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Li Y, Yu H, Xiong L, Wei Y, Li H, Ji X. Viral AMGs-driven pentose phosphate pathway in natural wetland. J Basic Microbiol 2024; 64:e2300569. [PMID: 38078780 DOI: 10.1002/jobm.202300569] [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: 09/28/2023] [Revised: 11/24/2023] [Accepted: 11/24/2023] [Indexed: 02/13/2024]
Abstract
Viruses exist anywhere on earth where there is life, and among them, virus-encoded auxiliary metabolic genes (AMGs) can maintain ecosystem balance and play a major role in the global ecosystem. Although the function of AMGs has been widely reported, the genetic diversity of AMGs in natural ecosystems is still poorly understood. Exploring the genetic diversity of viral community-wide AMGs is essential to gain insight into the complex interactions between viruses and hosts. In this article, we studied the phylogenetic tree, principal co-ordinates analysis (PCoA), α diversity, and metabolic pathways of viral auxiliary metabolism genes involved in the pentose phosphate pathway (PPP) through metagenomics, and the changes of metabolites and genes of host bacteria were further studied by using Pseudomonas mandelii SW-3 and its lytic phage based on metabolic flow and AMGs expression. We found that the viral AMGs in the Napahai plateau wetland were created by a combination of various external forces, which contributed to the rich genetic diversity, uniqueness, and differences of the virus, which promoted the reproduction of offspring and better adaptation to the environment. Overall, this study systematically describes the genetic diversity of AMGs associated with the PPP in plateau wetland ecosystems and further expands the understanding of phage-host unique interactions.
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Affiliation(s)
- Yanmei Li
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Hang Yu
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Lingling Xiong
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Yunlin Wei
- Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Haiyan Li
- Yunnan International Joint Laboratory of Research and Development of Crop Safety Production on Heavy Metal Pollution Areas, Medical School, Kunming University of Science and Technology, Kunming, China
| | - Xiuling Ji
- Yunnan International Joint Laboratory of Research and Development of Crop Safety Production on Heavy Metal Pollution Areas, Medical School, Kunming University of Science and Technology, Kunming, China
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2
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Garcia NS, Du M, Guindani M, McIlvin MR, Moran DM, Saito MA, Martiny AC. Proteome trait regulation of marine Synechococcus elemental stoichiometry under global change. THE ISME JOURNAL 2024; 18:wrae046. [PMID: 38513256 PMCID: PMC11020310 DOI: 10.1093/ismejo/wrae046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 02/27/2024] [Accepted: 03/19/2024] [Indexed: 03/23/2024]
Abstract
Recent studies have demonstrated regional differences in marine ecosystem C:N:P with implications for carbon and nutrient cycles. Due to strong co-variance, temperature and nutrient stress explain variability in C:N:P equally well. A reductionistic approach can link changes in individual environmental drivers with changes in biochemical traits and cell C:N:P. Thus, we quantified effects of temperature and nutrient stress on Synechococcus chemistry using laboratory chemostats, chemical analyses, and data-independent acquisition mass spectrometry proteomics. Nutrient supply accounted for most C:N:Pcell variability and induced tradeoffs between nutrient acquisition and ribosomal proteins. High temperature prompted heat-shock, whereas thermal effects via the "translation-compensation hypothesis" were only seen under P-stress. A Nonparametric Bayesian Local Clustering algorithm suggested that changes in lipopolysaccharides, peptidoglycans, and C-rich compatible solutes may also contribute to C:N:P regulation. Physiological responses match field-based trends in ecosystem stoichiometry and suggest a hierarchical environmental regulation of current and future ocean C:N:P.
