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Katsyv A, Kumar A, Saura P, Pöverlein MC, Freibert SA, T Stripp S, Jain S, Gamiz-Hernandez AP, Kaila VRI, Müller V, Schuller JM. Molecular Basis of the Electron Bifurcation Mechanism in the [FeFe]-Hydrogenase Complex HydABC. J Am Chem Soc 2023; 145:5696-5709. [PMID: 36811855 PMCID: PMC10021017 DOI: 10.1021/jacs.2c11683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
Electron bifurcation is a fundamental energy coupling mechanism widespread in microorganisms that thrive under anoxic conditions. These organisms employ hydrogen to reduce CO2, but the molecular mechanisms have remained enigmatic. The key enzyme responsible for powering these thermodynamically challenging reactions is the electron-bifurcating [FeFe]-hydrogenase HydABC that reduces low-potential ferredoxins (Fd) by oxidizing hydrogen gas (H2). By combining single-particle cryo-electron microscopy (cryoEM) under catalytic turnover conditions with site-directed mutagenesis experiments, functional studies, infrared spectroscopy, and molecular simulations, we show that HydABC from the acetogenic bacteria Acetobacterium woodii and Thermoanaerobacter kivui employ a single flavin mononucleotide (FMN) cofactor to establish electron transfer pathways to the NAD(P)+ and Fd reduction sites by a mechanism that is fundamentally different from classical flavin-based electron bifurcation enzymes. By modulation of the NAD(P)+ binding affinity via reduction of a nearby iron-sulfur cluster, HydABC switches between the exergonic NAD(P)+ reduction and endergonic Fd reduction modes. Our combined findings suggest that the conformational dynamics establish a redox-driven kinetic gate that prevents the backflow of the electrons from the Fd reduction branch toward the FMN site, providing a basis for understanding general mechanistic principles of electron-bifurcating hydrogenases.
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Affiliation(s)
- Alexander Katsyv
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt am Main 60438, Germany
| | - Anuj Kumar
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt am Main 60438, Germany.,SYNMIKRO Research Center and Department of Chemistry, Philipps-University of Marburg, Marburg 35032, Germany
| | - Patricia Saura
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm 10691, Sweden
| | - Maximilian C Pöverlein
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm 10691, Sweden
| | - Sven A Freibert
- Institut für Zytobiologie im Zentrum SYNMIKRO, Philipps-University of Marburg, Marburg 35032, Germany.,Core Facility "Protein Biochemistry and Spectroscopy", Marburg 35032, Germany
| | - Sven T Stripp
- Department of Physics, Experimental Molecular Biophysics, Freie Universität Berlin, Berlin 14195, Germany
| | - Surbhi Jain
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt am Main 60438, Germany
| | - Ana P Gamiz-Hernandez
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm 10691, Sweden
| | - Ville R I Kaila
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm 10691, Sweden
| | - Volker Müller
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt am Main 60438, Germany
| | - Jan M Schuller
- SYNMIKRO Research Center and Department of Chemistry, Philipps-University of Marburg, Marburg 35032, Germany
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Metatranscriptomic insights into the microbial electrosynthesis of acetate by Fe 2+/Ni 2+ addition. World J Microbiol Biotechnol 2023; 39:109. [PMID: 36879133 DOI: 10.1007/s11274-023-03554-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 02/21/2023] [Indexed: 03/08/2023]
Abstract
As important components of enzymes and coenzymes involved in energy transfer and Wood-Ljungdahl (WL) pathways, Fe2+ and Ni2+ supplementation may promote the acetate synthesis through CO2 reduction by the microbial electrosynthesis (MES). However, the effect of Fe2+ and Ni2+ addition on acetate production in MES and corresponding microbial mechanisms have not been fully studied. Therefore, this study investigated the effect of Fe2+ and Ni2+ addition on acetate production in MES, and explored the underlying microbial mechanism from the metatranscriptomic perspective. Both Fe2+ and Ni2+ addition enhanced acetate production of the MES, which was 76.9% and 110.9% higher than that of control, respectively. Little effect on phylum level and small changes in genus-level microbial composition was caused by Fe2+ and Ni2+ addition. Gene expression of 'Energy metabolism', especially in 'Carbon fixation pathways in prokaryotes' was up-regulated by Fe2+ and Ni2+ addition. Hydrogenase was found as an important energy transfer mediator for CO2 reduction and acetate synthesis. Fe2+ addition and Ni2+ addition respectively enhanced the expression of methyl branch and carboxyl branch of the WL pathway, and thus promoted acetate production. The study provided a metatranscriptomic insight into the effect of Fe2+ and Ni2+ on acetate production by CO2 reduction in MES.
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53
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Prioretti L, D’Ermo G, Infossi P, Kpebe A, Lebrun R, Bauzan M, Lojou E, Guigliarelli B, Giudici-Orticoni MT, Guiral M. Carbon Fixation in the Chemolithoautotrophic Bacterium Aquifex aeolicus Involves Two Low-Potential Ferredoxins as Partners of the PFOR and OGOR Enzymes. Life (Basel) 2023; 13:life13030627. [PMID: 36983784 PMCID: PMC10052474 DOI: 10.3390/life13030627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 02/21/2023] [Accepted: 02/22/2023] [Indexed: 02/27/2023] Open
Abstract
Aquifex aeolicus is a microaerophilic hydrogen- and sulfur -oxidizing bacterium that assimilates CO2 via the reverse tricarboxylic acid cycle (rTCA). Key enzymes of this pathway are pyruvate:ferredoxin oxidoreductase (PFOR) and 2-oxoglutarate:ferredoxin oxidoreductase (OGOR), which are responsible, respectively, for the reductive carboxylation of acetyl-CoA to pyruvate and of succinyl-CoA to 2-oxoglutarate, two energetically unfavorable reactions that require a strong reduction potential. We have confirmed, by biochemistry and proteomics, that A. aeolicus possesses a pentameric version of these enzyme complexes ((αβγδε)2) and that they are highly abundant in the cell. In addition, we have purified and characterized, from the soluble fraction of A. aeolicus, two low redox potential and oxygen-stable [4Fe-4S] ferredoxins (Fd6 and Fd7, E0 = −440 and −460 mV, respectively) and shown that they can physically interact and exchange electrons with both PFOR and OGOR, suggesting that they could be the physiological electron donors of the system in vivo. Shotgun proteomics indicated that all the enzymes assumed to be involved in the rTCA cycle are produced in the A. aeolicus cells. A number of additional enzymes, previously suggested to be part of a putative partial Wood-Ljungdahl pathway used for the synthesis of serine and glycine from CO2 were identified by mass spectrometry, but their abundance in the cell seems to be much lower than that of the rTCA cycle. Their possible involvement in carbon assimilation is discussed.
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Affiliation(s)
- Laura Prioretti
- CNRS, Bioénergétique et Ingénierie des Protéines, Aix Marseille Université, IMM, 13009 Marseille, France
| | - Giulia D’Ermo
- CNRS, Bioénergétique et Ingénierie des Protéines, Aix Marseille Université, IMM, 13009 Marseille, France
| | - Pascale Infossi
- CNRS, Bioénergétique et Ingénierie des Protéines, Aix Marseille Université, IMM, 13009 Marseille, France
| | - Arlette Kpebe
- CNRS, Bioénergétique et Ingénierie des Protéines, Aix Marseille Université, IMM, 13009 Marseille, France
| | - Régine Lebrun
- CNRS, Aix Marseille Université, IMM, 13009 Marseille, France
| | - Marielle Bauzan
- CNRS, Aix Marseille Université, IMM, 13009 Marseille, France
| | - Elisabeth Lojou
- CNRS, Bioénergétique et Ingénierie des Protéines, Aix Marseille Université, IMM, 13009 Marseille, France
| | - Bruno Guigliarelli
- CNRS, Bioénergétique et Ingénierie des Protéines, Aix Marseille Université, IMM, 13009 Marseille, France
| | | | - Marianne Guiral
- CNRS, Bioénergétique et Ingénierie des Protéines, Aix Marseille Université, IMM, 13009 Marseille, France
- Correspondence:
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54
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Anghel L, Rada S, Erhan RV. Structural Factors and Electron Transfer Mechanisms in Flavoenzymes. ANAL LETT 2023. [DOI: 10.1080/00032719.2023.2174131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Lilia Anghel
- Laboratory Physical and Quantum Chemistry, Institute of Chemistry, Chisinau, Republic of Moldova
| | - Simona Rada
- INCDTIM Cluj-Napoca, Cluj-Napoca, Romania
- Technical University of Cluj-Napoca, Cluj-Napoca, Romania
| | - Raul-Victor Erhan
- Department of Nuclear Physics, Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering, Magurele-Ilfov, Romania
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Gam ZBA, Thioye A, Cayol JL, Postec A, Bartoli-Joseph M, Vandecasteele C, Erauso G, Labat M. Thermospira aquatica gen. nov., sp. nov., a novel thermophilic spirochete isolated from a Tunisian hot spring, and description of the novel family Thermospiraceae. Int J Syst Evol Microbiol 2023; 73. [PMID: 36748411 DOI: 10.1099/ijsem.0.005690] [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: 01/26/2023] Open
Abstract
A novel thermophilic, anaerobic bacterium, strain F1F22T, was isolated from hot spring water collected in northern Tunisia. The cells were non-motile, Gram-negative and helical with hooked ends, 0.5×10-32 µm in size. Growth of the strain was observed at 45-70 °C (optimum, 55 °C), in 0.0-1.0 % (w/v) NaCl (optimum without NaCl) and at pH 6.5-8.5 (optimum, pH 7.5). Yeast extract was required for growth, and the strain grew on glucose, sucrose and maltose. The major fatty acids were C16:0 (40.2 %), iso-C16: 0 (30.2 %) and C16 :0 DMA (14.5 %). The genome consisted of a circular chromosome (2.5 Mb) containing 2672 predicted protein-encoding genes with a G+C content of 43.15 mol %. Based on a comparative 16S rRNA gene sequence analysis, strain F1F22T formed a deeply branching lineage within the phylum Spirochaetota, class Spirochaetia, order Brevinematales, and had only low sequence similarity to other species of the phylum (lower than 83 %). Genome-based analysis of average nucleotide identity and digital DNA-DNA hybridization of strain F1F22T with Treponema caldarium DSM 7334T, Brevinema andersonii ATCC 43811T and Spirochaeta thermophila DSM 6578T showed values between 63.26 and 63.52 %, and between 20 and 25 %. Hence, we propose strain F1F22T as a representative of a novel family (Thermospiraceae fam. nov.), genus and species of Brevinematales: Thermospira aquatica gen. nov., sp. nov. (type strain F1F22T=JCM 31314T=DSM 101182T).
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Affiliation(s)
- Zouhaier Ben Ali Gam
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO, Mediterranean Institute of Oceanography, 163 avenue de Luminy, F-13288, Marseille, France
| | - Abdoulaye Thioye
- Université Cheikh Anta Diop, Ecole Supérieure Polytechnique, Laboratoire de Microbiologie Appliquée et de Génie Industriel, BP 5005, Dakar-Fann, Dakar, Sénégal
| | - Jean-Luc Cayol
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO, Mediterranean Institute of Oceanography, 163 avenue de Luminy, F-13288, Marseille, France
| | - Anne Postec
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO, Mediterranean Institute of Oceanography, 163 avenue de Luminy, F-13288, Marseille, France
| | - Manon Bartoli-Joseph
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO, Mediterranean Institute of Oceanography, 163 avenue de Luminy, F-13288, Marseille, France
| | | | - Gaël Erauso
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO, Mediterranean Institute of Oceanography, 163 avenue de Luminy, F-13288, Marseille, France
| | - Marc Labat
- Aix Marseille Université, Université de Toulon, CNRS, IRD, MIO, Mediterranean Institute of Oceanography, 163 avenue de Luminy, F-13288, Marseille, France
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56
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Willemin MS, Hamelin R, Armand F, Holliger C, Maillard J. Proteome adaptations of the organohalide-respiring Desulfitobacterium hafniense strain DCB-2 to various energy metabolisms. Front Microbiol 2023; 14:1058127. [PMID: 36733918 PMCID: PMC9888536 DOI: 10.3389/fmicb.2023.1058127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 01/02/2023] [Indexed: 01/18/2023] Open
Abstract
Introduction Desulfitobacterium hafniense was isolated for its ability to use organohalogens as terminal electron acceptors via organohalide respiration (OHR). In contrast to obligate OHR bacteria, Desulfitobacterium spp. show a highly versatile energy metabolism with the capacity to use different electron donors and acceptors and to grow fermentatively. Desulfitobacterium genomes display numerous and apparently redundant members of redox enzyme families which confirm their metabolic potential. Nonetheless, the enzymes responsible for many metabolic traits are not yet identified. Methods In the present work, we conducted an extended proteomic study by comparing the proteomes of Desulfitobacterium hafniense strain DCB-2 cultivated in combinations of electron donors and acceptors, triggering five alternative respiratory metabolisms that include OHR, as well as fermentation. Tandem Mass Tag labelling proteomics allowed us to identify and quantify almost 60% of the predicted proteome of strain DCB-2 (2,796 proteins) in all six growth conditions. Raw data are available via ProteomeXchange with identifier PXD030393. Results and discussion This dataset was analyzed in order to highlight the proteins that were significantly up-regulated in one or a subset of growth conditions and to identify possible key players in the different energy metabolisms. The addition of sodium sulfide as reducing agent in the medium - a very widespread practice in the cultivation of strictly anaerobic bacteria - triggered the expression of the dissimilatory sulfite reduction pathway in relatively less favorable conditions such as fermentative growth on pyruvate, respiration with H2 as electron donor and OHR conditions. The presence of H2, CO2 and acetate in the medium induced several metabolic pathways involved in carbon metabolism including the Wood-Ljungdahl pathway and two pathways related to the fermentation of butyrate that rely on electron-bifurcating enzymes. While the predicted fumarate reductase appears to be constitutively expressed, a new lactate dehydrogenase and lactate transporters were identified. Finally, the OHR metabolism with 3-chloro-4-hydroxyphenylacetate as electron acceptor strongly induced proteins encoded in several reductive dehalogenase gene clusters, as well as four new proteins related to corrinoid metabolism. We believe that this extended proteomic database represents a new landmark in understanding the metabolic versatility of Desulfitobacterium spp. and provides a solid basis for addressing future research questions.
