1
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Energy conservation under extreme energy limitation: the role of cytochromes and quinones in acetogenic bacteria. Extremophiles 2021; 25:413-424. [PMID: 34480656 PMCID: PMC8578096 DOI: 10.1007/s00792-021-01241-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Accepted: 08/26/2021] [Indexed: 11/10/2022]
Abstract
Acetogenic bacteria are a polyphyletic group of organisms that fix carbon dioxide under anaerobic, non-phototrophic conditions by reduction of two mol of CO2 to acetyl-CoA via the Wood–Ljungdahl pathway. This pathway also allows for lithotrophic growth with H2 as electron donor and this pathway is considered to be one of the oldest, if not the oldest metabolic pathway on Earth for CO2 reduction, since it is coupled to the synthesis of ATP. How ATP is synthesized has been an enigma for decades, but in the last decade two ferredoxin-dependent respiratory chains were discovered. Those respiratory chains comprise of a cytochrome-free, ferredoxin-dependent respiratory enzyme complex, which is either the Rnf or Ech complex. However, it was discovered already 50 years ago that some acetogens contain cytochromes and quinones, but their role had only a shadowy existence. Here, we review the literature on the characterization of cytochromes and quinones in acetogens and present a hypothesis that they may function in electron transport chains in addition to Rnf and Ech.
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2
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Lemaire ON, Wagner T. Gas channel rerouting in a primordial enzyme: Structural insights of the carbon-monoxide dehydrogenase/acetyl-CoA synthase complex from the acetogen Clostridium autoethanogenum. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2020; 1862:148330. [PMID: 33080205 DOI: 10.1016/j.bbabio.2020.148330] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 10/01/2020] [Accepted: 10/15/2020] [Indexed: 10/23/2022]
Abstract
Clostridium autoethanogenum, the bacterial model for biological conversion of waste gases into biofuels, grows under extreme carbon-monoxide (CO) concentrations. The strictly anaerobic bacterium derives its entire cellular energy and carbon from this poisonous gas, therefore requiring efficient molecular machineries for CO-conversion. Here, we structurally and biochemically characterized the key enzyme of the CO-converting metabolism: the CO-dehydrogenase/Acetyl-CoA synthase (CODH/ACS). We obtained crystal structures of natively isolated complexes from fructose-grown and CO-grown C. autoethanogenum cultures. Both contain the same isoforms and if the overall structure adopts the classic α2β2 architecture, comparable to the model enzyme from Moorella thermoacetica, the ACS binds a different position on the CODH core. The structural characterization of a proteolyzed complex and the conservation of the binding interface in close homologs rejected the possibility of a crystallization artefact. Therefore, the internal CO-channeling system, critical to transfer CO generated at the C-cluster to the ACS active site, drastically differs in the complex from C. autoethanogenum. The 1.9-Å structure of the CODH alone provides an accurate picture of the new CO-routes, leading to the ACS core and reaching the surface. Increased gas accessibility would allow the simultaneous CO-oxidation and acetyl-CoA production. Biochemical experiments showed higher flexibility of the ACS subunit from C. autoethanogenum compared to M. thermoacetica, albeit monitoring similar CO-oxidation and formation rates. These results show a reshuffling of internal CO-tunnels during evolution of these Firmicutes, putatively leading to a bidirectional complex that ensure a high flux of CO-conversion toward energy conservation, acting as the main cellular powerplant.
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Affiliation(s)
- Olivier N Lemaire
- Max Planck Institute for Marine Microbiology, Celsiusstraße 1, 28359 Bremen, Germany
| | - Tristan Wagner
- Max Planck Institute for Marine Microbiology, Celsiusstraße 1, 28359 Bremen, Germany.
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3
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Cohen SE, Can M, Wittenborn EC, Hendrickson RA, Ragsdale SW, Drennan CL. Crystallographic Characterization of the Carbonylated A-Cluster in Carbon Monoxide Dehydrogenase/Acetyl-CoA Synthase. ACS Catal 2020; 10:9741-9746. [PMID: 33495716 PMCID: PMC7819276 DOI: 10.1021/acscatal.0c03033] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 08/10/2020] [Indexed: 12/30/2022]
Abstract
![]()
The
Wood–Ljungdahl pathway allows for autotrophic bacterial
growth on carbon dioxide, with the last step in acetyl-CoA synthesis
catalyzed by the bifunctional enzyme carbon monoxide dehydrogenase/acetyl-CoA
synthase (CODH/ACS). ACS uses a complex Ni–Fe–S metallocluster
termed the A-cluster to assemble acetyl-CoA from carbon monoxide,
a methyl moiety and coenzyme A. Here, we report the crystal structure
of CODH/ACS from Moorella thermoacetica with substrate
carbon monoxide bound at the A-cluster, a state previously uncharacterized
by crystallography. Direct structural characterization of this state
highlights the role of second sphere residues and conformational dynamics
in acetyl-CoA assembly, the biological equivalent of the Monsanto
process.