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Affiliation(s)
- Nathan S Garcia
- Department of Earth System Science, University of California, Irvine, Irvine, CA 92697, United States
| | - Mingyu Du
- Department of Statistics, University of California, Irvine, Irvine, CA 92697, United States
| | - Michele Guindani
- Department of Biostatistics, University of California, Los Angeles, Los Angeles, CA 90095, United States
| | - Matthew R McIlvin
- Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, United States
| | - Dawn M Moran
- Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, United States
| | - Mak A Saito
- Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, United States
| | - Adam C Martiny
- Department of Earth System Science, University of California, Irvine, Irvine, CA 92697, United States
- Department of Ecology and Evolutionary Biology, University of California, Irvine, Irvine, CA 92697, United States
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de Barros Dantas LL, Eldridge BM, Dorling J, Dekeya R, Lynch DA, Dodd AN. Circadian regulation of metabolism across photosynthetic organisms. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2023; 116:650-668. [PMID: 37531328 PMCID: PMC10953457 DOI: 10.1111/tpj.16405] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Revised: 07/15/2023] [Accepted: 07/18/2023] [Indexed: 08/04/2023]
Abstract
Circadian regulation produces a biological measure of time within cells. The daily cycle in the availability of light for photosynthesis causes dramatic changes in biochemical processes in photosynthetic organisms, with the circadian clock having crucial roles in adaptation to these fluctuating conditions. Correct alignment between the circadian clock and environmental day-night cycles maximizes plant productivity through its regulation of metabolism. Therefore, the processes that integrate circadian regulation with metabolism are key to understanding how the circadian clock contributes to plant productivity. This forms an important part of exploiting knowledge of circadian regulation to enhance sustainable crop production. Here, we examine the roles of circadian regulation in metabolic processes in source and sink organ structures of Arabidopsis. We also evaluate possible roles for circadian regulation in root exudation processes that deposit carbon into the soil, and the nature of the rhythmic interactions between plants and their associated microbial communities. Finally, we examine shared and differing aspects of the circadian regulation of metabolism between Arabidopsis and other model photosynthetic organisms, and between circadian control of metabolism in photosynthetic and non-photosynthetic organisms. This synthesis identifies a variety of future research topics, including a focus on metabolic processes that underlie biotic interactions within ecosystems.
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Affiliation(s)
| | - Bethany M. Eldridge
- Department of Cell and Developmental BiologyJohn Innes Centre, Norwich Research ParkNorwichUK
| | - Jack Dorling
- Department of Cell and Developmental BiologyJohn Innes Centre, Norwich Research ParkNorwichUK
| | - Richard Dekeya
- Department of Cell and Developmental BiologyJohn Innes Centre, Norwich Research ParkNorwichUK
| | - Deirdre A. Lynch
- Department of Cell and Developmental BiologyJohn Innes Centre, Norwich Research ParkNorwichUK
| | - Antony N. Dodd
- Department of Cell and Developmental BiologyJohn Innes Centre, Norwich Research ParkNorwichUK
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4
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Huang C, Duan X, Ge H, Xiao Z, Zheng L, Wang G, Dong J, Wang Y, Zhang Y, Huang X, An H, Xu W, Wang Y. Parallel Proteomic Comparison of Mutants With Altered Carbon Metabolism Reveals Hik8 Regulation of P II Phosphorylation and Glycogen Accumulation in a Cyanobacterium. Mol Cell Proteomics 2023; 22:100582. [PMID: 37225018 PMCID: PMC10315926 DOI: 10.1016/j.mcpro.2023.100582] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 05/18/2023] [Accepted: 05/19/2023] [Indexed: 05/26/2023] Open
Abstract
Carbon metabolism is central to photosynthetic organisms and involves the coordinated operation and regulation of numerous proteins. In cyanobacteria, proteins involved in carbon metabolism are regulated by multiple regulators including the RNA polymerase sigma factor SigE, the histidine kinases Hik8, Hik31 and its plasmid-borne paralog Slr6041, and the response regulator Rre37. To understand the specificity and the cross-talk of such regulations, we simultaneously and quantitatively compared the proteomes of the gene knockout mutants for the regulators. A number of proteins showing differential expression in one or more mutants were identified, including four proteins that are unanimously upregulated or downregulated in all five mutants. These represent the important nodes of the intricate and elegant regulatory network for carbon metabolism. Moreover, serine phosphorylation of PII, a key signaling protein sensing and regulating in vivo carbon/nitrogen (C/N) homeostasis through reversible phosphorylation, is massively increased with a concomitant significant decrease in glycogen content only in the hik8-knockout mutant, which also displays impaired dark viability. An unphosphorylatable PII S49A substitution restored the glycogen content and rescued the dark viability of the mutant. Together, our study not only establishes the quantitative relationship between the targets and the corresponding regulators and elucidated their specificity and cross-talk but also unveils that Hik8 regulates glycogen accumulation through negative regulation of PII phosphorylation, providing the first line of evidence that links the two-component system with PII-mediated signal transduction and implicates them in the regulation of carbon metabolism.
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Affiliation(s)
- Chengcheng Huang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China
| | - Xiaoxiao Duan
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China
| | - Haitao Ge
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Zhen Xiao
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China
| | - Limin Zheng
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China
| | - Gaojie Wang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China
| | - Jinghui Dong
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China
| | - Yan Wang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China
| | - Yuanya Zhang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Xiahe Huang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Hongyu An
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China
| | - Wu Xu
- Department of Chemistry, University of Louisiana at Lafayette, Lafayette, Louisiana, USA
| | - Yingchun Wang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China.
