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Beraud-Martínez LK, Betancourt-Lozano M, Gómez-Gil B, Asaff-Torres A, Monroy-Hermosillo OA, Franco-Nava MÁ. Methylotrophic methanogenesis induced by ammonia nitrogen in an anaerobic digestion system. Anaerobe 2024; 88:102877. [PMID: 38866129 DOI: 10.1016/j.anaerobe.2024.102877] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Revised: 05/08/2024] [Accepted: 06/06/2024] [Indexed: 06/14/2024]
Abstract
OBJECTIVES This lab-scale study aimed to investigate the effect of total ammonia nitrogen (TAN) stress on the methanogenic activity and the taxonomic and functional profiles of the microbial community of anaerobic sludge (AS) from a full-scale bioreactor. METHODS The AS was subjected to a stepwise increase in TAN every 14 days at concentrations of 1, 2, 2.5, 3, 3.5, and 4 g TAN/L (Acclimated-AS or AAS). This acclimation stage was followed by an ammonia stress stage (4 g/L). A blank-AS (BAS) was maintained without TAN during the acclimation stage. In the second stress stage (ST), the BAS was divided into two new treatments: a control (BAS') and one that received a shock load of TAN of 4 g/L (SBAS'). Methane production was measured, and a metagenomic analysis was conducted to describe the microbial community. RESULTS A decrease in the relative abundance of Methanothrix soehngenii of 16 % was related to a decrease of 23 % in the methanogenic capacity of AAS when comparing with the final stage of BAS. However, recovery was observed at 3.5 g TAN/L, and a shift to methylotrophic metabolism occurred, indicated by a 4-fold increase in abundance of Methanosarcina mazei. The functional analysis of sludge metagenomes indicated that no statistical differences (p > 0.05, RM ANOVA) were found in the relative abundance of methanogenic genes that initiate acetoclastic and hydrogenotrophic pathways (acetyl-CoA synthetase, ACSS; acetate kinase, ackA; phosphate acetyltransferase, pta; and formylmethanofuran dehydrogenase subunit A, fwdA) into the BAS and AAS during the acclimation phase. The same was observed between groups of genes associated with methanogenesis from methylated compounds. In contrast, statistical differences (p < 0.05, one-way ANOVA) in the relative abundance of these genes were recorded during ST. The functional profiles of the genes involved in acetoclastic, hydrogenotrophic, and methylotrophic methanogenic pathways were brought to light for acclimatation and stress experimental stages. CONCLUSIONS TAN inhibited methanogenic activity and acetoclastic metabolism. The gradual acclimatization to TAN leads to metabolic and taxonomic changes that allow for the subsequent recovery of methanogenic functionality. The study highlights the importance of adequate management of anaerobic bioprocesses with high nitrogen loads to maintain the methanogenic functionality of the microbial community.
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Affiliation(s)
- Liov Karel Beraud-Martínez
- Centro de Investigación en Alimentación y Desarrollo (CIAD), A. C. Unidad Mazatlán, Avenida Sábalo-Cerritos s/n, Mazatlán, Sinaloa, 82112, Mexico
| | - Miguel Betancourt-Lozano
- Centro de Investigación en Alimentación y Desarrollo (CIAD), A. C. Unidad Mazatlán, Avenida Sábalo-Cerritos s/n, Mazatlán, Sinaloa, 82112, Mexico
| | - Bruno Gómez-Gil
- Centro de Investigación en Alimentación y Desarrollo (CIAD), A. C. Unidad Mazatlán, Avenida Sábalo-Cerritos s/n, Mazatlán, Sinaloa, 82112, Mexico
| | - Ali Asaff-Torres
- Centro de Investigación en Alimentación y Desarrollo (CIAD), A.C. Unidad Hermosillo, Carretera Gustavo Enrique Astiazarán Rosas, No. 46, Col. La Victoria, CP. 83304, Hermosillo, Sonora, Mexico
| | - Oscar Armando Monroy-Hermosillo
- Universidad Autónoma Metropolitana. Biotechnology Department, Av. San Rafael Atlixco 186, Col. Vicentina, 09340, Iztapalapa, Cd. México, Mexico
| | - Miguel Ángel Franco-Nava
- Tecnológico Nacional de México, Campus Mazatlán, Calle Corsario 1 No. 203 Col. Urías, A.P. 757, Mazatlán, Sinaloa, 82070, Mexico.