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Affiliation(s)
- Steven E. Cohen
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Mehmet Can
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 04109, United States
| | - Elizabeth C. Wittenborn
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Rachel A. Hendrickson
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Stephen W. Ragsdale
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 04109, United States
| | - Catherine L. Drennan
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
- Howard Hughes Medical Institute, Cambridge, Massachusetts 02139, United States
- Bio-inspired Solar Energy Program, Canadian Institute for Advanced Research, Toronto, ON M5G 1M1, Canada
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4
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Burton R, Can M, Esckilsen D, Wiley S, Ragsdale SW. Production and properties of enzymes that activate and produce carbon monoxide. Methods Enzymol 2018; 613:297-324. [PMID: 30509471 PMCID: PMC6309614 DOI: 10.1016/bs.mie.2018.10.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The chapter focuses on the methods involved in producing and characterizing two key nickel-iron-sulfur enzymes in the Wood-Ljungdahl pathway (WLP) of anaerobic conversion of carbon dioxide fixation into acetyl-CoA: carbon monoxide dehydrogenase (CODH) and acetyl-CoA synthase (ACS). The WLP is used for biosynthesis of cell material and energy conservation by anaerobic bacteria and archaea, and it is central to several industrial biotechnology processes aimed at using syngas and waste gases for the production of fuels and chemicals. The pathway can run in reverse to allow organisms, e. g., methanogens and sulfate reducers, to grow on acetate. The CODH and ACS intertwine to form a tenacious CODH/ACS complex that converts CO2, a methyl group, and coenzyme A into acetyl-CoA. CODH also behaves as a modular unit that can function as an independent homodimer. Besides coupling to ACS, CODH can interact with hydrogenases to couple CO oxidation to H2 formation. These enzymes have been purified and characterized from several microbes.
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Affiliation(s)
- Rodney Burton
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Mehmet Can
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Daniel Esckilsen
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Seth Wiley
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Stephen W Ragsdale
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI, United States.
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5
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Thakur IS, Kumar M, Varjani SJ, Wu Y, Gnansounou E, Ravindran S. Sequestration and utilization of carbon dioxide by chemical and biological methods for biofuels and biomaterials by chemoautotrophs: Opportunities and challenges. BIORESOURCE TECHNOLOGY 2018; 256:478-490. [PMID: 29459105 DOI: 10.1016/j.biortech.2018.02.039] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 02/06/2018] [Accepted: 02/07/2018] [Indexed: 06/08/2023]
Abstract
To meet the CO2 emission reduction targets, carbon dioxide capture and utilization (CCU) comes as an evolve technology. CCU concept is turning into a feedstock and technologies have been developed for transformation of CO2 into useful organic products. At industrial scale, utilization of CO2 as raw material is not much significant as compare to its abundance. Mechanisms in nature have evolved for carbon concentration, fixation and utilization. Assimilation and subsequent conversion of CO2 into complex molecules are performed by the photosynthetic and chemolithotrophic organisms. In the last three decades, substantial research is carry out to discover chemical and biological conversion of CO2 in various synthetic and biological materials, such as carboxylic acids, esters, lactones, polymer biodiesel, bio-plastics, bio-alcohols, exopolysaccharides. This review presents an over view of catalytic transformation of CO2 into biofuels and biomaterials by chemical and biological methods.
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Affiliation(s)
- Indu Shekhar Thakur
- School of Environmental Sciences, JawaharNehru University, New Delhi 110067, India; Bioenergy and Energy Planning Research Group (BPE), IIC, ENAC, Station 18, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
| | - Manish Kumar
- School of Environmental Sciences, JawaharNehru University, New Delhi 110067, India
| | - Sunita J Varjani
- Gujarat Pollution Control Board, Sector-10A, Gandhinagar 382010, Gujarat, India; Bioenergy and Energy Planning Research Group (BPE), IIC, ENAC, Station 18, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Yonghong Wu
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, 71 East Beijing Road, Nanjing 210008, China.
| | - Edgard Gnansounou
- Bioenergy and Energy Planning Research Group (BPE), IIC, ENAC, Station 18, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
| | - Sindhu Ravindran
- Microbial Processes and Technology Division, CSIR-NIIST, Trivandrum, India
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Kumar M, Sundaram S, Gnansounou E, Larroche C, Thakur IS. Carbon dioxide capture, storage and production of biofuel and biomaterials by bacteria: A review. BIORESOURCE TECHNOLOGY 2018; 247:1059-1068. [PMID: 28951132 DOI: 10.1016/j.biortech.2017.09.050] [Citation(s) in RCA: 78] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2017] [Revised: 09/05/2017] [Accepted: 09/06/2017] [Indexed: 06/07/2023]
Abstract
Due to industrialization and urbanization, as humans continue to rely on fossil fuels, carbon dioxide (CO2) will inevitably be generated and result in an increase of Global Warming Gases (GWGs). However, their prospect is misted up because of the environmental and economic intimidation posed by probable climate shift, generally called it as the "green house effect". Among all GWGs, the major contributor in greenhouse effect is CO2. Mitigation strategies that include capture and storage of CO2 by biological means may reduce the impact of CO2 emissions on environment. The biological CO2 sequestration has significant advantage, since increasing atmospheric CO2 level supports productivity and overall storage capacity of the natural system. This paper reviews CO2 sequestration mechanism in bacteria and their pathways for production of value added products such as, biodiesel, bioplastics, extracellular polymeric substance (EPS), biosurfactants and other related biomaterials.
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Affiliation(s)
- Manish Kumar
- School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110 067, India
| | - Smita Sundaram
- Advanced Instrument Research Facility, Jawaharlal Nehru University, New Delhi 110 067, India
| | - Edgard Gnansounou
- Swiss Federal Institute of Technology Lausanne (EPFL), Lausanne, Switzerland
| | | | - Indu Shekhar Thakur
- School of Environmental Sciences, Jawaharlal Nehru University, New Delhi 110 067, India.
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7
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Abstract
Early parental influence led me first to medical school, but after developing a passion for biochemistry and sensing the need for a deeper foundation, I changed to chemistry. During breaks between semesters, I worked in various biochemistry labs to acquire a feeling for the different areas of investigation. The scientific puzzle that fascinated me most was the metabolism of the anaerobic bacterium Clostridium kluyveri, which I took on in 1965 in Karl Decker's lab in Freiburg, Germany. I quickly realized that little was known about the biochemistry of strict anaerobes such as clostridia, methanogens, acetogens, and sulfate-reducing bacteria and that these were ideal model organisms to study fundamental questions of energy conservation, CO2 fixation, and the evolution of metabolic pathways. My passion for anaerobes was born then and is unabated even after 50 years of study.