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Malic Enzyme, not Malate Dehydrogenase, Mainly Oxidizes Malate That Originates from the Tricarboxylic Acid Cycle in Cyanobacteria. mBio 2022; 13:e0218722. [PMID: 36314837 PMCID: PMC9765476 DOI: 10.1128/mbio.02187-22] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/27/2023] Open
Abstract
Oxygenic photoautotrophic bacteria, cyanobacteria, have the tricarboxylic acid (TCA) cycle, and metabolite production using the cyanobacterial TCA cycle has been spotlighted recently. The unicellular cyanobacterium Synechocystis sp. strain PCC 6803 (Synechocystis 6803) has been used in various studies on the cyanobacterial TCA cycle. Malate oxidation in the TCA cycle is generally catalyzed by malate dehydrogenase (MDH). However, Synechocystis 6803 MDH (SyMDH) is less active than MDHs from other organisms. Additionally, SyMDH uses only NAD+ as a coenzyme, unlike other TCA cycle enzymes from Synechocystis 6803 that use NADP+. These results suggest that MDH rarely catalyzes malate oxidation in the cyanobacterial TCA cycle. Another enzyme catalyzing malate oxidation is malic enzyme (ME). We clarified which enzyme oxidizes malate that originates from the cyanobacterial TCA cycle using analyses focusing on ME and MDH. In contrast to SyMDH, Synechocystis 6803 ME (SyME) showed high activity when NADP+ was used as a coenzyme. Unlike the Synechocystis 6803 mutant lacking SyMDH, the mutant lacking SyME accumulated malate in the cells. ME was more highly preserved in the cyanobacterial genomes than MDH. These results indicate that ME mainly oxidizes malate that originates from the cyanobacterial TCA cycle (named the ME-dependent TCA cycle). The ME-dependent TCA cycle generates NADPH, not NADH. This is consistent with previous reports that NADPH is an electron carrier in the cyanobacterial respiratory chain. Our finding suggests the diversity of enzymes involved in the TCA cycle in the organisms, and analyses such as those performed in this study are necessary to determine the enzymes. IMPORTANCE Oxygenic photoautotrophic bacteria, namely, cyanobacteria, have the tricarboxylic acid (TCA) cycle. Recently, metabolite production using the cyanobacterial TCA cycle has been well studied. To enhance the production volume of metabolites, understanding the biochemical properties of the cyanobacterial TCA cycle is required. Generally, malate dehydrogenase oxidizes malate in the TCA cycle. However, cyanobacterial malate dehydrogenase shows low activity and does not use NADP+ as a coenzyme, unlike other cyanobacterial TCA cycle enzymes. Our analyses revealed that another malate oxidation enzyme, the malic enzyme, mainly oxidizes malate that originates from the cyanobacterial TCA cycle. These findings provide better insights into metabolite production using the cyanobacterial TCA cycle. Furthermore, our findings suggest that the enzymes related to the TCA cycle vary from organism to organism and emphasize the importance of analyses to identify the enzymes such as those performed in this study.
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6
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Xie Y, Chen L, Sun T, Zhang W. Deciphering and engineering high-light tolerant cyanobacteria for efficient photosynthetic cell factories. Chin J Chem Eng 2021. [DOI: 10.1016/j.cjche.2020.11.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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7
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Makowka A, Nichelmann L, Schulze D, Spengler K, Wittmann C, Forchhammer K, Gutekunst K. Glycolytic Shunts Replenish the Calvin-Benson-Bassham Cycle as Anaplerotic Reactions in Cyanobacteria. MOLECULAR PLANT 2020; 13:471-482. [PMID: 32044444 DOI: 10.1016/j.molp.2020.02.002] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 12/16/2019] [Accepted: 01/10/2020] [Indexed: 05/07/2023]
Abstract
The recent discovery of the Entner-Doudoroff (ED) pathway as a third glycolytic route beside Embden-Meyerhof-Parnas (EMP) and oxidative pentose phosphate (OPP) pathway in oxygenic photoautotrophs requires a revision of their central carbohydrate metabolism. In this study, unexpectedly, we observed that deletion of the ED pathway alone, and even more pronounced in combination with other glycolytic routes, diminished photoautotrophic growth in continuous light in the cyanobacterium Synechocystis sp. PCC 6803. Furthermore, we found that the ED pathway is required for optimal glycogen catabolism in parallel to an operating Calvin-Benson-Bassham (CBB) cycle. It is counter-intuitive that glycolytic routes, which are a reverse to the CBB cycle and do not provide any additional biosynthetic intermediates, are important under photoautotrophic conditions. However, observations on the ability to reactivate an arrested CBB cycle revealed that they form glycolytic shunts that tap the cellular carbohydrate reservoir to replenish the cycle. Taken together, our results suggest that the classical view of the CBB cycle as an autocatalytic, completely autonomous cycle that exclusively relies on its own enzymes and CO2 fixation to regenerate ribulose-1,5-bisphosphate for Rubisco is an oversimplification. We propose that in common with other known autocatalytic cycles, the CBB cycle likewise relies on anaplerotic reactions to compensate for the depletion of intermediates, particularly in transition states and under fluctuating light conditions that are common in nature.