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Identification of a Novel Dehydrogenase from Gluconobacter oxydans for Degradation of Inhibitors Derived from Lignocellulosic Biomass. FERMENTATION-BASEL 2023. [DOI: 10.3390/fermentation9030286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/17/2023]
Abstract
Inhibitors from lignocellulosic biomass have become the bottleneck of biorefinery development. Gluconobacter oxydans DSM2003 showed a high performance of inhibitors degradation, which had a short lag time in non-detoxified corn stover hydrolysate and could convert 90% of aldehyde inhibitors to weaker toxic acids. In this study, an aldehyde dehydrogenase gene W826-RS0111485, which plays an important function in the conversion of aldehyde inhibitors in Gluconobacter oxydans DSM2003, was identified. W826-RS0111485 was found by protein profiling, then a series of enzymatic properties were determined and were heterologously expressed in E. coli. The results indicated that NADP is the most suitable cofactor of the enzyme when aldehyde inhibitor is the substrate, and it had the highest oxidation activity to furfural among several aldehyde inhibitors. Under the optimal reaction conditions (50 °C, pH 7.5), the Km and Vmax of the enzyme under furfural stress were 2.45 and 80.97, respectively, and the Kcat was 232.22 min−1. The biodetoxification performance experiments showed that the recombinant E. coli containing the target gene completely converted 1 g/L furfural to furoic acid within 8 h, while the control E. coli only converted 18% furfural within 8 h. It was further demonstrated that W826-RS0111485 played an important role in the detoxification of furfural. The mining of this inhibitor degradation gene could provide a theoretical basis for rational modification of industrial strains to enhance its capacity of inhibitor degradation in the future.
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Ou YF, Dong HP, McIlroy SJ, Crowe SA, Hallam SJ, Han P, Kallmeyer J, Simister RL, Vuillemin A, Leu AO, Liu Z, Zheng YL, Sun QL, Liu M, Tyson GW, Hou LJ. Expanding the phylogenetic distribution of cytochrome b-containing methanogenic archaea sheds light on the evolution of methanogenesis. THE ISME JOURNAL 2022; 16:2373-2387. [PMID: 35810262 PMCID: PMC9478090 DOI: 10.1038/s41396-022-01281-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 06/20/2022] [Accepted: 06/22/2022] [Indexed: 05/28/2023]
Abstract
Methane produced by methanogenic archaea has an important influence on Earth's changing climate. Methanogenic archaea are phylogenetically diverse and widespread in anoxic environments. These microorganisms can be divided into two subgroups based on whether or not they use b-type cytochromes for energy conservation. Methanogens with b-type cytochromes have a wider substrate range and higher growth yields than those without them. To date, methanogens with b-type cytochromes were found exclusively in the phylum "Ca. Halobacteriota" (formerly part of the phylum Euryarchaeota). Here, we present the discovery of metagenome-assembled genomes harboring methyl-coenzyme M reductase genes reconstructed from mesophilic anoxic sediments, together with the previously reported thermophilic "Ca. Methylarchaeum tengchongensis", representing a novel archaeal order, designated the "Ca. Methylarchaeales", of the phylum Thermoproteota (formerly the TACK superphylum). These microorganisms contain genes required for methyl-reducing methanogenesis and the Wood-Ljundahl pathway. Importantly, the genus "Ca. Methanotowutia" of the "Ca. Methylarchaeales" encode a cytochrome b-containing heterodisulfide reductase (HdrDE) and methanophenazine-reducing hydrogenase complex that have similar gene arrangements to those found in methanogenic Methanosarcinales. Our results indicate that members of the "Ca. Methylarchaeales" are methanogens with cytochromes and can conserve energy via membrane-bound electron transport chains. Phylogenetic and amalgamated likelihood estimation analyses indicate that methanogens with cytochrome b-containing electron transfer complexes likely evolved before diversification of Thermoproteota or "Ca. Halobacteriota" in the early Archean Eon. Surveys of public sequence databases suggest that members of the lineage are globally distributed in anoxic sediments and may be important players in the methane cycle.
