e., dispersed, aggregated, percolated, and orientationally aligned nanorods) for various potential applications.
Collapse
Affiliation(s)
- Shizhao Lu
- Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy Street, Newark, Delaware 19716, United States
| | - Zijie Wu
- Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy Street, Newark, Delaware 19716, United States
| | - Arthi Jayaraman
- Department of Chemical and Biomolecular Engineering, University of Delaware, 150 Academy Street, Newark, Delaware 19716, United States.,Department of Materials Science and Engineering, University of Delaware, 201 DuPont Hall, Newark, Delaware 19716, United States
| |
Collapse
|
11
|
Sun YL, Montz BJ, Selhorst R, Tang HY, Zhu J, Nevin KP, Woodard TL, Ribbe AE, Russell TP, Nonnenmann SS, Lovley DR, Emrick T. Solvent-Induced Assembly of Microbial Protein Nanowires into Superstructured Bundles. Biomacromolecules 2021; 22:1305-1311. [PMID: 33591727 DOI: 10.1021/acs.biomac.0c01790] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Protein-based electronic biomaterials represent an attractive alternative to traditional metallic and semiconductor materials due to their environmentally benign production and purification. However, major challenges hindering further development of these materials include (1) limitations associated with processing proteins in organic solvents and (2) difficulties in forming higher-order structures or scaffolds with multilength scale control. This paper addresses both challenges, resulting in the formation of one-dimensional bundles composed of electrically conductive protein nanowires harvested from the microbes Geobacter sulfurreducens and Escherichia coli. Processing these bionanowires from common organic solvents, such as hexane, cyclohexane, and DMF, enabled the production of multilength scale structures composed of distinctly visible pili. Transmission electron microscopy revealed striking images of bundled protein nanowires up to 10 μm in length and with widths ranging from 50-500 nm (representing assembly of tens to hundreds of nanowires). Conductive atomic force microscopy confirmed the presence of an appreciable nanowire conductivity in their bundled state. These results greatly expand the possibilities for fabricating a diverse array of protein nanowire-based electronic device architectures.
Collapse
Affiliation(s)
- Yun-Lu Sun
- Department of Microbiology, University of Massachusetts Amherst, Amherst, Massachusetts01003, United States
| | - Brian J Montz
- Department of Polymer Science and Engineering Department, University of Massachusetts Amherst, Amherst, Massachusetts01003, United States
| | - Ryan Selhorst
- Department of Polymer Science and Engineering Department, University of Massachusetts Amherst, Amherst, Massachusetts01003, United States
| | - Hai-Yan Tang
- Department of Microbiology, University of Massachusetts Amherst, Amherst, Massachusetts01003, United States
| | - Jiaxin Zhu
- Department of Mechanical and Industrial Engineering, University of Massachusetts Amherst, Amherst, Massachusetts01003, United States
| | - Kelly P Nevin
- Department of Microbiology, University of Massachusetts Amherst, Amherst, Massachusetts01003, United States
| | - Trevor L Woodard
- Department of Microbiology, University of Massachusetts Amherst, Amherst, Massachusetts01003, United States
| | - Alexander E Ribbe
- Department of Polymer Science and Engineering Department, University of Massachusetts Amherst, Amherst, Massachusetts01003, United States
| | - Thomas P Russell
- Department of Polymer Science and Engineering Department, University of Massachusetts Amherst, Amherst, Massachusetts01003, United States
| | - Stephen S Nonnenmann
- Department of Mechanical and Industrial Engineering, University of Massachusetts Amherst, Amherst, Massachusetts01003, United States
| | - Derek R Lovley
- Department of Microbiology, University of Massachusetts Amherst, Amherst, Massachusetts01003, United States
| | - Todd Emrick
- Department of Polymer Science and Engineering Department, University of Massachusetts Amherst, Amherst, Massachusetts01003, United States
| |
Collapse
|
12
|
Wang R, Li H, Sun J, Zhang L, Jiao J, Wang Q, Liu S. Nanomaterials Facilitating Microbial Extracellular Electron Transfer at Interfaces. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2004051. [PMID: 33325567 DOI: 10.1002/adma.202004051] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 09/03/2020] [Indexed: 06/12/2023]
Abstract
Electrochemically active bacteria can transport their metabolically generated electrons to anodes, or accept electrons from cathodes to synthesize high-value chemicals and fuels, via a process known as extracellular electron transfer (EET). Harnessing of this microbial EET process has led to the development of microbial bio-electrochemical systems (BESs), which can achieve the interconversion of electrical and chemical energy and enable electricity generation, hydrogen production, electrosynthesis, wastewater treatment, desalination, water and soil remediation, and sensing. Here, the focus is on the current understanding of the microbial EET process occurring at both the bacteria-electrode interface and the biotic interface, as well as some attempts to improve the EET by using various nanomaterials. The behavior of nanomaterials in different EET routes and their influence on the performance of BESs are described. The inherent mechanisms will guide rational design of EET-related materials and lead to a better understanding of EET mechanisms.