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Affiliation(s)
- Alexander Makowka
- Department of Biology, Botanical Institute, University Kiel, 24118 Kiel, Germany
| | - Lars Nichelmann
- Department of Biology, Botanical Institute, University Kiel, 24118 Kiel, Germany
| | - Dennis Schulze
- Institute for Systems Biotechnology, Saarland University, 66123 Saarbrücken, Germany
| | - Katharina Spengler
- Department of Biology, Botanical Institute, University Kiel, 24118 Kiel, Germany
| | - Christoph Wittmann
- Institute for Systems Biotechnology, Saarland University, 66123 Saarbrücken, Germany
| | - Karl Forchhammer
- Organismic Interactions Department, Interfaculty Institute for Microbiology and Infection Medicine, University Tübingen, 72076 Tübingen, Germany
| | - Kirstin Gutekunst
- Department of Biology, Botanical Institute, University Kiel, 24118 Kiel, Germany.
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8
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Shinde S, Zhang X, Singapuri SP, Kalra I, Liu X, Morgan-Kiss RM, Wang X. Glycogen Metabolism Supports Photosynthesis Start through the Oxidative Pentose Phosphate Pathway in Cyanobacteria. PLANT PHYSIOLOGY 2020; 182:507-517. [PMID: 31649110 PMCID: PMC6945877 DOI: 10.1104/pp.19.01184] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 10/17/2019] [Indexed: 06/07/2023]
Abstract
Cyanobacteria experience drastic changes in their carbon metabolism under daily light/dark cycles. During the day, the Calvin-Benson cycle fixes CO2 and diverts excess carbon into glycogen storage. At night, glycogen is degraded to support cellular respiration. The dark/light transition represents a universal environmental stress for cyanobacteria and other photosynthetic lifeforms. Recent studies revealed the essential genetic background necessary for the fitness of cyanobacteria during diurnal growth. However, the metabolic processes underlying the dark/light transition are not well understood. In this study, we observed that glycogen metabolism supports photosynthesis in the cyanobacterium Synechococcus elongatus PCC 7942 when photosynthesis reactions start upon light exposure. Compared with the wild type, the glycogen mutant ∆glgC showed a reduced photosynthetic efficiency and a slower P700+ rereduction rate when photosynthesis starts. Proteomic analyses indicated that glycogen is degraded through the oxidative pentose phosphate (OPP) pathway during the dark/light transition. We confirmed that the OPP pathway is essential for the initiation of photosynthesis and further showed that glycogen degradation through the OPP pathway contributes to the activation of key Calvin-Benson cycle enzymes by modulating NADPH levels. This strategy stimulates photosynthesis in cyanobacteria following dark respiration and stabilizes the Calvin-Benson cycle under fluctuating environmental conditions, thereby offering evolutionary advantages for photosynthetic organisms using the Calvin-Benson cycle for carbon fixation.
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Affiliation(s)
- Shrameeta Shinde
- Department of Microbiology, Miami University, Oxford, Ohio 45056
| | - Xiaohui Zhang
- Department of Microbiology, Miami University, Oxford, Ohio 45056
- School of Environmental Science and Engineering, Tianjin University, Tianjin 300354, China
| | | | - Isha Kalra
- Department of Microbiology, Miami University, Oxford, Ohio 45056
| | - Xianhua Liu
- School of Environmental Science and Engineering, Tianjin University, Tianjin 300354, China
| | | | - Xin Wang
- Department of Microbiology, Miami University, Oxford, Ohio 45056
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Welkie DG, Rubin BE, Diamond S, Hood RD, Savage DF, Golden SS. A Hard Day's Night: Cyanobacteria in Diel Cycles. Trends Microbiol 2019; 27:231-242. [PMID: 30527541 PMCID: PMC6377297 DOI: 10.1016/j.tim.2018.11.002] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 11/01/2018] [Accepted: 11/02/2018] [Indexed: 12/31/2022]
Abstract
Cyanobacteria are photosynthetic prokaryotes that are influential in global geochemistry and are promising candidates for industrial applications. Because the livelihood of cyanobacteria is directly dependent upon light, a comprehensive understanding of metabolism in these organisms requires taking into account the effects of day-night transitions and circadian regulation. These events synchronize intracellular processes with the solar day. Accordingly, metabolism is controlled and structured differently in cyanobacteria than in heterotrophic bacteria. Thus, the approaches applied to engineering heterotrophic bacteria will need to be revised for the cyanobacterial chassis. Here, we summarize important findings related to diurnal metabolism in cyanobacteria and present open questions in the field.