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Affiliation(s)
- Rudolf Kurt Thauer
- Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany;
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8
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Metabolic response of Clostridium ljungdahlii to oxygen exposure. Appl Environ Microbiol 2015; 81:8379-91. [PMID: 26431975 DOI: 10.1128/aem.02491-15] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Accepted: 09/23/2015] [Indexed: 12/31/2022] Open
Abstract
Clostridium ljungdahlii is an important synthesis gas-fermenting bacterium used in the biofuels industry, and a preliminary investigation showed that it has some tolerance to oxygen when cultured in rich mixotrophic medium. Batch cultures not only continue to grow and consume H2, CO, and fructose after 8% O2 exposure, but fermentation product analysis revealed an increase in ethanol concentration and decreased acetate concentration compared to non-oxygen-exposed cultures. In this study, the mechanisms for higher ethanol production and oxygen/reactive oxygen species (ROS) detoxification were identified using a combination of fermentation, transcriptome sequencing (RNA-seq) differential expression, and enzyme activity analyses. The results indicate that the higher ethanol and lower acetate concentrations were due to the carboxylic acid reductase activity of a more highly expressed predicted aldehyde oxidoreductase (CLJU_c24130) and that C. ljungdahlii's primary defense upon oxygen exposure is a predicted rubrerythrin (CLJU_c39340). The metabolic responses of higher ethanol production and oxygen/ROS detoxification were found to be linked by cofactor management and substrate and energy metabolism. This study contributes new insights into the physiology and metabolism of C. ljungdahlii and provides new genetic targets to generate C. ljungdahlii strains that produce more ethanol and are more tolerant to syngas contaminants.
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9
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Visser M, Worm P, Muyzer G, Pereira IAC, Schaap PJ, Plugge CM, Kuever J, Parshina SN, Nazina TN, Ivanova AE, Bernier-Latmani R, Goodwin LA, Kyrpides NC, Woyke T, Chain P, Davenport KW, Spring S, Klenk HP, Stams AJM. Genome analysis of Desulfotomaculum kuznetsovii strain 17(T) reveals a physiological similarity with Pelotomaculum thermopropionicum strain SI(T). Stand Genomic Sci 2013; 8:69-87. [PMID: 23961313 PMCID: PMC3739171 DOI: 10.4056/sigs.3627141] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Desulfotomaculum kuznetsovii is a moderately thermophilic member of the polyphyletic spore-forming genus Desulfotomaculum in the family Peptococcaceae. This species is of interest because it originates from deep subsurface thermal mineral water at a depth of about 3,000 m. D. kuznetsovii is a rather versatile bacterium as it can grow with a large variety of organic substrates, including short-chain and long-chain fatty acids, which are degraded completely to carbon dioxide coupled to the reduction of sulfate. It can grow methylotrophically with methanol and sulfate and autotrophically with H2 + CO2 and sulfate. For growth it does not require any vitamins. Here, we describe the features of D. kuznetsovii together with the genome sequence and annotation. The chromosome has 3,601,386 bp organized in one contig. A total of 3,567 candidate protein-encoding genes and 58 RNA genes were identified. Genes of the acetyl-CoA pathway, possibly involved in heterotrophic growth with acetate and methanol, and in CO2 fixation during autotrophic growth are present. Genomic comparison revealed that D. kuznetsovii shows a high similarity with Pelotomaculum thermopropionicum. Genes involved in propionate metabolism of these two strains show a strong similarity. However, main differences are found in genes involved in the electron acceptor metabolism.
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Affiliation(s)
- Michael Visser
- Wageningen University, Laboratory of Microbiology, Wageningen, the Netherlands
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10
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Saini R, Kapoor R, Kumar R, Siddiqi TO, Kumar A. CO2 utilizing microbes — A comprehensive review. Biotechnol Adv 2011; 29:949-60. [PMID: 21856405 DOI: 10.1016/j.biotechadv.2011.08.009] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2010] [Revised: 08/04/2011] [Accepted: 08/05/2011] [Indexed: 11/30/2022]
Affiliation(s)
- Rashmi Saini
- Department of Botany, North Campus, University of Delhi, New Delhi-110007, India
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11
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Martin DR, Misra A, Drake HL. Dissimilation of Carbon Monoxide to Acetic Acid by Glucose-Limited Cultures of Clostridium thermoaceticum. Appl Environ Microbiol 2010; 49:1412-7. [PMID: 16346807 PMCID: PMC241739 DOI: 10.1128/aem.49.6.1412-1417.1985] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Clostridium thermoaceticum was cultivated in glucose-limited media, and the dissimilation of CO to acetic acid was evaluated. We found that cultures catalyzed the rapid dissimilation of CO to acetic acid and CO(2), with the stoichiometry obtained for conversion approximating that predicted from the following reaction: 4CO + 2H(2)O --> CH(3)CO(2)H + 2CO(2). Growing cultures formed approximately 50 mmol (3 g) of CO-derived acetic acid per liter of culture, with the rate of maximal consumption approximating 9.1 mmol of CO consumed/h per liter of culture. In contrast, resting cells were found not to dissimilate CO to acetic acid. CO was incorporated, with equal distribution between the carboxyl and methyl carbons of acetic acid when the initial cultivation gas phase was 100% CO, whereas CO(2) preferentially entered the carboxyl carbon when the initial gas phase was 100% CO(2). Significantly, in the presence of saturating levels of CO, CO(2) preferentially entered the methyl carbon, whereas saturating levels of CO(2) yielded CO-derived labeling predominantly in the carboxyl carbon. These findings are discussed in relation to the path of carbon flow to acetic acid.