Collapse
Affiliation(s)
- Ruiwen Wang
- School of Life Science and Technology, State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin, 150090, China
| | - Huidong Li
- School of Life Science and Technology, State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin, 150090, China
| | - Jinzhi Sun
- School of Life Science and Technology, State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin, 150090, China
| | - Lu Zhang
- School of Life Science and Technology, State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin, 150090, China
| | - Jia Jiao
- School of Life Science and Technology, State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin, 150090, China
| | - Qingqing Wang
- School of Chemistry and Chemical Engineering, Micro- and Nanotechnology Research Center, Harbin Institute of Technology, Harbin, 150090, China
| | - Shaoqin Liu
- School of Life Science and Technology, State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin, 150090, China
| |
Collapse
|
13
|
Lovley DR, Yao J. Intrinsically Conductive Microbial Nanowires for 'Green' Electronics with Novel Functions. Trends Biotechnol 2021; 39:940-952. [PMID: 33419586 DOI: 10.1016/j.tibtech.2020.12.005] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2020] [Revised: 12/04/2020] [Accepted: 12/07/2020] [Indexed: 10/22/2022]
Abstract
Intrinsically conductive protein nanowires, microbially produced from inexpensive, renewable feedstocks, are a sustainable alternative to traditional nanowire electronic materials, which require high energy inputs and hazardous conditions/chemicals for fabrication and can be highly toxic. Pilin-based nanowires can be tailored for specific functions via the design of synthetic pilin genes to tune wire conductivity or introduce novel functionalities. Other microbially produced nanowire options for electronics may include cytochrome wires, curli fibers, and the conductive fibers of cable bacteria. Proof-of-concept protein nanowire electronics that have been successfully demonstrated include biomedical sensors, neuromorphic devices, and a device that generates electricity from ambient humidity. Further development of applications will require interdisciplinary teams of engineers, biophysicists, and synthetic biologists.
Collapse
Affiliation(s)
- Derek R Lovley
- Electrobiomaterials Institute, Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110819, China; Department of Microbiology, University of Massachusetts, Amherst, MA, USA; Institute for Applied Life Sciences (IALS), University of Massachusetts, Amherst, MA, USA.
| | - Jun Yao
- Institute for Applied Life Sciences (IALS), University of Massachusetts, Amherst, MA, USA; Department of Electrical and Computer Engineering, University of Massachusetts, Amherst, MA, USA; Department of Biomedical Engineering, University of Massachusetts, Amherst, MA, USA
| |
Collapse
|
14
|
Hou ZS, Sun YL, Li QS, Fan X, Cheng R. Smart bio-gel optofluidic Mach-Zehnder interferometers multiphoton-lithographically customized with chemo-mechanical-opto transduction and bio-triggered degradation. LAB ON A CHIP 2020; 20:3815-3823. [PMID: 32926039 DOI: 10.1039/d0lc00718h] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Stimulus-responsive optical polymers, especially gels, are enabling new-concept energy-transducing "smart" optics. Full exploitation of their molecule-derived tuning and integration with traditional micro/nano-optics/optoelectronics rely on the implementation of devices by advanced "intelligent" micro/nano-manufacturing technologies, especially photolithographies with wide compatibility. In light of the increasing need for an organic combination of smart optical materials and digital micro/nano-manufacturing, novel "smart" optical micro-switches, namely, stimulus-actuated Mach-Zehnder interferometers as a proof-of-concept demonstration, were prototyped with protein-based hydrogels via aqueous multiphoton femtosecond laser direct writing (FsLDW). Protein-based Mach-Zehnder-interferometric smart optical devices here display a morphological quality sufficient for optical applications (average surface roughness ≤∼20 nm), nano-precision three-dimensional (3D) geometry of these millimeter-scale devices and purposely structured distribution of photo-crosslinking degree. Moreover, the device configuration was customized with unbalanced branches in which meticulous stimulus-responsive ability can be realized by simply tuning the surrounding chemical stimuli (i.e., Na2SO4 concentration here). The "heterogeneous" configuration with unbalanced branches (i.e., different optical and stimulus-responsive features) exhibits as-designed "smart" switching of propagated near-infrared light (∼808 nm). These capabilities, along with total biodegradation, indicate the application promise of this gel-based optic construction strategy towards novel "intelligent", bio/eco-friendly, self-tuning or sensing photonic integrated systems like optofluidics.