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Affiliation(s)
- David G Welkie
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Benjamin E Rubin
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Spencer Diamond
- Department of Earth and Planetary Science, UC Berkeley, Berkeley, CA 94720, USA
| | - Rachel D Hood
- Department of Molecular and Cell Biology, UC Berkeley, Berkeley, CA 94720, USA
| | - David F Savage
- Department of Molecular and Cell Biology, UC Berkeley, Berkeley, CA 94720, USA
| | - Susan S Golden
- Center for Circadian Biology, University of California, San Diego, La Jolla, CA 92093, USA; Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA.
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10
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Elucidation of photoautotrophic carbon flux topology in Synechocystis PCC 6803 using genome-scale carbon mapping models. Metab Eng 2018. [DOI: 10.1016/j.ymben.2018.03.008] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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11
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Ueda K, Nakajima T, Yoshikawa K, Toya Y, Matsuda F, Shimizu H. Metabolic flux of the oxidative pentose phosphate pathway under low light conditions in Synechocystis sp. PCC 6803. J Biosci Bioeng 2018; 126:38-43. [PMID: 29499995 DOI: 10.1016/j.jbiosc.2018.01.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2017] [Revised: 01/15/2018] [Accepted: 01/30/2018] [Indexed: 10/17/2022]
Abstract
The role of the oxidative pentose phosphate pathway (oxPPP) in Synechocystis sp. PCC 6803 under mixotrophic conditions was investigated by 13C metabolic flux analysis. Cells were cultured under low (10 μmol m-2 s-1) and high light intensities (100 μmol m-2 s-1) in the presence of glucose. The flux of CO2 fixation by ribulose bisphosphate carboxylase/oxygenase under the high light condition was approximately 3-fold higher than that under the low light condition. Although no flux of the oxPPP was observed under the high light condition, flux of 0.08-0.19 mmol gDCW-1 h-1 in the oxPPP was observed under the low light condition. The balance between the consumption and production of NADPH suggested that approximately 10% of the total NADPH production was generated by the oxPPP under the low light condition. The growth phenotype of a mutant with deleted zwf, which encodes glucose-6-phosphate dehydrogenase in the oxPPP, was compared to that of the parental strain under low and high light conditions. Growth of the Δzwf mutant nearly stopped during the late growth phase under the low light condition, whereas the growth rates of the two strains were identical under the high light condition. These results indicate that NADPH production in the oxPPP is essential for anabolism under low light conditions. The oxPPP appears to play an important role in producing NADPH from glucose and ATP to compensate for NADPH shortage under low light conditions.
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Affiliation(s)
- Kentaro Ueda
- Department of Bioinformatic Engineering, Graduate School of Information Science and Technology, Osaka University, 1-5 Yamadaoka, Suita, Osaka 565-0871, Japan.
| | - Tsubasa Nakajima
- Department of Bioinformatic Engineering, Graduate School of Information Science and Technology, Osaka University, 1-5 Yamadaoka, Suita, Osaka 565-0871, Japan.
| | - Katsunori Yoshikawa
- Department of Bioinformatic Engineering, Graduate School of Information Science and Technology, Osaka University, 1-5 Yamadaoka, Suita, Osaka 565-0871, Japan.
| | - Yoshihiro Toya
- Department of Bioinformatic Engineering, Graduate School of Information Science and Technology, Osaka University, 1-5 Yamadaoka, Suita, Osaka 565-0871, Japan.
| | - Fumio Matsuda
- Department of Bioinformatic Engineering, Graduate School of Information Science and Technology, Osaka University, 1-5 Yamadaoka, Suita, Osaka 565-0871, Japan.
| | - Hiroshi Shimizu
- Department of Bioinformatic Engineering, Graduate School of Information Science and Technology, Osaka University, 1-5 Yamadaoka, Suita, Osaka 565-0871, Japan.
