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Wang Y, Chen X, Spengler K, Terberger K, Boehm M, Appel J, Barske T, Timm S, Battchikova N, Hagemann M, Gutekunst K. Pyruvate:ferredoxin oxidoreductase and low abundant ferredoxins support aerobic photomixotrophic growth in cyanobacteria. eLife 2022; 11:71339. [PMID: 35138247 PMCID: PMC8887894 DOI: 10.7554/elife.71339] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 02/06/2022] [Indexed: 11/24/2022] Open
Abstract
The decarboxylation of pyruvate is a central reaction in the carbon metabolism of all organisms. It is catalyzed by the pyruvate:ferredoxin oxidoreductase (PFOR) and the pyruvate dehydrogenase (PDH) complex. Whereas PFOR reduces ferredoxin, the PDH complex utilizes NAD+. Anaerobes rely on PFOR, which was replaced during evolution by the PDH complex found in aerobes. Cyanobacteria possess both enzyme systems. Our data challenge the view that PFOR is exclusively utilized for fermentation. Instead, we show, that the cyanobacterial PFOR is stable in the presence of oxygen in vitro and is required for optimal photomixotrophic growth under aerobic and highly reducing conditions while the PDH complex is inactivated. We found that cells rely on a general shift from utilizing NAD(H)- to ferredoxin-dependent enzymes under these conditions. The utilization of ferredoxins instead of NAD(H) saves a greater share of the Gibbs-free energy, instead of wasting it as heat. This obviously simultaneously decelerates metabolic reactions as they operate closer to their thermodynamic equilibrium. It is common thought that during evolution, ferredoxins were replaced by NAD(P)H due to their higher stability in an oxidizing atmosphere. However, the utilization of NAD(P)H could also have been favored due to a higher competitiveness because of an accelerated metabolism.
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Affiliation(s)
- Yingying Wang
- Department of Biology, Christian-Albrechts University, Kiel, Germany
| | - Xi Chen
- Department of Biology, Christian-Albrechts University, Kiel, Germany
| | | | | | - Marko Boehm
- Department of Molecular Plant Physiology, University of Kassel, Kassel, Germany
| | - Jens Appel
- Department of Molecular Plant Physiology, University of Kassel, Kassel, Germany
| | - Thomas Barske
- Plant Physiology Department, University of Rostock, Rostock, Germany
| | - Stefan Timm
- Plant Physiology Department, University of Rostock, Rostock, Germany
| | | | - Martin Hagemann
- Plant Physiology Department, University of Rostock, Rostock, Germany
| | - Kirstin Gutekunst
- Department of Molecular Plant Physiology, University of Kassel, Kassel, Germany
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Zha H, Chen Y, Wu J, Chang K, Lu Y, Zhang H, Xie J, Wang Q, Tang R, Li L. Characteristics of three microbial colonization states in the duodenum of the cirrhotic patients. Future Microbiol 2020; 15:855-868. [PMID: 32662659 DOI: 10.2217/fmb-2019-0270] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Aim: Investigation of characteristics of different duodenal microbial colonization states in patients with liver cirrhosis (LC). Materials & methods: Deep-sequencing analyses of the 16S rRNA gene V1-V3 regions were performed. Results: Both bacterial compositions and richness were different between the three-clustered LC microbiotas, in other words, Cluster_1_LC, Cluster_2_LC and Cluster_3_LC. Cluster_1_LC were more likely at severe dysbiosis status due to its lowest modified cirrhosis dysbiosis ratio. OTU12_Prevotella and OTU10_Comamonas were most associated with Cluster_1_LC and Cluster_3_LC, respectively, while OTU38_Alloprevotella was vital in Cluster_2_LC. Pyruvate-ferredoxin/flavodoxin oxidoreductase, dihydroorotate dehydrogenase and branched-chain amino acid transport system substrate-binding protein were most associated with Cluster_1_LC, Cluster_2_LC and Cluster_3_LC, respectively. Conclusion: The three duodenal microbial colonization states had distinct representative characteristics, which might reflect the health status of cirrhotic patients.