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Affiliation(s)
- D R Martin
- Microbial Physiology Laboratories, Department of Biology, The University of Mississippi, University, Mississippi 38677
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12
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13
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Ragsdale SW, Pierce E. Acetogenesis and the Wood-Ljungdahl pathway of CO(2) fixation. BIOCHIMICA ET BIOPHYSICA ACTA 2008; 1784:1873-98. [PMID: 18801467 PMCID: PMC2646786 DOI: 10.1016/j.bbapap.2008.08.012] [Citation(s) in RCA: 680] [Impact Index Per Article: 42.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2008] [Revised: 08/12/2008] [Accepted: 08/13/2008] [Indexed: 01/04/2023]
Abstract
Conceptually, the simplest way to synthesize an organic molecule is to construct it one carbon at a time. The Wood-Ljungdahl pathway of CO(2) fixation involves this type of stepwise process. The biochemical events that underlie the condensation of two one-carbon units to form the two-carbon compound, acetate, have intrigued chemists, biochemists, and microbiologists for many decades. We begin this review with a description of the biology of acetogenesis. Then, we provide a short history of the important discoveries that have led to the identification of the key components and steps of this usual mechanism of CO and CO(2) fixation. In this historical perspective, we have included reflections that hopefully will sketch the landscape of the controversies, hypotheses, and opinions that led to the key experiments and discoveries. We then describe the properties of the genes and enzymes involved in the pathway and conclude with a section describing some major questions that remain unanswered.
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Affiliation(s)
- Stephen W Ragsdale
- Department of Biological Chemistry, MSRB III, 5301, 1150 W. Medical Center Drive, University of Michigan, Ann Arbor, MI 48109-0606, USA.
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14
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Abstract
Acetogens utilize the acetyl-CoA Wood-Ljungdahl pathway as a terminal electron-accepting, energy-conserving, CO(2)-fixing process. The decades of research to resolve the enzymology of this pathway (1) preceded studies demonstrating that acetogens not only harbor a novel CO(2)-fixing pathway, but are also ecologically important, and (2) overshadowed the novel microbiological discoveries of acetogens and acetogenesis. The first acetogen to be isolated, Clostridium aceticum, was reported by Klaas Tammo Wieringa in 1936, but was subsequently lost. The second acetogen to be isolated, Clostridium thermoaceticum, was isolated by Francis Ephraim Fontaine and co-workers in 1942. C. thermoaceticum became the most extensively studied acetogen and was used to resolve the enzymology of the acetyl-CoA pathway in the laboratories of Harland Goff Wood and Lars Gerhard Ljungdahl. Although acetogenesis initially intrigued few scientists, this novel process fostered several scientific milestones, including the first (14)C-tracer studies in biology and the discovery that tungsten is a biologically active metal. The acetyl-CoA pathway is now recognized as a fundamental component of the global carbon cycle and essential to the metabolic potentials of many different prokaryotes. The acetyl-CoA pathway and variants thereof appear to be important to primary production in certain habitats and may have been the first autotrophic process on earth and important to the evolution of life. The purpose of this article is to (1) pay tribute to those who discovered acetogens and acetogenesis, and to those who resolved the acetyl-CoA pathway, and (2) highlight the ecology and physiology of acetogens within the framework of their scientific roots.
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Affiliation(s)
- Harold L Drake
- Department of Ecological Microbiology, University of Bayreuth, 95440 Bayreuth, Germany.
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15
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Oelgeschläger E, Rother M. Carbon monoxide-dependent energy metabolism in anaerobic bacteria and archaea. Arch Microbiol 2008; 190:257-69. [PMID: 18575848 DOI: 10.1007/s00203-008-0382-6] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2008] [Revised: 04/21/2008] [Accepted: 04/29/2008] [Indexed: 12/26/2022]
Abstract
Despite its toxicity for the majority of living matter on our planet, numerous microorganisms, both aerobic and anaerobic, can use carbon monoxide (CO) as a source of carbon and/or energy for growth. The capacity to employ carboxidotrophic energy metabolism anaerobically is found in phylogenetically diverse members of the Bacteria and the Archaea. The oxidation of CO is coupled to numerous respiratory processes, such as desulfurication, hydrogenogenesis, acetogenesis, and methanogenesis. Although as diverse as the organisms capable of it, any CO-dependent energy metabolism known depends on the presence of carbon monoxide dehydrogenase. This review summarizes recent insights into the CO-dependent physiology of anaerobic microorganisms with a focus on methanogenic archaea. Carboxidotrophic growth of Methanosarcina acetivorans, thought to strictly rely on the process of methanogenesis, also involves formation of methylated thiols, formate, and even acetogenesis, and, thus, exemplifies how the beneficial redox properties of CO can be exploited in unexpected ways by anaerobic microorganisms.
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Affiliation(s)
- Ellen Oelgeschläger
- Institut für Molekulare Biowissenschaften, Abteilung Molekulare Mikrobiologie und Bioenergetik, Johann Wolfgang Goethe-Universität, Max-von-Laue-Str. 9, 60438 Frankfurt am Main, Germany
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16
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Abstract
This review focuses on how microbes live on CO as a sole source of carbon and energy and with CO by generating carbon monoxide as a metabolic intermediate. The use of CO is a property of organisms that use the Wood-L jungdahl pathway of autotrophic growth. The review discusses when CO metabolism originated, when and how it was discovered, and what properties of CO are ideal for microbial growth. How CO sensing by a heme-containing transcriptional regulatory protein activates the expression of CO metabolism-linked genes is described. Two metalloenzymes are the cornerstones of growth with CO: CO dehydrogenase (CODH) and acetyl-CoA synthase (ACS). CODH oxidizes CO to CO2, providing low-potential electrons for the cell, or alternatively reduces CO2 to CO. The latter reaction, when coupled to ACS, forms a machine for generating acetyl-CoA from CO2 for cell carbon synthesis. The recently solved crystal structures of CODH and ACS along with spectroscopic measurements and computational studies provide insights into novel bio-organometallic catalytic mechanisms and into the nature of a 140 A gas channel that coordinates the generation and utilization of CO. The enzymes that are coupled to CODH/ACS are also described, with a focus on a corrinoid protein, a methyltransferase, and pyruvate ferredoxin oxidoreductase.