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Affiliation(s)
- Mathilde Stéphanie Willemin
- Laboratory for Environmental Biotechnology (LBE), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Romain Hamelin
- Proteomic Core Facility (PCF), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Florence Armand
- Proteomic Core Facility (PCF), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Christof Holliger
- Laboratory for Environmental Biotechnology (LBE), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Julien Maillard
- Laboratory for Environmental Biotechnology (LBE), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland,*Correspondence: Julien Maillard, ✉
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Bioinformatics and metabolic flux analysis highlight a new mechanism involved in lactate oxidation in Clostridium tyrobutyricum. INTERNATIONAL MICROBIOLOGY : THE OFFICIAL JOURNAL OF THE SPANISH SOCIETY FOR MICROBIOLOGY 2023:10.1007/s10123-022-00316-y. [PMID: 36609955 PMCID: PMC10397141 DOI: 10.1007/s10123-022-00316-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2022] [Revised: 12/04/2022] [Accepted: 12/20/2022] [Indexed: 01/09/2023]
Abstract
Climate change and environmental issues compel us to find alternatives to the production of molecules of interest from petrochemistry. This study aims at understanding the production of butyrate, hydrogen, and CO2 from the oxidation of lactate with acetate in Clostridium tyrobutyricum and thus proposes an alternative carbon source to glucose. This specie is known to produce more butyrate than the other butyrate-producing clostridia species due to a lack of solvent genesis phase. The recent discoveries on flavin-based electron bifurcation and confurcation mechanism as a mode of energy conservation led us to suggest a new metabolic scheme for the formation of butyrate from lactate-acetate co-metabolism. While searching for genes encoding for EtfAB complexes and neighboring genes in the genome of C. tyrobutyricum, we identified a cluster of genes involved in butyrate formation and another cluster involved in lactate oxidation homologous to Acetobacterium woodii. A phylogenetic approach encompassing other butyrate-producing and/or lactate-oxidizing species based on EtfAB complexes confirmed these results. A metabolic scheme on the production of butyrate, hydrogen, and CO2 from the lactate-acetate co-metabolism in C. tyrobutyricum was constructed and then confirmed with data of steady-state continuous culture. This in silico metabolic carbon flux analysis model showed the coherence of the scheme from the carbon recovery, the cofactor ratio, and the ATP yield. This study improves our understanding of the lactate oxidation metabolic pathways and the role of acetate and intracellular redox balance, and paves the way for the production of molecules of interest as butyrate and hydrogen with C. tyrobutyricum.
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Coskun ÖK, Gomez-Saez GV, Beren M, Ozcan D, Hosgormez H, Einsiedl F, Orsi WD. Carbon metabolism and biogeography of candidate phylum " Candidatus Bipolaricaulota" in geothermal environments of Biga Peninsula, Turkey. Front Microbiol 2023; 14:1063139. [PMID: 36910224 PMCID: PMC9992828 DOI: 10.3389/fmicb.2023.1063139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Accepted: 01/17/2023] [Indexed: 02/25/2023] Open
Abstract
Terrestrial hydrothermal springs and aquifers are excellent sites to study microbial biogeography because of their high physicochemical heterogeneity across relatively limited geographic regions. In this study, we performed 16S rRNA gene sequencing and metagenomic analyses of the microbial diversity of 11 different geothermal aquifers and springs across the tectonically active Biga Peninsula (Turkey). Across geothermal settings ranging in temperature from 43 to 79°C, one of the most highly represented groups in both 16S rRNA gene and metagenomic datasets was affiliated with the uncultivated phylum "Candidatus Bipolaricaulota" (former "Ca. Acetothermia" and OP1 division). The highest relative abundance of "Ca. Bipolaricaulota" was observed in a 68°C geothermal brine sediment, where it dominated the microbial community, representing 91% of all detectable 16S rRNA genes. Correlation analysis of "Ca. Bipolaricaulota" operational taxonomic units (OTUs) with physicochemical parameters indicated that salinity was the strongest environmental factor measured associated with the distribution of this novel group in geothermal fluids. Correspondingly, analysis of 23 metagenome-assembled genomes (MAGs) revealed two distinct groups of "Ca. Bipolaricaulota" MAGs based on the differences in carbon metabolism: one group encoding the bacterial Wood-Ljungdahl pathway (WLP) for H2 dependent CO2 fixation is selected for at lower salinities, and a second heterotrophic clade that lacks the WLP that was selected for under hypersaline conditions in the geothermal brine sediment. In conclusion, our results highlight that the biogeography of "Ca. Bipolaricaulota" taxa is strongly correlated with salinity in hydrothermal ecosystems, which coincides with key differences in carbon acquisition strategies. The exceptionally high relative abundance of apparently heterotrophic representatives of this novel candidate Phylum in geothermal brine sediment observed here may help to guide future enrichment experiments to obtain representatives in pure culture.
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Affiliation(s)
- Ömer K Coskun
- Department of Earth and Environmental Sciences, Paleontology and Geobiology, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Gonzalo V Gomez-Saez
- Department of Earth and Environmental Sciences, Paleontology and Geobiology, Ludwig-Maximilians-Universität München, Munich, Germany.,GeoBio-CenterLMU, Ludwig-Maximilians-Universität München, Munich, Germany
| | - Murat Beren
- Department of Geological Engineering, Istanbul University-Cerrahpasa, Istanbul, Türkiye
| | - Dogacan Ozcan
- Department of Geological Engineering, Istanbul University-Cerrahpasa, Istanbul, Türkiye
| | - Hakan Hosgormez
- Department of Geological Engineering, Istanbul University-Cerrahpasa, Istanbul, Türkiye
| | - Florian Einsiedl
- Chair of Hydrogeology, TUM School of Engineering and Design, Technical University of Munich, Munich, Germany
| | - William D Orsi
- Department of Earth and Environmental Sciences, Paleontology and Geobiology, Ludwig-Maximilians-Universität München, Munich, Germany.,GeoBio-CenterLMU, Ludwig-Maximilians-Universität München, Munich, Germany
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Van Nguyen T, Viver T, Mortier J, Liu B, Smets I, Bernaerts K, Faust K, Lavigne R, Poughon L, Dussap CG, Springael D. Isolation and characterization of a thermophilic chain elongating bacterium that produces the high commodity chemical n-caproate from polymeric carbohydrates. BIORESOURCE TECHNOLOGY 2023; 367:128170. [PMID: 36283667 DOI: 10.1016/j.biortech.2022.128170] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 10/15/2022] [Accepted: 10/17/2022] [Indexed: 06/16/2023]
Abstract
A thermophilic chain elongating bacterium, strain MDTJ8, was isolated from a thermophilic acidogenic anaerobic digestor producing n-caproate from human waste, growing optimally at 50-55 °C and pH 6.5. 16S rRNA gene analysis suggests that MDTJ8 represents a new species/genus within a group currently composed of mesophilic chain elongators of the Oscillospiraceae family. Genome analysis showed that strain MDTJ8 contains homologues of genes encoding for chain elongation and energy conservation but also indicated n-caproate production from carbohydrates including polymeric substances. This was confirmed by culturing experiments in which MDTJ8 converted, at pH 6.5 and 55 °C, mono-, di- and polymeric carbohydrates (starch and hemicellulose) to n-caproate reaching concentrations up to 283 mg/L and accounting for up to 10 % of the measured fermentation products. MDTJ8 is the first axenic organism that thermophilically performs chain elongation, opening doors to understand and intensify thermophilic bioprocesses targeting anaerobic digestion towards the production of the value-added chemical n-caproate.
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Affiliation(s)
- Tinh Van Nguyen
- Division of Soil and Water Management, KU Leuven, Kasteelpark Arenberg 20, B-3001 Heverlee, Belgium; Institut Pascal, Université Clermont Auvergne, Avenue Blaise Pascal 4, F-63178 Aubiére cedex, France
| | - Tomeu Viver
- Marine Microbiology Group, Mediterranean Institute of Advanced Studies (CSIC-UIB), C/Miquel Marqués 21, 07190 Esporles, Spain
| | - Jonah Mortier
- Division of Soil and Water Management, KU Leuven, Kasteelpark Arenberg 20, B-3001 Heverlee, Belgium
| | - Bin Liu
- Laboratory of Molecular Bacteriology (Rega Institute), KU Leuven, Herestraat 49, B-3000 Leuven, Belgium
| | - Ilse Smets
- Chemical Reactor Engineering and Safety, KU Leuven, Celestijnenlaan 200F, B-3001 Heverlee, Belgium
| | - Kristel Bernaerts
- Chemical Reactor Engineering and Safety, KU Leuven, Celestijnenlaan 200F, B-3001 Heverlee, Belgium
| | - Karoline Faust
- Laboratory of Molecular Bacteriology (Rega Institute), KU Leuven, Herestraat 49, B-3000 Leuven, Belgium
| | - Rob Lavigne
- Laboratory of Gene Technology, KU Leuven, Kasteelpark Arenberg 21, B-3001 Heverlee, Belgium
| | - Laurent Poughon
- Institut Pascal, Université Clermont Auvergne, Avenue Blaise Pascal 4, F-63178 Aubiére cedex, France
| | - Claude-Gilles Dussap
- Institut Pascal, Université Clermont Auvergne, Avenue Blaise Pascal 4, F-63178 Aubiére cedex, France
| | - Dirk Springael
- Division of Soil and Water Management, KU Leuven, Kasteelpark Arenberg 20, B-3001 Heverlee, Belgium.
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Boyd ES, Spietz RL, Kour M, Colman DR. A naturalist perspective of microbiology: Examples from methanogenic archaea. Environ Microbiol 2023; 25:184-198. [PMID: 36367391 DOI: 10.1111/1462-2920.16285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2022] [Accepted: 11/09/2022] [Indexed: 11/13/2022]
Abstract
Storytelling has been the primary means of knowledge transfer over human history. The effectiveness and reach of stories are improved when the message is appropriate for the target audience. Oftentimes, the stories that are most well received and recounted are those that have a clear purpose and that are told from a variety of perspectives that touch on the varied interests of the target audience. Whether scientists realize or not, they are accustomed to telling stories of their own scientific discoveries through the preparation of manuscripts, presentations, and lectures. Perhaps less frequently, scientists prepare review articles or book chapters that summarize a body of knowledge on a given subject matter, meant to be more holistic recounts of a body of literature. Yet, by necessity, such summaries are often still narrow in their scope and are told from the perspective of a particular discipline. In other words, interdisciplinary reviews or book chapters tend to be the rarity rather than the norm. Here, we advocate for and highlight the benefits of interdisciplinary perspectives on microbiological subjects.
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Affiliation(s)
- Eric S Boyd
- Department of Microbiology and Cell Biology, Montana State University, Bozeman, Montana, USA
| | - Rachel L Spietz
- Department of Microbiology and Cell Biology, Montana State University, Bozeman, Montana, USA
| | - Manjinder Kour
- Department of Microbiology and Cell Biology, Montana State University, Bozeman, Montana, USA
| | - Daniel R Colman
- Department of Microbiology and Cell Biology, Montana State University, Bozeman, Montana, USA
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61
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Carr S, Buan NR. Insights into the biotechnology potential of Methanosarcina. Front Microbiol 2022; 13:1034674. [PMID: 36590411 PMCID: PMC9797515 DOI: 10.3389/fmicb.2022.1034674] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Accepted: 10/28/2022] [Indexed: 12/23/2022] Open
Abstract
Methanogens are anaerobic archaea which conserve energy by producing methane. Found in nearly every anaerobic environment on earth, methanogens serve important roles in ecology as key organisms of the global carbon cycle, and in industry as a source of renewable biofuels. Environmentally, methanogenic archaea play an essential role in the reintroducing unavailable carbon to the carbon cycle by anaerobically converting low-energy, terminal metabolic degradation products such as one and two-carbon molecules into methane which then returns to the aerobic portion of the carbon cycle. In industry, methanogens are commonly used as an inexpensive source of renewable biofuels as well as serving as a vital component in the treatment of wastewater though this is only the tip of the iceberg with respect to their metabolic potential. In this review we will discuss how the efficient central metabolism of methanoarchaea could be harnessed for future biotechnology applications.