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Affiliation(s)
- Ya-Fei Ou
- State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200241, China
| | - Hong-Po Dong
- State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200241, China.
| | - Simon J McIlroy
- Centre for Microbiome Research, School of Biomedical Sciences, Queensland University of Technology (QUT), Translational Research Institute, Woolloongabba, QLD, 4102, Australia
| | - Sean A Crowe
- Ecosystem Services, Commercialization Platforms, and Entrepreneurship (ECOSCOPE) Training Program, University of British Columbia, Vancouver, BC, Canada
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| | - Steven J Hallam
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| | - Ping Han
- Key Laboratory of Geographic Information Science, Ministry of Education, East China Normal University, Shanghai, 200241, China
| | - Jens Kallmeyer
- GFZ German Research Centre for Geosciences, Section Geomicrobiology, Potsdam, Germany
| | - Rachel L Simister
- Ecosystem Services, Commercialization Platforms, and Entrepreneurship (ECOSCOPE) Training Program, University of British Columbia, Vancouver, BC, Canada
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| | - Aurele Vuillemin
- GFZ German Research Centre for Geosciences, Section Geomicrobiology, Potsdam, Germany
| | - Andy O Leu
- Centre for Microbiome Research, School of Biomedical Sciences, Queensland University of Technology (QUT), Translational Research Institute, Woolloongabba, QLD, 4102, Australia
| | - Zhanfei Liu
- Marine Science Institute, The University of Texas at Austin, Port Aransas, TX, 78373, USA
| | - Yan-Ling Zheng
- Key Laboratory of Geographic Information Science, Ministry of Education, East China Normal University, Shanghai, 200241, China
| | - Qian-Li Sun
- State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200241, China
| | - Min Liu
- Key Laboratory of Geographic Information Science, Ministry of Education, East China Normal University, Shanghai, 200241, China
| | - Gene W Tyson
- Centre for Microbiome Research, School of Biomedical Sciences, Queensland University of Technology (QUT), Translational Research Institute, Woolloongabba, QLD, 4102, Australia
| | - Li-Jun Hou
- State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200241, China.
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Energy Conservation and Hydrogenase Function in Methanogenic Archaea, in Particular the Genus Methanosarcina. Microbiol Mol Biol Rev 2019; 83:83/4/e00020-19. [PMID: 31533962 DOI: 10.1128/mmbr.00020-19] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The biological production of methane is vital to the global carbon cycle and accounts for ca. 74% of total methane emissions. The organisms that facilitate this process, methanogenic archaea, belong to a large and phylogenetically diverse group that thrives in a wide range of anaerobic environments. Two main subgroups exist within methanogenic archaea: those with and those without cytochromes. Although a variety of metabolisms exist within this group, the reduction of growth substrates to methane using electrons from molecular hydrogen is, in a phylogenetic sense, the most widespread methanogenic pathway. Methanogens without cytochromes typically generate methane by the reduction of CO2 with electrons derived from H2, formate, or secondary alcohols, generating a transmembrane ion gradient for ATP production via an Na+-translocating methyltransferase (Mtr). These organisms also conserve energy with a novel flavin-based electron bifurcation mechanism, wherein the endergonic reduction of ferredoxin is facilitated by the exergonic reduction of a disulfide terminal electron acceptor coupled to either H2 or formate oxidation. Methanogens that utilize cytochromes have a broader substrate range, and can convert acetate and methylated compounds to methane, in addition to the ability to reduce CO2 Cytochrome-containing methanogens are able to supplement the ion motive force generated by Mtr with an H+-translocating electron transport system. In both groups, enzymes known as hydrogenases, which reversibly interconvert protons and electrons to molecular hydrogen, play a central role in the methanogenic process. This review discusses recent insight into methanogen metabolism and energy conservation mechanisms with a particular focus on the genus Methanosarcina.