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Affiliation(s)
- Stephen W Ragsdale
- Department of Biochemistry, Beadle Center, University of Nebraska, Lincoln, NE 68588-0664, USA.
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17
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18
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Doukov TI, Iverson TM, Seravalli J, Ragsdale SW, Drennan CL. A Ni-Fe-Cu center in a bifunctional carbon monoxide dehydrogenase/acetyl-CoA synthase. Science 2002; 298:567-72. [PMID: 12386327 DOI: 10.1126/science.1075843] [Citation(s) in RCA: 385] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
A metallocofactor containing iron, sulfur, copper, and nickel has been discovered in the enzyme carbon monoxide dehydrogenase/acetyl-CoA (coenzyme A) synthase from Moorella thermoacetica (f. Clostridium thermoaceticum). Our structure at 2.2 angstrom resolution reveals that the cofactor responsible for the assembly of acetyl-CoA contains a [Fe4S4] cubane bridged to a copper-nickel binuclear site. The presence of these three metals together in one cluster was unanticipated and suggests a newly discovered role for copper in biology. The different active sites of this bifunctional enzyme complex are connected via a channel, 138 angstroms long, that provides a conduit for carbon monoxide generated at the C-cluster on one subunit to be incorporated into acetyl-CoA at the A-cluster on the other subunit.
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Affiliation(s)
- Tzanko I Doukov
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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19
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20
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Affiliation(s)
- S W Ragsdale
- Department of Biochemistry, Beadle Center, University of Nebraska, Lincoln 68588-0622, USA.
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21
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Affiliation(s)
- F C Wedler
- Department of Molecular and Cell Biology, Althause Laboratory, Pennsylvania State University, University Park 16802, USA
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22
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Roberts JR, Lu WP, Ragsdale SW. Acetyl-coenzyme A synthesis from methyltetrahydrofolate, CO, and coenzyme A by enzymes purified from Clostridium thermoaceticum: attainment of in vivo rates and identification of rate-limiting steps. J Bacteriol 1992; 174:4667-76. [PMID: 1624454 PMCID: PMC206262 DOI: 10.1128/jb.174.14.4667-4676.1992] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Many anaerobic bacteria fix CO2 via the acetyl-coenzyme A (CoA) (Wood) pathway. Carbon monoxide dehydrogenase (CODH), a corrinoid/iron-sulfur protein (C/Fe-SP), methyltransferase (MeTr), and an electron transfer protein such as ferredoxin II play pivotal roles in the conversion of methyltetrahydrofolate (CH3-H4folate), CO, and CoA to acetyl-CoA. In the study reported here, our goals were (i) to optimize the method for determining the activity of the synthesis of acetyl-CoA, (ii) to evaluate how closely the rate of synthesis of acetyl-CoA by purified enzymes approaches the rate at which whole cells synthesize acetate, and (iii) to determine which steps limit the rate of acetyl-CoA synthesis. In this study, CODH, MeTr, C/Fe-SP, and ferredoxin were purified from Clostridium thermoaceticum to apparent homogeneity. We optimized conditions for studying the synthesis of acetyl-CoA and found that when the reaction is dependent upon MeTr, the rate is 5.3 mumol min-1 mg-1 of MeTr. This rate is approximately 10-fold higher than that reported previously and is as fast as that predicted on the basis of the rate of in vivo acetate synthesis. When the reaction is dependent upon CODH, the rate of acetyl-CoA synthesis is approximately 0.82 mumol min-1 mg-1, approximately 10-fold higher than that observed previously; however, it is still lower than the rate of in vivo acetate synthesis. It appears that at least two steps in the overall synthesis of acetyl-CoA from CH3-H4folate, CO, and CoA can be partially rate limiting. At optimal conditions of low pH (approximately 5.8) and low ionic strength, the rate-limiting step involves methylation of CODH by the methylated C/Fe-SP. At higher pH values and/or higher ionic strength, transfer of the methyl group of CH3-H4folate to the C/Fe-SP becomes rate limiting.
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Affiliation(s)
- J R Roberts
- Department of Chemistry, University of Wisconsin, Milwaukee 53201
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Gorst C, Ragsdale S. Characterization of the NiFeCO complex of carbon monoxide dehydrogenase as a catalytically competent intermediate in the pathway of acetyl-coenzyme A synthesis. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)54763-3] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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24
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Acetate formation from CO and CO2 by cell extracts of Peptostreptococcus productus (strain Marburg). Arch Microbiol 1991. [DOI: 10.1007/bf00418191] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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25
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Reductive activation of the coenzyme A/acetyl-CoA isotopic exchange reaction catalyzed by carbon monoxide dehydrogenase from Clostridium thermoaceticum and its inhibition by nitrous oxide and carbon monoxide. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(19)67831-2] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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26
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Abstract
We know of three routes that organisms have evolved to synthesize complex organic molecules from CO2: the Calvin cycle, the reverse tricarboxylic acid cycle, and the reductive acetyl-CoA pathway. This review describes the enzymatic steps involved in the acetyl-CoA pathway, also called the Wood pathway, which is the major mechanism of CO2 fixation under anaerobic conditions. The acetyl-CoA pathway is also able to form acetyl-CoA from carbon monoxide. There are two parts to the acetyl-CoA pathway: (1) reduction of CO2 to methyltetrahydrofolate (methyl-H4folate) and (2) synthesis of acetyl-CoA from methyl-H4folate, a carboxyl donor such as CO or CO2, and CoA. This pathway is unique in that the major intermediates are enzyme-bound and are often organometallic complexes. Our current understanding of the pathway is based on radioactive and stable isotope tracer studies, purification of the component enzymes (some extremely oxygen sensitive), and identification of the enzyme-bound intermediates by chromatographic, spectroscopic, and electrochemical techniques. This review describes the remarkable series of enzymatic steps involved in acetyl-CoA formation by this pathway that is a key component of the global carbon cycle.