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Affiliation(s)
- Hua Zha
- State Key Laboratory for Diagnosis & Treatment of Infectious Diseases, Collaborative Innovation Center for Diagnosis & Treatment of Infectious Diseases, National Clinical Research Center for Infectious Diseases, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China.,School of Biological Sciences, The University of Auckland, Auckland, New Zealand.,Institute of Marine Science, The University of Auckland, Auckland, New Zealand
| | - Yanfei Chen
- State Key Laboratory for Diagnosis & Treatment of Infectious Diseases, Collaborative Innovation Center for Diagnosis & Treatment of Infectious Diseases, National Clinical Research Center for Infectious Diseases, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China
| | - Jieyun Wu
- School of Biological Sciences, The University of Auckland, Auckland, New Zealand.,Plant Health & Environment Laboratory, Ministry for Primary Industries, Auckland, New Zealand
| | - Kevin Chang
- Department of Statistics, The University of Auckland, Auckland, New Zealand
| | - Yanmeng Lu
- State Key Laboratory for Diagnosis & Treatment of Infectious Diseases, Collaborative Innovation Center for Diagnosis & Treatment of Infectious Diseases, National Clinical Research Center for Infectious Diseases, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China
| | - Hua Zhang
- State Key Laboratory for Diagnosis & Treatment of Infectious Diseases, Collaborative Innovation Center for Diagnosis & Treatment of Infectious Diseases, National Clinical Research Center for Infectious Diseases, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China
| | - Jiaojiao Xie
- State Key Laboratory for Diagnosis & Treatment of Infectious Diseases, Collaborative Innovation Center for Diagnosis & Treatment of Infectious Diseases, National Clinical Research Center for Infectious Diseases, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China
| | - Qiangqiang Wang
- State Key Laboratory for Diagnosis & Treatment of Infectious Diseases, Collaborative Innovation Center for Diagnosis & Treatment of Infectious Diseases, National Clinical Research Center for Infectious Diseases, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China
| | - Ruiqi Tang
- State Key Laboratory for Diagnosis & Treatment of Infectious Diseases, Collaborative Innovation Center for Diagnosis & Treatment of Infectious Diseases, National Clinical Research Center for Infectious Diseases, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China
| | - Lanjuan Li
- State Key Laboratory for Diagnosis & Treatment of Infectious Diseases, Collaborative Innovation Center for Diagnosis & Treatment of Infectious Diseases, National Clinical Research Center for Infectious Diseases, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China
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Pernil R, Schleiff E. Metalloproteins in the Biology of Heterocysts. Life (Basel) 2019; 9:E32. [PMID: 30987221 PMCID: PMC6616624 DOI: 10.3390/life9020032] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 03/18/2019] [Accepted: 03/28/2019] [Indexed: 12/15/2022] Open
Abstract
Cyanobacteria are photoautotrophic microorganisms present in almost all ecologically niches on Earth. They exist as single-cell or filamentous forms and the latter often contain specialized cells for N₂ fixation known as heterocysts. Heterocysts arise from photosynthetic active vegetative cells by multiple morphological and physiological rearrangements including the absence of O₂ evolution and CO₂ fixation. The key function of this cell type is carried out by the metalloprotein complex known as nitrogenase. Additionally, many other important processes in heterocysts also depend on metalloproteins. This leads to a high metal demand exceeding the one of other bacteria in content and concentration during heterocyst development and in mature heterocysts. This review provides an overview on the current knowledge of the transition metals and metalloproteins required by heterocysts in heterocyst-forming cyanobacteria. It discusses the molecular, physiological, and physicochemical properties of metalloproteins involved in N₂ fixation, H₂ metabolism, electron transport chains, oxidative stress management, storage, energy metabolism, and metabolic networks in the diazotrophic filament. This provides a detailed and comprehensive picture on the heterocyst demands for Fe, Cu, Mo, Ni, Mn, V, and Zn as cofactors for metalloproteins and highlights the importance of such metalloproteins for the biology of cyanobacterial heterocysts.
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Affiliation(s)
- Rafael Pernil
- Institute for Molecular Biosciences, Goethe University Frankfurt, Max-von-Laue-Straβe 9, 60438 Frankfurt am Main, Germany.
| | - Enrico Schleiff
- Institute for Molecular Biosciences, Goethe University Frankfurt, Max-von-Laue-Straβe 9, 60438 Frankfurt am Main, Germany.
- Frankfurt Institute for Advanced Studies, Ruth-Moufang-Straße 1, 60438 Frankfurt am Main, Germany.
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Max-von-Laue-Straβe 15, 60438 Frankfurt am Main, Germany.