Collapse
Affiliation(s)
- Zhi-Shan Hou
- State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instrument, Tsinghua University, Haidian, Beijing 100084, China
| | | | | | | | | |
Collapse
|
15
|
Lovley DR, Holmes DE. Protein Nanowires: the Electrification of the Microbial World and Maybe Our Own. J Bacteriol 2020; 202:e00331-20. [PMID: 32747429 PMCID: PMC7515249 DOI: 10.1128/jb.00331-20] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Electrically conductive protein nanowires appear to be widespread in the microbial world and are a revolutionary "green" material for the fabrication of electronic devices. Electrically conductive pili (e-pili) assembled from type IV pilin monomers have independently evolved multiple times in microbial history as have electrically conductive archaella (e-archaella) assembled from homologous archaellin monomers. A role for e-pili in long-range (micrometer) extracellular electron transport has been demonstrated in some microbes. The surprising finding of e-pili in syntrophic bacteria and the role of e-pili as conduits for direct interspecies electron transfer have necessitated a reassessment of routes for electron flux in important methanogenic environments, such as anaerobic digesters and terrestrial wetlands. Pilin monomers similar to those found in e-pili may also be a major building block of the conductive "cables" that transport electrons over centimeter distances through continuous filaments of cable bacteria consisting of a thousand cells or more. Protein nanowires harvested from microbes have many functional and sustainability advantages over traditional nanowire materials and have already yielded novel electronic devices for sustainable electricity production, neuromorphic memory, and sensing. e-pili can be mass produced with an Escherichia coli chassis, providing a ready source of material for electronics as well as for studies on the basic mechanisms for long-range electron transport along protein nanowires. Continued exploration is required to better understand the electrification of microbial communities with microbial nanowires and to expand the "green toolbox" of sustainable materials for wiring and powering the emerging "Internet of things."
Collapse
Affiliation(s)
- Derek R Lovley
- Department of Microbiology, University of Massachusetts, Amherst, Massachusetts, USA
- Institute of Applied Life Sciences, University of Massachusetts, Amherst, Massachusetts, USA
| | - Dawn E Holmes
- Department of Microbiology, University of Massachusetts, Amherst, Massachusetts, USA
- Department of Physical and Biological Sciences, Western New England University, Springfield, Massachusetts, USA
| |
Collapse
|
16
|
Roy S, Xie O, Dorval Courchesne N. Challenges in engineering conductive protein fibres: Disentangling the knowledge. CAN J CHEM ENG 2020. [DOI: 10.1002/cjce.23836] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Sophia Roy
- Department of Chemical Engineering McGill University Montréal Québec Canada
| | - Oliver Xie
- Department of Chemical Engineering McGill University Montréal Québec Canada
| | | |
Collapse
|
17
|
Wei W, Plymale A, Zhu Z, Ma X, Liu F, Yu XY. In Vivo Molecular Insights into Syntrophic Geobacter Aggregates. Anal Chem 2020; 92:10402-10411. [PMID: 32614167 DOI: 10.1021/acs.analchem.0c00653] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Direct interspecies electron transfer (DIET) has been considered as a novel and highly efficient strategy in both natural anaerobic environments and artificial microbial fuel cells. A syntrophic model consisting of Geobacter metallireducens and Geobacter sulfurreducens was studied in this work. We conducted in vivo molecular mapping of the outer surface of the syntrophic community as the interface of nutrients and energy exchange. System for Analysis at the Liquid Vacuum Interface combined with time-of-flight secondary ion mass spectrometry was employed to capture the molecular distribution of syntrophic Geobacter communities in the living and hydrated state. Principal component analysis with selected peaks revealed that syntrophic Geobacter aggregates were well differentiated from other control samples, including syntrophic planktonic cells, pure cultured planktonic cells, and single population biofilms. Our in vivo imaging indicated that a unique molecular surface was formed. Specifically, aromatic amino acids, phosphatidylethanolamine components, and large water clusters were identified as key components that favored the DIET of syntrophic Geobacter aggregates. Moreover, the molecular changes in depths of the Geobacter aggregates were captured using dynamic depth profiling. Our findings shed new light on the interface components supporting electron transfer in syntrophic communities based on in vivo molecular imaging.
