scholarly journals Syntrophic interspecies electron transfer drives carbon fixation and growth by Rhodopseudomonas palustris under dark, anoxic conditions

2021 ◽  
Vol 7 (27) ◽  
pp. eabh1852
Author(s):  
Xing Liu ◽  
Lingyan Huang ◽  
Christopher Rensing ◽  
Jie Ye ◽  
Kenneth H. Nealson ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Carbon Fixation ◽  
Rhodopseudomonas Palustris ◽  
Reducing Power ◽  
Extracellular Electron Transfer ◽  
Geobacter Metallireducens ◽  
Electron Transfer Pathway ◽  
Anoxygenic Phototrophs ◽  
Anoxic Environments ◽  
Genes Encoding

In natural anoxic environments, anoxygenic photosynthetic bacteria fix CO2 by photoheterotrophy, photoautotrophy, or syntrophic anaerobic photosynthesis. Here, we describe electroautotrophy, a previously unidentified dark CO2 fixation mode enabled by the electrosyntrophic interaction between Geobacter metallireducens and Rhodopseudomonas palustris. After an electrosyntrophic coculture is formed, electrons are transferred either directly or indirectly (via electron shuttles) from G. metallireducens to R. palustris, thereby providing reducing power and energy for the dark CO2 fixation. Transcriptomic analyses demonstrated the high expression of genes encoding for the extracellular electron transfer pathway in G. metallireducens and the Calvin-Benson-Bassham carbon fixation cycle in R. palustris. Given that sediments constitute one of the most ubiquitous and abundant niches on Earth and that, at depth, most of the sedimentary niche is both anoxic and dark, dark carbon fixation provides a metabolic window for the survival of anoxygenic phototrophs, as well as an as-yet unappreciated contribution to the global carbon cycle.

scholarly journals Putative Extracellular Electron Transfer in Methanogenic Archaea

2021 ◽  
Vol 12 ◽  
Author(s):  
Kailin Gao ◽  
Yahai Lu
Keyword(s):  
Electron Transfer ◽  
Methanogenic Archaea ◽  
Methanosarcina Barkeri ◽  
Extracellular Electron Transfer ◽  
Future Research ◽  
Methanosarcina Acetivorans ◽  
Geobacter Metallireducens ◽  
Methanosarcina Mazei ◽  
Current State ◽  
Electron Transfers

It has been suggested that a few methanogens are capable of extracellular electron transfers. For instance, Methanosarcina barkeri can directly capture electrons from the coexisting microbial cells of other species. Methanothrix harundinacea and Methanosarcina horonobensis retrieve electrons from Geobacter metallireducens via direct interspecies electron transfer (DIET). Recently, Methanobacterium, designated strain YSL, has been found to grow via DIET in the co-culture with Geobacter metallireducens. Methanosarcina acetivorans can perform anaerobic methane oxidation and respiratory growth relying on Fe(III) reduction through the extracellular electron transfer. Methanosarcina mazei is capable of electromethanogenesis under the conditions where electron-transfer mediators like H2 or formate are limited. The membrane-bound multiheme c-type cytochromes (MHC) and electrically-conductive cellular appendages have been assumed to mediate the extracellular electron transfer in bacteria like Geobacter and Shewanella species. These molecules or structures are rare but have been recently identified in a few methanogens. Here, we review the current state of knowledge for the putative extracellular electron transfers in methanogens and highlight the opportunities and challenges for future research.

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 His/Met heme ligation in the PioA outer membrane cytochrome enabling light-driven extracellular electron transfer by Rhodopseudomonas palustris TIE-1

2020 ◽  
Vol 31 (35) ◽  
pp. 354002
Author(s):  
Dao-Bo Li ◽  
Marcus J Edwards ◽  
Anthony W Blake ◽  
Simone E Newton-Payne ◽  
Samuel E H Piper ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Outer Membrane ◽  
Rhodopseudomonas Palustris ◽  
Extracellular Electron Transfer ◽  
Heme Ligation

scholarly journals Small-Molecule Acetylation Controls the Degradation of Benzoate and Photosynthesis inRhodopseudomonas palustris

mBio ◽  
2018 ◽  
Vol 9 (5) ◽  
Author(s):  
Chelsey M. VanDrisse ◽  
Jorge C. Escalante-Semerena
Keyword(s):  
Rhodopseudomonas Palustris ◽  
Photosynthetic Apparatus ◽  
Reducing Power ◽  
Proton Motive Force ◽  
Motive Force ◽  
Light Harvesting Complexes ◽  
Pigment Synthesis ◽  
Content Type ◽  
Genes Encoding

ABSTRACTThe degradation of lignin-derived aromatic compounds such as benzoate has been extensively studied inRhodopseudomonas palustris, and the chemistry underpinning the conversion of benzoate to acetyl coenzyme A (acetyl-CoA) is well understood. Here we characterize the last unknown gene, badL,of thebad(benzoic acid degradation) cluster. BadL function is required for growth under photoheterotrophic conditions with benzoate as the organic carbon source (i.e., light plus anoxia). On the basis of bioinformatics andin vivoandin vitrodata, we show that BadL, aGcn5-relatedN-acetyltransferase (GNAT) (PF00583), acetylates aminobenzoates to yield acetamidobenzoates. The latter relieved repression of thebadDEFGABoperon by binding to BadM, triggering the synthesis of enzymes that activate and dearomatize the benzene ring. We also show that acetamidobenzoates are required for the expression of genes encoding the photosynthetic reaction center light-harvesting complexes through a BadM-independent mechanism. The effect of acetamidobenzoates on pigment synthesis is new and different than their effect on the catabolism of benzoate.IMPORTANCEThis work shows that the BadL protein ofRhodopseudomonas palustrishasN-acetyltransferase activity and that this activity is required for the catabolism of benzoate under photosynthetic conditions in this bacterium.R. palustrisoccupies lignin-rich habitats, making its benzoate-degrading capability critical for the recycling of this important, energy-rich biopolymer. This work identifies the product of the BadL enzyme as acetamidobenzoates, which were needed to derepress genes encoding benzoate-degrading enzymes and proteins of the photosynthetic apparatus responsible for the generation of the proton motive force under anoxia in the presence of light. In short, acetamidobenzoates potentially coordinate the use of benzoate as a source of reducing power and carbon with the generation of a light-driven proton motive force that fuels ATP synthesis, motility, transport, and many other processes in the metabolically versatile bacteriumR. palustris.