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Affiliation(s)
| | - Nicole R. Buan
- Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, NE, United States
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62
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Huang Y, Cai B, Dong H, Li H, Yuan J, Xu H, Wu H, Xu Z, Sun D, Dang Y, Holmes DE. Enhancing anaerobic digestion of food waste with granular activated carbon immobilized with riboflavin. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 851:158172. [PMID: 35988634 DOI: 10.1016/j.scitotenv.2022.158172] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 08/16/2022] [Accepted: 08/16/2022] [Indexed: 06/15/2023]
Abstract
Previous studies have shown that anaerobic digestion of food waste can be enhanced by addition of conductive materials that stimulate direct interspecies electron transfer (DIET) between bacteria and methanogens. However, at extremely high organic loading rates (OLRs), volatile fatty acids (VFAs) still tend to accumulate even in the presence of conductive materials because of an imbalance between the formation of fermentation products and the rate of methanogenesis. In this study, granular activated carbon (GAC) immobilized with riboflavin (GAC-riboflavin) was added to an anaerobic digester treating food waste. The GAC-riboflavin reactor operated stably at OLRs as high as 11.5 kgCOD/ (m3·d) and kept VFA concentrations below 69.4 mM, COD removal efficiencies, methane production rates, and biogas methane concentrations were much higher in the GAC-riboflavin reactor than the GAC- and non-amended reactors. Transcripts associated with genes that code for proteins involved in DIET based metabolism were somewhat more highly expressed by Methanothrix in the GAC-riboflavin reactor. However, it is unlikely that riboflavin acted as an electron shuttle to stimulate DIET. Rather, it seemed to provide nutrients that enhanced the growth of microorganisms involved in the anaerobic digestion process, including those that are capable of DIET.
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Affiliation(s)
- Yinhui Huang
- Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China
| | - Boquan Cai
- Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China
| | - He Dong
- Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China
| | - Haoyong Li
- Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China
| | - Jie Yuan
- Wukong Chuangxiang Techolology Co, Ltd, Beijing 100083, China
| | - Haiyu Xu
- Xinneng Qinglin (Beijing) Technology Co., Ltd, Beijing 100083, China
| | - Hongbin Wu
- Xinneng Qinglin (Beijing) Technology Co., Ltd, Beijing 100083, China
| | - Ziyao Xu
- Lingxi Medical Technology (Beijing) Co., Ltd, Beijing 100083, China
| | - Dezhi Sun
- Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China
| | - Yan Dang
- Beijing Key Laboratory for Source Control Technology of Water Pollution, Engineering Research Center for Water Pollution Source Control and Eco-remediation, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China.
| | - Dawn E Holmes
- Department of Physical and Biological Sciences, Western New England University, 1215 Wilbraham Rd, Springfield, MA 01119, USA
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63
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Dhar V, Singh R. Biohydrogen production potential with sulfate and nitrate removal by heat-pretreated enriched sulfate-reducing microorganisms-based bioelectrochemical system. Arch Microbiol 2022; 205:7. [PMID: 36454386 DOI: 10.1007/s00203-022-03352-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 11/06/2022] [Accepted: 11/21/2022] [Indexed: 12/03/2022]
Abstract
In this study, heat-pretreated sulfate-reducing bacteria (SRBs) were evaluated for simultaneous sulfate and nitrate removal in a bioelectrochemical system (BES). The effect of the applied potential of 20 mV to SRBs was evaluated at a sulfate concentration of 3 g/L and/or nitrate concentration of 0.5 g/L supplemented before heat pretreatment for sulfate and nitrate removal. The highest H2 production of 2.24 ± 0.04 mM/L in heat-pretreated culture was observed in the presence of sulfate at an applied potential of 20 mV (BHE-S). Simultaneous reduction of sulfate and nitrate was significant in BESs supplemented with either sulfate or nitrate during heat-shock pretreatment of the culture. The highest SO42- removal of 88.91 ± 0.8% was found in culture heat pretreated with NO3- and applied with 20 mV potential (BHE-N). The kinetics of heat-pretreated culture showed higher R2 and ultimate potential for H2 on the continuous application of 20 mV potential.
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Affiliation(s)
- Varsha Dhar
- School of Environment and Sustainable Development, Central University of Gujarat, Gandhinagar, 382030, India
| | - Rajesh Singh
- School of Environment and Sustainable Development, Central University of Gujarat, Gandhinagar, 382030, India.
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64
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Acosta-Grinok M, Vázquez S, Guiliani N, Marín S, Demergasso C. Looking for the mechanism of arsenate respiration of Fusibacter sp. strain 3D3, independent of ArrAB. Front Microbiol 2022; 13:1029886. [PMID: 36532432 PMCID: PMC9751042 DOI: 10.3389/fmicb.2022.1029886] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2022] [Accepted: 11/08/2022] [Indexed: 12/02/2022] Open
Abstract
The literature has reported the isolation of arsenate-dependent growing microorganisms which lack a canonical homolog for respiratory arsenate reductase, ArrAB. We recently isolated an arsenate-dependent growing bacterium from volcanic arsenic-bearing environments in Northern Chile, Fusibacter sp. strain 3D3 (Fas) and studied the arsenic metabolism in this Gram-positive isolate. Features of Fas deduced from genome analysis and comparative analysis with other arsenate-reducing microorganisms revealed the lack of ArrAB coding genes and the occurrence of two arsC genes encoding for putative cytoplasmic arsenate reductases named ArsC-1 and ArsC-2. Interestingly, ArsC-1 and ArsC-2 belong to the thioredoxin-coupled family (because of the redox-active disulfide protein used as reductant), but they conferred differential arsenate resistance to the E. coli WC3110 ΔarsC strain. PCR experiments confirmed the absence of arrAB genes and results obtained using uncouplers revealed that Fas growth is linked to the proton gradient. In addition, Fas harbors ferredoxin-NAD+ oxidoreductase (Rnf) and electron transfer flavoprotein (etf) coding genes. These are key molecular markers of a recently discovered flavin-based electron bifurcation mechanism involved in energy conservation, mainly in anaerobic metabolisms regulated by the cellular redox state and mostly associated with cytoplasmic enzyme complexes. At least three electron-bifurcating flavoenzyme complexes were evidenced in Fas, some of them shared in conserved genomic regions by other members of the Fusibacter genus. These physiological and genomic findings permit us to hypothesize the existence of an uncharacterized arsenate-dependent growth metabolism regulated by the cellular redox state in the Fusibacter genus.
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Affiliation(s)
| | - Susana Vázquez
- Cátedra de Biotecnología, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Buenos Aires, Argentina,Instituto de Nanobiotecnología (NANOBIOTEC), Universidad de Buenos Aires (UBA) - Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Nicolás Guiliani
- Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Antofagasta, Chile
| | - Sabrina Marín
- Biotechnology Center, Universidad Católica del Norte, Antofagasta, Chile
| | - Cecilia Demergasso
- Biotechnology Center, Universidad Católica del Norte, Antofagasta, Chile,Nucleus for the Study of Cancer at a Basic, Applied, and Clinical Level, Universidad Católica del Norte, Antofagasta, Chile,*Correspondence: Cecilia Demergasso,
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65
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Vinod Mouli MSS, Kumar Mishra A. Divergent Crystallographic Architecture for Silver‐Flavin Complexes Induced via pH Variation. ChemistrySelect 2022. [DOI: 10.1002/slct.202202126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- M. S. S. Vinod Mouli
- Department of Chemistry Indian Institute of Technology Hyderabad Kandi Sangareddy 502285 Telangana
| | - Ashutosh Kumar Mishra
- Department of Chemistry Indian Institute of Technology Hyderabad Kandi Sangareddy 502285 Telangana
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66
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Site-Differentiated Iron–Sulfur Cluster Ligation Affects Flavin-Based Electron Bifurcation Activity. Metabolites 2022; 12:metabo12090823. [PMID: 36144227 PMCID: PMC9503767 DOI: 10.3390/metabo12090823] [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] [Received: 08/05/2022] [Revised: 08/25/2022] [Accepted: 08/28/2022] [Indexed: 11/16/2022] Open
Abstract
Electron bifurcation is an elegant mechanism of biological energy conversion that effectively couples three different physiologically relevant substrates. As such, enzymes that perform this function often play critical roles in modulating cellular redox metabolism. One such enzyme is NADH-dependent reduced-ferredoxin: NADP+ oxidoreductase (NfnSL), which couples the thermodynamically favorable reduction of NAD+ to drive the unfavorable reduction of ferredoxin from NADPH. The interaction of NfnSL with its substrates is constrained to strict stoichiometric conditions, which ensures minimal energy losses from non-productive intramolecular electron transfer reactions. However, the determinants for this are not well understood. One curious feature of NfnSL is that both initial acceptors of bifurcated electrons are unique iron–sulfur (FeS) clusters containing one non-cysteinyl ligand each. The biochemical impact and mechanistic roles of site-differentiated FeS ligands are enigmatic, despite their incidence in many redox active enzymes. Herein, we describe the biochemical study of wild-type NfnSL and a variant in which one of the site-differentiated ligands has been replaced with a cysteine. Results of dye-based steady-state kinetics experiments, substrate-binding measurements, biochemical activity assays, and assessments of electron distribution across the enzyme indicate that this site-differentiated ligand in NfnSL plays a role in maintaining fidelity of the coordinated reactions performed by the two electron transfer pathways. Given the commonality of these cofactors, our findings have broad implications beyond electron bifurcation and mechanistic biochemistry and may inform on means of modulating the redox balance of the cell for targeted metabolic engineering approaches.
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67
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Furlan C, Chongdar N, Gupta P, Lubitz W, Ogata H, Blaza JN, Birrell JA. Structural insight on the mechanism of an electron-bifurcating [FeFe] hydrogenase. eLife 2022; 11:79361. [PMID: 36018003 PMCID: PMC9499530 DOI: 10.7554/elife.79361] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 08/25/2022] [Indexed: 11/24/2022] Open
Abstract
Electron bifurcation is a fundamental energy conservation mechanism in nature in which two electrons from an intermediate-potential electron donor are split so that one is sent along a high-potential pathway to a high-potential acceptor and the other is sent along a low-potential pathway to a low-potential acceptor. This process allows endergonic reactions to be driven by exergonic ones and is an alternative, less recognized, mechanism of energy coupling to the well-known chemiosmotic principle. The electron-bifurcating [FeFe] hydrogenase from Thermotoga maritima (HydABC) requires both NADH and ferredoxin to reduce protons generating hydrogen. The mechanism of electron bifurcation in HydABC remains enigmatic in spite of intense research efforts over the last few years. Structural information may provide the basis for a better understanding of spectroscopic and functional information. Here, we present a 2.3 Å electron cryo-microscopy structure of HydABC. The structure shows a heterododecamer composed of two independent 'halves' each made of two strongly interacting HydABC heterotrimers connected via a [4Fe-4S] cluster. A central electron transfer pathway connects the active sites for NADH oxidation and for proton reduction. We identified two conformations of a flexible iron-sulfur cluster domain: a 'closed bridge' and an 'open bridge' conformation, where a Zn2+ site may act as a 'hinge' allowing domain movement. Based on these structural revelations, we propose a possible mechanism of electron bifurcation in HydABC where the flavin mononucleotide serves a dual role as both the electron bifurcation center and as the NAD+ reduction/NADH oxidation site.
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Affiliation(s)
- Chris Furlan
- Structural Biology Laboratory and York Biomedical Research Institute, Department of Chemistry, The University of York, York, United Kingdom
| | - Nipa Chongdar
- Max Planck Institute for Chemical Energy Conversion, Muelheim an der Ruhr, Germany
| | - Pooja Gupta
- Structural Biology Laboratory and York Biomedical Research Institute, Department of Chemistry, The University of York, York, United Kingdom
| | - Wolfgang Lubitz
- Max Planck Institute for Chemical Energy Conversion, Muelheim an der Ruhr, Germany
| | - Hideaki Ogata
- Division of Materials Science, Nara Institute of Science and Technology, Ikoma, Japan.,Graduate School of Life Science, University of Hyogo, Hyogo, Japan
| | - James N Blaza
- Structural Biology Laboratory and York Biomedical Research Institute, Department of Chemistry, The University of York, York, United Kingdom
| | - James A Birrell
- Max Planck Institute for Chemical Energy Conversion, Muelheim an der Ruhr, Germany
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68
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Abdollahi M, Al Sbei S, Rosenbaum MA, Harnisch F. The oxygen dilemma: The challenge of the anode reaction for microbial electrosynthesis from CO2. Front Microbiol 2022; 13:947550. [PMID: 35992647 PMCID: PMC9381829 DOI: 10.3389/fmicb.2022.947550] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Accepted: 07/06/2022] [Indexed: 11/13/2022] Open
Abstract
Microbial electrosynthesis (MES) from CO2 provides chemicals and fuels by driving the metabolism of microorganisms with electrons from cathodes in bioelectrochemical systems. These microorganisms are usually strictly anaerobic. At the same time, the anode reaction of bioelectrochemical systems is almost exclusively water splitting through the oxygen evolution reaction (OER). This creates a dilemma for MES development and engineering. Oxygen penetration to the cathode has to be excluded to avoid toxicity and efficiency losses while assuring low resistance. We show that this dilemma derives a strong need to identify novel reactor designs when using the OER as an anode reaction or to fully replace OER with alternative oxidation reactions.