Collapse
Affiliation(s)
- Wenchao Wei
- Key Laboratory of Coastal Biology and Utilization, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, Shandong 264003, P. R. China.,Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States.,University of Chinese Academy of Sciences, Beijing 100049, P. R. China
| | - Andrew Plymale
- Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Zihua Zhu
- Environmental and Molecular Science Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Xiang Ma
- Department of Chemistry, Grand View University, Des Moines, Iowa 50316, United States
| | - Fanghua Liu
- Key Laboratory of Coastal Biology and Utilization, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai, Shandong 264003, P. R. China
| | - Xiao-Ying Yu
- Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| |
Collapse
|
18
|
Li F, Wang D, Zhou J, Men D, Zhan XE. Design and biosynthesis of functional protein nanostructures. SCIENCE CHINA-LIFE SCIENCES 2020; 63:1142-1158. [PMID: 32253589 DOI: 10.1007/s11427-019-1641-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 02/05/2020] [Indexed: 02/06/2023]
Abstract
Proteins are one of the major classes of biomolecules that execute biological functions for maintenance of life. Various kinds of nanostructures self-assembled from proteins have been created in nature over millions of years of evolution, including protein nanowires, layers and nanocages. These protein nanostructures can be reconstructed and equipped with desired new functions. Learning from and manipulating the self-assembly of protein nanostructures not only help to deepen our understanding of the nature of life but also offer new routes to fabricate novel nanomaterials for diverse applications. This review summarizes the recent research progress in this field, focusing on the characteristics, functionalization strategies, and applications of protein nanostructures.
Collapse
Affiliation(s)
- Feng Li
- State Key Laboratory of Virology, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, 430071, China.
| | - Dianbing Wang
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Juan Zhou
- State Key Laboratory of Virology, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, 430071, China
| | - Dong Men
- State Key Laboratory of Virology, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, 430071, China
| | - Xian-En Zhan
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China.
| |
Collapse
|
19
|
Ueki T, Walker DJF, Woodard TL, Nevin KP, Nonnenmann SS, Lovley DR. An Escherichia coli Chassis for Production of Electrically Conductive Protein Nanowires. ACS Synth Biol 2020; 9:647-654. [PMID: 32125829 DOI: 10.1021/acssynbio.9b00506] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Geobacter sulfurreducens' pilin-based electrically conductive protein nanowires (e-PNs) are a revolutionary electronic material. They offer novel options for electronic sensing applications and have the remarkable ability to harvest electrical energy from atmospheric humidity. However, technical constraints limit mass cultivation and genetic manipulation of G. sulfurreducens. Therefore, we designed a strain of Escherichia coli to express e-PNs by introducing a plasmid that contained an inducible operon with E. coli genes for type IV pili biogenesis machinery and a synthetic gene designed to yield a peptide monomer that could be assembled into e-PNs. The e-PNs expressed in E. coli and harvested with a simple filtration method had the same diameter (3 nm) and conductance as e-PNs expressed in G. sulfurreducens. These results, coupled with the robustness of E. coli for mass cultivation and the extensive E. coli toolbox for genetic manipulation, greatly expand the opportunities for large-scale fabrication of novel e-PNs.
Collapse
Affiliation(s)
- Toshiyuki Ueki
- Department of Microbiology, University of Massachusetts-Amherst, Amherst, Massachusetts 01003, United States
- Institute for Applied Life Sciences, University of Massachusetts-Amherst, Amherst, Massachusetts 01003, United States
| | - David J. F. Walker
- Department of Microbiology, University of Massachusetts-Amherst, Amherst, Massachusetts 01003, United States
- Institute for Applied Life Sciences, University of Massachusetts-Amherst, Amherst, Massachusetts 01003, United States
| | - Trevor L. Woodard
- Department of Microbiology, University of Massachusetts-Amherst, Amherst, Massachusetts 01003, United States
| | - Kelly P. Nevin
- Department of Microbiology, University of Massachusetts-Amherst, Amherst, Massachusetts 01003, United States
| | - Stephen S. Nonnenmann
- Institute for Applied Life Sciences, University of Massachusetts-Amherst, Amherst, Massachusetts 01003, United States
- Department of Mechanical and Industrial Engineering, University of Massachusetts-Amherst, Amherst, Massachusetts 01003, United States
| | - Derek R. Lovley
- Department of Microbiology, University of Massachusetts-Amherst, Amherst, Massachusetts 01003, United States
- Institute for Applied Life Sciences, University of Massachusetts-Amherst, Amherst, Massachusetts 01003, United States
