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Rasmussen AN, Tolar BB, Bargar JR, Boye K, Francis CA. Diverse and unconventional methanogens, methanotrophs, and methylotrophs in metagenome-assembled genomes from subsurface sediments of the Slate River floodplain, Crested Butte, CO, USA. mSystems 2024; 9:e0031424. [PMID: 38940520 PMCID: PMC11264602 DOI: 10.1128/msystems.00314-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Accepted: 06/06/2024] [Indexed: 06/29/2024] Open
Abstract
We use metagenome-assembled genomes (MAGs) to understand single-carbon (C1) compound-cycling-particularly methane-cycling-microorganisms in montane riparian floodplain sediments. We generated 1,233 MAGs (>50% completeness and <10% contamination) from 50- to 150-cm depth below the sediment surface capturing the transition between oxic, unsaturated sediments and anoxic, saturated sediments in the Slate River (SR) floodplain (Crested Butte, CO, USA). We recovered genomes of putative methanogens, methanotrophs, and methylotrophs (n = 57). Methanogens, found only in deep, anoxic depths at SR, originate from three different clades (Methanoregulaceae, Methanotrichaceae, and Methanomassiliicoccales), each with a different methanogenesis pathway; putative methanotrophic MAGs originate from within the Archaea (Candidatus Methanoperedens) in anoxic depths and uncultured bacteria (Ca. Binatia) in oxic depths. Genomes for canonical aerobic methanotrophs were not recovered. Ca. Methanoperedens were exceptionally abundant (~1,400× coverage, >50% abundance in the MAG library) in one sample that also contained aceticlastic methanogens, indicating a potential C1/methane-cycling hotspot. Ca. Methylomirabilis MAGs from SR encode pathways for methylotrophy but do not harbor methane monooxygenase or nitrogen reduction genes. Comparative genomic analysis supports that one clade within the Ca. Methylomirabilis genus is not methanotrophic. The genetic potential for methylotrophy was widespread, with over 10% and 19% of SR MAGs encoding a methanol dehydrogenase or substrate-specific methyltransferase, respectively. MAGs from uncultured Thermoplasmata archaea in the Ca. Gimiplasmatales (UBA10834) contain pathways that may allow for anaerobic methylotrophic acetogenesis. Overall, MAGs from SR floodplain sediments reveal a potential for methane production and consumption in the system and a robust potential for methylotrophy.IMPORTANCEThe cycling of carbon by microorganisms in subsurface environments is of particular relevance in the face of global climate change. Riparian floodplain sediments contain high organic carbon that can be degraded into C1 compounds such as methane, methanol, and methylamines, the fate of which depends on the microbial metabolisms present as well as the hydrological conditions and availability of oxygen. In the present study, we generated over 1,000 MAGs from subsurface sediments from a montane river floodplain and recovered genomes for microorganisms that are capable of producing and consuming methane and other C1 compounds, highlighting a robust potential for C1 cycling in subsurface sediments both with and without oxygen. Archaea from the Ca. Methanoperedens genus were exceptionally abundant in one sample, indicating a potential C1/methane-cycling hotspot in the Slate River floodplain system.
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Affiliation(s)
- Anna N. Rasmussen
- Department of Earth System Science, Stanford University, Stanford, California, USA
- SLAC National Accelerator Laboratory, Menlo Park, California, USA
| | - Bradley B. Tolar
- Department of Earth System Science, Stanford University, Stanford, California, USA
| | - John R. Bargar
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington, USA
| | - Kristin Boye
- SLAC National Accelerator Laboratory, Menlo Park, California, USA
| | - Christopher A. Francis
- Department of Earth System Science, Stanford University, Stanford, California, USA
- Oceans Department, Stanford University, Stanford, California, USA
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Friedeheim L, Boeren S, Sánchez-Andrea I, Stams AJM, Sousa DZ. Alcohol dehydrogenase system acts as the sole pathway for methanol oxidation in Desulfofundulus kuznetsovii strain TPOSR. Antonie Van Leeuwenhoek 2024; 117:47. [PMID: 38427176 PMCID: PMC10907483 DOI: 10.1007/s10482-024-01937-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Accepted: 01/28/2024] [Indexed: 03/02/2024]
Abstract
Desulfofundulus kuznetsovii is a thermophilic, spore-forming sulphate-reducing bacterium in the family Peptococcaceae. In this study, we describe a newly isolated strain of D. kuznetsovii, strain TPOSR, and compare its metabolism to the type strain D. kuznetsovii 17T. Both strains grow on a large variety of alcohols, such as methanol, ethanol and propane-diols, coupled to the reduction of sulphate. Strain 17T metabolizes methanol via two routes, one involving a cobalt-dependent methyl transferase and the other using a cobalt-independent alcohol dehydrogenase. However, strain TPOSR, which shares 97% average nucleotide identity with D. kuznetsovii strain 17T, lacks several genes from the methyl transferase operon found in strain 17T. The gene encoding the catalytically active methyl transferase subunit B is missing, indicating that strain TPOSR utilizes the alcohol dehydrogenase pathway exclusively. Both strains grew with methanol during cobalt starvation, but growth was impaired. Strain 17T was more sensitive to cobalt deficiency, due to the repression of its methyl transferase system. Our findings shed light on the metabolic diversity of D. kuznetsovii and their metabolic differences of encoding one or two routes for the conversion of methanol.
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Affiliation(s)
- Lukas Friedeheim
- Laboratory of Microbiology, Wageningen University and Research, Wageningen, The Netherlands
| | - Sjef Boeren
- Laboratory of Biochemistry, Wageningen University and Research, Wageningen, The Netherlands
| | - Irene Sánchez-Andrea
- Laboratory of Microbiology, Wageningen University and Research, Wageningen, The Netherlands
| | - Alfons J M Stams
- Laboratory of Microbiology, Wageningen University and Research, Wageningen, The Netherlands
| | - Diana Z Sousa
- Laboratory of Microbiology, Wageningen University and Research, Wageningen, The Netherlands.
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Moon J, Schubert A, Poehlein A, Daniel R, Müller V. A new metabolic trait in an acetogen: Mixed acid fermentation of fructose in a methylene-tetrahydrofolate reductase mutant of Acetobacterium woodii. ENVIRONMENTAL MICROBIOLOGY REPORTS 2023; 15:339-351. [PMID: 37150590 PMCID: PMC10472528 DOI: 10.1111/1758-2229.13160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Accepted: 04/20/2023] [Indexed: 05/09/2023]
Abstract
To inactivate the Wood-Ljungdahl pathway in the acetogenic model bacterium Acetobacterium woodii, the genes metVF encoding two of the subunits of the methylene-tetrahydrofolate reductase were deleted. As expected, the mutant did not grow on C1 compounds and also not on lactate, ethanol or butanediol. In contrast to a mutant in which the first enzyme of the pathway (hydrogen-dependent CO2 reductase) had been genetically deleted, cells were able to grow on fructose, albeit with lower rates and yields than the wild-type. Growth was restored by addition of an external electron sink, glycine betaine + CO2 or caffeate. Resting cells pre-grown on fructose plus an external electron acceptor fermented fructose to two acetate and four hydrogen, that is, performed hydrogenogenesis. Cells pre-grown under fermentative conditions on fructose alone redirected carbon and electrons to form lactate, formate, ethanol as well as hydrogen. Apparently, growth on fructose alone induced enzymes for mixed acid fermentation (MAF). Transcriptome analyses revealed enzymes potentially involved in MAF and a quantitative model for MAF from fructose in A. woodii is presented.
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Affiliation(s)
- Jimyung Moon
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular BiosciencesJohann Wolfgang Goethe UniversityFrankfurtGermany
| | - Anja Schubert
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular BiosciencesJohann Wolfgang Goethe UniversityFrankfurtGermany
| | - Anja Poehlein
- Göttingen Genomics Laboratory, Institute for Microbiology and GeneticsGeorg August UniversityGöttingenGermany
| | - Rolf Daniel
- Göttingen Genomics Laboratory, Institute for Microbiology and GeneticsGeorg August UniversityGöttingenGermany
| | - Volker Müller
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular BiosciencesJohann Wolfgang Goethe UniversityFrankfurtGermany
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Moon J, Schubert A, Waschinger LM, Müller V. Reprogramming the metabolism of an acetogenic bacterium to homoformatogenesis. THE ISME JOURNAL 2023:10.1038/s41396-023-01411-2. [PMID: 37061584 DOI: 10.1038/s41396-023-01411-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Revised: 03/30/2023] [Accepted: 04/04/2023] [Indexed: 04/17/2023]
Abstract
Methyl groups are abundant in anoxic environments and their utilization as carbon and energy sources by microorganisms involves oxidation of the methyl groups to CO2, followed by transfer of the electrons to an acceptor. In acetogenic bacteria, the electron acceptor is CO2 that is reduced to enzyme bound carbon monoxide, the precursor of the carboxyl group in acetate. Here, we describe the generation of a mutant of the acetogen Acetobacterium woodii in which the last step in methyl group oxidation, formate oxidation to CO2 catalyzed by the HDCR enzyme, has been genetically deleted. The mutant grew on glycine betaine as methyl group donor, and in contrast to the wild type, formed formate alongside acetate, in a 1:2 ratio, demonstrating that methyl group oxidation stopped at the level of formate and reduced electron carriers were reoxidized by CO2 reduction to acetate. In the presence of the alternative electron acceptor caffeate, CO2 was no longer reduced to acetate, formate was the only product and all the carbon went to formate. Apparently, acetogenesis was not required to sustain formatogenic growth. This is the first demonstration of a genetic reprogramming of an acetogen into a formatogen that grows by homoformatogenesis from methyl groups. Formate production from methyl groups is not only of biotechnological interest but also for the mechanism of electron transfer in syntrophic interactions in anoxic environments.
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Affiliation(s)
- Jimyung Moon
- Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Max-von-Laue Str. 9, D-60438, Frankfurt, Germany
| | - Anja Schubert
- Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Max-von-Laue Str. 9, D-60438, Frankfurt, Germany
| | - Lara M Waschinger
- Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Max-von-Laue Str. 9, D-60438, Frankfurt, Germany
| | - Volker Müller
- Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Max-von-Laue Str. 9, D-60438, Frankfurt, Germany.