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Abstract
Anaerobic methane oxidation in archaea is often presented to operate via a pathway of “reverse methanogenesis”. However, if the cumulative reactions of a methanogen are run in reverse there is no apparent way to conserve energy. Recent findings suggest that chemiosmotic coupling enzymes known from their use in methylotrophic and acetoclastic methanogens—in addition to unique terminal reductases—biochemically facilitate energy conservation during complete CH4 oxidation to CO2. The apparent enzyme modularity of these organisms highlights how microbes can arrange their energy metabolisms to accommodate diverse chemical potentials in various ecological niches, even in the extreme case of utilizing “reverse” thermodynamic potentials.
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Hocking WP, Stokke R, Roalkvam I, Steen IH. Identification of key components in the energy metabolism of the hyperthermophilic sulfate-reducing archaeon Archaeoglobus fulgidus by transcriptome analyses. Front Microbiol 2014; 5:95. [PMID: 24672515 PMCID: PMC3949148 DOI: 10.3389/fmicb.2014.00095] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 02/20/2014] [Indexed: 11/23/2022] Open
Abstract
Energy conservation via the pathway of dissimilatory sulfate reduction is present in a diverse group of prokaryotes, but is most comprehensively studied in Deltaproteobacteria. In this study, whole-genome microarray analyses were used to provide a model of the energy metabolism of the sulfate-reducing archaeon Archaeoglobus fulgidus, based on comparative analysis of litoautotrophic growth with H2/CO2 and thiosulfate, and heterotrophic growth on lactate with sulfate or thiosulfate. Only 72 genes were expressed differentially between the cultures utilizing sulfate or thiosulfate, whereas 269 genes were affected by a shift in energy source. We identified co-located gene cluster encoding putative lactate dehydrogenases (LDHs; lldD, dld, lldEFG), also present in sulfate-reducing bacteria. These enzymes may take part in energy conservation in A. fulgidus by specifically linking lactate oxidation with APS reduction via the Qmo complex. High transcriptional levels of Fqo confirm an important role of F420H2, as well as a menaquinone-mediated electron transport chain, during heterotrophic growth. A putative periplasmic thiosulfate reductase was identified by specific up-regulation. Also, putative genes for transport of sulfate and sulfite are discussed. We present a model for hydrogen metabolism, based on the probable bifurcation reaction of the Mvh:Hdl hydrogenase, which may inhibit the utilization of Fdred for energy conservation. Energy conservation is probably facilitated via menaquinone to multiple membrane-bound heterodisulfide reductase (Hdr) complexes and the DsrC protein—linking periplasmic hydrogenase (Vht) to the cytoplasmic reduction of sulfite. The ambiguous roles of genes corresponding to fatty acid metabolism induced during growth with H2 are discussed. Putative co-assimilation of organic acids is favored over a homologous secondary carbon fixation pathway, although both mechanisms may contribute to conserve the amount of Fdred needed during autotrophic growth with H2.