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Affiliation(s)
- S W Ragsdale
- Department of Chemistry, University of Wisconsin-Milwaukee
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Hsu TD, Lux MF, Drake HL. Expression of an aromatic-dependent decarboxylase which provides growth-essential CO2 equivalents for the acetogenic (Wood) pathway of Clostridium thermoaceticum. J Bacteriol 1990; 172:5901-7. [PMID: 2120194 PMCID: PMC526910 DOI: 10.1128/jb.172.10.5901-5907.1990] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The acetogen Clostridium thermoaceticum generates growth-essential CO2 equivalents from carboxylated aromatic compounds (e.g., 4-hydroxybenzoate), and these CO2 equivalents are likely integrated into the acetogenic pathway (T. Hsu, S. L. Daniel, M. F. Lux, and H. L. Drake, J. Bacteriol. 172:212-217, 1990). By using 4-hydroxybenzoate as a model substrate, an assay was developed to study the expression and activity of the decarboxylase involved in the activation of aromatic carboxyl groups. The aromatic-dependent decarboxylase was induced by carboxylated aromatic compounds in the early stages of growth and was not repressed by glucose or other acetogenic substrates; nonutilizable carboxylated aromatic compounds did not induce the decarboxylase. The decarboxylase activity displayed saturation kinetics at both whole-cell and cell extract levels, was sensitive to oxidation, and was not affected by exogenous energy sources. However, at the whole-cell level, metabolic inhibitors decreased the decarboxylase activity. Supplemental biotin or avidin did not significantly affect decarboxylation. The aromatic-dependent decarboxylase was specific for benzoates with a hydroxyl group in the para position of the aromatic ring; the meta position could be occupied by various substituent groups (-H, -OH, -OCH3, -Cl, or -F). The carboxyl carbon from [carboxyl-14C] vanillate went primarily to 14CO2 in short-term decarboxylase assays. During growth, the aromatic carboxyl group went primarily to CO2 under CO2-enriched conditions. However, under CO2-limited conditions, the aromatic carboxyl carbon went nearly totally to acetate, with equal distribution between the carboxyl and methyl carbons, thus demonstrating that acetate could be totally synthesized from aromatic carboxyl groups. In contrast, when cocultivated (i.e., supplemented) with CO under CO2-limited conditions, the aromatic carboxyl group went primarily to the methyl carbon of acetate.
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Affiliation(s)
- T D Hsu
- Department of Biology, University of Mississippi, University 38677
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28
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Rajagopal BS, Lespinat PA, Fauque G, LeGall J, Berlier YM. Mass-spectrometric studies of the interrelations among hydrogenase, carbon monoxide dehydrogenase, and methane-forming activities in pure and mixed cultures of Desulfovibrio vulgaris, Desulfovibrio desulfuricans, and Methanosarcina barkeri. Appl Environ Microbiol 1989; 55:2123-9. [PMID: 2508553 PMCID: PMC203043 DOI: 10.1128/aem.55.9.2123-2129.1989] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The activities of pure and mixed cultures of Desulfovibrio vulgaris and Methanosarcina barkeri in the exponential growth phase were monitored by measuring changes in dissolved-gas concentration by membrane-inlet mass spectrometry. M. barkeri grown under H2-CO2 or methanol produced limited amounts of methane and practically no hydrogen from either substrate. The addition of CO resulted in a transient H2 production concomitant with CO consumption. Hydrogen was then taken up, and CH4 production increased. All these events were suppressed by KCN, which inhibited carbon monoxide dehydrogenase activity. Therefore, with both substrates, H2 appeared to be an intermediate in CO reduction to CH4. The cells grown on H2-CO2 consumed 4 mol of CO and produced 1 mol of CH4. Methanol-grown cells reduced CH3OH with H2 resulting from carbon monoxide dehydrogenase activity, and the ratio was then 1 mol of CH4 to 1 mol of CO. Only 12CH4 and no 13CH4 was obtained from 13CO, indicating that CO could not be the direct precursor of CH4. In mixed cultures of D. vulgaris and M. barkeri on lactate, an initial burst of H2 was observed, followed by a lower level of production, whereas methane synthesis was linear with time. Addition of CO to the mixed culture also resulted in transient extra H2 production but had no inhibitory effect upon CH4 formation, even when the sulfate reducer was D. vulgaris Hildenborough, whose periplasmic iron hydrogenase is very sensitive to CO. The hydrogen transfer is therefore probably mediated by a less CO-sensitive nickel-iron hydrogenase from either of both species.