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Ricci L, Seifert A, Bernacchi S, Fino D, Pirri CF, Re A. Leveraging substrate flexibility and product selectivity of acetogens in two-stage systems for chemical production. Microb Biotechnol 2023; 16:218-237. [PMID: 36464980 PMCID: PMC9871533 DOI: 10.1111/1751-7915.14172] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Revised: 10/31/2022] [Accepted: 11/08/2022] [Indexed: 12/09/2022] Open
Abstract
Carbon dioxide (CO2 ) stands out as sustainable feedstock for developing a circular carbon economy whose energy supply could be obtained by boosting the production of clean hydrogen from renewable electricity. H2 -dependent CO2 gas fermentation using acetogenic microorganisms offers a viable solution of increasingly demonstrated value. While gas fermentation advances to achieve commercial process scalability, which is currently limited to a few products such as acetate and ethanol, it is worth taking the best of the current state-of-the-art technology by its integration within innovative bioconversion schemes. This review presents multiple scenarios where gas fermentation by acetogens integrate into double-stage biotechnological production processes that use CO2 as sole carbon feedstock and H2 as energy carrier for products' synthesis. In the integration schemes here reviewed, the first stage can be biotic or abiotic while the second stage is biotic. When the first stage is biotic, acetogens act as a biological platform to generate chemical intermediates such as acetate, formate and ethanol that become substrates for a second fermentation stage. This approach holds the potential to enhance process titre/rate/yield metrics and products' spectrum. Alternatively, when the first stage is abiotic, the integrated two-stage scheme foresees, in the first stage, the catalytic transformation of CO2 into C1 products that, in the second stage, can be metabolized by acetogens. This latter scheme leverages the metabolic flexibility of acetogens in efficient utilization of the products of CO2 abiotic hydrogenation, namely formate and methanol, to synthesize multicarbon compounds but also to act as flexible catalysts for hydrogen storage or production.
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Affiliation(s)
- Luca Ricci
- Department of Applied Science and TechnologyPolitecnico di TorinoTurinItaly
- Centre for Sustainable Future TechnologiesFondazione Istituto Italiano di TecnologiaTurinItaly
| | | | | | - Debora Fino
- Department of Applied Science and TechnologyPolitecnico di TorinoTurinItaly
- Centre for Sustainable Future TechnologiesFondazione Istituto Italiano di TecnologiaTurinItaly
| | - Candido Fabrizio Pirri
- Department of Applied Science and TechnologyPolitecnico di TorinoTurinItaly
- Centre for Sustainable Future TechnologiesFondazione Istituto Italiano di TecnologiaTurinItaly
| | - Angela Re
- Department of Applied Science and TechnologyPolitecnico di TorinoTurinItaly
- Centre for Sustainable Future TechnologiesFondazione Istituto Italiano di TecnologiaTurinItaly
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Cobalamin Riboswitches Are Broadly Sensitive to Corrinoid Cofactors to Enable an Efficient Gene Regulatory Strategy. mBio 2022; 13:e0112122. [PMID: 35993747 PMCID: PMC9600662 DOI: 10.1128/mbio.01121-22] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
In bacteria, many essential metabolic processes are controlled by riboswitches, gene regulatory RNAs that directly bind and detect metabolites. Highly specific effector binding enables riboswitches to respond to a single biologically relevant metabolite. Cobalamin riboswitches are a potential exception because over a dozen chemically similar but functionally distinct cobalamin variants (corrinoid cofactors) exist in nature. Here, we measured cobalamin riboswitch activity in vivo using a Bacillus subtilis fluorescent reporter system and found, among 38 tested riboswitches, a subset responded to corrinoids promiscuously, while others were semiselective. Analyses of chimeric riboswitches and structural models indicate, unlike other riboswitch classes, cobalamin riboswitches indirectly differentiate among corrinoids by sensing differences in their structural conformation. This regulatory strategy aligns riboswitch-corrinoid specificity with cellular corrinoid requirements in a B. subtilis model. Thus, bacteria can employ broadly sensitive riboswitches to cope with the chemical diversity of essential metabolites. IMPORTANCE Some bacterial mRNAs contain a region called a riboswitch which controls gene expression by binding to a metabolite in the cell. Typically, riboswitches sense and respond to a limited range of cellular metabolites, often just one type. In this work, we found the cobalamin (vitamin B12) riboswitch class is an exception, capable of sensing and responding to multiple variants of B12-collectively called corrinoids. We found cobalamin riboswitches vary in corrinoid specificity with some riboswitches responding to each of the corrinoids we tested, while others responding only to a subset of corrinoids. Our results suggest the latter class of riboswitches sense intrinsic conformational differences among corrinoids in order to support the corrinoid-specific needs of the cell. These findings provide insight into how bacteria sense and respond to an exceptionally diverse, often essential set of enzyme cofactors.
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Kremp F, Müller V. Methanol and methyl group conversion in acetogenic bacteria: biochemistry, physiology and application. FEMS Microbiol Rev 2021; 45:5903270. [PMID: 32901799 DOI: 10.1093/femsre/fuaa040] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Accepted: 08/29/2020] [Indexed: 12/24/2022] Open
Abstract
The production of bulk chemicals mostly depends on exhausting petroleum sources and leads to emission of greenhouse gases. Within the last decades the urgent need for alternative sources has increased and the development of bio-based processes received new attention. To avoid the competition between the use of sugars as food or fuel, other feedstocks with high availability and low cost are needed, which brought acetogenic bacteria into focus. This group of anaerobic organisms uses mixtures of CO2, CO and H2 for the production of mostly acetate and ethanol. Also methanol, a cheap and abundant bulk chemical produced from methane, is a suitable substrate for acetogenic bacteria. In methylotrophic acetogens the methyl group is transferred to the Wood-Ljungdahl pathway, a pathway to reduce CO2 to acetate via a series of C1-intermediates bound to tetrahydrofolic acid. Here we describe the biochemistry and bioenergetics of methanol conversion in the biotechnologically interesting group of anaerobic, acetogenic bacteria. Further, the bioenergetics of biochemical production from methanol is discussed.
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Affiliation(s)
- Florian Kremp
- Department of Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany
| | - Volker Müller
- Department of Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Max-von-Laue Str. 9, D-60438 Frankfurt, Germany
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Kim JY, Park S, Jeong J, Lee M, Kang B, Jang SH, Jeon J, Jang N, Oh S, Park ZY, Chang IS. Methanol supply speeds up synthesis gas fermentation by methylotrophic-acetogenic bacterium, Eubacterium limosum KIST612. BIORESOURCE TECHNOLOGY 2021; 321:124521. [PMID: 33321298 DOI: 10.1016/j.biortech.2020.124521] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 11/29/2020] [Accepted: 12/04/2020] [Indexed: 06/12/2023]
Abstract
This study analyzed the effect of methanol on the metabolism of syngas components (i.e., H2 and CO) by the syngas fermenting acetogenic strain E. limosum KIST612. The culture characteristics and relevant proteomic expressions (as fold changes) were carefully analyzed under CO/CO2 and H2/CO2 conditions with and without methanol addition, as well as, under methanol/CO2 conditions. The culture characteristics (specific growth rate and H2 consumption rate) under H2/CO2 conditions were greatly enhanced in the presence of methanol, by 4.0 and 2.7 times, respectively. However, the promoting effect of methanol was not significant under CO/CO2 conditions. Proteomic fold changes in most enzyme expression levels in the Wood-Ljungdahl pathway and chemiosmotic energy conservation also exhibited high correspondence between methanol and H2/CO2 but not between methanol and CO/CO2. These findings suggest the advantages of methanol addition to H2/CO2 for biomass enhancement and faster consumption of gaseous substrates during syngas fermentation.
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Affiliation(s)
- Ji-Yeon Kim
- School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology, 123 Cheomdan-gwagiro, Buk-gu, Gwangju 61005, Republic of Korea
| | - Sehoon Park
- School of Life Sciences, Gwangju Institute of Science and Technology, 123 Cheomdan-gwagiro, Buk-gu, Gwangju 61005, Republic of Korea
| | - Jiyeong Jeong
- School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology, 123 Cheomdan-gwagiro, Buk-gu, Gwangju 61005, Republic of Korea
| | - Mungyu Lee
- School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology, 123 Cheomdan-gwagiro, Buk-gu, Gwangju 61005, Republic of Korea
| | - Byeongchan Kang
- School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology, 123 Cheomdan-gwagiro, Buk-gu, Gwangju 61005, Republic of Korea
| | - Se Hwan Jang
- School of Life Sciences, Gwangju Institute of Science and Technology, 123 Cheomdan-gwagiro, Buk-gu, Gwangju 61005, Republic of Korea
| | - Jinsung Jeon
- School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology, 123 Cheomdan-gwagiro, Buk-gu, Gwangju 61005, Republic of Korea
| | - Nulee Jang
- School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology, 123 Cheomdan-gwagiro, Buk-gu, Gwangju 61005, Republic of Korea
| | - Soyoung Oh
- School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology, 123 Cheomdan-gwagiro, Buk-gu, Gwangju 61005, Republic of Korea
| | - Zee-Yong Park
- School of Life Sciences, Gwangju Institute of Science and Technology, 123 Cheomdan-gwagiro, Buk-gu, Gwangju 61005, Republic of Korea.
| | - In Seop Chang
- School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology, 123 Cheomdan-gwagiro, Buk-gu, Gwangju 61005, Republic of Korea
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Müller V. New Horizons in Acetogenic Conversion of One-Carbon Substrates and Biological Hydrogen Storage. Trends Biotechnol 2019; 37:1344-1354. [DOI: 10.1016/j.tibtech.2019.05.008] [Citation(s) in RCA: 75] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 05/17/2019] [Accepted: 05/23/2019] [Indexed: 01/12/2023]
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Puentes Jácome LA, Wang PH, Molenda O, Li YXJJ, Islam MA, Edwards EA. Sustained Dechlorination of Vinyl Chloride to Ethene in Dehalococcoides-Enriched Cultures Grown without Addition of Exogenous Vitamins and at Low pH. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:11364-11374. [PMID: 31441646 DOI: 10.1021/acs.est.9b02339] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Trichloroethene (TCE) bioremediation has been demonstrated at field sites using microbial cultures harboring TCE-respiring Dehalococcoides whose growth is cobalamin (vitamin B12)-dependent. Bioaugmentation cultures grown ex situ with ample exogenous vitamins and at neutral pH may become vitamin-limited or inhibited by acidic pH once injected into field sites, resulting in incomplete TCE dechlorination and accumulation of vinyl chloride (VC). Here, we report growth of the Dehalococcoides-containing bioaugmentation culture KB-1 in a TCE-amended mineral medium devoid of vitamins and in a VC-amended mineral medium at low pH (6.0 and 5.5). In these cultures, Acetobacterium, which can synthesize 5,6-dimethylbenzimidazole (DMB), the lower ligand of cobalamin, and Sporomusa are dominant acetogens. At neutral pH, Acetobacterium supports complete TCE dechlorination by Dehalococcoides at millimolar levels with a substantial increase in cobalamin (∼20-fold). Sustained dechlorination of VC to ethene was achieved at pH as low as 5.5. Below pH 5.0, dechlorination was not stimulated by DMB supplementation but was restored by raising pH to neutral. Cell-extract assays revealed that vinyl chloride reductase activity declines significantly below pH 6.0 and is undetectable below pH 5.0. This study highlights the importance of cobamide-producing populations and pH in microbial dechlorinating communities for successful bioremediation at field sites.