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Singh S, Shrivastava AK. In silico characterization and transcriptomic analysis of nif family genes from Anabaena sp. PCC7120. Cell Biol Toxicol 2017; 33:467-482. [DOI: 10.1007/s10565-017-9388-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Accepted: 02/13/2017] [Indexed: 12/12/2022]
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Vuorijoki L, Tiwari A, Kallio P, Aro EM. Inactivation of iron-sulfur cluster biogenesis regulator SufR in Synechocystis sp. PCC 6803 induces unique iron-dependent protein-level responses. Biochim Biophys Acta Gen Subj 2017; 1861:1085-1098. [PMID: 28216046 DOI: 10.1016/j.bbagen.2017.02.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Revised: 01/31/2017] [Accepted: 02/14/2017] [Indexed: 10/20/2022]
Abstract
BACKGROUND Iron-sulfur (Fe-S) clusters are protein-bound cofactors associated with cellular electron transport and redox sensing, with multiple specific functions in oxygen-evolving photosynthetic cyanobacteria. The aim here was to elucidate protein-level effects of the transcriptional repressor SufR involved in the regulation of Fe-S cluster biogenesis in the cyanobacterium Synechocystis sp. PCC 6803. METHODS The approach was to quantitate 94 pre-selected target proteins associated with various metabolic functions using SRM in Synechocystis. The evaluation was conducted in response to sufR deletion under different iron conditions, and complemented with EPR analysis on the functionality of the photosystems I and II as well as with RT-qPCR to verify the effects of SufR also on transcript level. RESULTS The results on both protein and transcript levels show that SufR acts not only as a repressor of the suf operon when iron is available but also has other direct and indirect functions in the cell, including maintenance of the expression of pyruvate:ferredoxin oxidoreductase NifJ and other Fe-S cluster proteins under iron sufficient conditions. Furthermore, the results imply that in the absence of iron the suf operon is repressed by some additional regulatory mechanism independent of SufR. CONCLUSIONS The study demonstrates that Fe-S cluster metabolism in Synechocystis is stringently regulated, and has complex interactions with multiple primary functions in the cell, including photosynthesis and central carbon metabolism. GENERAL SIGNIFICANCE The study provides new insight into the regulation of Fe-S cluster biogenesis via suf operon, and the associated wide-ranging protein-level changes in photosynthetic cyanobacteria.
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Affiliation(s)
- Linda Vuorijoki
- Molecular Plant Biology, Department of Biochemistry, University of Turku, FI-20014 Turku, Finland.
| | - Arjun Tiwari
- Molecular Plant Biology, Department of Biochemistry, University of Turku, FI-20014 Turku, Finland.
| | - Pauli Kallio
- Molecular Plant Biology, Department of Biochemistry, University of Turku, FI-20014 Turku, Finland.
| | - Eva-Mari Aro
- Molecular Plant Biology, Department of Biochemistry, University of Turku, FI-20014 Turku, Finland.
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6
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Modular electron-transport chains from eukaryotic organelles function to support nitrogenase activity. Proc Natl Acad Sci U S A 2017; 114:E2460-E2465. [PMID: 28193863 DOI: 10.1073/pnas.1620058114] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
A large number of genes are necessary for the biosynthesis and activity of the enzyme nitrogenase to carry out the process of biological nitrogen fixation (BNF), which requires large amounts of ATP and reducing power. The multiplicity of the genes involved, the oxygen sensitivity of nitrogenase, plus the demand for energy and reducing power, are thought to be major obstacles to engineering BNF into cereal crops. Genes required for nitrogen fixation can be considered as three functional modules encoding electron-transport components (ETCs), proteins required for metal cluster biosynthesis, and the "core" nitrogenase apoenzyme, respectively. Among these modules, the ETC is important for the supply of reducing power. In this work, we have used Escherichia coli as a chassis to study the compatibility between molybdenum and the iron-only nitrogenases with ETC modules from target plant organelles, including chloroplasts, root plastids, and mitochondria. We have replaced an ETC module present in diazotrophic bacteria with genes encoding ferredoxin-NADPH oxidoreductases (FNRs) and their cognate ferredoxin counterparts from plant organelles. We observe that the FNR-ferredoxin module from chloroplasts and root plastids can support the activities of both types of nitrogenase. In contrast, an analogous ETC module from mitochondria could not function in electron transfer to nitrogenase. However, this incompatibility could be overcome with hybrid modules comprising mitochondrial NADPH-dependent adrenodoxin oxidoreductase and the Anabaena ferredoxins FdxH or FdxB. We pinpoint endogenous ETCs from plant organelles as power supplies to support nitrogenase for future engineering of diazotrophy in cereal crops.