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Affiliation(s)
- Maliheh Abdollahi
- Department of Environmental Microbiology, UFZ-Helmholtz Centre for Environmental Research, Leipzig, Germany
| | - Sara Al Sbei
- Bio Pilot Plant, Leibniz Institute for Natural Product Research and Infection Biology - Hans-Knöll Institute, Jena, Germany
| | - Miriam A. Rosenbaum
- Bio Pilot Plant, Leibniz Institute for Natural Product Research and Infection Biology - Hans-Knöll Institute, Jena, Germany
- Faculty of Biological Sciences, Friedrich Schiller University Jena, Jena, Germany
| | - Falk Harnisch
- Department of Environmental Microbiology, UFZ-Helmholtz Centre for Environmental Research, Leipzig, Germany
- *Correspondence: Falk Harnisch,
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69
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Reconsidering the in vivo functions of Clostridial Stickland amino acid fermentations. Anaerobe 2022; 76:102600. [PMID: 35709938 PMCID: PMC9831356 DOI: 10.1016/j.anaerobe.2022.102600] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Accepted: 06/03/2022] [Indexed: 01/13/2023]
Abstract
Stickland amino acid fermentations occur primarily among species of Clostridia. An ancient form of metabolism, Stickland fermentations use amino acids as electron acceptors in the absence of stronger oxidizing agents and provide metabolic capabilities to support growth when other fermentable substrates, such as carbohydrates, are lacking. The reactions were originally described as paired fermentations of amino acid electron donors, such as the branched-chain amino acids, with recipients that include proline and glycine. We present a redox-focused view of Stickland metabolism following electron flow through metabolically diverse oxidative reactions and the defined-substrate reductase systems, including for proline and glycine, and the role of dual redox pathways for substrates such as leucine and ornithine. Genetic studies and Environment and Gene Regulatory Interaction Network (EGRIN) models for the pathogen Clostridioides difficile have improved our understanding of the regulation and metabolic recruitment of these systems, and their functions in modulating inter-species interactions within host-pathogen-commensal systems and uses in industrial and environmental applications.
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70
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Winiarska A, Hege D, Gemmecker Y, Kryściak-Czerwenka J, Seubert A, Heider J, Szaleniec M. Tungsten Enzyme Using Hydrogen as an Electron Donor to Reduce Carboxylic Acids and NAD . ACS Catal 2022; 12:8707-8717. [PMID: 35874620 PMCID: PMC9295118 DOI: 10.1021/acscatal.2c02147] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Tungsten-dependent
aldehyde oxidoreductases (AORs) catalyze the
oxidation of aldehydes to acids and are the only known enzymes reducing
non-activated acids using electron donors with low redox potentials.
We report here that AOR from Aromatoleum aromaticum (AORAa) catalyzes the reduction of organic
acids not only with low-potential Eu(II) or Ti(III) complexes but
also with H2 as an electron donor. Additionally, AORAa catalyzes the H2-dependent reduction
of NAD+ or benzyl viologen. The rate of H2-dependent
NAD+ reduction equals to 10% of that of aldehyde oxidation,
representing the highest H2 turnover rate observed among
the Mo/W enzymes. As AORAa simultaneously
catalyzes the reduction of acids and NAD+, we designed
a cascade reaction utilizing a NAD(P)H-dependent alcohol dehydrogenase
to reduce organic acids to the corresponding alcohols with H2 as the only reductant. The newly discovered W-hydrogenase side activity
of AORAa may find applications in either
NADH recycling or conversion of carboxylic acids to more useful biochemicals.
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Affiliation(s)
- Agnieszka Winiarska
- Jerzy Haber Institute of Catalysis and Surface Chemistry Polish Academy of Sciences, Kraków 30-239, Poland
| | - Dominik Hege
- Faculty of Biology, Philipps-Universität Marburg, Marburg D-35043, Germany
| | - Yvonne Gemmecker
- Faculty of Biology, Philipps-Universität Marburg, Marburg D-35043, Germany
| | - Joanna Kryściak-Czerwenka
- Jerzy Haber Institute of Catalysis and Surface Chemistry Polish Academy of Sciences, Kraków 30-239, Poland
| | - Andreas Seubert
- Faculty of Chemistry, Philipps-Universität Marburg, Marburg D-35043, Germany
| | - Johann Heider
- Faculty of Biology, Philipps-Universität Marburg, Marburg D-35043, Germany.,Center for Synthetic Microbiology, Philipps-Universität Marburg, Marburg D-35043, Germany
| | - Maciej Szaleniec
- Jerzy Haber Institute of Catalysis and Surface Chemistry Polish Academy of Sciences, Kraków 30-239, Poland
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71
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Schut GJ, Haja DK, Feng X, Poole FL, Li H, Adams MWW. An Abundant and Diverse New Family of Electron Bifurcating Enzymes With a Non-canonical Catalytic Mechanism. Front Microbiol 2022; 13:946711. [PMID: 35875533 PMCID: PMC9304861 DOI: 10.3389/fmicb.2022.946711] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 06/15/2022] [Indexed: 11/13/2022] Open
Abstract
Microorganisms utilize electron bifurcating enzymes in metabolic pathways to carry out thermodynamically unfavorable reactions. Bifurcating FeFe-hydrogenases (HydABC) reversibly oxidize NADH (E′∼−280 mV, under physiological conditions) and reduce protons to H2 gas (E°′−414 mV) by coupling this endergonic reaction to the exergonic reduction of protons by reduced ferredoxin (Fd) (E′∼−500 mV). We show here that HydABC homologs are surprisingly ubiquitous in the microbial world and are represented by 57 phylogenetically distinct clades but only about half are FeFe-hydrogenases. The others have replaced the hydrogenase domain with another oxidoreductase domain or they contain additional subunits, both of which enable various third reactions to be reversibly coupled to NAD+ and Fd reduction. We hypothesize that all of these enzymes carry out electron bifurcation and that their third substrates can include hydrogen peroxide, pyruvate, carbon monoxide, aldehydes, aryl-CoA thioesters, NADP+, cofactor F420, formate, and quinones, as well as many yet to be discovered. Some of the enzymes are proposed to be integral membrane-bound proton-translocating complexes. These different functionalities are associated with phylogenetically distinct clades and in many cases with specific microbial phyla. We propose that this new and abundant class of electron bifurcating enzyme be referred to as the Bfu family whose defining feature is a conserved bifurcating BfuBC core. This core contains FMN and six iron sulfur clusters and it interacts directly with ferredoxin (Fd) and NAD(H). Electrons to or from the third substrate are fed into the BfuBC core via BfuA. The other three known families of electron bifurcating enzyme (abbreviated as Nfn, EtfAB, and HdrA) contain a special FAD that bifurcates electrons to high and low potential pathways. The Bfu family are proposed to use a different electron bifurcation mechanism that involves a combination of FMN and three adjacent iron sulfur clusters, including a novel [2Fe-2S] cluster with pentacoordinate and partial non-Cys coordination. The absolute conservation of the redox cofactors of BfuBC in all members of the Bfu enzyme family indicate they have the same non-canonical mechanism to bifurcate electrons. A hypothetical catalytic mechanism is proposed as a basis for future spectroscopic analyses of Bfu family members.
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Affiliation(s)
- Gerrit J. Schut
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
| | - Dominik K. Haja
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
| | - Xiang Feng
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, United States
| | - Farris L. Poole
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
| | - Huilin Li
- Department of Structural Biology, Van Andel Institute, Grand Rapids, MI, United States
| | - Michael W. W. Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
- *Correspondence: Michael W. W. Adams, ; orcid.org/0000-0002-9796-5014
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72
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Wang C, Wang Y, Wang Y, Liu L, Wang D, Ju F, Xia Y, Zhang T. Impacts of food waste to sludge ratios on microbial dynamics and functional traits in thermophilic digesters. WATER RESEARCH 2022; 219:118590. [PMID: 35597218 DOI: 10.1016/j.watres.2022.118590] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Revised: 04/18/2022] [Accepted: 05/10/2022] [Indexed: 06/15/2023]
Abstract
A self-stabilizing microbial community lays the foundation of the efficient biochemical reactions of the anaerobic digestion (AD) process. Despite extensive profiling of microbial community dynamics under varying operating parameters, the effects of food waste (FW) to feeding sewage sludge (FSS) ratios on the microbial assembly, functional traits, and syntrophic interspecies interactions in thermophilic microbial consortia remain poorly understood. Here, we investigated the long-term impacts of the FW: FSS ratio on the thermophilic AD microbiome using genome-centric metagenomics. Both the short reads (SRs) assembly, and the iterative hybrid assembly (IHA) of SRs and nanopore long reads (LRs) were used to reconstruct metagenome-assembled genomes (MAGs) and four microbial clusters were identified, demonstrating different microbial dynamics patterns in response to varying FW:FSS ratios. Cluster C1-C3 were comprised of full functional members with genetic potentials in fulfilling empirical AD biochemical reactions, wherein, syntrophic decarboxylating acetogens could interact with methanogens, and some microbes could be energized by the electron bifurcation mechanism to drive thermodynamics unfavorable reactions. We found the co-existence of both acetogenic and hydrogenotrophic methanogens in the AD microbiome, and they altered their trophic groups to scavenge the methanogenic substrates in ensuring the methane generation in digesters with different FW:FSS ratios. Another interesting observation was that two phylogenetically close Thermotogota species showed a possible strong competition on carbon source inferred by the nearly complete genetic overlap of their relevant pathways.
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Affiliation(s)
- Chunxiao Wang
- Environmental Microbiome Engineering and Biotechnology Laboratory, Center for Environmental Engineering Research, Department of Civil Engineering, The University of Hong Kong, Hong Kong SAR, China
| | - Yulin Wang
- Environmental Microbiome Engineering and Biotechnology Laboratory, Center for Environmental Engineering Research, Department of Civil Engineering, The University of Hong Kong, Hong Kong SAR, China; State Key Laboratory of Microbial Biotechnology, Shandong University, Qingdao 266237, China
| | - Yubo Wang
- Key Laboratory of Coastal Environment and Resources of Zhejiang Province, School of Engineering, Westlake University, 18 Shilongshan Road, Hangzhou 310024, China
| | - Lei Liu
- Environmental Microbiome Engineering and Biotechnology Laboratory, Center for Environmental Engineering Research, Department of Civil Engineering, The University of Hong Kong, Hong Kong SAR, China
| | - Dou Wang
- Environmental Microbiome Engineering and Biotechnology Laboratory, Center for Environmental Engineering Research, Department of Civil Engineering, The University of Hong Kong, Hong Kong SAR, China
| | - Feng Ju
- Key Laboratory of Coastal Environment and Resources of Zhejiang Province, School of Engineering, Westlake University, 18 Shilongshan Road, Hangzhou 310024, China
| | - Yu Xia
- State Environmental Protection Key Laboratory of Integrated Surface Water-Groundwater Pollution Control, School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Tong Zhang
- Environmental Microbiome Engineering and Biotechnology Laboratory, Center for Environmental Engineering Research, Department of Civil Engineering, The University of Hong Kong, Hong Kong SAR, China.
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73
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Kayastha K, Katsyv A, Himmrich C, Welsch S, Schuller JM, Ermler U, Müller V. Structure-based electron-confurcation mechanism of the Ldh-EtfAB complex. eLife 2022; 11:77095. [PMID: 35748623 PMCID: PMC9232219 DOI: 10.7554/elife.77095] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 05/22/2022] [Indexed: 01/22/2023] Open
Abstract
Lactate oxidation with NAD+ as electron acceptor is a highly endergonic reaction. Some anaerobic bacteria overcome the energetic hurdle by flavin-based electron bifurcation/confurcation (FBEB/FBEC) using a lactate dehydrogenase (Ldh) in concert with the electron-transferring proteins EtfA and EtfB. The electron cryo-microscopically characterized (Ldh-EtfAB)2 complex of Acetobacterium woodii at 2.43 Å resolution consists of a mobile EtfAB shuttle domain located between the rigid central Ldh and the peripheral EtfAB base units. The FADs of Ldh and the EtfAB shuttle domain contact each other thereby forming the D (dehydrogenation-connected) state. The intermediary Glu37 and Glu139 may harmonize the redox potentials between the FADs and the pyruvate/lactate pair crucial for FBEC. By integrating Alphafold2 calculations a plausible novel B (bifurcation-connected) state was obtained allowing electron transfer between the EtfAB base and shuttle FADs. Kinetic analysis of enzyme variants suggests a correlation between NAD+ binding site and D-to-B-state transition implicating a 75° rotation of the EtfAB shuttle domain. The FBEC inactivity when truncating the ferredoxin domain of EtfA substantiates its role as redox relay. Lactate oxidation in Ldh is assisted by the catalytic base His423 and a metal center. On this basis, a comprehensive catalytic mechanism of the FBEC process was proposed.
