scholarly journals Reversing an extracellular electron transfer pathway for electrode-driven NADH generation

2018 ◽  
Author(s):  
Nicholas M. Tefft ◽  
Michaela A. TerAvest
Keyword(s):  
Electron Transfer ◽  
Shewanella Oneidensis ◽  
Electrical Energy ◽  
Genetically Engineered ◽  
Extracellular Electron Transfer ◽  
Microbial Electrosynthesis ◽  
Electron Transfer Pathway ◽  
Background Strain ◽  
Nadh Dehydrogenases ◽  
Electron Sink

AbstractMicrobial 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 engineered an inward electron transfer pathway inShewanella oneidensisMR-1. The pathway 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 have 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-deficientS. oneidensisbackground 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 genetically engineered microbial electrosynthesis platform and will enable a new focus on synthesis of specific compounds using electrical energy.

scholarly journals A Hybrid Extracellular Electron Transfer Pathway Enhances the Survival of Vibrio natriegens

2020 ◽  
Vol 86 (19) ◽  
Author(s):  
Bridget E. Conley ◽  
Matthew T. Weinstock ◽  
Daniel R. Bond ◽  
Jeffrey A. Gralnick
Keyword(s):  
Electron Transfer ◽  
Shewanella Oneidensis ◽  
Anaerobic Respiration ◽  
Basic Research ◽  
Extracellular Electron Transfer ◽  
Content Type ◽  
Electron Transfer Pathway ◽  
Sedimentary Environments ◽  
Genetic Potential ◽  
Iron And Manganese

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.

scholarly journals Pyruvate accelerates palladium reduction by regulating catabolism and electron transfer pathway in Shewanella oneidensis

2021 ◽  
Author(s):  
Yuan-Yuan Cheng ◽  
Wen-Jing Wang ◽  
Shi-Ting Ding ◽  
Ming-Xing Zhang ◽  
Ai-Guo Tang ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Carbon Source ◽  
Time Window ◽  
Carbon Sources ◽  
Shewanella Oneidensis ◽  
Underlying Mechanism ◽  
Extracellular Electron Transfer ◽  
Resting Cells ◽  
Electron Transfer Pathway ◽  
Specific Regulation

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.

scholarly journals NADH dehydrogenases Nuo and Nqr1 contribute to extracellular electron transfer by Shewanella oneidensis MR-1 in bioelectrochemical systems

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Cody S. Madsen ◽  
Michaela A. TerAvest
Keyword(s):  
Electron Transfer ◽  
Shewanella Oneidensis ◽  
Extracellular Electron Transfer ◽  
Growth Defect ◽  
Bioelectrochemical Systems ◽  
Terminal Electron Acceptor ◽  
Nadh Dehydrogenases ◽  
Level Of Understanding ◽  
High Level

Abstract Shewanella oneidensis MR-1 is quickly becoming a synthetic biology workhorse for bioelectrochemical technologies due to a high level of understanding of its interaction with electrodes. Transmembrane electron transfer via the Mtr pathway has been well characterized, however, the role of NADH dehydrogenases in feeding electrons to Mtr has been only minimally studied in S. oneidensis MR-1. Four NADH dehydrogenases are encoded in the genome, suggesting significant metabolic flexibility in oxidizing NADH under a variety of conditions. A strain lacking the two dehydrogenases essential for aerobic growth exhibited a severe growth defect with an anode (+0.4 VSHE) or Fe(III)-NTA as the terminal electron acceptor. Our study reveals that the same NADH dehydrogenase complexes are utilized under oxic conditions or with a high potential anode. Our study also supports the previously indicated importance of pyruvate dehydrogenase activity in producing NADH during anerobic lactate metabolism. Understanding the role of NADH in extracellular electron transfer may help improve biosensors and give insight into other applications for bioelectrochemical systems.

Mtr extracellular electron-transfer pathways in Fe(III)-reducing or Fe(II)-oxidizing bacteria: a genomic perspective

2012 ◽  
Vol 40 (6) ◽  
pp. 1261-1267 ◽  
Author(s):  
Liang Shi ◽  
Kevin M. Rosso ◽  
John M. Zachara ◽  
James K. Fredrickson
Keyword(s):  
Electron Transfer ◽  
Cell Envelope ◽  
Shewanella Oneidensis ◽  
Extracellular Electron Transfer ◽  
Bacterial Cells ◽  
Electron Transfer Pathway ◽  
Protein Components ◽  
Micro Organisms ◽  
Reducing Bacteria ◽  
Mediate Electron Transfer