scholarly journals Two Routes for Extracellular Electron Transfer in Enterococcus faecalis

2020 ◽  
Vol 202 (7) ◽  
Author(s):  
Lars Hederstedt ◽  
Lo Gorton ◽  
Galina Pankratova
Keyword(s):  
Electron Transfer ◽  
Enterococcus Faecalis ◽  
Microbial Fuel Cells ◽  
Cell Envelope ◽  
Reductase Activity ◽  
Reducing Power ◽  
Extracellular Electron Transfer ◽  
Ferric Reductase ◽  
Ferric Ions ◽  
Content Type

ABSTRACT Enterococcus faecalis cells are known to have ferric reductase activity and the ability to transfer electrons generated in metabolism to the external environment. We have isolated mutants defective in ferric reductase activity and studied their electron transfer properties to electrodes mediated by ferric ions and an osmium complex-modified redox polymer (OsRP). Electron transfer mediated with ferric ions and ferric reductase activity were both found to be dependent on the membrane-associated Ndh3 and EetA proteins, consistent with findings in Listeria monocytogenes. In contrast, electron transfer mediated with OsRP was independent of these two proteins. Quinone in the cell membrane was required for the electron transfer with both mediators. The combined results demonstrate that extracellular electron transfer from reduced quinone to ferric ions and to OsRP occurs via different routes in the cell envelope of E. faecalis. IMPORTANCE The transfer of reducing power in the form of electrons, generated in the catabolism of nutrients, from a bacterium to an extracellular acceptor appears to be common in nature. The electron acceptor can be another cell or abiotic material. Such extracellular electron transfer contributes to syntrophic metabolism and is of wide environmental, industrial, and medical importance. Electron transfer between microorganisms and electrodes is fundamental in microbial fuel cells for energy production and for electricity-driven synthesis of chemical compounds in cells. In contrast to the much-studied extracellular electron transfer mediated by cell surface exposed cytochromes, little is known about components and mechanisms for such electron transfer in organisms without these cytochromes and in Gram-positive bacteria such as E. faecalis, which is a commensal gut lactic acid bacterium and opportunistic pathogen.

scholarly journals Electrochemical Study on the Extracellular Electron Transfer Pathway from Shewanella Strain Hac319 to Electrodes

2018 ◽  
Vol 34 (10) ◽  
pp. 1177-1182 ◽  
Author(s):  
Ryosuke TAKEUCHI ◽  
Yu SUGIMOTO ◽  
Yuki KITAZUMI ◽  
Osamu SHIRAI ◽  
Jun OGAWA ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electrochemical Study ◽  
Extracellular Electron Transfer ◽  
Electron Transfer Pathway

scholarly journals Crossing the Wall: Characterization of the Multiheme Cytochromes Involved in the Extracellular Electron Transfer Pathway of Thermincola ferriacetica

2021 ◽  
Vol 9 (2) ◽  
pp. 293
Author(s):  
Marisa M. Faustino ◽  
Bruno M. Fonseca ◽  
Nazua L. Costa ◽  
Diana Lousa ◽  
Ricardo O. Louro ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Structural Model ◽  
Added Value ◽  
Extracellular Electron Transfer ◽  
Electron Transfer Pathway ◽  
E Coli ◽  
Sustainable Technologies ◽  
Gram Positive Bacteria ◽  
Electron Transfer Processes

Bioelectrochemical systems (BES) are emerging as a suite of versatile sustainable technologies to produce electricity and added-value compounds from renewable and carbon-neutral sources using electroactive organisms. The incomplete knowledge on the molecular processes that allow electroactive organisms to exchange electrons with electrodes has prevented their real-world implementation. In this manuscript we investigate the extracellular electron transfer processes performed by the thermophilic Gram-positive bacteria belonging to the Thermincola genus, which were found to produce higher levels of current and tolerate higher temperatures in BES than mesophilic Gram-negative bacteria. In our study, three multiheme c-type cytochromes, Tfer_0070, Tfer_0075, and Tfer_1887, proposed to be involved in the extracellular electron transfer pathway of T. ferriacetica, were cloned and over-expressed in E. coli. Tfer_0070 (ImdcA) and Tfer_1887 (PdcA) were purified and biochemically characterized. The electrochemical characterization of these proteins supports a pathway of extracellular electron transfer via these two proteins. By contrast, Tfer_0075 (CwcA) could not be stabilized in solution, in agreement with its proposed insertion in the peptidoglycan wall. However, based on the homology with the outer-membrane cytochrome OmcS, a structural model for CwcA was developed, providing a molecular perspective into the mechanisms of electron transfer across the peptidoglycan layer in Thermincola.

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