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Affiliation(s)
- Kanwal Kayastha
- Departments of Molecular Membrane Biology of the Max-Planck-Institut for Biophysics, Frankfurt am Main, Germany
| | - Alexander Katsyv
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Goethe University, Frankfurt am Main, Germany
| | - Christina Himmrich
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Goethe University, Frankfurt am Main, Germany
| | - Sonja Welsch
- Central Electron Microscopy Facility, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Jan M Schuller
- SYNMICRO Research Center and Department of Chemistry, Philipps University, Marburg, Germany
| | - Ulrich Ermler
- Departments of Molecular Membrane Biology of the Max-Planck-Institut for Biophysics, Frankfurt am Main, Germany
| | - Volker Müller
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Goethe University, Frankfurt am Main, Germany
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74
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Ramírez GA, Keshri J, Vahrson I, Garber AI, Berrang ME, Cox NA, González-Cerón F, Aggrey SE, Oakley BB. Cecal Microbial Hydrogen Cycling Potential Is Linked to Feed Efficiency Phenotypes in Chickens. Front Vet Sci 2022; 9:904698. [PMID: 35799838 PMCID: PMC9255636 DOI: 10.3389/fvets.2022.904698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Accepted: 05/19/2022] [Indexed: 11/24/2022] Open
Abstract
In chickens, early life exposure to environmental microbes has long-lasting impacts on gastrointestinal (GI) microbiome development and host health and growth, via mechanisms that remain uncharacterized. In this study, we demonstrated that administrating a fecal microbiome transplant (FMT) from adults to day-of-hatch chicks results in significantly higher body mass of birds and decreased residual feed intake (RFI), implying enhanced feed efficiency, at 6 weeks of age. To assess the potential mechanisms through which FMT affects adult bird phenotype, we combined 16 S rRNA gene amplification, metagenomic, and comparative genomic approaches to survey the composition and predicted activities of the resident microbiome of various GI tract segments. Early life FMT exposure had a long-lasting significant effect on the microbial community composition and function of the ceca but not on other GI segments. Within the ceca of 6-week-old FMT birds, hydrogenotrophic microbial lineages and genes were most differentially enriched. The results suggest that thermodynamic regulation in the cecum, in this case via hydrogenotrophic methanogenic and sulfur-cycling lineages, potentially serving as hydrogen sinks, may enhance fermentative efficiency and dietary energy harvest capacity. Our study provides a specific mechanism of action through which early-life microbiome transplants modulate market-relevant phenotypes in poultry and, thereby, may represent a significant advance toward microbiome-focused sustainable agriculture.
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Affiliation(s)
- Gustavo Antonio Ramírez
- College of Veterinary Medicine, Western University of Health Sciences, Pomona, CA, United States
- Leon H. Charney School of Marine Sciences, Haifa University, Haifa, Israel
| | - Jitendra Keshri
- College of Veterinary Medicine, Western University of Health Sciences, Pomona, CA, United States
| | - Isabella Vahrson
- College of Veterinary Medicine, Western University of Health Sciences, Pomona, CA, United States
| | - Arkadiy I. Garber
- School of Life Sciences, Arizona State University, Tempe, AZ, United States
| | - Mark E. Berrang
- Poultry Microbiological Safety and Processing Research Unit, USDA Agricultural Research Service, Athens, GA, United States
| | - Nelson A. Cox
- Poultry Microbiological Safety and Processing Research Unit, USDA Agricultural Research Service, Athens, GA, United States
| | - Fernando González-Cerón
- Departamento de Zootecnia, Chapingo Autonomous University, Estado de Mexico, Mexico
- NutriGenomics Laboratory, Department of Poultry Science, University of Georgia, Athens, GA, United States
| | - Samuel E. Aggrey
- NutriGenomics Laboratory, Department of Poultry Science, University of Georgia, Athens, GA, United States
| | - Brian B. Oakley
- College of Veterinary Medicine, Western University of Health Sciences, Pomona, CA, United States
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75
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Benito-Vaquerizo S, Parera Olm I, de Vroet T, Schaap PJ, Sousa DZ, Martins Dos Santos VAP, Suarez-Diez M. Genome-scale metabolic modelling enables deciphering ethanol metabolism via the acrylate pathway in the propionate-producer Anaerotignum neopropionicum. Microb Cell Fact 2022; 21:116. [PMID: 35710409 PMCID: PMC9205015 DOI: 10.1186/s12934-022-01841-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 05/26/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Microbial production of propionate from diluted streams of ethanol (e.g., deriving from syngas fermentation) is a sustainable alternative to the petrochemical production route. Yet, few ethanol-fermenting propionigenic bacteria are known, and understanding of their metabolism is limited. Anaerotignum neopropionicum is a propionate-producing bacterium that uses the acrylate pathway to ferment ethanol and CO2 to propionate and acetate. In this work, we used computational and experimental methods to study the metabolism of A. neopropionicum and, in particular, the pathway for conversion of ethanol into propionate. RESULTS Our work describes iANEO_SB607, the first genome-scale metabolic model (GEM) of A. neopropionicum. The model was built combining the use of automatic tools with an extensive manual curation process, and it was validated with experimental data from this and published studies. The model predicted growth of A. neopropionicum on ethanol, lactate, sugars and amino acids, matching observed phenotypes. In addition, the model was used to implement a dynamic flux balance analysis (dFBA) approach that accurately predicted the fermentation profile of A. neopropionicum during batch growth on ethanol. A systematic analysis of the metabolism of A. neopropionicum combined with model simulations shed light into the mechanism of ethanol fermentation via the acrylate pathway, and revealed the presence of the electron-transferring complexes NADH-dependent reduced ferredoxin:NADP+ oxidoreductase (Nfn) and acryloyl-CoA reductase-EtfAB, identified for the first time in this bacterium. CONCLUSIONS The realisation of the GEM iANEO_SB607 is a stepping stone towards the understanding of the metabolism of the propionate-producer A. neopropionicum. With it, we have gained insight into the functioning of the acrylate pathway and energetic aspects of the cell, with focus on the fermentation of ethanol. Overall, this study provides a basis to further exploit the potential of propionigenic bacteria as microbial cell factories.
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Affiliation(s)
- Sara Benito-Vaquerizo
- Laboratory of Systems and Synthetic Biology, Wageningen University & Research, Stippeneng 4, Wageningen, 6708WE, The Netherlands
| | - Ivette Parera Olm
- Laboratory of Microbiology, Wageningen University & Research, Stippeneng 4, Wageningen, 6708WE, The Netherlands
| | - Thijs de Vroet
- Laboratory of Microbiology, Wageningen University & Research, Stippeneng 4, Wageningen, 6708WE, The Netherlands
| | - Peter J Schaap
- Laboratory of Systems and Synthetic Biology, Wageningen University & Research, Stippeneng 4, Wageningen, 6708WE, The Netherlands
| | - Diana Z Sousa
- Laboratory of Microbiology, Wageningen University & Research, Stippeneng 4, Wageningen, 6708WE, The Netherlands.,Centre for Living Technologies, Alliance TU/e, WUR, UU, UMC Utrecht, Vening Meinesz building C, Princetonlaan 6, Utrecht, 3584 CB, The Netherlands
| | - Vitor A P Martins Dos Santos
- Laboratory of Systems and Synthetic Biology, Wageningen University & Research, Stippeneng 4, Wageningen, 6708WE, The Netherlands.,Bioprocess Engineering, Wageningen University & Research, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands
| | - Maria Suarez-Diez
- Laboratory of Systems and Synthetic Biology, Wageningen University & Research, Stippeneng 4, Wageningen, 6708WE, The Netherlands.
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76
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Sorokin DY, Merkel AY, Messina E, Tugui C, Pabst M, Golyshin PN, Yakimov MM. Anaerobic carboxydotrophy in sulfur-respiring haloarchaea from hypersaline lakes. THE ISME JOURNAL 2022; 16:1534-1546. [PMID: 35132120 PMCID: PMC9123189 DOI: 10.1038/s41396-022-01206-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/03/2021] [Revised: 01/03/2022] [Accepted: 01/27/2022] [Indexed: 05/24/2023]
Abstract
Anaerobic carboxydotrophy is a widespread catabolic trait in bacteria, with two dominant pathways: hydrogenogenic and acetogenic. The marginal mode by direct oxidation to CO2 using an external e-acceptor has only a few examples. Use of sulfidic sediments from two types of hypersaline lakes in anaerobic enrichments with CO as an e-donor and elemental sulfur as an e-acceptor led to isolation of two pure cultures of anaerobic carboxydotrophs belonging to two genera of sulfur-reducing haloarchaea: Halanaeroarchaeum sp. HSR-CO from salt lakes and Halalkaliarchaeum sp. AArc-CO from soda lakes. Anaerobic growth of extremely halophilic archaea with CO was obligatory depended on the presence of elemental sulfur as the electron acceptor and yeast extract as the carbon source. CO served as a direct electron donor and H2 was not generated from CO when cells were incubated with or without sulfur. The genomes of the isolates encode a catalytic Ni,Fe-CODH subunit CooS (distantly related to bacterial homologs) and its Ni-incorporating chaperone CooC (related to methanogenic homologs) within a single genomic locus. Similar loci were also present in a genome of the type species of Halalkaliarchaeum closely related to AArc-CO, and the ability for anaerobic sulfur-dependent carboxydotrophy was confirmed for three different strains of this genus. Moreover, similar proteins are encoded in three of the four genomes of recently described carbohydrate-utilizing sulfur-reducing haloarchaea belonging to the genus Halapricum and in two yet undescribed haloarchaeal species. Overall, this work demonstrated for the first time the potential for anaerobic sulfur-dependent carboxydotrophy in extremely halophilic archaea.
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Affiliation(s)
- Dimitry Y Sorokin
- Winogradsky Institute of Microbiology, Federal Research Centre of Biotechnology, Russian Academy of Sciences, Moscow, Russia.
- Department of Biotechnology, Delft University of Technology, Delft, The Netherlands.
| | - Alexander Y Merkel
- Winogradsky Institute of Microbiology, Federal Research Centre of Biotechnology, Russian Academy of Sciences, Moscow, Russia
| | - Enzo Messina
- IRBIM-CNR, Spianata S.Raineri 86, 98122, Messina, Italy
| | - Claudia Tugui
- Department of Biotechnology, Delft University of Technology, Delft, The Netherlands
| | - Martin Pabst
- Department of Biotechnology, Delft University of Technology, Delft, The Netherlands
| | - Peter N Golyshin
- School of Natural Sciences, Bangor University, Gwynedd, LL57 2UW, UK
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77
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Vigil W, Tran J, Niks D, Schut GJ, Ge X, Adams MWW, Hille R. The reductive half-reaction of two bifurcating electron-transferring flavoproteins: Evidence for changes in flavin reduction potentials mediated by specific conformational changes. J Biol Chem 2022; 298:101927. [PMID: 35429498 PMCID: PMC9127580 DOI: 10.1016/j.jbc.2022.101927] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 04/06/2022] [Accepted: 04/07/2022] [Indexed: 10/25/2022] Open
Abstract
The EtfAB components of two bifurcating flavoprotein systems, the crotonyl-CoA-dependent NADH:ferredoxin oxidoreductase from the bacterium Megasphaera elsdenii and the menaquinone-dependent NADH:ferredoxin oxidoreductase from the archaeon Pyrobaculum aerophilum, have been investigated. With both proteins, we find that removal of the electron-transferring flavin adenine dinucleotide (FAD) moiety from both proteins results in an uncrossing of the reduction potentials of the remaining bifurcating FAD; this significantly stabilizes the otherwise very unstable semiquinone state, which accumulates over the course of reductive titrations with sodium dithionite. Furthermore, reduction of both EtfABs depleted of their electron-transferring FAD by NADH was monophasic with a hyperbolic dependence of reaction rate on the concentration of NADH. On the other hand, NADH reduction of the replete proteins containing the electron-transferring FAD was multiphasic, consisting of a fast phase comparable to that seen with the depleted proteins followed by an intermediate phase that involves significant accumulation of FAD⋅-, again reflecting uncrossing of the half-potentials of the bifurcating FAD. This is then followed by a slow phase that represents the slow reduction of the electron-transferring FAD to FADH-, with reduction of the now fully reoxidized bifurcating FAD by a second equivalent of NADH. We suggest that the crossing and uncrossing of the reduction half-potentials of the bifurcating FAD is due to specific conformational changes that have been structurally characterized.
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Affiliation(s)
- Wayne Vigil
- Department of Biochemistry, University of California, Riverside, California, USA
| | - Jessica Tran
- Department of Biochemistry, University of California, Riverside, California, USA
| | - Dimitri Niks
- Department of Biochemistry, University of California, Riverside, California, USA
| | - Gerrit J Schut
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Xiaoxuan Ge
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Michael W W Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Russ Hille
- Department of Biochemistry, University of California, Riverside, California, USA.
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78
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Henriques Pereira DP, Leethaus J, Beyazay T, do Nascimento Vieira A, Kleinermanns K, Tüysüz H, Martin WF, Preiner M. Role of geochemical protoenzymes (geozymes) in primordial metabolism: specific abiotic hydride transfer by metals to the biological redox cofactor NAD . FEBS J 2022; 289:3148-3162. [PMID: 34923745 PMCID: PMC9306933 DOI: 10.1111/febs.16329] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Revised: 12/09/2021] [Accepted: 12/17/2021] [Indexed: 12/17/2022]
Abstract
Hydrogen gas, H2 , is generated in serpentinizing hydrothermal systems, where it has supplied electrons and energy for microbial communities since there was liquid water on Earth. In modern metabolism, H2 is converted by hydrogenases into organically bound hydrides (H- ), for example, the cofactor NADH. It transfers hydrides among molecules, serving as an activated and biologically harnessed form of H2 . In serpentinizing systems, minerals can also bind hydrides and could, in principle, have acted as inorganic hydride donors-possibly as a geochemical protoenzyme, a 'geozyme'- at the origin of metabolism. To test this idea, we investigated the ability of H2 to reduce NAD+ in the presence of iron (Fe), cobalt (Co) and nickel (Ni), metals that occur in serpentinizing systems. In the presence of H2 , all three metals specifically reduce NAD+ to the biologically relevant form, 1,4-NADH, with up to 100% conversion rates within a few hours under alkaline aqueous conditions at 40 °C. Using Henry's law, the partial pressure of H2 in our reactions corresponds to 3.6 mm, a concentration observed in many modern serpentinizing systems. While the reduction of NAD+ by Ni is strictly H2 -dependent, experiments in heavy water (2 H2 O) indicate that native Fe can reduce NAD+ both with and without H2 . The results establish a mechanistic connection between abiotic and biotic hydride donors, indicating that geochemically catalysed, H2 -dependent NAD+ reduction could have preceded the hydrogenase-dependent reaction in evolution.