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Affiliation(s)
- Luz A Puentes Jácome
- Department of Chemical Engineering and Applied Chemistry , University of Toronto , Toronto , Ontario M5S 3E5 , Canada
| | - Po-Hsiang Wang
- Department of Chemical Engineering and Applied Chemistry , University of Toronto , Toronto , Ontario M5S 3E5 , Canada
| | - Olivia Molenda
- Department of Chemical Engineering and Applied Chemistry , University of Toronto , Toronto , Ontario M5S 3E5 , Canada
| | - Yi Xuan Jine-Jine Li
- Department of Chemical Engineering and Applied Chemistry , University of Toronto , Toronto , Ontario M5S 3E5 , Canada
| | - M Ahsanul Islam
- Department of Chemical Engineering and Applied Chemistry , University of Toronto , Toronto , Ontario M5S 3E5 , Canada
| | - Elizabeth A Edwards
- Department of Chemical Engineering and Applied Chemistry , University of Toronto , Toronto , Ontario M5S 3E5 , Canada
- Department of Cell and Systems Biology , University of Toronto , Toronto , Ontario M5S 3G5 , Canada
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Sokolovskaya OM, Mok KC, Park JD, Tran JLA, Quanstrom KA, Taga ME. Cofactor Selectivity in Methylmalonyl Coenzyme A Mutase, a Model Cobamide-Dependent Enzyme. mBio 2019; 10:e01303-19. [PMID: 31551329 PMCID: PMC6759758 DOI: 10.1128/mbio.01303-19] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 08/23/2019] [Indexed: 12/25/2022] Open
Abstract
Cobamides, a uniquely diverse family of enzyme cofactors related to vitamin B12, are produced exclusively by bacteria and archaea but used in all domains of life. While it is widely accepted that cobamide-dependent organisms require specific cobamides for their metabolism, the biochemical mechanisms that make cobamides functionally distinct are largely unknown. Here, we examine the effects of cobamide structural variation on a model cobamide-dependent enzyme, methylmalonyl coenzyme A (CoA) mutase (MCM). The in vitro binding affinity of MCM for cobamides can be dramatically influenced by small changes in the structure of the lower ligand of the cobamide, and binding selectivity differs between bacterial orthologs of MCM. In contrast, variations in the lower ligand have minor effects on MCM catalysis. Bacterial growth assays demonstrate that cobamide requirements of MCM in vitro largely correlate with in vivo cobamide dependence. This result underscores the importance of enzyme selectivity in the cobamide-dependent physiology of bacteria.IMPORTANCE Cobamides, including vitamin B12, are enzyme cofactors used by organisms in all domains of life. Cobamides are structurally diverse, and microbial growth and metabolism vary based on cobamide structure. Understanding cobamide preference in microorganisms is important given that cobamides are widely used and appear to mediate microbial interactions in host-associated and aquatic environments. Until now, the biochemical basis for cobamide preferences was largely unknown. In this study, we analyzed the effects of the structural diversity of cobamides on a model cobamide-dependent enzyme, methylmalonyl-CoA mutase (MCM). We found that very small changes in cobamide structure could dramatically affect the binding affinity of cobamides to MCM. Strikingly, cobamide-dependent growth of a model bacterium, Sinorhizobium meliloti, largely correlated with the cofactor binding selectivity of S. meliloti MCM, emphasizing the importance of cobamide-dependent enzyme selectivity in bacterial growth and cobamide-mediated microbial interactions.
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Affiliation(s)
- Olga M Sokolovskaya
- Department of Plant & Microbial Biology, University of California Berkeley, Berkeley, California, USA
- Department of Chemistry, University of California Berkeley, Berkeley, California, USA
| | - Kenny C Mok
- Department of Plant & Microbial Biology, University of California Berkeley, Berkeley, California, USA
| | - Jong Duk Park
- Department of Plant & Microbial Biology, University of California Berkeley, Berkeley, California, USA
| | - Jennifer L A Tran
- Department of Plant & Microbial Biology, University of California Berkeley, Berkeley, California, USA
| | - Kathryn A Quanstrom
- Department of Plant & Microbial Biology, University of California Berkeley, Berkeley, California, USA
| | - Michiko E Taga
- Department of Plant & Microbial Biology, University of California Berkeley, Berkeley, California, USA
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12
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Kremp F, Poehlein A, Daniel R, Müller V. Methanol metabolism in the acetogenic bacterium Acetobacterium woodii. Environ Microbiol 2018; 20:4369-4384. [PMID: 30003650 DOI: 10.1111/1462-2920.14356] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 07/07/2018] [Indexed: 11/29/2022]
Abstract
Methanol derived from plant tissue is ubiquitous in anaerobic sediments and a good substrate for anaerobes growing on C1 compounds such as methanogens and acetogens. In contrast to methanogens little is known about the physiology, biochemistry and bioenergetics of methanol utilization in acetogenic bacteria. To fill this gap, we have used the model acetogen Acetobacterium woodii to study methanol metabolism using physiological and biochemical experiments paired with molecular studies and transcriptome analysis. These studies identified the genes and enzymes involved in acetogenesis from methanol and the redox carriers involved. We will present the first comprehensive model for carbon and electron flow from methanol in an acetogen and the bioenergetics of acetogenesis from methanol.
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Affiliation(s)
- Florian Kremp
- Department of Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Max-von-Laue Str. 9, D-60438, Frankfurt, Germany
| | - Anja Poehlein
- Göttingen Genomics Laboratory, Institute for Microbiology and Genetics, Georg August University, Grisebachstr. 8, D-37077, Göttingen, Germany
| | - Rolf Daniel
- Göttingen Genomics Laboratory, Institute for Microbiology and Genetics, Georg August University, Grisebachstr. 8, D-37077, Göttingen, Germany
| | - Volker Müller
- Department of Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Max-von-Laue Str. 9, D-60438, Frankfurt, Germany
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13
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Lechtenfeld M, Heine J, Sameith J, Kremp F, Müller V. Glycine betaine metabolism in the acetogenic bacteriumAcetobacterium woodii. Environ Microbiol 2018; 20:4512-4525. [DOI: 10.1111/1462-2920.14389] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Revised: 08/10/2018] [Accepted: 08/17/2018] [Indexed: 12/01/2022]
Affiliation(s)
- Mats Lechtenfeld
- Department of Molecular Microbiology & BioenergeticsInstitute of Molecular Biosciences, Johann Wolfgang Goethe University Max‐von‐Laue Str. 9, D‐60438 Frankfurt Germany
| | - Julia Heine
- Department of Molecular Microbiology & BioenergeticsInstitute of Molecular Biosciences, Johann Wolfgang Goethe University Max‐von‐Laue Str. 9, D‐60438 Frankfurt Germany
| | - Janin Sameith
- Department of Molecular Microbiology & BioenergeticsInstitute of Molecular Biosciences, Johann Wolfgang Goethe University Max‐von‐Laue Str. 9, D‐60438 Frankfurt Germany
| | - Florian Kremp
- Department of Molecular Microbiology & BioenergeticsInstitute of Molecular Biosciences, Johann Wolfgang Goethe University Max‐von‐Laue Str. 9, D‐60438 Frankfurt Germany
| | - Volker Müller
- Department of Molecular Microbiology & BioenergeticsInstitute of Molecular Biosciences, Johann Wolfgang Goethe University Max‐von‐Laue Str. 9, D‐60438 Frankfurt Germany
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The deep-subsurface sulfate reducer Desulfotomaculum kuznetsovii employs two methanol-degrading pathways. Nat Commun 2018; 9:239. [PMID: 29339722 PMCID: PMC5770442 DOI: 10.1038/s41467-017-02518-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Accepted: 12/06/2017] [Indexed: 11/08/2022] Open
Abstract
Methanol is generally metabolized through a pathway initiated by a cobalamine-containing methanol methyltransferase by anaerobic methylotrophs (such as methanogens and acetogens), or through oxidation to formaldehyde using a methanol dehydrogenase by aerobes. Methanol is an important substrate in deep-subsurface environments, where thermophilic sulfate-reducing bacteria of the genus Desulfotomaculum have key roles. Here, we study the methanol metabolism of Desulfotomaculum kuznetsovii strain 17T, isolated from a 3000-m deep geothermal water reservoir. We use proteomics to analyze cells grown with methanol and sulfate in the presence and absence of cobalt and vitamin B12. The results indicate the presence of two methanol-degrading pathways in D. kuznetsovii, a cobalt-dependent methanol methyltransferase and a cobalt-independent methanol dehydrogenase, which is further confirmed by stable isotope fractionation. This is the first report of a microorganism utilizing two distinct methanol conversion pathways. We hypothesize that this gives D. kuznetsovii a competitive advantage in its natural environment.
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15
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Mingo FS, Diekert G, Studenik S. Enrichment of Desulfitobacterium spp. from forest and grassland soil using the O-demethylation of phenyl methyl ethers as a growth-selective process. Microbiology (Reading) 2016; 162:224-235. [DOI: 10.1099/mic.0.000218] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Felix Sebastian Mingo
- Department of Applied and Ecological Microbiology, Institute of Microbiology, Friedrich Schiller University Jena, Philosophenweg 12, 07743 Jena, Germany
| | - Gabriele Diekert
- Department of Applied and Ecological Microbiology, Institute of Microbiology, Friedrich Schiller University Jena, Philosophenweg 12, 07743 Jena, Germany
| | - Sandra Studenik
- Department of Applied and Ecological Microbiology, Institute of Microbiology, Friedrich Schiller University Jena, Philosophenweg 12, 07743 Jena, Germany
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16
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Adaptation of the autotrophic acetogen Sporomusa ovata to methanol accelerates the conversion of CO2 to organic products. Sci Rep 2015; 5:16168. [PMID: 26530351 PMCID: PMC4632017 DOI: 10.1038/srep16168] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Accepted: 10/08/2015] [Indexed: 12/21/2022] Open
Abstract
Acetogens are efficient microbial catalysts for bioprocesses converting C1 compounds into organic products. Here, an adaptive laboratory evolution approach was implemented to adapt Sporomusa ovata for faster autotrophic metabolism and CO2 conversion to organic chemicals. S. ovata was first adapted to grow quicker autotrophically with methanol, a toxic C1 compound, as the sole substrate. Better growth on different concentrations of methanol and with H2-CO2 indicated the adapted strain had a more efficient autotrophic metabolism and a higher tolerance to solvent. The growth rate on methanol was increased 5-fold. Furthermore, acetate production rate from CO2 with an electrode serving as the electron donor was increased 6.5-fold confirming that the acceleration of the autotrophic metabolism of the adapted strain is independent of the electron donor provided. Whole-genome sequencing, transcriptomic, and biochemical studies revealed that the molecular mechanisms responsible for the novel characteristics of the adapted strain were associated with the methanol oxidation pathway and the Wood-Ljungdahl pathway of acetogens along with biosynthetic pathways, cell wall components, and protein chaperones. The results demonstrate that an efficient strategy to increase rates of CO2 conversion in bioprocesses like microbial electrosynthesis is to evolve the microbial catalyst by adaptive laboratory evolution to optimize its autotrophic metabolism.