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Hasunuma T, Matsuda M, Kondo A. Improved sugar-free succinate production by Synechocystis sp. PCC 6803 following identification of the limiting steps in glycogen catabolism. Metab Eng Commun 2016; 3:130-141. [PMID: 29468119 PMCID: PMC5779724 DOI: 10.1016/j.meteno.2016.04.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Revised: 04/05/2016] [Accepted: 04/29/2016] [Indexed: 12/11/2022] Open
Abstract
Succinate produced by microorganisms can replace currently used petroleum-based succinate but typically requires mono- or poly-saccharides as a feedstock. The cyanobacterium Synechocystis sp. PCC6803 can produce organic acids such as succinate from CO2 not supplemented with sugars under dark anoxic conditions using an unknown metabolic pathway. The TCA cycle in cyanobacteria branches into oxidative and reductive routes. Time-course analyses of the metabolome, transcriptome and metabolic turnover described here revealed dynamic changes in the metabolism of Synechocystis sp. PCC6803 cultivated under dark anoxic conditions, allowing identification of the carbon flow and rate-limiting steps in glycogen catabolism. Glycogen biosynthesized from CO2 assimilated during periods of light exposure is catabolized to succinate via glycolysis, the anaplerotic pathway, and the reductive TCA cycle under dark anoxic conditions. Expression of the phosphoenolpyruvate (PEP) carboxylase gene (ppc) was identified as a rate-limiting step in succinate biosynthesis and this rate limitation was alleviated by ppc overexpression, resulting in improved succinate excretion. The sugar-free succinate production was further enhanced by the addition of bicarbonate. In vivo labeling with NaH13CO3 clearly showed carbon incorporation into succinate via the anaplerotic pathway. Bicarbonate is in equilibrium with CO2. Succinate production by Synechocystis sp. PCC6803 therefore holds significant promise for CO2 capture and utilization. The cyanobacterium Synechocystis produces succinate under dark anoxic condition. Multi-omics revealed dynamic change in metabolism under dark anoxic condition. Carbon flow and rate-limiting steps in glycogen catabolism was elucidated. PEP carboxylase gene overexpression improved Synechocystis succinate production. Bicarbonate addition to medium dramatically improved succinate production.
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Affiliation(s)
- Tomohisa Hasunuma
- Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
| | - Mami Matsuda
- Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
| | - Akihiko Kondo
- Biomass Engineering Program, RIKEN, 1-7-22 Suehiro, Tsurumi, Yokohama, Kanagawa 230-0045, Japan.,Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
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8
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Zhang S, Liu Y, Bryant DA. Metabolic engineering of Synechococcus sp. PCC 7002 to produce poly-3-hydroxybutyrate and poly-3-hydroxybutyrate-co-4-hydroxybutyrate. Metab Eng 2015; 32:174-183. [DOI: 10.1016/j.ymben.2015.10.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Revised: 09/13/2015] [Accepted: 10/05/2015] [Indexed: 11/29/2022]
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9
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Ludwig M, Bryant DA. Transcription Profiling of the Model Cyanobacterium Synechococcus sp. Strain PCC 7002 by Next-Gen (SOLiD™) Sequencing of cDNA. Front Microbiol 2011; 2:41. [PMID: 21779275 PMCID: PMC3133671 DOI: 10.3389/fmicb.2011.00041] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Accepted: 02/22/2011] [Indexed: 11/24/2022] Open
Abstract
The genome of the unicellular, euryhaline cyanobacterium Synechococcus sp. PCC 7002 encodes about 3200 proteins. Transcripts were detected for nearly all annotated open reading frames by a global transcriptomic analysis by Next-Generation (SOLiD™) sequencing of cDNA. In the cDNA samples sequenced, ∼90% of the mapped sequences were derived from the 16S and 23S ribosomal RNAs and ∼10% of the sequences were derived from mRNAs. In cells grown photoautotrophically under standard conditions [38°C, 1% (v/v) CO(2) in air, 250 μmol photons m(-2) s(-1)], the highest transcript levels (up to 2% of the total mRNA for the most abundantly transcribed genes; e.g., cpcAB, psbA, psaA) were generally derived from genes encoding structural components of the photosynthetic apparatus. High-light exposure for 1 h caused changes in transcript levels for genes encoding proteins of the photosynthetic apparatus, Type-1 NADH dehydrogenase complex and ATP synthase, whereas dark incubation for 1 h resulted in a global decrease in transcript levels for photosynthesis-related genes and an increase in transcript levels for genes involved in carbohydrate degradation. Transcript levels for pyruvate kinase and the pyruvate dehydrogenase complex decreased sharply in cells incubated in the dark. Under dark anoxic (fermentative) conditions, transcript changes indicated a global decrease in transcripts for respiratory proteins and suggested that cells employ an alternative phosphoenolpyruvate degradation pathway via phosphoenolpyruvate synthase (ppsA) and the pyruvate:ferredoxin oxidoreductase (nifJ). Finally, the data suggested that an apparent operon involved in tetrapyrrole biosynthesis and fatty acid desaturation, acsF2-ho2-hemN2-desF, may be regulated by oxygen concentration.