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Affiliation(s)
| | - Jana Leethaus
- Institute for Molecular EvolutionHeinrich Heine UniversityDüsseldorfGermany
| | - Tugce Beyazay
- Max‐Planck‐Institut für KohlenforschungMülheim an der RuhrGermany
| | | | - Karl Kleinermanns
- Institute for Physical ChemistryHeinrich Heine UniversityDüsseldorfGermany
| | - Harun Tüysüz
- Max‐Planck‐Institut für KohlenforschungMülheim an der RuhrGermany
| | - William F. Martin
- Institute for Molecular EvolutionHeinrich Heine UniversityDüsseldorfGermany
| | - Martina Preiner
- Department of Ocean SystemsRoyal Netherlands Institute for Sea ResearchDen BurgThe Netherlands
- Department of Earth SciencesUtrecht UniversityThe Netherlands
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79
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He Y, Wang S, Han X, Shen J, Lu Y, Zhao J, Shen C, Qiao L. Photosynthesis of Acetate by Sporomusa ovata-CdS Biohybrid System. ACS APPLIED MATERIALS & INTERFACES 2022; 14:23364-23374. [PMID: 35576621 DOI: 10.1021/acsami.2c01918] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Sporomusa ovata, a typical electroautotrophic microorganism, has been utilized in bioelectrosynthesis for carbon dioxide fixation to multicarbon organic chemicals. However, additional photovoltaic devices are normally needed to convert photo energy to electric energy to power the carbon dioxide fixation, which restricts the overall energy conversion efficiency. Herein, we report Sporomusa ovata-CdS biohybrids for artificial photosynthesis driven by light without any other power source. The quantum yield can reach 16.8 ± 9%, and the active duration time of the system can last for 5 days. During the artificial photosynthesis, carbon dioxide is first reduced to formate and finally converted to acetate via the Wood-Ljungdahl pathway. The carbon dioxide fixation, electron transfer, energy metabolism, and reactive oxygen species damage repair processes in the biohybrid system were characterized by proteomic analysis. Key enzymes, e.g., flavoprotein, ferredoxin, formate-tetrahydrofolate ligase, 5-methyltetrahydrofolate:corrinoid iron-sulfur protein methyltransferase, thioredoxin, and rubrerythrin, were found up-regulated in the biohybrid system. The findings are helpful in understanding the mechanism of the artificial photosynthesis and useful for the development of new biohybrid systems using genetically engineered microbes in the future. The study is expected to boost the development of bioabiotic hybrid system in solar energy harvest.
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Affiliation(s)
- Ying He
- Department of Chemistry, and Shanghai Stomatological Hospital, Fudan University, Shanghai 200000, China
| | - Shurong Wang
- Department of Chemistry, and Shanghai Stomatological Hospital, Fudan University, Shanghai 200000, China
| | - Xinyue Han
- Department of Chemistry, and Shanghai Stomatological Hospital, Fudan University, Shanghai 200000, China
| | - Jiayuan Shen
- Department of Chemistry, and Shanghai Stomatological Hospital, Fudan University, Shanghai 200000, China
| | - Yanwei Lu
- Department of Chemistry, and Shanghai Stomatological Hospital, Fudan University, Shanghai 200000, China
| | - Jinzhi Zhao
- Department of Chemistry, and Shanghai Stomatological Hospital, Fudan University, Shanghai 200000, China
| | - Chengpin Shen
- Shanghai Omicsolution Co., Ltd., Shanghai 200000, China
| | - Liang Qiao
- Department of Chemistry, and Shanghai Stomatological Hospital, Fudan University, Shanghai 200000, China
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80
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Klask CM, Jäger B, Casini I, Angenent LT, Molitor B. Genetic Evidence Reveals the Indispensable Role of the rseC Gene for Autotrophy and the Importance of a Functional Electron Balance for Nitrate Reduction in Clostridium ljungdahlii. Front Microbiol 2022; 13:887578. [PMID: 35615511 PMCID: PMC9124969 DOI: 10.3389/fmicb.2022.887578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 03/31/2022] [Indexed: 11/20/2022] Open
Abstract
For Clostridium ljungdahlii, the RNF complex plays a key role for energy conversion from gaseous substrates such as hydrogen and carbon dioxide. In a previous study, a disruption of RNF-complex genes led to the loss of autotrophy, while heterotrophy was still possible via glycolysis. Furthermore, it was shown that the energy limitation during autotrophy could be lifted by nitrate supplementation, which resulted in an elevated cellular growth and ATP yield. Here, we used CRISPR-Cas12a to delete: (1) the RNF complex-encoding gene cluster rnfCDGEAB; (2) the putative RNF regulator gene rseC; and (3) a gene cluster that encodes for a putative nitrate reductase. The deletion of either rnfCDGEAB or rseC resulted in a complete loss of autotrophy, which could be restored by plasmid-based complementation of the deleted genes. We observed a transcriptional repression of the RNF-gene cluster in the rseC-deletion strain during autotrophy and investigated the distribution of the rseC gene among acetogenic bacteria. To examine nitrate reduction and its connection to the RNF complex, we compared autotrophic and heterotrophic growth of our three deletion strains with either ammonium or nitrate. The rnfCDGEAB- and rseC-deletion strains failed to reduce nitrate as a metabolic activity in non-growing cultures during autotrophy but not during heterotrophy. In contrast, the nitrate reductase deletion strain was able to grow in all tested conditions but lost the ability to reduce nitrate. Our findings highlight the important role of the rseC gene for autotrophy, and in addition, contribute to understand the connection of nitrate reduction to energy metabolism.
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Affiliation(s)
- Christian-Marco Klask
- Environmental Biotechnology Group, Geo- and Environmental Science Center, University of Tübingen, Tübingen, Germany
| | - Benedikt Jäger
- Environmental Biotechnology Group, Geo- and Environmental Science Center, University of Tübingen, Tübingen, Germany
| | - Isabella Casini
- Environmental Biotechnology Group, Geo- and Environmental Science Center, University of Tübingen, Tübingen, Germany
| | - Largus T. Angenent
- Environmental Biotechnology Group, Geo- and Environmental Science Center, University of Tübingen, Tübingen, Germany
- Cluster of Excellence – Controlling Microbes to Fight Infections, University of Tübingen, Tübingen, Germany
- Max Planck Institute for Biology Tübingen, Tübingen, Germany
| | - Bastian Molitor
- Environmental Biotechnology Group, Geo- and Environmental Science Center, University of Tübingen, Tübingen, Germany
- Cluster of Excellence – Controlling Microbes to Fight Infections, University of Tübingen, Tübingen, Germany
- *Correspondence: Bastian Molitor,
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81
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Deng X, Luo D, Okamoto A. Electrode hydrophilicity enhanced the rate of extracellular electron uptake in Desulfovibrio ferrophilus IS5. Electrochim Acta 2022. [DOI: 10.1016/j.electacta.2022.140504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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82
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An uncharacteristically low-potential flavin governs the energy landscape of electron bifurcation. Proc Natl Acad Sci U S A 2022; 119:e2117882119. [PMID: 35290111 PMCID: PMC8944662 DOI: 10.1073/pnas.2117882119] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Nature has long been an inspiration for materials design, as it exemplifies exquisite control of both matter and energy. Electron bifurcation, a mechanism employed in biological systems to drive thermodynamically unfavorable and energetically challenging chemical reactions, is one such example. A key feature of bifurcating enzymes is the ability of a single redox cofactor to distribute a pair of electrons across two spatially separated electron transfer pathways. Here, we report on the empirical determination of both the one-electron potential and two-electron potential of the bifurcating flavin cofactor in the NADH-dependent ferredoxin-NADP+ oxidoreductase I (NfnSL) enzyme. Insights arising from the defined energy landscape of this bifurcation site may underlie the design of synthetic catalysts capable of generating high-energy intermediates. Electron bifurcation, an energy-conserving process utilized extensively throughout all domains of life, represents an elegant means of generating high-energy products from substrates with less reducing potential. The coordinated coupling of exergonic and endergonic reactions has been shown to operate over an electrochemical potential of ∼1.3 V through the activity of a unique flavin cofactor in the enzyme NADH-dependent ferredoxin-NADP+ oxidoreductase I. The inferred energy landscape has features unprecedented in biochemistry and presents novel energetic challenges, the most intriguing being a large thermodynamically uphill step for the first electron transfer of the bifurcation reaction. However, ambiguities in the energy landscape at the bifurcating site deriving from overlapping flavin spectral signatures have impeded a comprehensive understanding of the specific mechanistic contributions afforded by thermodynamic and kinetic factors. Here, we elucidate an uncharacteristically low two-electron potential of the bifurcating flavin, resolving the energetic challenge of the first bifurcation event.
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83
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Kelly WJ, Mackie RI, Attwood GT, Janssen PH, McAllister TA, Leahy SC. Hydrogen and formate production and utilisation in the rumen and the human colon. Anim Microbiome 2022; 4:22. [PMID: 35287765 PMCID: PMC8919644 DOI: 10.1186/s42523-022-00174-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Accepted: 03/02/2022] [Indexed: 12/31/2022] Open
Abstract
Molecular hydrogen (H2) and formate (HCOO-) are metabolic end products of many primary fermenters in the mammalian gut. Both play a vital role in fermentation where they are electron sinks for individual microbes in an anaerobic environment that lacks external electron acceptors. If H2 and/or formate accumulate within the gut ecosystem, the ability of primary fermenters to regenerate electron carriers may be inhibited and microbial metabolism and growth disrupted. Consequently, H2- and/or formate-consuming microbes such as methanogens and homoacetogens play a key role in maintaining the metabolic efficiency of primary fermenters. There is increasing interest in identifying approaches to manipulate mammalian gut environments for the benefit of the host and the environment. As H2 and formate are important mediators of interspecies interactions, an understanding of their production and utilisation could be a significant entry point for the development of successful interventions. Ruminant methane mitigation approaches are discussed as a model to help understand the fate of H2 and formate in gut systems.
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Affiliation(s)
- William J Kelly
- New Zealand Agricultural Greenhouse Gas Research Centre (NZAGRC), Palmerston North, New Zealand
- AgResearch, Grasslands Research Centre, Palmerston North, New Zealand
| | | | - Graeme T Attwood
- AgResearch, Grasslands Research Centre, Palmerston North, New Zealand
| | - Peter H Janssen
- AgResearch, Grasslands Research Centre, Palmerston North, New Zealand
| | | | - Sinead C Leahy
- New Zealand Agricultural Greenhouse Gas Research Centre (NZAGRC), Palmerston North, New Zealand.
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84
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Westerholm M, Calusinska M, Dolfing J. Syntrophic propionate-oxidizing bacteria in methanogenic systems. FEMS Microbiol Rev 2022; 46:fuab057. [PMID: 34875063 PMCID: PMC8892533 DOI: 10.1093/femsre/fuab057] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 12/03/2021] [Indexed: 12/04/2022] Open
Abstract
The mutual nutritional cooperation underpinning syntrophic propionate degradation provides a scant amount of energy for the microorganisms involved, so propionate degradation often acts as a bottleneck in methanogenic systems. Understanding the ecology, physiology and metabolic capacities of syntrophic propionate-oxidizing bacteria (SPOB) is of interest in both engineered and natural ecosystems, as it offers prospects to guide further development of technologies for biogas production and biomass-derived chemicals, and is important in forecasting contributions by biogenic methane emissions to climate change. SPOB are distributed across different phyla. They can exhibit broad metabolic capabilities in addition to syntrophy (e.g. fermentative, sulfidogenic and acetogenic metabolism) and demonstrate variations in interplay with cooperating partners, indicating nuances in their syntrophic lifestyle. In this review, we discuss distinctions in gene repertoire and organization for the methylmalonyl-CoA pathway, hydrogenases and formate dehydrogenases, and emerging facets of (formate/hydrogen/direct) electron transfer mechanisms. We also use information from cultivations, thermodynamic calculations and omic analyses as the basis for identifying environmental conditions governing propionate oxidation in various ecosystems. Overall, this review improves basic and applied understanding of SPOB and highlights knowledge gaps, hopefully encouraging future research and engineering on propionate metabolism in biotechnological processes.