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17
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Methanogenic degradation of lignin-derived monoaromatic compounds by microbial enrichments from rice paddy field soil. Sci Rep 2015; 5:14295. [PMID: 26399549 PMCID: PMC4585845 DOI: 10.1038/srep14295] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Accepted: 08/24/2015] [Indexed: 11/08/2022] Open
Abstract
Anaerobic degradation of lignin-derived aromatics is an important metabolism for carbon and nutrient cycles in soil environments. Although there are some studies on degradation of lignin-derived aromatics by nitrate- and sulfate-reducing bacteria, knowledge on their degradation under methanogenic conditions are quite limited. In this study, methanogenic microbial communities were enriched from rice paddy field soil with lignin-derived methoxylated monoaromatics (vanillate and syringate) and their degradation intermediates (protocatechuate, catechol, and gallate) as the sole carbon and energy sources. Archaeal community analysis disclosed that both aceticlastic (Methanosarcina sp.) and hydrogenotrophic (Methanoculleus sp. and Methanocella sp.) methanogens dominated in all of the enrichments. Bacterial community analysis revealed the dominance of acetogenic bacteria (Sporomusa spp.) only in the enrichments on the methoxylated aromatics, suggesting that Sporomusa spp. initially convert vanillate and syringate into protocatechuate and gallate, respectively, with acetogenesis via O-demethylation. As the putative ring-cleavage microbes, bacteria within the phylum Firmicutes were dominantly detected from all of the enrichments, while the dominant phylotypes were not identical between enrichments on vanillate/protocatechuate/catechol (family Peptococcaceae bacteria) and on syringate/gallate (family Ruminococcaceae bacteria). This study demonstrates the importance of cooperation among acetogens, ring-cleaving fermenters/syntrophs and aceticlastic/hydrogenotrophic methanogens for degradation of lignin-derived aromatics under methanogenic conditions.
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18
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Visser M, Pieterse MM, Pinkse MWH, Nijsse B, Verhaert PDEM, de Vos WM, Schaap PJ, Stams AJM. Unravelling the one-carbon metabolism of the acetogen Sporomusa strain An4 by genome and proteome analysis. Environ Microbiol 2015; 18:2843-55. [PMID: 26147498 DOI: 10.1111/1462-2920.12973] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Revised: 06/19/2015] [Accepted: 06/26/2015] [Indexed: 01/06/2023]
Abstract
The Sporomusa genus comprises anaerobic spore-forming acetogenic bacteria that stain Gram-negative. Sporomusa species typically grow with one-carbon substrates and N-methylated compounds. In the degradation of these compounds methyltransferases are involved. In addition, Sporomusa species can grow autotrophically with H2 and CO2 , and use a variety of sugars for acetogenic growth. Here we describe a genome analysis of Sporomusa strain An4 and a proteome analysis of cells grown under five different conditions. Comparison of the genomes of Sporomusa strain An4 and Sporomusa ovata strain H1 indicated that An4 is a S. ovata strain. Proteome analysis showed a high abundance of several methyltransferases, predominantly trimethylamine methyltransferases, during growth with betaine, whereas trimethylamine is one of the main end-products of betaine degradation. In methanol degradation methyltransferases are also involved. In methanol-utilizing methanogens, two methyltransferases catalyse methanol conversion, methyltransferase 1 composed of subunits MtaB and MtaC and methyltransferase 2, also called MtaA. The two methyltransferase 1 subunits MtaB and MtaC were highly abundant when strain An4 was grown with methanol. However, instead of MtaA a methyltetrahydrofolate methyltransferase was synthesized. We propose a novel methanol degradation pathway in Sporomusa strain An4 that uses a methyltetrahydrofolate methyltransferase instead of MtaA.
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Affiliation(s)
- Michael Visser
- Laboratory of Microbiology, Wageningen University, Stippeneng 4, 6708 WE, Wageningen, The Netherlands.
| | - Mervin M Pieterse
- Department of Biotechnology, Technische Universiteit Delft, Julianalaan 67, 2628 BC, Delft, The Netherlands.,Netherlands Proteomics Centre, Julianalaan 67, 2628 BC, Delft, The Netherlands
| | - Martijn W H Pinkse
- Department of Biotechnology, Technische Universiteit Delft, Julianalaan 67, 2628 BC, Delft, The Netherlands.,Netherlands Proteomics Centre, Julianalaan 67, 2628 BC, Delft, The Netherlands
| | - Bart Nijsse
- Laboratory of Systems and Synthetic Biology, Wageningen University, Stippeneng 4, 6708 WE, Wageningen, The Netherlands
| | - Peter D E M Verhaert
- Department of Biotechnology, Technische Universiteit Delft, Julianalaan 67, 2628 BC, Delft, The Netherlands.,Netherlands Proteomics Centre, Julianalaan 67, 2628 BC, Delft, The Netherlands
| | - Willem M de Vos
- Laboratory of Microbiology, Wageningen University, Stippeneng 4, 6708 WE, Wageningen, The Netherlands.,Department of Veterinary Biosciences, Helsinki University, Helsinki, Finland.,Department of Bacteriology and Immunology, Helsinki University, Helsinki, Finland
| | - Peter J Schaap
- Laboratory of Systems and Synthetic Biology, Wageningen University, Stippeneng 4, 6708 WE, Wageningen, The Netherlands
| | - Alfons J M Stams
- Laboratory of Microbiology, Wageningen University, Stippeneng 4, 6708 WE, Wageningen, The Netherlands.,CEB-Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057, Braga, Portugal
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19
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Heterotrimeric NADH-oxidizing methylenetetrahydrofolate reductase from the acetogenic bacterium Acetobacterium woodii. J Bacteriol 2015; 197:1681-9. [PMID: 25733614 DOI: 10.1128/jb.00048-15] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 02/24/2015] [Indexed: 01/11/2023] Open
Abstract
UNLABELLED The methylenetetrahydrofolate reductase (MTHFR) of acetogenic bacteria catalyzes the reduction of methylene-THF, which is highly exergonic with NADH as the reductant. Therefore, the enzyme was suggested to be involved in energy conservation by reducing ferredoxin via electron bifurcation, followed by Na(+) translocation by the Rnf complex. The enzyme was purified from Acetobacterium woodii and shown to have an unprecedented subunit composition containing the three subunits RnfC2, MetF, and MetV. The stable complex contained 2 flavin mononucleotides (FMN), 23.5 ± 1.2 Fe and 24.5 ± 1.5 S, which fits well to the predicted six [4Fe4S] clusters in MetV and RnfC2. The enzyme catalyzed NADH:methylviologen and NADH:ferricyanide oxidoreductase activity but also methylene-tetrahydrofolate (THF) reduction with NADH as the reductant. The NADH:methylene-THF reductase activity was high (248 U/mg) and not stimulated by ferredoxin. Furthermore, reduction of ferredoxin, alone or in the presence of methylene-THF and NADH, was never observed. MetF or MetVF was not able to catalyze the methylene-THF-dependent oxidation of NADH, but MetVF could reduce methylene-THF using methyl viologen as the electron donor. The purified MTHFR complex did not catalyze the reverse reaction, the endergonic oxidation of methyl-THF with NAD(+) as the acceptor, and this reaction could not be driven by reduced ferredoxin. However, addition of protein fractions made the oxidation of methyl-THF to methylene-THF coupled to NAD(+) reduction possible. Our data demonstrate that the MTHFR of A. woodii catalyzes methylene-THF reduction according to the following reaction: NADH + methylene-THF → methyl-THF + NAD(+). The differences in the subunit compositions of MTHFRs of bacteria are discussed in the light of their different functions. IMPORTANCE Energy conservation in the acetogenic bacterium Acetobacterium woodii involves ferredoxin reduction followed by a chemiosmotic mechanism involving Na(+)-translocating ferredoxin oxidation and a Na(+)-dependent F1Fo ATP synthase. All redox enzymes of the pathway have been characterized except the methylenetetrahydrofolate reductase (MTHFR). Here we report the purification of the MTHFR of A. woodii, which has an unprecedented heterotrimeric structure. The enzyme reduces methylene-THF with NADH. Ferredoxin did not stimulate the reaction; neither was it oxidized or reduced with NADH. Since the last enzyme with a potential role in energy metabolism of A. woodii has now been characterized, we can propose a quantitative bioenergetic scheme for acetogenesis from H2 plus CO2 in the model acetogen A. woodii.
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20
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Mingo FS, Studenik S, Diekert G. Conversion of phenyl methyl ethers byDesulfitobacteriumspp. and screening for the genes involved. FEMS Microbiol Ecol 2014; 90:783-90. [DOI: 10.1111/1574-6941.12433] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Revised: 09/09/2014] [Accepted: 09/30/2014] [Indexed: 11/29/2022] Open
Affiliation(s)
- Felix S. Mingo
- Department of Applied and Ecological Microbiology; Institute of Microbiology; Friedrich Schiller University Jena; Jena Germany
| | - Sandra Studenik
- Department of Applied and Ecological Microbiology; Institute of Microbiology; Friedrich Schiller University Jena; Jena Germany
| | - Gabriele Diekert
- Department of Applied and Ecological Microbiology; Institute of Microbiology; Friedrich Schiller University Jena; Jena Germany
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21
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Ko Y, Ashok S, Ainala SK, Sankaranarayanan M, Chun AY, Jung GY, Park S. Coenzyme B12 can be produced by engineered Escherichia coli under both anaerobic and aerobic conditions. Biotechnol J 2014; 9:1526-35. [PMID: 25146562 DOI: 10.1002/biot.201400221] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Revised: 06/23/2014] [Accepted: 08/20/2014] [Indexed: 01/27/2023]
Abstract
Coenzyme B12 (Vitamin B12 ) is one of the most complex biomolecules and an essential cofactor required for the catalytic activity of many enzymes. Pseudomonas denitrificans synthesizes coenzyme B12 in an oxygen-dependent manner using a pathway encoded by more than 25 genes that are located in six different operons. Escherichia coli, a robust and suitable host for metabolic engineering was used to produce coenzyme B12 . These genes were cloned into three compatible plasmids and expressed heterologously in E. coli BL21 (DE3). Real-time PCR, SDS-PAGE analysis and bioassay showed that the recombinant E. coli expressed the coenzyme B12 synthetic genes and successfully produced coenzyme B12 . However, according to the quantitative determination by inductively coupled plasma-mass spectrometry, the amount of coenzyme B12 produced by the recombinant E. coli (0.21 ± 0.02 μg/g cdw) was approximately 13-fold lower than that by P. denitrificans (2.75 ± 0.22 μg/g cdw). Optimization of the culture conditions to improve the production of coenzyme B12 by the recombinant E. coli was successful, and the highest titer (0.65 ± 0.03 μg/g cdw) of coenzyme B12 was obtained. Interestingly, although the synthesis of coenzyme B12 in P. denitrificans is strictly oxygen-dependent, the recombinant E. coli could produce coenzyme B12 under anaerobic conditions.