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12
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Puszynska AM, O'Shea EK. Switching of metabolic programs in response to light availability is an essential function of the cyanobacterial circadian output pathway. eLife 2017; 6. [PMID: 28430105 PMCID: PMC5400509 DOI: 10.7554/elife.23210] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2016] [Accepted: 02/21/2017] [Indexed: 12/22/2022] Open
Abstract
The transcription factor RpaA is the master regulator of circadian transcription in cyanobacteria, driving genome-wide oscillations in mRNA abundance. Deletion of rpaA has no effect on viability in constant light conditions, but renders cells inviable in cycling conditions when light and dark periods alternate. We investigated the mechanisms underlying this viability defect, and demonstrate that the rpaA- strain cannot maintain appropriate energy status at night, does not accumulate carbon reserves during the day, and is defective in transcription of genes crucial for utilization of carbohydrate stores at night. Reconstruction of carbon utilization pathways combined with provision of an external carbon source restores energy charge and viability of the rpaA- strain in light/dark cycling conditions. Our observations highlight how a circadian output pathway controls and temporally coordinates essential pathways in carbon metabolism to maximize fitness of cells facing periodic energy limitations. DOI:http://dx.doi.org/10.7554/eLife.23210.001 The cycle of day and night is one of the most recurrent and predictable environmental changes on our planet. Consequently, organisms have evolved mechanisms that allow them to measure time over 24 hours and prepare for the periodic changes between light and dark. These mechanisms, known as circadian clocks, alter the activity of some of the organism’s genes in a rhythmic way across the course of a day. This in turn causes certain behaviors and biological activities of the organism to follow a daily cycle. The bacterium Synechococcus elongatus needs to be able to track the daily cycle of light and dark because it performs photosynthesis and depends on sunlight to form sugars, which can later be broken down to release energy. The time information encoded in the circadian clock of S. elongatus is transmitted to the protein RpaA, which drives the regular circadian changes in gene activity in the cell. If RpaA is removed from the cell or prevented from working, S. elongatus can no longer control rhythmic gene activity and is unable to survive the night. To better understand how the circadian system schedules biological tasks to help an organism to survive, Puszynska and O'Shea studied S. elongatus cells. This revealed that the bacteria normally prepare for darkness by storing sugars during the day and activating several genes at dusk to make enzymes that are required to break down stored sugars. This provides the cells with energy that they need to survive the night. But mutant cells that lack the gene that produces RpaA do not prepare for darkness; they do not accumulate a store of sugars during the day or activate the vital genes at dusk. They have low internal energy levels in the dark and they cannot survive long periods of darkness. Providing the mutant cells with sugar and restoring the activity of the genes responsible for breaking down sugar enabled the cells to maintain energy in darkness and survive the night. It therefore appears that one role of the circadian system of S. elongatus is to coordinate building up sugar reserves during the day with breaking down sugar stores to generate energy during the night. Puszynska and O'Shea also found many other genes that are not activated at dusk in the mutant cells. It will therefore be important to study whether other pathways that help cells to survive and grow are defective in these mutant cells. DOI:http://dx.doi.org/10.7554/eLife.23210.002
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Affiliation(s)
- Anna M Puszynska
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States.,Faculty of Arts and Sciences Center for Systems Biology, Harvard University, Cambridge, United States.,Howard Hughes Medical Institute, Harvard University, Cambridge, United States
| | - Erin K O'Shea
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States.,Faculty of Arts and Sciences Center for Systems Biology, Harvard University, Cambridge, United States.,Howard Hughes Medical Institute, Harvard University, Cambridge, United States.,Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
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Abernathy MH, Yu J, Ma F, Liberton M, Ungerer J, Hollinshead WD, Gopalakrishnan S, He L, Maranas CD, Pakrasi HB, Allen DK, Tang YJ. Deciphering cyanobacterial phenotypes for fast photoautotrophic growth via isotopically nonstationary metabolic flux analysis. BIOTECHNOLOGY FOR BIOFUELS 2017; 10:273. [PMID: 29177008 PMCID: PMC5691832 DOI: 10.1186/s13068-017-0958-y] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 11/06/2017] [Indexed: 05/09/2023]
Abstract
BACKGROUND Synechococcus elongatus UTEX 2973 is the fastest growing cyanobacterium characterized to date. Its genome was found to be 99.8% identical to S. elongatus 7942 yet it grows twice as fast. Current genome-to-phenome mapping is still poorly performed for non-model organisms. Even for species with identical genomes, cell phenotypes can be strikingly different. To understand Synechococcus 2973's fast-growth phenotype and its metabolic features advantageous to photo-biorefineries, 13C isotopically nonstationary metabolic flux analysis (INST-MFA), biomass compositional analysis, gene knockouts, and metabolite profiling were performed on both strains under various growth conditions. RESULTS The Synechococcus 2973 flux maps show substantial carbon flow through the Calvin cycle, glycolysis, photorespiration and pyruvate kinase, but minimal flux through the malic enzyme and oxidative pentose phosphate pathways under high light/CO2 conditions. During fast growth, its pool sizes of key metabolites in central pathways were lower than suboptimal growth. Synechococcus 2973 demonstrated similar flux ratios to Synechococcus 7942 (under fast growth conditions), but exhibited greater carbon assimilation, higher NADPH concentrations, higher energy charge (relative ATP ratio over ADP and AMP), less accumulation of glycogen, and potentially metabolite channeling. Furthermore, Synechococcus 2973 has very limited flux through the TCA pathway with small pool sizes of acetyl-CoA/TCA intermediates under all growth conditions. CONCLUSIONS This study employed flux analysis to investigate phenotypic heterogeneity among two cyanobacterial strains with near-identical genome background. The flux/metabolite profiling, biomass composition analysis, and genetic modification results elucidate a highly effective metabolic topology for CO2 assimilatory and biosynthesis in Synechococcus 2973. Comparisons across multiple Synechococcus strains indicate faster metabolism is also driven by proportional increases in both photosynthesis and key central pathway fluxes. Moreover, the flux distribution in Synechococcus 2973 supports the use of its strong sugar phosphate pathways for optimal bio-productions. The integrated methodologies in this study can be applied for characterizing non-model microbial metabolism.