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Affiliation(s)
- William P Hocking
- Department of Biology, Centre for Geobiology, University of Bergen Bergen, Norway
| | - Runar Stokke
- Department of Biology, Centre for Geobiology, University of Bergen Bergen, Norway
| | - Irene Roalkvam
- Department of Biology, Centre for Geobiology, University of Bergen Bergen, Norway
| | - Ida H Steen
- Department of Biology, Centre for Geobiology, University of Bergen Bergen, Norway
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Glass JB, Orphan VJ. Trace metal requirements for microbial enzymes involved in the production and consumption of methane and nitrous oxide. Front Microbiol 2012; 3:61. [PMID: 22363333 PMCID: PMC3282944 DOI: 10.3389/fmicb.2012.00061] [Citation(s) in RCA: 158] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Accepted: 02/05/2012] [Indexed: 01/15/2023] Open
Abstract
Fluxes of greenhouse gases to the atmosphere are heavily influenced by microbiological activity. Microbial enzymes involved in the production and consumption of greenhouse gases often contain metal cofactors. While extensive research has examined the influence of Fe bioavailability on microbial CO(2) cycling, fewer studies have explored metal requirements for microbial production and consumption of the second- and third-most abundant greenhouse gases, methane (CH(4)), and nitrous oxide (N(2)O). Here we review the current state of biochemical, physiological, and environmental research on transition metal requirements for microbial CH(4) and N(2)O cycling. Methanogenic archaea require large amounts of Fe, Ni, and Co (and some Mo/W and Zn). Low bioavailability of Fe, Ni, and Co limits methanogenesis in pure and mixed cultures and environmental studies. Anaerobic methane oxidation by anaerobic methanotrophic archaea (ANME) likely occurs via reverse methanogenesis since ANME possess most of the enzymes in the methanogenic pathway. Aerobic CH(4) oxidation uses Cu or Fe for the first step depending on Cu availability, and additional Fe, Cu, and Mo for later steps. N(2)O production via classical anaerobic denitrification is primarily Fe-based, whereas aerobic pathways (nitrifier denitrification and archaeal ammonia oxidation) require Cu in addition to, or possibly in place of, Fe. Genes encoding the Cu-containing N(2)O reductase, the only known enzyme capable of microbial N(2)O conversion to N(2), have only been found in classical denitrifiers. Accumulation of N(2)O due to low Cu has been observed in pure cultures and a lake ecosystem, but not in marine systems. Future research is needed on metalloenzymes involved in the production of N(2)O by enrichment cultures of ammonia oxidizing archaea, biological mechanisms for scavenging scarce metals, and possible links between metal bioavailability and greenhouse gas fluxes in anaerobic environments where metals may be limiting due to sulfide-metal scavenging.
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Affiliation(s)
- Jennifer B. Glass
- Division of Geological and Planetary Sciences, California Institute of TechnologyPasadena, CA, USA
| | - Victoria J. Orphan
- Division of Geological and Planetary Sciences, California Institute of TechnologyPasadena, CA, USA
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Role of nickel in high rate methanol degradation in anaerobic granular sludge bioreactors. Biodegradation 2008; 19:725-37. [PMID: 18247139 PMCID: PMC2493520 DOI: 10.1007/s10532-008-9177-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2007] [Accepted: 01/15/2008] [Indexed: 10/28/2022]
Abstract
The effect of nickel deprivation from the influent of a mesophilic (30 degrees C) methanol fed upflow anaerobic sludge bed (UASB) reactor was investigated by coupling the reactor performance to the evolution of the Methanosarcina population of the bioreactor sludge. The reactor was operated at pH 7.0 and an organic loading rate (OLR) of 5-15 g COD l(-1) day(-1) for 191 days. A clear limitation of the specific methanogenic activity (SMA) on methanol due to the absence of nickel was observed after 129 days of bioreactor operation: the SMA of the sludge in medium with the complete trace metal solution except nickel amounted to 1.164 (+/-0.167) g CH(4)-COD g VSS(-1) day(-1) compared to 2.027 (+/-0.111) g CH(4)-COD g VSS(-1) day(-1) in a medium with the complete (including nickel) trace metal solution. The methanol removal efficiency during these 129 days was 99%, no volatile fatty acid (VFA) accumulation was observed and the size of the Methanosarcina population increased compared to the seed sludge. Continuation of the UASB reactor operation with the nickel limited sludge lead to incomplete methanol removal, and thus methanol accumulation in the reactor effluent from day 142 onwards. This methanol accumulation subsequently induced an increase of the acetogenic activity in the UASB reactor on day 160. On day 165, 77% of the methanol fed to the system was converted to acetate and the Methanosarcina population size had substantially decreased. Inclusion of 0.5 muM Ni (dosed as NiCl(2)) to the influent from day 165 onwards lead to the recovery of the methanol removal efficiency to 99% without VFA accumulation within 2 days of bioreactor operation.