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Affiliation(s)
- Yeounjoo Ko
- School of Chemical and Biomolecular Engineering, Pusan National University, Busan, South Korea
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22
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Seth EC, Taga ME. Nutrient cross-feeding in the microbial world. Front Microbiol 2014; 5:350. [PMID: 25071756 PMCID: PMC4086397 DOI: 10.3389/fmicb.2014.00350] [Citation(s) in RCA: 183] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 06/23/2014] [Indexed: 12/25/2022] Open
Abstract
The stability and function of a microbial community depends on nutritional interactions among community members such as the cross-feeding of essential small molecules synthesized by a subset of the population. In this review, we describe examples of microbe–microbe and microbe–host cofactor cross-feeding, a type of interaction that influences the forms of metabolism carried out within a community. Cofactor cross-feeding can contribute to both the health and nutrition of a host organism, the virulence and persistence of pathogens, and the composition and function of environmental communities. By examining the impact of shared cofactors on microbes from pure culture to natural communities, we stand to gain a better understanding of the interactions that link microbes together, which may ultimately be a key to developing strategies for manipulating microbial communities with human health, agricultural, and environmental implications.
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Affiliation(s)
- Erica C Seth
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA USA
| | - Michiko E Taga
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA USA
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23
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Yamamuro A, Kouzuma A, Abe T, Watanabe K. Metagenomic analyses reveal the involvement of syntrophic consortia in methanol/electricity conversion in microbial fuel cells. PLoS One 2014; 9:e98425. [PMID: 24852573 PMCID: PMC4031174 DOI: 10.1371/journal.pone.0098425] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Accepted: 05/02/2014] [Indexed: 11/23/2022] Open
Abstract
Methanol is widely used in industrial processes, and as such, is discharged in large quantities in wastewater. Microbial fuel cells (MFCs) have the potential to recover electric energy from organic pollutants in wastewater; however, the use of MFCs to generate electricity from methanol has not been reported. In the present study, we developed single-chamber MFCs that generated electricity from methanol at the maximum power density of 220 mW m−2 (based on the projected area of the anode). In order to reveal how microbes generate electricity from methanol, pyrosequencing of 16S rRNA-gene amplicons and Illumina shotgun sequencing of metagenome were conducted. The pyrosequencing detected in abundance Dysgonomonas, Sporomusa, and Desulfovibrio in the electrolyte and anode and cathode biofilms, while Geobacter was detected only in the anode biofilm. Based on known physiological properties of these bacteria, it is considered that Sporomusa converts methanol into acetate, which is then utilized by Geobacter to generate electricity. This speculation is supported by results of shotgun metagenomics of the anode-biofilm microbes, which reconstructed relevant catabolic pathways in these bacteria. These results suggest that methanol is anaerobically catabolized by syntrophic bacterial consortia with electrodes as electron acceptors.
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Affiliation(s)
- Ayaka Yamamuro
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
| | - Atsushi Kouzuma
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
| | - Takashi Abe
- Graduate School of Science and Technology, Niigata University, Niigata, Niigata, Japan
| | - Kazuya Watanabe
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
- * E-mail:
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24
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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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25
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Growth inhibition of Sporomusa ovata by incorporation of benzimidazole bases into cobamides. J Bacteriol 2013; 195:1902-11. [PMID: 23417488 DOI: 10.1128/jb.01282-12] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Phenolyl cobamides are unique members of a class of cobalt-containing cofactors that includes vitamin B12 (cobalamin). Cobamide cofactors facilitate diverse reactions in prokaryotes and eukaryotes. Phenolyl cobamides are structurally and chemically distinct from the more commonly used benzimidazolyl cobamides such as cobalamin, as the lower axial ligand is a phenolic group rather than a benzimidazole. The functional significance of this difference is not well understood. Here we show that in the bacterium Sporomusa ovata, the only organism known to synthesize phenolyl cobamides, several cobamide-dependent acetogenic metabolisms have a requirement or preference for phenolyl cobamides. The addition of benzimidazoles to S. ovata cultures results in a decrease in growth rate when grown on methanol, 3,4-dimethoxybenzoate, H2 plus CO2, or betaine. Suppression of native p-cresolyl cobamide synthesis and production of benzimidazolyl cobamides occur upon the addition of benzimidazoles, indicating that benzimidazolyl cobamides are not functionally equivalent to the phenolyl cobamide cofactors produced by S. ovata. We further show that S. ovata is capable of incorporating other phenolic compounds into cobamides that function in methanol metabolism. These results demonstrate that S. ovata can incorporate a wide range of compounds as cobamide lower ligands, despite its preference for phenolyl cobamides in the metabolism of certain energy substrates. To our knowledge, S. ovata is unique among cobamide-dependent organisms in its preferential utilization of phenolyl cobamides.
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26
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Chan CH, Escalante-Semerena JC. ArsAB, a novel enzyme from Sporomusa ovata activates phenolic bases for adenosylcobamide biosynthesis. Mol Microbiol 2011; 81:952-67. [PMID: 21696461 DOI: 10.1111/j.1365-2958.2011.07741.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In the homoacetogenic bacterium Sporomusa ovata, phenol and p-cresol are converted into α-ribotides, which are incorporated into biologically active cobamides (Cbas) whose lower ligand bases do not form axial co-ordination bonds with the cobalt ion of the corrin ring. Here we report the identity of two S. ovata genes that encode an enzyme that transfers the phosphoribosyl group of nicotinate mononucleotide (NaMN) to phenol or p-cresol, yielding α-O-glycosidic ribotides. The alluded genes were named arsA and arsB (for alpha-ribotide synthesis), arsA and arsB were isolated from a genomic DNA library of S. ovata. A positive selection strategy using an Escherichia coli strain devoid of NaMN:5,6-dimethylbenzimidazole (DMB) phosphoribosyltransferase (CobT) activity was used to isolate a fragment of S. ovata DNA that contained arsA and arsB, whose nucleotide sequences overlapped by 8 bp. SoArsAB was isolated to homogeneity, shown to be functional as a heterodimer, and to have highest activity at pH 9. SoArsAB also activated DMB to its α-N-glycosidic ribotide. Previously characterized CobT-like enzymes activate DMB but do not activate phenolics. NMR spectroscopy was used to confirm the incorporation of phenol into the cobamide, and mass spectrometry was used to identify SoArsAB reaction products.
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Affiliation(s)
- Chi Ho Chan
- Department of Bacteriology, University of Wisconsin, 1550 Linden Drive, Madison, WI 53706-1521, USA
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27
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The ether-cleaving methyltransferase system of the strict anaerobe Acetobacterium dehalogenans: analysis and expression of the encoding genes. J Bacteriol 2008; 191:588-99. [PMID: 19011025 DOI: 10.1128/jb.01104-08] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Anaerobic O-demethylases are inducible multicomponent enzymes which mediate the cleavage of the ether bond of phenyl methyl ethers and the transfer of the methyl group to tetrahydrofolate. The genes of all components (methyltransferases I and II, CP, and activating enzyme [AE]) of the vanillate- and veratrol-O-demethylases of Acetobacterium dehalogenans were sequenced and analyzed. In A. dehalogenans, the genes for methyltransferase I, CP, and methyltransferase II of both O-demethylases are clustered. The single-copy gene for AE is not included in the O-demethylase gene clusters. It was found that AE grouped with COG3894 proteins, the function of which was unknown so far. Genes encoding COG3894 proteins with 20 to 41% amino acid sequence identity with AE are present in numerous genomes of anaerobic microorganisms. Inspection of the domain structure and genetic context of these orthologs predicts that these are also reductive activases for corrinoid enzymes (RACEs), such as carbon monoxide dehydrogenase/acetyl coenzyme A synthases or anaerobic methyltransferases. The genes encoding the O-demethylase components were heterologously expressed with a C-terminal Strep-tag in Escherichia coli, and the recombinant proteins methyltransferase I, CP, and AE were characterized. Gel shift experiments showed that the AE comigrated with the CP. The formation of other protein complexes with the O-demethylase components was not observed under the conditions used. The results point to a strong interaction of the AE with the CP. This is the first report on the functional heterologous expression of acetogenic phenyl methyl ether-cleaving O-demethylases.
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Atypical one-carbon metabolism of an acetogenic and hydrogenogenic Moorella thermoacetica strain. Arch Microbiol 2008; 191:123-31. [DOI: 10.1007/s00203-008-0435-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2008] [Revised: 09/19/2008] [Accepted: 09/24/2008] [Indexed: 10/21/2022]
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29
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Jin JS, Zhao YF, Nakamura N, Akao T, Kakiuchi N, Hattori M. Isolation and characterization of a human intestinal bacterium, Eubacterium sp. ARC-2, capable of demethylating arctigenin, in the essential metabolic process to enterolactone. Biol Pharm Bull 2007; 30:904-11. [PMID: 17473433 DOI: 10.1248/bpb.30.904] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Plant lignans, such as pinoresinol diglucoside, secoisolariciresinol diglucoside and arctiin, are metabolized to mammalian lignans, enterolactone or enterodiol, by human intestinal bacteria. Their metabolic processes include deglucosylation, ring cleavage, demethylation, dehydroxylation and oxidation. Here we isolated an intestinal bacterium capable of demethylating arctigenin, an aglycone of arctiin, to 2,3-bis(3,4-dihydroxybenzyl)butyrolactone (1) from human feces, and identified as an Eubacterium species (E. sp. ARC-2), which is similar to Eubacterium limosum on the basis of morphological and biochemical properties and 16S rRNA gene sequencing. By incubating with E. sp. ARC-2, arctigenin was converted to 1 through stepwise demethylation. Demethylation of arctigenin by E. sp. ARC-2 was tetrahydrofolate- and ATP-dependent, indicating that the reaction was catalyzed by methyltransferase. Moreover, E. sp. ARC-2 transformed secoisolariciresinol to 2,3-bis(3,4-dihydroxybenzyl)-1,4-butanediol by demethylation.