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Affiliation(s)
- Maria Westerholm
- Department of Molecular Sciences, Swedish University of Agricultural Sciences, BioCentre, Almas allé 5, SE-75007 Uppsala, Sweden
| | - Magdalena Calusinska
- Environmental Research and Innovation Department, Luxembourg Institute of Science and Technology, rue du Brill 41, L-4422 Belvaux, Luxembourg
| | - Jan Dolfing
- Faculty of Energy and Environment, Northumbria University, Wynne Jones 2.11, Ellison Place, Newcastle-upon-Tyne NE1 8QH, UK
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85
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Morra S. Fantastic [FeFe]-Hydrogenases and Where to Find Them. Front Microbiol 2022; 13:853626. [PMID: 35308355 PMCID: PMC8924675 DOI: 10.3389/fmicb.2022.853626] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Accepted: 02/10/2022] [Indexed: 01/01/2023] Open
Abstract
[FeFe]-hydrogenases are complex metalloenzymes, key to microbial energy metabolism in numerous organisms. During anaerobic metabolism, they dissipate excess reducing equivalents by using protons from water as terminal electron acceptors, leading to hydrogen production. This reaction is coupled to reoxidation of specific redox partners [ferredoxins, NAD(P)H or cytochrome c3], that can be used either individually or simultaneously (via flavin-based electron bifurcation). [FeFe]-hydrogenases also serve additional physiological functions such as H2 uptake (oxidation), H2 sensing, and CO2 fixation. This broad functional spectrum is enabled by a modular architecture and vast genetic diversity, which is not fully explored and understood. This Mini Review summarises recent advancements in identifying and characterising novel [FeFe]-hydrogenases, which has led to expanding our understanding of their multiple roles in metabolism and functional mechanisms. For example, while numerous well-known [FeFe]-hydrogenases are irreversibly damaged by oxygen, some newly discovered enzymes display intrinsic tolerance. These findings demonstrate that oxygen sensitivity varies between different [FeFe]-hydrogenases: in some cases, protection requires the presence of exogenous compounds such as carbon monoxide or sulphide, while in other cases it is a spontaneous built-in mechanism that relies on a reversible conformational change. Overall, it emerges that additional research is needed to characterise new [FeFe]-hydrogenases as this will reveal further details on the physiology and mechanisms of these enzymes that will enable potential impactful applications.
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Affiliation(s)
- Simone Morra
- Faculty of Engineering, University of Nottingham, Nottingham, United Kingdom
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86
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Luo S, Lin PP, Nieh LY, Liao GB, Tang PW, Chen C, Liao JC. A cell-free self-replenishing CO2-fixing system. Nat Catal 2022. [DOI: 10.1038/s41929-022-00746-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
AbstractBiological CO2 fixation is so far the most effective means for CO2 reduction at scale and accounts for most of the CO2 fixed on Earth. Through this process, carbon is fixed in cellular components and biomass during organismal growth. To uncouple CO2 fixation from growth and cellular regulation, cell-free CO2 fixation systems represent an alternative approach since the rate can be independently manipulated. Here we designed an oxygen-insensitive, self-replenishing CO2 fixation system with opto-sensing. The system comprises a synthetic reductive glyoxylate and pyruvate synthesis (rGPS) cycle and the malyl-CoA-glycerate (MCG) pathway to produce acetyl-coenzyme A (CoA), pyruvate and malate from CO2, which are also intermediates in the cycle. We solved various problems associated with the in vitro system, and implemented opto-sensing modules to control the regeneration of cofactors. We accomplished sustained operation for 6 hours with a CO2-fixing rate comparable to or greater than typical CO2 fixation rates of photosynthetic or lithoautotrophic organisms.
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87
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Deka RK, Deka A, Liu WZ, Norgard MV, Brautigam CA. Inhibition of bacterial FMN transferase: A potential avenue for countering antimicrobial resistance. Protein Sci 2022; 31:545-551. [PMID: 34796555 PMCID: PMC8819833 DOI: 10.1002/pro.4241] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 10/01/2021] [Accepted: 11/15/2021] [Indexed: 02/03/2023]
Abstract
Antibiotic resistance is a challenge for the control of bacterial infections. In an effort to explore unconventional avenues for antibacterial drug development, we focused on the FMN-transferase activity of the enzyme Ftp from the syphilis spirochete, Treponema pallidum (Ftp_Tp). This enzyme, which is only found in prokaryotes and trypanosomatids, post-translationally modifies proteins in the periplasm, covalently linking FMN (from FAD) to proteins that typically are important for establishing an essential electrochemical gradient across the cytoplasmic membrane. As such, Ftp inhibitors potentially represent a new class of antimicrobials. Previously, we showed that AMP is both a product of the Ftp_tp-catalyzed reaction and an inhibitor of the enzyme. As a preliminary step in exploiting this property to develop a novel Ftp_Tp inhibitor, we have used structural and solution studies to examine the inhibitory and enzyme-binding properties of several adenine-based nucleosides, with particular focus on the 2-position of the purine ring. Implications for future drug design are discussed.
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Affiliation(s)
- Ranjit K. Deka
- Department of MicrobiologyUT Southwestern Medical CenterDallasTexasUSA
| | | | - Wei Z. Liu
- Department of MicrobiologyUT Southwestern Medical CenterDallasTexasUSA
| | | | - Chad A. Brautigam
- Department of MicrobiologyUT Southwestern Medical CenterDallasTexasUSA,Department of BiophysicsUT Southwestern Medical CenterDallasTexasUSA
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88
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Tang Y, Sun J, Dong B, Dai X. Thermal Hydrolysis Pretreatment-Anaerobic Digestion Promotes Plant-Growth Biostimulants Production from Sewage Sludge by Upregulating Aromatic Amino Acids Transformation and Quinones Supply. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:1938-1950. [PMID: 35005906 DOI: 10.1021/acs.est.1c06506] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Micromolecular plant-growth biostimulants (micro-PBs) production from sewage sludge is attracting increasing interest, as it is expected to enhance the fertilizing effect of sludge for land application. This study attempted to promote effective micro-PBs production from sewage sludge through thermal hydrolysis pretreatment-anaerobic digestion (THP-AD) and explore the underpinning regulation mechanisms. Results showed that the highest effective micro-PB production in digested sludge was achieved in THP(160 °C)-AD by day 12, with 80.73 mg/kg volatile solid (VS) of phytohormones and 417.75 mg/kg VS of allelochemicals, and these effective micro-PBs all originated from aromatic amino acids (AAAs). The metabolomic and metagenomic results revealed that, as compared with THP(120 °C)-AD and AD without THP, THP(160°C)-AD uniquely upregulated AAAs biosynthesis and consequently improved AAAs metabolism toward effective micro-PBs production. Further exploration of related microbial pathways and metabolites suggested that the upregulated AAAs biosynthesis in THP(160 °C)-AD in the early stage was partially attributed to the enhanced carbohydrate release. More importantly, the results showed that the amount of quinones, which probably facilitate energy generation via acting as electron-transfer mediators, was significantly positively correlated with the abundance of AAAs biosynthesis genes (R2 = 0.93). Hence, the improved initial release and biosynthesis of quinones are critical in enhancing the AAAs biosynthesis in THP(160 °C)-AD. Moreover, the enhanced quinones supply and the consequent active AAAs transformation in THP(160 °C)-AD reinforced the humification process, highly supporting effective micro-PBs stabilization. The important roles of quinones in effective micro-PBs production and stabilization in sludge anaerobic digestion should be considered in technology development for micro-PBs recovery.
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Affiliation(s)
- Yanfei Tang
- State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
| | - Jing Sun
- State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
- Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
| | - Bin Dong
- State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
| | - Xiaohu Dai
- State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
- Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
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89
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Payne N, Kpebe A, Guendon C, Baffert C, Ros J, Lebrun R, Denis Y, Shintu L, Brugna M. The electron-bifurcating FeFe-hydrogenase Hnd is involved in ethanol metabolism in Desulfovibrio fructosovorans grown on pyruvate. Mol Microbiol 2022; 117:907-920. [PMID: 35066935 DOI: 10.1111/mmi.14881] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2021] [Revised: 01/19/2022] [Accepted: 01/19/2022] [Indexed: 11/28/2022]
Abstract
Desulfovibrio fructosovorans, a sulfate-reducing bacterium, possesses six gene clusters encoding six hydrogenases catalyzing the reversible oxidation of H2 into protons and electrons. Among them, Hnd is an electron-bifurcating hydrogenase, coupling the exergonic reduction of NAD+ to the endergonic reduction of a ferredoxin with electrons derived from H2 . It was previously hypothesized that its biological function involves the production of NADPH necessary for biosynthetic purposes. However, it was subsequently demonstrated that Hnd is instead a NAD+ -reducing enzyme, thus its specific function has yet to be established. To understand the physiological role of Hnd in D. fructosovorans, we compared the hnd deletion mutant with the wild-type strain grown on pyruvate. Growth, metabolites production and comsumption, and gene expression were compared under three different growth conditions. Our results indicate that hnd is strongly regulated at the transcriptional level and that its deletion has a drastic effect on the expression of genes for two enzymes, an aldehyde ferredoxin oxidoreductase and an alcohol dehydrogenase. We demonstrated here that Hnd is involved in ethanol metabolism when bacteria grow fermentatively and proposed that Hnd might oxidize part of the H2 produced during fermentation generating both NADH and reduced ferredoxin for ethanol production via its electron bifurcation mechanism.
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Affiliation(s)
| | | | | | | | - Julien Ros
- CNRS, Aix Marseille Univ, BIP, Marseille, France
| | - Régine Lebrun
- CNRS, Aix Marseille Univ, Plate-forme Protéomique de l'IMM, FR 3479, Marseille Protéomique (MaP), Marseille, France
| | - Yann Denis
- CNRS, Aix Marseille Univ, Plate-forme Transcriptomique, Marseille, France
| | - Laetitia Shintu
- CNRS, Aix Marseille Univ, Centrale Marseille, ISM2, Marseille, France
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90
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Pavan M, Reinmets K, Garg S, Mueller AP, Marcellin E, Köpke M, Valgepea K. Advances in systems metabolic engineering of autotrophic carbon oxide-fixing biocatalysts towards a circular economy. Metab Eng 2022; 71:117-141. [DOI: 10.1016/j.ymben.2022.01.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 01/24/2022] [Accepted: 01/25/2022] [Indexed: 12/16/2022]
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91
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Sato R, Amao Y. Carbonic anhydrase/formate dehydrogenase bienzymatic system for CO 2 capture, utilization and storage. REACT CHEM ENG 2022. [DOI: 10.1039/d1re00405k] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
In order to establish carbon capture, utilization, and storage (CCUS) technology, a system consisting of two different biocatalysts (formate dehydrogenase from Candida boidinii; CbFDH and carbonic anhydrase from bovine erythrocytes; CA) is developed.
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Affiliation(s)
- Ryohei Sato
- Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Yutaka Amao
- Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
- Research Centre for Artificial Photosynthesis (ReCAP), Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
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92
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Mostafa A, Im S, Kim J, Lim KH, Kim I, Kim DH. Electron bifurcation reactions in dark fermentation: An overview for better understanding and improvement. BIORESOURCE TECHNOLOGY 2022; 344:126327. [PMID: 34785332 DOI: 10.1016/j.biortech.2021.126327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 11/07/2021] [Accepted: 11/09/2021] [Indexed: 06/13/2023]
Abstract
Electron bifurcation (EB) is the most recently found mode of energy conservation, which involves both exergonic and endergonic electron transfer reactions to minimize energy loss. Several works have been devoted on EB reactions (EBRs) in anaerobic digestion but limited in dark fermentative hydrogen production (DF). Two main electron carriers in DF are ferredoxin (Fd) and reduced nicotinamide adenine dinucleotide (NADH), complicatedly involved in EB. Here, i) the importance of EB involvement in DF, ii) all EBRs possible to present in DF, as well as iii) the limitation of previous studies that tried incorporating any of EBRs in DF metabolic model, were highlighted. In addition, the concept of using metagenomic analysis for estimating the share of each EB reaction in the metabolic model, was proposed. This review is expected to initiate a new wave for studying EB, as a tool for explaining and predicting DF products.
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Affiliation(s)
- Alsayed Mostafa
- Department of Smart-city Engineering, Inha University, 100 Inha-ro, Michuhol-gu, Incheon 22212, Republic of Korea
| | - Seongwon Im
- Department of Smart-city Engineering, Inha University, 100 Inha-ro, Michuhol-gu, Incheon 22212, Republic of Korea
| | - Jimin Kim
- Department of Smart-city Engineering, Inha University, 100 Inha-ro, Michuhol-gu, Incheon 22212, Republic of Korea
| | - Kyeong-Ho Lim
- Department of Civil and Environmental Engineering, Kongju National University, Cheonan, Chungnam 31080, Republic of Korea
| | - Ijung Kim
- Department of Civil and Environmental Engineering, Hongik University, 94 Wausan-ro, Mapo-gu, Seoul 04066, Republic of Korea
| | - Dong-Hoon Kim
- Department of Smart-city Engineering, Inha University, 100 Inha-ro, Michuhol-gu, Incheon 22212, Republic of Korea.
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93
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Mouli MSSV, Mishra AK. Formation of the silver-flavin coordination polymers and their morphological studies. CrystEngComm 2022. [DOI: 10.1039/d2ce00071g] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This Communication describes the formation of 1D-coordination polymeric motifs involving modified flavin analog connected together through intervening silver ions. Rare bidentate coordination mode for model flavin was achieved with silver...