Originally discovered in the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1 (MR-1), key components of the Mtr (i.e. metal-reducing) pathway exist in all strains of metal-reducing Shewanella characterized. The protein components identified to date for the Mtr pathway of MR-1 include four multihaem c-Cyts (c-type cytochromes), CymA, MtrA, MtrC and OmcA, and a porin-like outer membrane protein MtrB. They are strategically positioned along the width of the MR-1 cell envelope to mediate electron transfer from the quinone/quinol pool in the inner membrane to Fe(III)-containing minerals external to the bacterial cells. A survey of microbial genomes has identified homologues of the Mtr pathway in other dissimilatory Fe(III)-reducing bacteria, including Aeromonas hydrophila, Ferrimonas balearica and Rhodoferax ferrireducens, and in the Fe(II)-oxidizing bacteria Dechloromonas aromatica RCB, Gallionella capsiferriformans ES-2 and Sideroxydans lithotrophicus ES-1. The apparent widespread distribution of Mtr pathways in both Fe(III)-reducing and Fe(II)-oxidizing bacteria suggests a bidirectional electron transfer role, and emphasizes the importance of this type of extracellular electron-transfer pathway in microbial redox transformation of iron. The organizational and electron-transfer characteristics of the Mtr pathways may be shared by other pathways used by micro-organisms for exchanging electrons with their extracellular environments.

scholarly journals NADH dehydrogenases contribute to extracellular electron transfer byShewanella oneidensisMR-1 in bioelectrochemical systems

2019 ◽  
Author(s):  
Cody S. Madsen ◽  
Michaela A. TerAvest
Keyword(s):  
Electron Transfer ◽  
Shewanella Oneidensis ◽  
Extracellular Electron Transfer ◽  
Growth Defect ◽  
Bioelectrochemical Systems ◽  
Terminal Electron Acceptor ◽  
Nadh Dehydrogenases ◽  
Level Of Understanding ◽  
High Level

AbstractShewanella oneidensisMR-1 is quickly becoming a synthetic biology workhorse for bioelectrochemical technologies due to a high level of understanding of its interaction with electrodes. Transmembrane electron transfer via the Mtr pathway has been well characterized, however, the role of NADH dehydrogenases in feeding electrons to Mtr has been only minimally studied inS. oneidensisMR-1. Four NADH dehydrogenases are encoded in the genome, suggesting significant metabolic flexibility in oxidizing NADH under a variety of conditions. Strains containing in-frame deletions of each of these dehydrogenases were grown in anodic bioelectrochemical systems with N-acetylglucosamine or D,L-lactate as the carbon source to determine impact on extracellular electron transfer. A strain lacking the two dehydrogenases essential for aerobic growth exhibited a severe growth defect with an anode (+0.4 VSHE) or Fe(III)-NTA as the terminal electron acceptor. Our study reveals that the same NADH dehydrogenase complexes are utilized under oxic conditions or with a high potential anode. Understanding the role of NADH in extracellular electron transfer may help improve biosensors and give insight into other applications for bioelectrochemical systems.TOC Graphic

Impact of Graphitic Structures in Pyrogenic Carbon on Microbial Reduction of Ferrihydrite

2021 ◽  
Author(s):  
wentao yu ◽  
baoliang chen
Keyword(s):  
Electron Transfer ◽  
Pyrolysis Temperature ◽  
Shewanella Oneidensis ◽  
Exchange Capacity ◽  
Microbial Reduction ◽  
Systematic Evaluation ◽  
Extracellular Electron Transfer ◽  
Pyrogenic Carbon ◽  
The Impact

<p>Pyrogenic carbon plays important roles in microbial reduction of ferrihydrite by shuttling electrons in the extracellular electron transfer (EET) processes. Despite its importance, a full assessment on the impact of graphitic structures in pyrogenic carbon on microbial reduction of ferrihydrite has not been conducted. This study is a systematic evaluation of microbial ferrihydrite reduction by Shewanella oneidensis MR-1 in the presence of pyrogenic carbon with various graphitization extents. The results showed that the rates and extents of microbial ferrihydrite reduction were significantly enhanced in the presence of pyrogenic carbon, and increased with increasing pyrolysis temperature. Combined spectroscopic and electrochemical analyses suggested that the rate of microbial ferrihydrite reduction were dependent on the electrical conductivity of pyrogenic carbon (i.e., graphitization extent), rather than the electron exchange capacity. The key role of graphitic structures in pyrogenic carbon in mediating EET was further evidenced by larger microbial electrolysis current with pyrogenic carbon prepared at higher pyrolysis temperatures. This study provides new insights into the electron transfer in the pyrogenic carbon-mediated microbial reduction of ferrihydrite.</p>

Identifying the potential extracellular electron transfer pathways from a c-type cytochrome network

2014 ◽  
Vol 10 (12) ◽  
pp. 3138-3146 ◽  
Author(s):  
De-Wu Ding ◽  
Jun Xu ◽  
Ling Li ◽  
Jian-Ming Xie ◽  
Xiao Sun
Keyword(s):  
Electron Transfer ◽  
Shewanella Oneidensis ◽  
Extracellular Electron Transfer ◽  
Genome Wide ◽  
A Genome ◽  
Electron Transfer Pathways

A genome-wide c-type cytochrome network was constructed to explore the extracellular electron transfer pathways in Shewanella oneidensis MR-1.

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