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Affiliation(s)
- Jong-Sik Jin
- Institute of Natural Medicine, University of Toyama, Toyama, Japan
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30
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Dilling S, Imkamp F, Schmidt S, Müller V. Regulation of caffeate respiration in the acetogenic bacterium Acetobacterium woodii. Appl Environ Microbiol 2007; 73:3630-6. [PMID: 17416687 PMCID: PMC1932707 DOI: 10.1128/aem.02060-06] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The anaerobic acetogenic bacterium Acetobacterium woodii can conserve energy by oxidation of various substrates coupled to either carbonate or caffeate respiration. We used a cell suspension system to study the regulation and kinetics of induction of caffeate respiration. After addition of caffeate to suspensions of fructose-grown cells, there was a lag phase of about 90 min before caffeate reduction commenced. However, in the presence of tetracycline caffeate was not reduced, indicating that de novo protein synthesis is required for the ability to respire caffeate. Induction also took place in the presence of CO(2), and once a culture was induced, caffeate and CO(2) were used simultaneously as electron acceptors. Induction of caffeate reduction was also observed with H(2) plus CO(2) as the substrate, but the lag phase was much longer. Again, caffeate and CO(2) were used simultaneously as electron acceptors. In contrast, during oxidation of methyl groups derived from methanol or betaine, acetogenesis was the preferred energy-conserving pathway, and caffeate reduction started only after acetogenesis was completed. The differential flow of reductants was also observed with suspensions of resting cells in which caffeate reduction was induced prior to harvest of the cells. These cell suspensions utilized caffeate and CO(2) simultaneously with fructose or hydrogen as electron donors, but CO(2) was preferred over caffeate during methyl group oxidation. Caffeate-induced resting cells could reduce caffeate and also p-coumarate or ferulate with hydrogen as the electron donor. p-Coumarate or ferulate also served as an inducer for caffeate reduction. Interestingly, caffeate-induced cells reduced ferulate in the absence of an external reductant, indicating that caffeate also induces the enzymes required for oxidation of the methyl group of ferulate.
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Affiliation(s)
- Sabrina Dilling
- Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Max-von-Laue-Str. 9, D-60438 Frankfurt, Germany
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31
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Siebert A, Schubert T, Engelmann T, Studenik S, Diekert G. Veratrol-O-demethylase of Acetobacterium dehalogenans: ATP-dependent reduction of the corrinoid protein. Arch Microbiol 2005; 183:378-84. [PMID: 15968525 DOI: 10.1007/s00203-005-0001-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2004] [Revised: 03/31/2005] [Accepted: 05/04/2005] [Indexed: 10/25/2022]
Abstract
The anaerobic veratrol O-demethylase mediates the transfer of the methyl group of the phenyl methyl ether veratrol to tetrahydrofolate. The primary methyl group acceptor is the cobalt of a corrinoid protein, which has to be in the +1 oxidation state to bind the methyl group. Due to the negative redox potential of the cob(II)/cob(I)alamin couple, autoxidation of the cobalt may accidentally occur. In this study, the reduction of the corrinoid to the superreduced [Co(I)] state was investigated. The ATP-dependent reduction of the corrinoid protein of the veratrol O-demethylase was shown to be dependent on titanium(III) citrate as electron donor and on an activating enzyme. In the presence of ATP, activating enzyme, and Ti(III), the redox potential versus the standard hydrogen electrode (E (SHE)) of the cob(II)alamin/cob(I)alamin couple in the corrinoid protein was determined to be -290 mV (pH 7.5), whereas E (SHE) at pH 7.5 was lower than -450 mV in the absence of either activating enzyme or ATP. ADP, AMP, or GTP could not replace ATP in the activation reaction. The ATP analogue adenosine-5'-(beta,gamma-imido)triphosphate (AMP-PNP, 2-4 mM) completely inhibited the corrinoid reduction in the presence of ATP (2 mM).
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Affiliation(s)
- Anke Siebert
- Institut für Mikrobiologie, FSU Jena, Lehrstuhl für Angewandte und Okologische Mikrobiologie, Philosophenweg 12, 07743 Jena, Germany
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32
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Demethylation of Ferulic Acid and Feruloyl-arabinoxylan by Microbial Cell Extracts. Lebensm Wiss Technol 2002. [DOI: 10.1006/fstl.2001.0856] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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33
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Lomans BP, Leijdekkers P, Wesselink JJ, Bakkes P, Pol A, van der Drift C, den Camp HJ. Obligate sulfide-dependent degradation of methoxylated aromatic compounds and formation of methanethiol and dimethyl sulfide by a freshwater sediment isolate, Parasporobacterium paucivorans gen. nov., sp. nov. Appl Environ Microbiol 2001; 67:4017-23. [PMID: 11525999 PMCID: PMC93123 DOI: 10.1128/aem.67.9.4017-4023.2001] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Methanethiol (MT) and dimethyl sulfide (DMS) have been shown to be the dominant volatile organic sulfur compounds in freshwater sediments. Previous research demonstrated that in these habitats MT and DMS are derived mainly from the methylation of sulfide. In order to identify the microorganisms that are responsible for this type of MT and DMS formation, several sulfide-rich freshwater sediments were amended with two potential methyl group-donating compounds, syringate and 3,4,5-trimethoxybenzoate (0.5 mM). The addition of these methoxylated aromatic compounds resulted in excess accumulation of MT and DMS in all sediment slurries even though methanogenic consumption of MT and DMS occurred. From one of the sediment slurries tested, a novel anaerobic bacterium was isolated with syringate as the sole carbon source. The strain, designated Parasporobacterium paucivorans, produced MT and DMS from the methoxy groups of syringate. The hydroxylated aromatic residue (gallate) was converted to acetate and butyrate. Like Sporobacterium olearium, another methoxylated aromatic compound-degrading bacterium, the isolate is a member of the XIVa cluster of the low-GC-content Clostridiales group. However, the new isolate differs from all other known methoxylated aromatic compound-degrading bacteria because it was able to degrade syringate in significant amounts only in the presence of sulfide.
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MESH Headings
- Bacteria, Anaerobic/classification
- Bacteria, Anaerobic/growth & development
- Bacteria, Anaerobic/isolation & purification
- Bacteria, Anaerobic/metabolism
- Biodegradation, Environmental
- Fresh Water/chemistry
- Fresh Water/microbiology
- Genes, rRNA
- Geologic Sediments/chemistry
- Geologic Sediments/microbiology
- Hydrocarbons, Aromatic/metabolism
- Molecular Sequence Data
- RNA, Ribosomal, 16S/genetics
- Sequence Analysis, DNA
- Sulfhydryl Compounds/metabolism
- Sulfides/metabolism
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Affiliation(s)
- B P Lomans
- Department of Microbiology, Faculty of Science, University of Nijmegen, NL-6525 ED Nijmegen, The Netherlands
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34
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Jansen M, Hansen TA. Non-growth-associated demethylation of dimethylsulfoniopropionate by (homo)acetogenic bacteria. Appl Environ Microbiol 2001; 67:300-6. [PMID: 11133459 PMCID: PMC92569 DOI: 10.1128/aem.67.1.300-306.2001] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The demethylation of the algal osmolyte dimethylsulfoniopropionate (DMSP) to methylthiopropionate (MTPA) by (homo)acetogenic bacteria was studied. Five Eubacterium limosum strains (including the type strain), Sporomusa ovata DSM 2662(T), Sporomusa sphaeroides DSM 2875(T), and Acetobacterium woodii DSM 1030(T) were shown to demethylate DMSP stoichiometrically to MTPA. The (homo)acetogenic fermentation based on this demethylation did not result in any significant increase in biomass. The analogous demethylation of glycine betaine to dimethylglycine does support growth of acetogens. In batch cultures of E. limosum PM31 DMSP and glycine betaine were demethylated simultaneously. In mixed substrates experiments with fructose-DMSP or methanol-DMSP, DMSP was used rapidly but only after exhaustion of the fructose or the methanol. In steady-state fructose-limited chemostat cultures (at a dilution rate of 0.03 h(-1)) with DMSP as a second reservoir substrate, DMSP was biotransformed to MTPA but this did not result in higher biomass values than in cultures without DMSP; cells from such cultures demethylated DMSP at rates of approximately 50 nmol min(-1) mg of protein(-1), both after growth in the presence of DMSP and after growth in its absence. In cell extracts of glycine betaine-grown strain PM31, DMSP demethylation activities of 21 to 24 nmol min(-1) mg of protein(-1) were detected with tetrahydrofolate as a methyl acceptor; the activities seen with glycine betaine were approximately 10-fold lower. A speculative explanation for the demethylation of DMSP without an obvious benefit for the organism is that the DMSP-demethylating activity is catalyzed by the glycine betaine-demethylating enzyme and that a transport-related factor, in particular a higher energy demand for DMSP transport across the cytoplasmic membrane than for glycine betaine transport, may reduce the overall ATP yield of the fermentation to virtually zero.
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Affiliation(s)
- M Jansen
- Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, NL-9750 AA Haren, The Netherlands
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35
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Hur H, Rafii F. Biotransformation of the isoflavonoids biochanin A, formononetin, and glycitein by Eubacterium limosum. FEMS Microbiol Lett 2000; 192:21-5. [PMID: 11040423 DOI: 10.1111/j.1574-6968.2000.tb09353.x] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Eubacterium limosum (ATCC 8486), a strict anaerobe from the human intestinal tract that is capable of O-demethylation of several compounds, was tested for the ability to metabolize three methoxylated isoflavonoids, biochanin A, formononetin, and glycitein. High-performance liquid chromatography elution profiles of metabolites produced from biochanin A, formononetin, and glycitein showed peaks that had identical retention times to authentic genistein, daidzein, and 6,7,4'-trihydroxyisoflavone, respectively. The metabolites were identified, using an on line liquid chromatography-electrospray mass spectrometer. E. limosum produced 61.4 microM of genistein and 13.2 microM of daidzein from 100 microM of biochanin A and formononetin, after 26 days incubation. O-demethylase activity is cell-associated and was not detected in the extracellular fraction of bacterial culture. This is the first study in which conversion of biochanin A, and formononetin to more potent phytoestrogens by a bacterium has been shown.