| |
Collapse
|
20
|
Abstract
The study of electrically conductive protein nanowires in Geobacter sulfurreducens has led to new concepts for long-range extracellular electron transport, as well as for the development of sustainable conductive materials and electronic devices with novel functions. Until recently, electrically conductive pili (e-pili), assembled from the PilA pilin monomer, were the only known Geobacter protein nanowires. However, filaments comprised of the multi-heme c-type cytochrome, OmcS, are present in some preparations of G. sulfurreducens outer-surface proteins. The purpose of this review is to evaluate the available evidence on the in vivo expression of e-pili and OmcS filaments and their biological function. Abundant literature demonstrates that G. sulfurreducens expresses e-pili, which are required for long-range electron transport to Fe (III) oxides and through conductive biofilms. In contrast, there is no definitive evidence yet that wild-type G. sulfurreducens express long filaments of OmcS extending from the cells, and deleting the gene for OmcS actually increases biofilm conductivity. The literature does not support the concern that many previous studies on e-pili were mistakenly studying OmcS filaments. For example, heterologous expression of the aromatic-rich pilin monomer of Geobacter metallireducens in G. sulfurreducens increases the conductivity of individual nanowires more than 5,000-fold, whereas expression of an aromatic-poor pilin reduced conductivity more than 1,000-fold. This more than million-fold range in nanowire conductivity was achieved while maintaining the 3-nm diameter characteristic of e-pili. Purification methods that eliminate all traces of OmcS yield highly conductive e-pili, as does heterologous expression of the e-pilin monomer in microbes that do not produce OmcS or any other outer-surface cytochromes. Future studies of G. sulfurreducens expression of protein nanowires need to be cognizant of the importance of maintaining environmentally relevant growth conditions because artificial laboratory culture conditions can rapidly select against e-pili expression. Principles derived from the study of e-pili have enabled identification of non-cytochrome protein nanowires in diverse bacteria and archaea. A similar search for cytochrome appendages is warranted. Both e-pili and OmcS filaments offer design options for the synthesis of protein-based "green" electronics, which may be the primary driving force for the study of these structures in the near future.
Collapse
Affiliation(s)
- Derek R. Lovley
- Department of Microbiology, Institute for Applied Life Sciences, University of Massachusetts, Amherst, MA, United States
| | | |
Collapse
|
21
|
Filman DJ, Marino SF, Ward JE, Yang L, Mester Z, Bullitt E, Lovley DR, Strauss M. Cryo-EM reveals the structural basis of long-range electron transport in a cytochrome-based bacterial nanowire. Commun Biol 2019; 2:219. [PMID: 31240257 PMCID: PMC6584659 DOI: 10.1038/s42003-019-0448-9] [Citation(s) in RCA: 91] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Accepted: 04/30/2019] [Indexed: 01/16/2023] Open
Abstract
Electrically conductive pili from Geobacter species, termed bacterial nanowires, are intensely studied for their biological significance and potential in the development of new materials. Using cryo-electron microscopy, we have characterized nanowires from conductive G. sulfurreducens pili preparations that are composed solely of head-to-tail stacked monomers of the six-heme C-type cytochrome OmcS. The unique fold of OmcS - closely wrapped around a continuous stack of hemes that can serve as an uninterrupted path for electron transport - generates a scaffold that supports the unbranched chain of hemes along the central axis of the filament. We present here, at 3.4 Å resolution, the structure of this cytochrome-based filament and discuss its possible role in long-range biological electron transport.
Collapse
Affiliation(s)
- David J. Filman
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115 USA
| | - Stephen F. Marino
- German Federal Institute of Risk Assessment, Unit Bacterial Toxins, Department of Biological Safety, Max-Dohrn-Str. 8–10, Berlin, 10589 Germany
| | - Joy E. Ward
- Department of Microbiology and Institute for Applied Life Sciences, University of Massachusetts, Amherst, MA 01002 USA
| | - Lu Yang
- National Research Council Canada, Montreal Road Ottawa, ON 1200 Canada
| | - Zoltán Mester
- National Research Council Canada, Montreal Road Ottawa, ON 1200 Canada
| | - Esther Bullitt
- Department of Physiology & Biophysics, Boston University School of Medicine, 700 Albany Street, Boston, MA 02118 USA
| | - Derek R. Lovley
- Department of Microbiology and Institute for Applied Life Sciences, University of Massachusetts, Amherst, MA 01002 USA
| | - Mike Strauss
- Department of Anatomy and Cell Biology, McGill University, 3640 University St, Montreal, H3A 2B2 QC Canada
| |
Collapse
|