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Affiliation(s)
- B S Rajagopal
- Section d'Enzymologie et Biochimie Bactérienne, CEN Cadarache, Saint Paul Lez Durance, France
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Abstract
To detect autotrophic CO2 assimilation in cell extracts of Methanococcus maripaludis, lactate dehydrogenase and NADH were added to convert pyruvate formed from autotrophically synthesized acetyl coenzyme A to lactate. The lactate produced was determined spectrophotometrically. When CO2 fixation was pulled in the direction of lactate synthesis, CO2 reduction to methane was inhibited. Bromoethanesulfonate (BES), a potent inhibitor of methanogenesis, enhanced lactate synthesis, and methyl coenzyme M inhibited it in the absence of BES. Lactate synthesis was dependent on CO2 and H2, but H2 + CO2-independent synthesis was also observed. In cell extracts, the rate of lactate synthesis was about 1.2 nmol min-1 mg of protein-1. When BES was added, the rate of lactate synthesis increased to 2.3 nmol min-1 mg of protein-1. Because acetyl coenzyme A did not stimulate lactate synthesis, pyruvate synthase may have been the limiting activity in these assays. Radiolabel from 14CO2 was incorporated into lactate. The percentages of radiolabel in the C-1, C-2, and C-3 positions of lactate were 73, 33, and 11%, respectively. Both carbon monoxide and formaldehyde stimulated lactate synthesis. 14CH2O was specifically incorporated into the C-3 of lactate, and 14CO was incorporated into the C-1 and C-2 positions. Low concentrations of cyanide also inhibited autotrophic growth, CO dehydrogenase activity, and autotrophic lactate synthesis. These observations are in agreement with the acetogenic pathway of autotrophic CO2 assimilation.
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Affiliation(s)
- J Shieh
- Department of Microbiology, University of Georgia, Athens 30602
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Misra AK, Bose NK, Johnson J. Use of anaerobic bacteria in generating fuels and chemicals from coal. Appl Biochem Biotechnol 1988. [DOI: 10.1007/bf02779166] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Kerby R, Zeikus JG. Catabolic enzymes of the acetogen Butyribacterium methylotrophicum grown on single-carbon substrates. J Bacteriol 1987; 169:5605-9. [PMID: 3316188 PMCID: PMC214000 DOI: 10.1128/jb.169.12.5605-5609.1987] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
When grown on formate, formate-CO, and methanol-CO, Butyribacterium methylotrophicum contained high levels of tetrahydrofolate (H4folate) and required enzymes, carbon monoxide dehydrogenase, formate dehydrogenase, and hydrogenase. The activities of methylene-H4folate reductase were comparable to other H4 folate activities (which ranged from 0.55 to 9.28 mumol/min per mg of protein) when measured by an improved procedure. The H4folate activities in formate-grown cells were twice those found in formate-CO-grown cells. This result correlated with a growth yield on formate that was one-half that on formate-CO. The stoichiometry of the formyl-H4folate synthetase reaction was 1 mol of ATP per 1 mol of formate. The methylene-H4folate dehydrogenase was NAD+ dependent. We conclude that B. methylotrophicum utilizes these enzymes in homoacetogenic catabolism.
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Affiliation(s)
- R Kerby
- Department of Bacteriology, University of Wisconsin, Madison 53706
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Länge S, Fuchs G. Autotrophic synthesis of activated acetic acid from CO2 in Methanobacterium thermoautotrophicum. Synthesis from tetrahydromethanopterin-bound C1 units and carbon monoxide. EUROPEAN JOURNAL OF BIOCHEMISTRY 1987; 163:147-54. [PMID: 3102234 DOI: 10.1111/j.1432-1033.1987.tb10748.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The synthesis of acetyl-CoA from CO2, H2, and various C1 compounds was studied in vitro with extracts and with protein fractions of Methanobacterium thermoautotrophicum. Acetyl-CoA synthesis from CO2 and H2 by extracts required CO2 reduction to CH4 to proceed. Both processes were highly stimulated by formaldehyde which served as the carbon precursor of both CH4 and the CH3 group of acetate. Carbon monoxide in combination with formaldehyde dramatically stimulated the acetyl-CoA synthesis up to 150-fold. In this system, which did not require CO2 reduction to the formaldehyde and CO level, acetyl-CoA synthesis was no longer dependent on CH4 formation. The soluble (100,000 X g supernatant) cell protein was resolved into a protein fraction [45-60% (NH4)2SO4-fraction] which catalyzed acetyl-CoA synthesis at a specific rate of 15 nmol X min-1 X (equivalent of mg cell protein)-1 (60 degrees C). This oxygen-sensitive enzyme reaction required dithioerythritol for activity and was strictly dependent on coenzyme A, CO, and N5,N10-methylene tetrahydromethanopterin, N5-methyl tetrahydromethanopterin or formaldehyde plus tetrahydromethanopterin. The incorporation of formaldehyde is explained by the spontaneous formation of methylene tetrahydromethanopterin. The product of the reaction, acetyl-CoA, was quantitatively derived from CO (carboxyl of acetate) and a C1 derivative of tetrahydromethanopterin (methyl of acetate). The C1 derivative of tetrahydromethanopterin could not be replaced by a C1 derivative of tetrahydrofolate or by methyl-coenzyme M; ATP was not required. The active protein fraction contained CO dehydrogenase and at least on corrinoid protein. These results provide strong biochemical arguments for the proposed mechanism of autotrophic acetyl-CoA synthesis in Methanobacterium.