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Affiliation(s)
- H Hur
- Division of Microbiology, National Center for Toxicological Research, US FDA, Jefferson, AR 72079, USA
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36
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Sonoki T, Obi T, Kubota S, Higashi M, Masai E, Katayama Y. Coexistence of two different O demethylation systems in lignin metabolism by Sphingomonas paucimobilis SYK-6: cloning and sequencing of the lignin biphenyl-specific O-demethylase (LigX) gene. Appl Environ Microbiol 2000; 66:2125-32. [PMID: 10788391 PMCID: PMC101464 DOI: 10.1128/aem.66.5.2125-2132.2000] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sphingomonas paucimobilis SYK-6 can grow on several dimeric model compounds of lignin as a carbon and energy source. It has O demethylation systems on three kinds of substrates: 5, 5'-dehydrodivanillic acid (DDVA), syringate, and vanillate. We previously reported the cloning of a gene involved in the tetrahydrofolate-dependent O demethylation of syringate and vanillate. In the study reported here, we cloned the gene responsible for DDVA O demethylation. Using nitrosoguanidine mutagenesis, a mutant strain, NT-1, which could not degrade DDVA but could degrade syringate and vanillate, was isolated and was used to clone the gene responsible for the O demethylation of DDVA by complementation. Sequencing analysis showed an open reading frame (designated ligX) of 1,266 bp in this fragment. The deduced amino acid sequence of LigX had similarity to class I type oxygenases. LigX was involved in O demethylation activity on DDVA but not on vanillate and syringate. DDVA O demethylation activity in S. paucimobilis SYK-6 cell extracts was inhibited by addition of the LigX polyclonal antiserum. Thus, LigX is an essential enzyme for DDVA O demethylation in SYK-6. S. paucimobilis SYK-6 has two O demethylation systems: one is an oxygenative demethylase system, and the other is a tetrahydrofolate-dependent methyltransferase system.
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Affiliation(s)
- T Sonoki
- Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan.
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37
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Coulter C, Hamilton JT, McRoberts WC, Kulakov L, Larkin MJ, Harper DB. Halomethane:bisulfide/halide ion methyltransferase, an unusual corrinoid enzyme of environmental significance isolated from an aerobic methylotroph using chloromethane as the sole carbon source. Appl Environ Microbiol 1999; 65:4301-12. [PMID: 10508052 PMCID: PMC91570 DOI: 10.1128/aem.65.10.4301-4312.1999] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/1999] [Accepted: 07/20/1999] [Indexed: 11/20/2022] Open
Abstract
A novel dehalogenating/transhalogenating enzyme, halomethane:bisulfide/halide ion methyltransferase, has been isolated from the facultatively methylotrophic bacterium strain CC495, which uses chloromethane (CH(3)Cl) as the sole carbon source. Purification of the enzyme to homogeneity was achieved in high yield by anion-exchange chromatography and gel filtration. The methyltransferase was composed of a 67-kDa protein with a corrinoid-bound cobalt atom. The purified enzyme was inactive but was activated by preincubation with 5 mM dithiothreitol and 0.5 mM CH(3)Cl; then it catalyzed methyl transfer from CH(3)Cl, CH(3)Br, or CH(3)I to the following acceptor ions (in order of decreasing efficacy): I(-), HS(-), Cl(-), Br(-), NO(2)(-), CN(-), and SCN(-). Spectral analysis indicated that cobalt in the native enzyme existed as cob(II)alamin, which upon activation was reduced to the cob(I)alamin state and then was oxidized to methyl cob(III)alamin. During catalysis, the enzyme shuttles between the methyl cob(III)alamin and cob(I)alamin states, being alternately demethylated by the acceptor ion and remethylated by halomethane. Mechanistically the methyltransferase shows features in common with cobalamin-dependent methionine synthase from Escherichia coli. However, the failure of specific inhibitors of methionine synthase such as propyl iodide, N(2)O, and Hg(2+) to affect the methyltransferase suggests significant differences. During CH(3)Cl degradation by strain CC495, the physiological acceptor ion for the enzyme is probably HS(-), a hypothesis supported by the detection in cell extracts of methanethiol oxidase and formaldehyde dehydrogenase activities which provide a metabolic route to formate. 16S rRNA sequence analysis indicated that strain CC495 clusters with Rhizobium spp. in the alpha subdivision of the Proteobacteria and is closely related to strain IMB-1, a recently isolated CH(3)Br-degrading bacterium (T. L. Connell Hancock, A. M. Costello, M. E. Lidstrom, and R. S. Oremland, Appl. Environ. Microbiol. 64:2899-2905, 1998). The presence of this methyltransferase in bacterial populations in soil and sediments, if widespread, has important environmental implications.
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Affiliation(s)
- C Coulter
- Microbial Biochemistry Section, School of Agriculture and Food Science, Belfast, United Kingdom
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38
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Verhagen FJ, Swarts HJ, Wijnberg JB, Field JA. Biotransformation of the major fungal metabolite 3,5-dichloro- p-anisyl alcohol under anaerobic conditions and its role in formation of Bis(3,5-dichloro-4-Hydroxyphenyl)methane. Appl Environ Microbiol 1998; 64:3225-31. [PMID: 9726864 PMCID: PMC106714 DOI: 10.1128/aem.64.9.3225-3231.1998] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Higher fungi have a widespread capacity for biosynthesis of organohalogens. Commonly occurring chloroaromatic fungal metabolites can end up in anaerobic microniches at the boundary of fungal colonies and wetland soils. The aim of this study was to investigate the environmental fate of a major fungal metabolite, 3, 5-dichloro-p-anisyl alcohol, under anaerobic conditions. This compound was incubated with methanogenic sludge to study its biotransformation reactions. Initially, 3,5-dichloro-p-anisyl alcohol was readily demethylated in stoichiometric quantities to 3, 5-dichloro-4-hydroxybenzyl alcohol. The demethylated product was converted further via two routes: a biotic route leading to the formation of 3,5-dichloro-4-hydroxybenzoate and 2,6-dichlorophenol, as well as an abiotic route leading to the formation of bis(3, 5-dichloro-4-hydroxyphenyl)methane. In the first route, the benzyl alcohol moiety on the aromatic ring was oxidized, giving 3, 5-dichloro-4-hydroxybenzoate as a transient or accumulating product, depending on the type of methanogenic sludge used. In sludge previously adapted to low-molecular-weight lignin from straw, a part of the 3,5-dichloro-4-hydroxybenzoate was decarboxylated, yielding detectable levels of 2,6-dichlorophenol. In the second route, 3, 5-dichloro-4-hydroxybenzyl alcohol dimerized, leading to the formation of a tetrachlorinated bisphenolic compound, which was identified as bis(3,5-dichloro-4-hydroxyphenyl)methane. Since formation of this dimer was also observed in incubations with autoclaved sludge spiked with 3,5-dichloro-4-hydroxybenzyl alcohol, it was concluded that its formation was due to an abiotic process. However, demethylation of the fungal metabolite by biological processes was a prerequisite for dimerization. The most probable reaction mechanism leading to the formation of the tetrachlorinated dimer in the absence of oxygen is presented, and the possible environmental implications of its natural occurrence are discussed.
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Affiliation(s)
- F J Verhagen
- Division of Industrial Microbiology, Department of Food Technology and Nutritional Sciences, Wageningen Agricultural University, Wageningen, The Netherlands.
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39
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Schnyder A, Darbre T, Keese R. Methyltransfer von Methanol auf Co-Cobyrinate: ein Modell für die Coenzym-B12-abhängige Methyltransferase? Angew Chem Int Ed Engl 1998. [DOI: 10.1002/(sici)1521-3757(19980504)110:9<1301::aid-ange1301>3.0.co;2-s] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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40
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Nishikawa S, Sonoki T, Kasahara T, Obi T, Kubota S, Kawai S, Morohoshi N, Katayama Y. Cloning and sequencing of the Sphingomonas (Pseudomonas) paucimobilis gene essential for the O demethylation of vanillate and syringate. Appl Environ Microbiol 1998; 64:836-42. [PMID: 9501423 PMCID: PMC106335 DOI: 10.1128/aem.64.3.836-842.1998] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Sphingomonas (Pseudomonas) paucimobilis SYK-6 is able to grow on 5,5'-dehydrodivanillic acid (DDVA), syringate, vanillate, and other dimeric model compounds of lignin as a sole carbon source. Nitrosoguanidine mutagenesis of S. paucimobilis SYK-6 was performed, and two mutants with altered DDVA degradation pathways were isolated. The mutant strain NT-1 could not degrade DDVA, but could degrade syringate, vanillate, and 2,2',3'-trihydroxy-3-methoxy-5,5'-dicarboxybiphenyl (OH-DDVA). Strain DC-49 could slowly assimilate DDVA, but could degrade neither vanillate nor syringate, although it could degrade protocatechuate and 3-O-methylgallate. A complementing DNA fragment of strain DC-49 was isolated from the cosmid library of strain SYK-6. The minimum DNA fragment complementing DC-49 was determined to be the 1.8-kbp insert of pKEX2.0. Sequencing analysis showed an open reading frame of 1,671 bp in this fragment, and a similarity search indicated that the deduced amino acid sequence of this open reading frame had significant similarity (60%) to the formyltetrahydrofolate synthetase of Clostridium thermoaceticum.
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Affiliation(s)
- S Nishikawa
- New Products & Technology Laboratory, Cosmo Research Institute, Saitama, Japan.
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41
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Mägli A, Messmer M, Leisinger T. Metabolism of Dichloromethane by the Strict Anaerobe Dehalobacterium formicoaceticum. Appl Environ Microbiol 1998; 64:646-50. [PMID: 16349505 PMCID: PMC106096 DOI: 10.1128/aem.64.2.646-650.1998] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/1997] [Accepted: 11/07/1997] [Indexed: 11/20/2022] Open
Abstract
The metabolism of dichloromethane by Dehalobacterium formicoaceticum in cell suspensions and crude cell extracts was investigated. The organism is a strictly anaerobic gram-positive bacterium that utilizes exclusively dichloromethane as a growth substrate and ferments this compound to formate and acetate in a molar ratio of 2:1. When [C]dichloromethane was degraded by cell suspensions, formate, the methyl group of acetate, and minor amounts of methanol were labeled, but there was no nuclear magnetic resonance signal corresponding to the carboxyl group of acetate. This finding and previously established carbon and electron balances suggested that dichloromethane was converted to methylene tetrahydrofolate, of which two-thirds was oxidized to formate while one-third gave rise to acetate by incorporation of CO(2) from the medium in the acetyl coenzyme A synthase reaction. When crude desalted extracts were incubated in the presence of dichloromethane, tetrahydrofolate, ATP, methyl viologen, and molecular hydrogen, dichloromethane and tetrahydrofolate were consumed, with the concomitant formation of stoichiometric amounts of methylene tetrahydrofolate. The in vitro transfer of the methylene group of dichloromethane onto tetrahydrofolate required substoichiometric amounts of ATP. The reaction was inhibited in a light-reversible fashion by 20 muM propyl iodide, thus suggesting involvement of a Co(I) corrinoid in the anoxic dehalogenation of dichloromethane. D. formicoaceticum exhibited normal growth with 0.8 mM sodium in the medium, and crude extracts contained ATPase activity that was partially inhibited by N,N'-dicyclohexylcarbodiimide and azide. During growth with dichloromethane, the organism thus may conserve energy not only by substrate-level phosphorylation but also by a chemiosmotic mechanism involving a sodium-independent F(0)F(1)-type ATP synthase.