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94
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Jing X, Liu X, Zhang Z, Wang X, Rensing C, Zhou S. Anode respiration-dependent biological nitrogen fixation by Geobacter sulfurreducens. WATER RESEARCH 2022; 208:117860. [PMID: 34798422 DOI: 10.1016/j.watres.2021.117860] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 10/04/2021] [Accepted: 11/08/2021] [Indexed: 06/13/2023]
Abstract
The present nitrogen fixation industry is usually energy-intensive and environmentally detrimental. Therefore, it is appealing to find alternatives. Here, we achieved both a synchronized biological nitrogen fixation and electric energy production by using Geobacter sulfurreducens in a microbial electrochemical system. The results showed that G. sulfurreducens was able to fix nitrogen depending on anode respiration, producing a maximum current density of 0.17 ± 0.015 mA cm-2 and a nitrogen-fixing activity of ca. 0.78 μmol C2H4 mg protein-1 h-1, thereby achieving a net total nitrogen-fixing rate of ca. 5.6 mg L-1 day-1. Specifically, nitrogen fixation did not impair coulombic efficiency. Transcriptomic and metabolic analyses demonstrated that anode respiration provided sufficient energy to drive nitrogen fixation, and in turn nitrogen fixation promoted anode respiration of the cell by increasing acetate catabolism but reducing acetate anabolism. Furthermore, we showed that G. sulfurreducens could be supplied in a bioelectrochemical system for N-deficient wastewater treatment to relieve N-deficiency stress contributing to the formation of an electroactive biofilm, thereby simultaneously achieving nitrogen fixation, current generation and dissoluble organic carbon removal. Our study revealed a synergistic effect between biological nitrogen fixation and current generation by G. sulfurreducens, providing a green nitrogen fixation alternative through shifting the nitrogen fixation field from energy consumption to energy production and having implications for N-deficient wastewater treatment.
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Affiliation(s)
- Xianyue Jing
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, China
| | - Xing Liu
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, China.
| | - Zhishuai Zhang
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, China
| | - Xin Wang
- MOE Key Laboratory of Pollution Processes and Environmental Criteria, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, China
| | - Christopher Rensing
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, China
| | - Shungui Zhou
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, China.
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95
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Yoshikawa T, Makino F, Miyata T, Suzuki Y, Tanaka H, Namba K, Kano K, Sowa K, Kitazumi Y, Shirai O. Multiple electron transfer pathways of tungsten-containing formate dehydrogenase in direct electron transfer-type bioelectrocatalysis. Chem Commun (Camb) 2022; 58:6478-6481. [DOI: 10.1039/d2cc01541b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Tungsten-containing formate dehydrogenase from Methylorubrum extroquens AM1 (FoDH1)—a promising biocatalyst for the interconversion of carbon dioxide/formate and nicotine adenine dinucleotide (NAD+)/NADH redox couples—was investigated from structural biology and bioelectrochemistry. FoDH1...
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96
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Response to substrate limitation by a marine sulfate-reducing bacterium. THE ISME JOURNAL 2022; 16:200-210. [PMID: 34285365 PMCID: PMC8692349 DOI: 10.1038/s41396-021-01061-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 07/04/2021] [Accepted: 07/06/2021] [Indexed: 02/07/2023]
Abstract
Sulfate-reducing microorganisms (SRM) in subsurface sediments live under constant substrate and energy limitation, yet little is known about how they adapt to this mode of life. We combined controlled chemostat cultivation and transcriptomics to examine how the marine sulfate reducer, Desulfobacterium autotrophicum, copes with substrate (sulfate or lactate) limitation. The half-saturation uptake constant (Km) for lactate was 1.2 µM, which is the first value reported for a marine SRM, while the Km for sulfate was 3 µM. The measured residual lactate concentration in our experiments matched values observed in situ in marine sediments, supporting a key role of SRM in the control of lactate concentrations. Lactate limitation resulted in complete lactate oxidation via the Wood-Ljungdahl pathway and differential overexpression of genes involved in uptake and metabolism of amino acids as an alternative carbon source. D. autotrophicum switched to incomplete lactate oxidation, rerouting carbon metabolism in response to sulfate limitation. The estimated free energy was significantly lower during sulfate limitation (-28 to -33 kJ mol-1 sulfate), suggesting that the observed metabolic switch is under thermodynamic control. Furthermore, we detected the upregulation of putative sulfate transporters involved in either high or low affinity uptake in response to low or high sulfate concentration.
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97
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Yurgel SN, Qu Y, Rice JT, Ajeethan N, Zink EM, Brown JM, Purvine S, Lipton MS, Kahn ML. Specialization in a Nitrogen-Fixing Symbiosis: Proteome Differences Between Sinorhizobium medicae Bacteria and Bacteroids. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2021; 34:1409-1422. [PMID: 34402628 DOI: 10.1094/mpmi-07-21-0180-r] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Using tandem mass spectrometry (MS/MS), we analyzed the proteome of Sinorhizobium medicae WSM419 growing as free-living cells and in symbiosis with Medicago truncatula. In all, 3,215 proteins were identified, over half of the open reading frames predicted from the genomic sequence. The abundance of 1,361 proteins displayed strong lifestyle bias. In total, 1,131 proteins had similar levels in bacteroids and free-living cells, and the low levels of 723 proteins prevented statistically significant assignments. Nitrogenase subunits comprised approximately 12% of quantified bacteroid proteins. Other major bacteroid proteins included symbiosis-specific cytochromes and FixABCX, which transfer electrons to nitrogenase. Bacteroids had normal levels of proteins involved in amino acid biosynthesis, glycolysis or gluconeogenesis, and the pentose phosphate pathway; however, several amino acid degradation pathways were repressed. This suggests that bacteroids maintain a relatively independent anabolic metabolism. Tricarboxylic acid cycle proteins were highly expressed in bacteroids and no other catabolic pathway emerged as an obvious candidate to supply energy and reductant to nitrogen fixation. Bacterial stress response proteins were induced in bacteroids. Many WSM419 proteins that are not encoded in S. meliloti Rm1021 were detected, and understanding the functions of these proteins might clarify why S. medicae WSM419 forms a more effective symbiosis with M. truncatula than S. meliloti Rm1021.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
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Affiliation(s)
- Svetlana N Yurgel
- Department of Plant, Food and Environmental Sciences, Faculty of Agriculture, Dalhousie University, P.O. Box 550, Truro, Nova Scotia, B2N 5E3, Canada
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, U.S.A
| | - Yi Qu
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, U.S.A
| | - Jennifer T Rice
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, U.S.A
| | - Nivethika Ajeethan
- Department of Plant, Food and Environmental Sciences, Faculty of Agriculture, Dalhousie University, P.O. Box 550, Truro, Nova Scotia, B2N 5E3, Canada
- Faculty of Technology, University of Jaffna, Sri Lanka
| | - Erika M Zink
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, U.S.A
| | - Joseph M Brown
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, U.S.A
| | - Sam Purvine
- Environmental Molecular Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, U.S.A
| | - Mary S Lipton
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, U.S.A
| | - Michael L Kahn
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, U.S.A
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164-6340, U.S.A
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98
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Balch WE, Ferry JG. The Wolfe cycle of carbon dioxide reduction to methane revisited and the Ralph Stoner Wolfe legacy at 100 years. Adv Microb Physiol 2021; 79:1-23. [PMID: 34836609 DOI: 10.1016/bs.ampbs.2021.07.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Methanogens are a component of anaerobic microbial consortia decomposing biomass to CO2 and CH4 that is an essential link in the global carbon cycle. One of two major pathways of methanogenesis involves reduction of the methyl group of acetate to CH4 with electrons from oxidation of the carbonyl group while the other involves reduction of CO2 to CH4 with electrons from H2 or formate. Pioneering investigations of the CO2 reduction pathway by Ralph S. Wolfe in the 70s and 80s contributed findings impacting the broader fields of biochemistry and microbiology that directed discovery of the domain Archaea and expanded research on anaerobic microbes for decades that continues to the present. This review presents an historical overview of the CO2 reduction pathway (Wolfe cycle) with recent developments, and an account of Wolfe's larger and enduring impact on the broad field of biology 100 years after his birth.
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Affiliation(s)
- William E Balch
- Department of Molecular Medicine, Scripps Research, La Jolla, CA, United States
| | - James G Ferry
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA, United States.
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99
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Qin Z, Yu S, Chen J, Zhou J. Dehydrogenases of acetic acid bacteria. Biotechnol Adv 2021; 54:107863. [PMID: 34793881 DOI: 10.1016/j.biotechadv.2021.107863] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 10/26/2021] [Accepted: 10/26/2021] [Indexed: 12/13/2022]
Abstract
Acetic acid bacteria (AAB) are a group of bacteria that can oxidize many substrates such as alcohols and sugar alcohols and play important roles in industrial biotechnology. A majority of industrial processes that involve AAB are related to their dehydrogenases, including PQQ/FAD-dependent membrane-bound dehydrogenases and NAD(P)+-dependent cytoplasmic dehydrogenases. These cofactor-dependent dehydrogenases must effectively regenerate their cofactors in order to function continuously. For PQQ, FAD and NAD(P)+ alike, regeneration is directly or indirectly related to the electron transport chain (ETC) of AAB, which plays an important role in energy generation for aerobic cell growth. Furthermore, in changeable natural habitats, ETC components of AAB can be regulated so that the bacteria survive in different environments. Herein, the progressive cascade in an application of AAB, including key dehydrogenases involved in the application, regeneration of dehydrogenase cofactors, ETC coupling with cofactor regeneration and ETC regulation, is systematically reviewed and discussed. As they have great application value, a deep understanding of the mechanisms through which AAB function will not only promote their utilization and development but also provide a reference for engineering of other industrial strains.
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Affiliation(s)
- Zhijie Qin
- School of Biotechnology and Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; Jiangsu Provisional Research Center for Bioactive Product Processing Technology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China
| | - Shiqin Yu
- School of Biotechnology and Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China
| | - Jian Chen
- School of Biotechnology and Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; Science Center for Future Foods, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; Jiangsu Provisional Research Center for Bioactive Product Processing Technology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China
| | - Jingwen Zhou
- School of Biotechnology and Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; National Engineering Laboratory for Cereal Fermentation Technology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China; Jiangsu Provisional Research Center for Bioactive Product Processing Technology, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, China.
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100
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Yi J, Huang H, Liang J, Wang R, Liu Z, Li F, Wang S. A Heterodimeric Reduced-Ferredoxin-Dependent Methylenetetrahydrofolate Reductase from Syngas-Fermenting Clostridium ljungdahlii. Microbiol Spectr 2021; 9:e0095821. [PMID: 34643446 PMCID: PMC8515935 DOI: 10.1128/spectrum.00958-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2021] [Accepted: 08/31/2021] [Indexed: 11/20/2022] Open
Abstract
The strict anaerobe Clostridium ljungdahlii can ferment CO or H2/CO2 via the Wood-Ljungdahl pathway to acetate, ethanol, and 2,3-butanediol. This ability has attracted considerable interest, since it can be used for syngas fermentation to produce biofuels and biochemicals. However, the key enzyme methylenetetrahydrofolate reductase (MTHFR) in the Wood-Ljungdahl pathway of the strain has not been characterized, and its physiological electron donor is unclear. In this study, we purified the enzyme 46-fold with a benzyl viologen reduction activity of 41.2 U/mg from C. ljungdahlii cells grown on CO. It is composed of two subunits, MetF (31.5 kDa) and MetV (23.5 kDa), and has an apparent molecular mass of 62.2 kDa. The brownish yellow protein contains 0.73 flavin mononucleotide (FMN) and 7.4 Fe, in agreement with the prediction that MetF binds one flavin and MetV binds two [4Fe4S] clusters. It cannot use NAD(P)H as its electron donor or catalyze an electron-bifurcating reaction in combination with ferredoxin as an electron acceptor. The reduced recombinant ferredoxin, flavodoxin, and thioredoxin of C. ljungdahlii can serve as electron donors with specific activities of 91.2, 22.1, and 7.4 U/mg, respectively. The apparent Km values for reduced ferredoxin and flavodoxin were around 1.46 μM and 0.73 μM, respectively. Subunit composition and phylogenetic analysis showed that the enzyme from C. ljungdahlii belongs to MetFV-type MTHFR, which is a heterodimer, and uses reduced ferredoxin as its electron donor. Based on these results, we discuss the energy metabolism of C. ljungdahlii when it grows on CO or H2 plus CO2. IMPORTANCE Syngas, a mixture of CO, CO2, and H2, is the main component of steel mill waste gas and also can be generated by the gasification of biomass and urban domestic waste. Its fermentation to biofuels and biocommodities has attracted attention due to the economic and environmental benefits of this process. Clostridium ljungdahlii is one of the superior acetogens used in the technology. However, the biochemical mechanism of its gas fermentation via the Wood-Ljungdahl pathway is not completely clear. In this study, the key enzyme, methylenetetrahydrofolate reductase (MTHFR), was characterized and found to be a non-electron-bifurcating heterodimer with reduced ferredoxin as its electron donor, representing another example of MetFV-type MTHFR. The findings will form the basis for a deeper understanding of the energy metabolism of syngas fermentation by C. ljungdahlii, which is valuable for developing metabolic engineering strains and efficient syngas fermentation technologies.
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Affiliation(s)
- Jihong Yi
- State Key Laboratory of Microbial Technology, Microbial Technology Institute, Shandong University, Qingdao, People’s Republic of China
| | - Haiyan Huang
- School of Basic Medicine, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, People’s Republic of China
| | - Jiyu Liang
- State Key Laboratory of Microbial Technology, Microbial Technology Institute, Shandong University, Qingdao, People’s Republic of China
| | - Rufei Wang
- State Key Laboratory of Microbial Technology, Microbial Technology Institute, Shandong University, Qingdao, People’s Republic of China
| | - Ziyong Liu
- Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, People’s Republic of China
| | - Fuli Li
- Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, People’s Republic of China
| | - Shuning Wang
- State Key Laboratory of Microbial Technology, Microbial Technology Institute, Shandong University, Qingdao, People’s Republic of China
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