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Affiliation(s)
- Marcus Ludwig
- Department of Biochemistry and Molecular Biology, The Pennsylvania State UniversityUniversity Park, PA, USA
| | - Donald A. Bryant
- Department of Biochemistry and Molecular Biology, The Pennsylvania State UniversityUniversity Park, PA, USA
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10
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Synechococcus sp. strain PCC 7002 nifJ mutant lacking pyruvate:ferredoxin oxidoreductase. Appl Environ Microbiol 2011; 77:2435-44. [PMID: 21317262 DOI: 10.1128/aem.02792-10] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The nifJ gene codes for pyruvate:ferredoxin oxidoreductase (PFOR), which reduces ferredoxin during fermentative catabolism of pyruvate to acetyl-coenzyme A (acetyl-CoA). A nifJ knockout mutant was constructed that lacks one of two pathways for the oxidation of pyruvate in the cyanobacterium Synechococcus sp. strain PCC 7002. Remarkably, the photoautotrophic growth rate of this mutant increased by 20% relative to the wild-type (WT) rate under conditions of light-dark cycling. This result is attributed to an increase in the quantum yield of photosystem II (PSII) charge separation as measured by photosynthetic electron turnover efficiency determined using fast-repetition-rate fluorometry (F(v)/F(m)). During autofermentation, the excretion of acetate and lactate products by nifJ mutant cells decreased 2-fold and 1.2-fold, respectively. Although nifJ cells displayed higher in vitro hydrogenase activity than WT cells, H(2) production in vivo was 1.3-fold lower than the WT level. Inhibition of acetate-CoA ligase and pyruvate dehydrogenase complex by glycerol eliminated acetate production, with a resulting loss of reductant and a 3-fold decrease in H(2) production by nifJ cells compared to WT cells. Continuous electrochemical detection of dissolved H(2) revealed two temporally resolved phases of H(2) production during autofermentation, a minor first phase and a major second phase. The first phase was attributed to reduction of ferredoxin, because its level decreased 2-fold in nifJ cells. The second phase was attributed to glycolytic NADH production and decreased 20% in nifJ cells. Measurement of the intracellular NADH/NAD(+) ratio revealed that the reductant generated by PFOR contributing to the first phase of H(2) production was not in equilibrium with bulk NADH/NAD(+) and that the second phase corresponded to the equilibrium NADH-mediated process.
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Bothe H, Schmitz O, Yates MG, Newton WE. Nitrogen fixation and hydrogen metabolism in cyanobacteria. Microbiol Mol Biol Rev 2010; 74:529-51. [PMID: 21119016 PMCID: PMC3008169 DOI: 10.1128/mmbr.00033-10] [Citation(s) in RCA: 174] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
This review summarizes recent aspects of (di)nitrogen fixation and (di)hydrogen metabolism, with emphasis on cyanobacteria. These organisms possess several types of the enzyme complexes catalyzing N(2) fixation and/or H(2) formation or oxidation, namely, two Mo nitrogenases, a V nitrogenase, and two hydrogenases. The two cyanobacterial Ni hydrogenases are differentiated as either uptake or bidirectional hydrogenases. The different forms of both the nitrogenases and hydrogenases are encoded by different sets of genes, and their organization on the chromosome can vary from one cyanobacterium to another. Factors regulating the expression of these genes are emerging from recent studies. New ideas on the potential physiological and ecological roles of nitrogenases and hydrogenases are presented. There is a renewed interest in exploiting cyanobacteria in solar energy conversion programs to generate H(2) as a source of combustible energy. To enhance the rates of H(2) production, the emphasis perhaps needs not to be on more efficient hydrogenases and nitrogenases or on the transfer of foreign enzymes into cyanobacteria. A likely better strategy is to exploit the use of radiant solar energy by the photosynthetic electron transport system to enhance the rates of H(2) formation and so improve the chances of utilizing cyanobacteria as a source for the generation of clean energy.