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Affiliation(s)
- A Mägli
- Mikrobiologisches Institut, ETH Zürich, CH-8092 Zürich, Switzerland
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42
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Florencio L, Field JA, Lettinga G. HIGH-RATE ANAEROBIC TREATMENT OF ALCOHOLIC WASTEWATERS. BRAZILIAN JOURNAL OF CHEMICAL ENGINEERING 1997. [DOI: 10.1590/s0104-66321997000400016] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/03/2023]
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43
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Kamlage B, Gruhl B, Blaut M. Isolation and characterization of two new homoacetogenic hydrogen-utilizing bacteria from the human intestinal tract that are closely related to Clostridium coccoides. Appl Environ Microbiol 1997; 63:1732-8. [PMID: 9143110 PMCID: PMC168470 DOI: 10.1128/aem.63.5.1732-1738.1997] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Two gram-positive, strictly anoxic, coccoid- to rod-shaped strains of bacteria, Clostridium coccoides 1410 and C. coccoides 3110, were isolated from human feces on the typical homoacetogenic substrates formate plus H2 plus CO2 (strain 1410) and vanillate plus H2 plus CO2 (strain 3110) in the presence of 2-bromoethanesulfonate to inhibit methanogenesis. On the basis of 16S rRNA sequencing, DNA-DNA hybridization, and physiological and morphological parameters, both isolates are closely related to C. coccoides DSM 935T. The G+C contents of the DNA were 46.1 and 46.2 mol% for C. coccoides 1410 and C. coccoides 3110, respectively. Cytochromes could not be detected. Formate was degraded exclusively to acetate, whereas vanillate was O-demethylated, resulting in acetate and 3,4-dihydroxybenzoate, the latter being further decarboxylated to catechol. In the presence of organic substrates, H2 was cometabolized to acetate, but both strains failed to grow autotrophically. Lactose, lactulose, sorbitol, glucose, and various other carbohydrates supported growth as well. Untypical of homoacetogens, glucose and sorbitol were fermented not exclusively to acetate; instead, considerable amounts of succinate and D-lactate were produced. H2 was evolved from carbohydrates only in negligible traces. Acetogenesis from formate plus H2 plus CO2 or vanillate plus H2 plus CO2 was constitutive, whereas utilization of carbohydrates was inducible. Hydrogenase, CO dehydrogenase, formate dehydrogenase, and all of the tetrahydrofolic acid-dependent, C1 compound-converting enzymes of the acetyl-coenzyme A pathway of homoacetogenesis were present in cell extracts.
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Affiliation(s)
- B Kamlage
- German Institute of Human Nutrition (DIfE), Department of Gastrointestinal Microbiology, Potsdam-Rehbrücke, Germany.
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44
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Abstract
Aromatic compounds comprise a wide variety of low-molecular-mass natural compounds (amino acids, quinones, flavonoids, etc.) and biopolymers (lignin, melanin). They are almost exclusively degraded by microorganisms. Aerobic aromatic metabolism is characterised by the extensive use of molecular oxygen. Monoxygenases and dioxygenases are essential for the hydroxylation and cleavage of aromatic ring structures. Accordingly, the characteristic central intermediates of the aerobic pathways (e.g. catechol) are readily attacked oxidatively. Anaerobic aromatic catabolism requires, of necessity, a quite different strategy. The basic features of this metabolism have emerged from studies on bacteria that degrade soluble aromatic substrates to CO2 in the complete absence of molecular oxygen. Essential to anaerobic aromatic metabolism is the replacement of all the oxygen-dependent steps by an alternative set of novel reactions and the formation of different central intermediates (e.g. benzoyl-CoA) for breaking the aromaticity and cleaving the ring; notably, in anaerobic pathways, the aromatic ring is reduced rather than oxidised. The two-electron reduction of benzoyl-CoA to a cyclic diene requires the cleavage of two molecules of ATP to ADP and P1 and is catalysed by benzoyl-CoA reductase. After nitrogenase, this is the second enzyme known which overcomes the high activation energy required for reduction of a chemically stable bond by coupling electron transfer to the hydrolysis of ATP. The alicyclic product cyclohex-1,5-diene-1-carboxyl-CoA is oxidised to acetyl-CoA via a modified beta-oxidation pathway; the ring structure is opened hydrolytically. Some phenolic compounds are anaerobically transformed to resorcinol (1,3-dihydroxybenzene) or phloroglucinol (1,3,5-trihydroxybenzene). These intermediates are also first reduced and then as alicyclic products oxidised to acetyl-CoA. This review gives an outline of the anaerobic pathways which allow bacteria to utilize aromatics even in the absence of oxygen. We focus on previously unknown reactions and on the enzymes characteristic for such novel metabolism.
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Affiliation(s)
- J Heider
- Institut für Biologie II, Universităt Freiburg, Germany
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45
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Fröstl JM, Seifritz C, Drake HL. Effect of nitrate on the autotrophic metabolism of the acetogens Clostridium thermoautotrophicum and Clostridium thermoaceticum. J Bacteriol 1996; 178:4597-603. [PMID: 8755890 PMCID: PMC178229 DOI: 10.1128/jb.178.15.4597-4603.1996] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Although nitrate stimulated the capacity of Clostridium thermoautotrophicum and Clostridium thermoaceticum to oxidize (utilize) substrates under heterotrophic conditions, it inhibited autotrophic H2-CO2-dependent growth. Under basal medium conditions, nitrate was also inhibitory to the use of one-carbon substrates (i.e., CO, formate, methanol, or the O-methyl groups of vanillate or syringate) as sole carbon energy sources. This inhibitory effect of nitrate was bypassed when both O-methyl groups and CO were provided concomitantly; H2-CO2 did not replace CO. These results indicated that nitrate blocked the reduction of CO2 to the methyl and carbonyl levels. On the basis of the inability of acetogenic cells (i.e., cells cultivated without nitrate) to consume or reduce nitrate in resting-cell assays, the capacity to dissimilate nitrate was not constitutive. Nitrate had no appreciable effect on the specific activities of enzymes central to the acetyl-coenzyme A (CoA) pathway. However, membranes obtained from cells cultivated under nitrate-dissimilating conditions were deficient in the b-type cytochrome that was typical of membranes from acetogenic cells, i.e., cells dependent upon the synthesis of acetate for the conservation of energy. Collectively, these findings indicated that (i) C. thermoautotrophicum and C. thermoaceticum cannot engage the carbon-fixing capacities of the acetyl-CoA pathway in the presence of nitrate and (ii) the nitrate block on the acetyl-CoA pathway occurs via an alteration in electron transport.
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Affiliation(s)
- J M Fröstl
- Lehrstuhl für Okologische Mikrobiologie, BITOK, Universität Bayreuth,Germany
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46
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Affiliation(s)
- G F White
- School of Molecular and Medical Biosciences, University of Wales, Cardiff.
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47
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Hanselmann K, Kaiser J, Wenk M, Schön R, Bachofen R. Growth on methanol and conversion of methoxylated aromatic substrates by Desulfotomaculum orientis in the presence and absence of sulfate. Microbiol Res 1995. [DOI: 10.1016/s0944-5013(11)80021-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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48
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H2 as an energy source for mixotrophic acetogenesis from the reduction of CO2 and syringate by Acetobacterium woodii and Eubacterium limosum. Curr Microbiol 1995. [DOI: 10.1007/bf00298382] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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49
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Abstract
Activity of glycine decarboxylase decreased by 60-70% after the isolated pea leaf mitochondria were aged for 5 h in the absence of glycine and was completely lost after 24 h. The reverse reaction, i.e., production of glycine from serine, ammonium, dihydrolipoate, and bicarbonate, was also inhibited in these aged mitochondria. Glycine decarboxylase could be reactivated by both exogenous and endogenous ATP. The latter was formed during the oxidation of succinate, malate, or oxoglutarate. Glycine decarboxylase consists of four subunits (P-, H-, L-, and T-proteins). The aged mitochondria were able to catalyze the exchange of [14C]-bicarbonate-glycine and the oxidation of dihydrolipoate, indicating the persistence of P-, H-, and L-protein activities. Serine hydroxymethyltransferase catalyzes the formation of serine from methylene tetrahydrofolate and another glycine and molecule at the last reaction of glycine oxidation. The aged mitochondria were able to catalyze the formation of methylene tetrahydrofolate from [14C]serine and its reverse reaction. Therefore, it was concluded that the loss of glycine decarboxylase activity was due to an inhibition of the reaction catalyzed by T-protein, which required ATP for its activation.
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Affiliation(s)
- Q Zhang
- Department of Botany, University of Adelaide, Australia
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50
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Kreft JU, Schink B. O-demethylation by the homoacetogenic anaerobe Holophaga foetida studied by a new photometric methylation assay using electrochemically produced cob(I)alamin. EUROPEAN JOURNAL OF BIOCHEMISTRY 1994; 226:945-51. [PMID: 7813485 DOI: 10.1111/j.1432-1033.1994.00945.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The previously studied complete methyl transfer sequence of tetrahydrofolate-dependent O-demethylation catalyzed by Holophaga foetida strain TMBS4 extracts was separated into two steps using cobalamins as non-physiological substrates: electrochemically produced cob(I) alamin served as methyl acceptor for phenyl methyl ether demethylation, yielding methylcob(III)alamin (reaction I), and methylcob(III)alamin served as donor for tetrahydrofolate methylation, yielding 5-methyl tetrahydrofolate (reaction II). Both reactions were measured with a new and direct photometric assay of cob(I)alamin methylation (or the reverse reaction) at 540 nm, the isobestic wavelength of the cob(II)alamin/cob(I)alamin redox couple (delta epsilon 540 = 4.40 nM-1.cm-1. The rates of reactions I and II were proportional to protein concentration, unlike the complete reaction sequence. Small components of cell extract did not affect activity of reactions I and II. Isovanillate demethylation by extracts of synringate-grown cells (reaction I) required reductive activation by cob(I)alamin and was inhibited and inactivated by cob(II)alamin, indicating that the reaction mechanism was a nucleophilic attack of an enzyme-bound corrinoid in the reduced Co(I) state on the methyl carbon of the ether, rather than a radical attack. Only phenyl methyl ethers were demethylated; demethylation rates were enhanced by ortho-hydroxyl or para-carboxyl groups, but reduced by additional meta substituents. The rate of isovanillate demethylation was 81 nmol.min-1.(mg protein)-1 [0.76 mM cob(I)alamin] and apparent kinetic constants for cob(I)alamin were: Km = 1.2 mM, Vmax = 220 nmol min-1.(mg protein)-1, and Vmax/Km = 180 nmol.min-1.(mg protein) 1.mM-1 3,5-Dihydroxyanisole demethylation by extracts of 3,5-dihydroxyanisole-grown cells (also reaction I) was much slower. Reaction II did not require activation; specific activity and the specificity constant for methylcob(III)alamin were much lower.
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Affiliation(s)
- J U Kreft
- Fakultät für Biologie, Universität Konstanz, Germany
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