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Schauder R, Eikmanns B, Thauer RK, Widdel F, Fuchs G. Acetate oxidation to CO2 in anaerobic bacteria via a novel pathway not involving reactions of the citric acid cycle. Arch Microbiol 1986. [DOI: 10.1007/bf00446775] [Citation(s) in RCA: 97] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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40
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Energetics of CO formation and CO oxidation in cell suspensions of Acetobacterium woodii. Arch Microbiol 1986. [DOI: 10.1007/bf00409889] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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41
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Kellum R, Drake HL. Effects of carbon monoxide on one-carbon enzymes and energetics ofClostridium thermoaceticum. FEMS Microbiol Lett 1986. [DOI: 10.1111/j.1574-6968.1986.tb01345.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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42
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Pezacka E, Wood HG. The autotrophic pathway of acetogenic bacteria. Role of CO dehydrogenase disulfide reductase. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(17)35983-5] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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43
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Evans JN, Tolman CJ, Roberts MF. Indirect observation by 13C NMR spectroscopy of a novel CO2 fixation pathway in methanogens. Science 1986; 231:488-91. [PMID: 3079919 DOI: 10.1126/science.3079919] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
High-field carbon-13 nuclear magnetic resonance (NMR) spectroscopy has been used to monitor the isotopic dilution of doubly carbon-13-labeled precursors for 2,3-cyclopyrophosphoglycerate, a novel primary metabolite that occurs in certain methanogens. A unique carbon dioxide fixation pathway that gives rise to asymmetric labeling of acetyl coenzyme A has been demonstrated in Methanobacterium thermoautotrophicum. The effect of selected metabolic inhibitors on the labeled species in the pathway has been examined by NMR. These techniques establish a general, sensitive method for the delineation of convergent biosynthetic pathways.
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Wood HG, Ragsdale SW, Pezacka E. The acetyl-CoA pathway: a newly discovered pathway of autotrophic growth. Trends Biochem Sci 1986. [DOI: 10.1016/0968-0004(86)90223-9] [Citation(s) in RCA: 88] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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45
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Genetics and Biochemistry of Clostridium Relevant to Development of Fermentation Processes. ADVANCES IN APPLIED MICROBIOLOGY 1986. [DOI: 10.1016/s0065-2164(08)70438-6] [Citation(s) in RCA: 126] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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46
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Ragsdale SW, Wood HG, Antholine WE. Evidence that an iron-nickel-carbon complex is formed by reaction of CO with the CO dehydrogenase from Clostridium thermoaceticum. Proc Natl Acad Sci U S A 1985; 82:6811-4. [PMID: 2995986 PMCID: PMC390777 DOI: 10.1073/pnas.82.20.6811] [Citation(s) in RCA: 129] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The interaction between carbon monoxide and the CO dehydrogenase from Clostridium thermoaceticum was studied by electron spin resonance (ESR) techniques. When the enzyme reacts with CO, a paramagnetic complex is formed which previously was shown, by isotope substitution, to be due to a nickel-carbon species. In this paper, we demonstrate that iron is also a component of this ESR-detectable complex. When the iron in the enzyme is replaced with 57Fe, a broadening of 18 G in the g parallel and 7 G in the g perpendicular region is seen. This hyperfine interaction is probably due to more than one iron atom in the complex. Coenzyme A influences this ESR spectrum. In the absence of CoA, the ESR spectrum consists of two superimposed signals, which were simulated using the following ESR parameters: signal 1, with g = 2.074 and g = 2.028, and signal 2 with gx = 2.062, gy = 2.047, and gz = 2.028. CoA converts signal 2 into signal 1. Since iron, nickel, and carbon all are part of this ESR-detectable complex, we propose that these atoms exist in a spin-coupled complex with net spin = 1/2, analogous to other iron-sulfur centers in which the metals are bridged by acid-labile sulfide.
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Krzycki JA, Lehman LJ, Zeikus JG. Acetate catabolism by Methanosarcina barkeri: evidence for involvement of carbon monoxide dehydrogenase, methyl coenzyme M, and methylreductase. J Bacteriol 1985; 163:1000-6. [PMID: 3928595 PMCID: PMC219231 DOI: 10.1128/jb.163.3.1000-1006.1985] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The pathway of acetate catabolism in Methanosarcina barkeri strain MS was studied by using a recently developed assay for methanogenesis from acetate by soluble enzymes in cell extracts. Extracts incubated with [2-14C]acetate, hydrogen, and ATP formed 14CH4 and [14C]methyl coenzyme M as products. The apparent Km for acetate conversion to methane was 5 mM. In the presence of excess acetate, both the rate and duration of methane production was dependent on ATP. Acetyl phosphate replaced the cell extract methanogenic requirement for both acetate and ATP (the Km for ATP was 2 mM). Low concentrations of bromoethanesulfonic acid and cyanide, inhibitors of methylreductase and carbon monoxide dehydrogenase, respectively, greatly reduced the rate of methanogenesis. Precipitation of CO dehydrogenase in cell extracts by antibodies raised to 95% purified enzyme inhibited both CO dehydrogenase and acetate-to-methane conversion activity. The data are consistent with a model of acetate catabolism in which methylreductase, methyl coenzyme M, CO dehydrogenase, and acetate-activating enzymes are components. These results are discussed in relation to acetate uptake and rate-limiting transformation mechanisms in methane formation.
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Jansen K, Fuchs G, Thauer RK. Autotrophic CO2fixation byDesulfovibrio baarsii: Demonstration of enzyme activities characteristic for the acetyl-CoA pathway. FEMS Microbiol Lett 1985. [DOI: 10.1111/j.1574-6968.1985.tb00812.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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In bacteria which grow on simple reductants, generation of a proton gradient involves extracytoplasmic oxidation of substrate. Microbiol Rev 1985; 49:140-57. [PMID: 2989673 PMCID: PMC373027 DOI: 10.1128/mr.49.2.140-157.1985] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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50
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R�hlemann M, Ziegler K, Stupperich E, Fuchs G. Detection of acetyl coenzyme A as an early CO2 assimilation intermediate in Methanobacterium. Arch Microbiol 1985. [DOI: 10.1007/bf00428856] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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