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Affiliation(s)
- Mary H. Abernathy
- Department of Energy, Environmental and Chemical Engineering, Washington University, St. Louis, MO 63130 USA
| | - Jingjie Yu
- Department of Biology, Temple University, Philadelphia, PA 19122 USA
| | - Fangfang Ma
- Donald Danforth Plant Science Center, St. Louis, MO 63132 USA
| | - Michelle Liberton
- Department of Biology, Washington University, St. Louis, MO 63130 USA
| | - Justin Ungerer
- Department of Biology, Washington University, St. Louis, MO 63130 USA
| | - Whitney D. Hollinshead
- Department of Energy, Environmental and Chemical Engineering, Washington University, St. Louis, MO 63130 USA
| | - Saratram Gopalakrishnan
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA 16802 USA
| | - Lian He
- Department of Energy, Environmental and Chemical Engineering, Washington University, St. Louis, MO 63130 USA
| | - Costas D. Maranas
- Department of Chemical Engineering, The Pennsylvania State University, University Park, PA 16802 USA
| | - Himadri B. Pakrasi
- Department of Energy, Environmental and Chemical Engineering, Washington University, St. Louis, MO 63130 USA
- Department of Biology, Washington University, St. Louis, MO 63130 USA
| | - Doug K. Allen
- Donald Danforth Plant Science Center, St. Louis, MO 63132 USA
- United States Department of Agriculture, Agricultural Research Service, St. Louis, MO 63132 USA
| | - Yinjie J. Tang
- Department of Energy, Environmental and Chemical Engineering, Washington University, St. Louis, MO 63130 USA
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Unique attributes of cyanobacterial metabolism revealed by improved genome-scale metabolic modeling and essential gene analysis. Proc Natl Acad Sci U S A 2016; 113:E8344-E8353. [PMID: 27911809 DOI: 10.1073/pnas.1613446113] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The model cyanobacterium, Synechococcus elongatus PCC 7942, is a genetically tractable obligate phototroph that is being developed for the bioproduction of high-value chemicals. Genome-scale models (GEMs) have been successfully used to assess and engineer cellular metabolism; however, GEMs of phototrophic metabolism have been limited by the lack of experimental datasets for model validation and the challenges of incorporating photon uptake. Here, we develop a GEM of metabolism in S. elongatus using random barcode transposon site sequencing (RB-TnSeq) essential gene and physiological data specific to photoautotrophic metabolism. The model explicitly describes photon absorption and accounts for shading, resulting in the characteristic linear growth curve of photoautotrophs. GEM predictions of gene essentiality were compared with data obtained from recent dense-transposon mutagenesis experiments. This dataset allowed major improvements to the accuracy of the model. Furthermore, discrepancies between GEM predictions and the in vivo dataset revealed biological characteristics, such as the importance of a truncated, linear TCA pathway, low flux toward amino acid synthesis from photorespiration, and knowledge gaps within nucleotide metabolism. Coupling of strong experimental support and photoautotrophic modeling methods thus resulted in a highly accurate model of S. elongatus metabolism that highlights previously unknown areas of S. elongatus biology.