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Affiliation(s)
- Hermann Bothe
- Botanical Institute, The University of Cologne, Zülpicher Str. 47b, D-50923 Cologne, Germany.
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Bothe H, Tripp HJ, Zehr JP. Unicellular cyanobacteria with a new mode of life: the lack of photosynthetic oxygen evolution allows nitrogen fixation to proceed. Arch Microbiol 2010; 192:783-90. [DOI: 10.1007/s00203-010-0621-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2010] [Revised: 07/27/2010] [Accepted: 08/13/2010] [Indexed: 10/19/2022]
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13
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Cheng Y, Li JH, Shi L, Wang L, Latifi A, Zhang CC. A pair of iron-responsive genes encoding protein kinases with a Ser/Thr kinase domain and a His kinase domain are regulated by NtcA in the Cyanobacterium Anabaena sp. strain PCC 7120. J Bacteriol 2006; 188:4822-9. [PMID: 16788191 PMCID: PMC1482992 DOI: 10.1128/jb.00258-06] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The filamentous cyanobacterium Anabaena sp. strain PCC 7120 can fix N(2) when combined nitrogen is not available in the growth medium. It has a family of 13 genes encoding proteins with both a Ser/Thr kinase domain and a His kinase domain. The function of these enzymes is unknown. Two of them are encoded by pkn41 (alr0709) and pkn42 (alr0710). These two genes are separated by only 72 bp on the chromosome, and our results indicate that they are cotranscribed. The expression of pkn41 and pkn42 is induced by iron deprivation irrespective of the nature of the nitrogen source. Mutants inactivating either pkn41, pkn42, or both grow similarly to the wild type under normal conditions, but their growth is impaired either in the presence of an iron chelator or under conditions of nitrogen fixation and iron limitation, two situations where the demand for iron is particularly strong. Consistent with these results, these mutants display lower iron content than the wild type and a higher level of expression for nifJ1 and nifJ2, which encode pyruvate:ferredoxin oxidoreductases. Both nifJ1 and nifJ2 are known to be induced by iron limitation. NtcA, a global regulatory factor for different metabolic pathways, binds to the putative promoter region of pkn41, and the induction of pkn41 in response to iron limitation no longer occurs in an ntcA mutant. Our results suggest that ntcA not only regulates the expression of genes involved in nitrogen and carbon metabolism but also coordinates iron acquisition and nitrogen metabolism by activating the expression of pkn41 and pkn42.
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Affiliation(s)
- Yong Cheng
- National Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, People's Republic of China
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Ikeda T, Ochiai T, Morita S, Nishiyama A, Yamada E, Arai H, Ishii M, Igarashi Y. Anabolic five subunit-type pyruvate:ferredoxin oxidoreductase from Hydrogenobacter thermophilus TK-6. Biochem Biophys Res Commun 2006; 340:76-82. [PMID: 16343420 DOI: 10.1016/j.bbrc.2005.11.155] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2005] [Accepted: 11/30/2005] [Indexed: 10/25/2022]
Abstract
The thermophilic, obligately chemolithoautotrophic hydrogen-oxidizing bacterium, Hydrogenobacter thermophilus TK-6, assimilates carbon dioxide via the reductive tricarboxylic acid cycle. A gene cluster, porEDABG, encoding pyruvate:ferredoxin oxidoreductase (POR), which plays a key role in this cycle, was cloned and sequenced. The nucleotide sequence and the gene organization were similar to those of the five subunit-type 2-oxoglutarate:ferredoxin oxidoreductase from this strain, although the anabolic POR had been previously reported to consist of four subunits. A small protein (8 kDa) encoded by porE, which had not been detected in the previous work, was identified in the purified recombinant POR expressed in Escherichia coli, indicating that the enzyme is also a five-subunit type. Incorporation of PorE in the wild-type POR enzyme was confirmed by immunological analysis. PorA, PorB, PorG, and PorE were similar to the alpha, beta, gamma, and delta subunits of the four subunit-type 2-oxoacid oxidoreductases, respectively, and had conserved specific motifs. PorD had no specific motifs but was essential for the expression of the active enzyme.
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Affiliation(s)
- Takeshi Ikeda
- Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
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