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Abstract
Members of the genus Methanosarcina are strictly anaerobic archaea that derive their metabolic energy from the conversion of a restricted number of substrates to methane. H2 + CO2 are converted to CH4 via the CO2-reducing pathway, while methanol and methylamines are metabolized by the methylotrophic pathway. Two novel electron transport systems are involved in the process of methanogenesis. Both systems are able to use a heterodisulfide as electron acceptor and either H2 or F420H2 as electron acceptors and generate a proton-motive force by redox potential-driven H(+)-translocation. The H2:heterodisulfide oxidoreductase is composed of an F420-nonreducing hydrogenase and the heterodisulfide reductase. The latter protein is also part of the F420H2:heterodisulfide oxidoreductase system. The second component of this system is referred to as F420H2 dehydrogenase. The archaeal protein is a homologue of complex I of the respiratory chain from bacteria and mitochondria. This review focuses on the biochemical and genetic characteristics of the three energy-transducing enzymes and on the mechanisms of ion translocation.
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Affiliation(s)
- Uwe Deppenmeier
- Department of Biological Sciences, University of Wisconsin-Milwaukee, PO Box 413, Milwaukee, Wisconsin 53201, USA.
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Abken HJ, Tietze M, Brodersen J, Bäumer S, Beifuss U, Deppenmeier U. Isolation and characterization of methanophenazine and function of phenazines in membrane-bound electron transport of Methanosarcina mazei Gö1. J Bacteriol 1998; 180:2027-32. [PMID: 9555882 PMCID: PMC107126 DOI: 10.1128/jb.180.8.2027-2032.1998] [Citation(s) in RCA: 150] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
A hydrophobic, redox-active component with a molecular mass of 538 Da was isolated from lyophilized membranes of Methanosarcina mazei Gö1 by extraction with isooctane. After purification on a high-performance liquid chromatography column, the chemical structure was analyzed by mass spectroscopy and nuclear magnetic resonance studies. The component was called methanophenazine and represents a 2-hydroxyphenazine derivative which is connected via an ether bridge to a polyisoprenoid side chain. Since methanophenazine was almost insoluble in aqueous buffers, water-soluble phenazine derivatives were tested for their ability to interact with membrane-bound enzymes involved in electron transport and energy conservation. The purified F42OH2 dehydrogenase from M. mazei Gö1 showed highest activity with 2-hydroxyphenazine and 2-bromophenazine as electron acceptors when F420H2 was added. Phenazine-1-carboxylic acid and phenazine proved to be less effective. The Km values for 2-hydroxyphenazine and phenazine were 35 and 250 microM, respectively. 2-Hydroxyphenazine was also reduced by molecular hydrogen catalyzed by an F420-nonreactive hydrogenase which is present in washed membrane preparations. Furthermore, the membrane-bound heterodisulfide reductase was able to use reduced 2-hydroxyphenazine as an electron donor for the reduction of CoB-S-S-CoM. Considering all these results, it is reasonable to assume that methanophenazine plays an important role in vivo in membrane-bound electron transport of M. mazei Gö1.
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Affiliation(s)
- H J Abken
- Institut für Mikrobiologie und Genetik, Georg-August-Universität, Göttingen, Germany
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