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15
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Albers SC, Peebles CAM. Evaluating Light-Induced Promoters for the Control of Heterologous Gene Expression inSynechocystis sp. PCC 6803. Biotechnol Prog 2016; 33:45-53. [DOI: 10.1002/btpr.2396] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 10/07/2016] [Indexed: 11/09/2022]
Affiliation(s)
- Stevan C. Albers
- Cell and Molecular Biology Graduate Program; Colorado State University; Fort Collins CO 80523
| | - Christie A. M. Peebles
- Cell and Molecular Biology Graduate Program; Colorado State University; Fort Collins CO 80523
- Dept. of Chemical and Biological Engineering; Colorado State University; Fort Collins CO 80523
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16
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Abstract
Synechococcus elongatus PCC 7942 is a model organism used for studying photosynthesis and the circadian clock, and it is being developed for the production of fuel, industrial chemicals, and pharmaceuticals. To identify a comprehensive set of genes and intergenic regions that impacts fitness in S. elongatus, we created a pooled library of ∼ 250,000 transposon mutants and used sequencing to identify the insertion locations. By analyzing the distribution and survival of these mutants, we identified 718 of the organism's 2,723 genes as essential for survival under laboratory conditions. The validity of the essential gene set is supported by its tight overlap with well-conserved genes and its enrichment for core biological processes. The differences noted between our dataset and these predictors of essentiality, however, have led to surprising biological insights. One such finding is that genes in a large portion of the TCA cycle are dispensable, suggesting that S. elongatus does not require a cyclic TCA process. Furthermore, the density of the transposon mutant library enabled individual and global statements about the essentiality of noncoding RNAs, regulatory elements, and other intergenic regions. In this way, a group I intron located in tRNA(Leu), which has been used extensively for phylogenetic studies, was shown here to be essential for the survival of S. elongatus. Our survey of essentiality for every locus in the S. elongatus genome serves as a powerful resource for understanding the organism's physiology and defines the essential gene set required for the growth of a photosynthetic organism.
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17
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Shultzaberger RK, Boyd JS, Diamond S, Greenspan RJ, Golden SS. Giving Time Purpose: The Synechococcus elongatus Clock in a Broader Network Context. Annu Rev Genet 2015; 49:485-505. [PMID: 26442846 DOI: 10.1146/annurev-genet-111212-133227] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Early research on the cyanobacterial clock focused on characterizing the genes needed to keep, entrain, and convey time within the cell. As the scope of assays used in molecular genetics has expanded to capture systems-level properties (e.g., RNA-seq, ChIP-seq, metabolomics, high-throughput screening of genetic variants), so has our understanding of how the clock fits within and influences a broader cellular context. Here we review the work that has established a global perspective of the clock, with a focus on (a) an emerging network-centric view of clock architecture, (b) mechanistic insights into how temporal and environmental cues are transmitted and integrated within this network,
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Affiliation(s)
- Ryan K Shultzaberger
- Center for Circadian Biology, University of California San Diego, La Jolla, USA, 92093.,Kavli Institute for Brain and Mind, University of California San Diego, La Jolla, USA, 92093
| | - Joseph S Boyd
- Center for Circadian Biology, University of California San Diego, La Jolla, USA, 92093.,Division of Biological Sciences, University of California San Diego, La Jolla, USA, 92093
| | - Spencer Diamond
- Center for Circadian Biology, University of California San Diego, La Jolla, USA, 92093.,Division of Biological Sciences, University of California San Diego, La Jolla, USA, 92093
| | - Ralph J Greenspan
- Center for Circadian Biology, University of California San Diego, La Jolla, USA, 92093.,Kavli Institute for Brain and Mind, University of California San Diego, La Jolla, USA, 92093
| | - Susan S Golden
- Center for Circadian Biology, University of California San Diego, La Jolla, USA, 92093.,Division of Biological Sciences, University of California San Diego, La Jolla, USA, 92093
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18
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Characterisation of an opcA Mutant of the Unicellular Cyanobacterium Synechocystis sp. PCC 6803. Curr Microbiol 2015; 71:572-8. [DOI: 10.1007/s00284-015-0889-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Accepted: 06/28/2015] [Indexed: 11/26/2022]
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19
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The circadian oscillator in Synechococcus elongatus controls metabolite partitioning during diurnal growth. Proc Natl Acad Sci U S A 2015; 112:E1916-25. [PMID: 25825710 DOI: 10.1073/pnas.1504576112] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Synechococcus elongatus PCC 7942 is a genetically tractable model cyanobacterium that has been engineered to produce industrially relevant biomolecules and is the best-studied model for a prokaryotic circadian clock. However, the organism is commonly grown in continuous light in the laboratory, and data on metabolic processes under diurnal conditions are lacking. Moreover, the influence of the circadian clock on diurnal metabolism has been investigated only briefly. Here, we demonstrate that the circadian oscillator influences rhythms of metabolism during diurnal growth, even though light-dark cycles can drive metabolic rhythms independently. Moreover, the phenotype associated with loss of the core oscillator protein, KaiC, is distinct from that caused by absence of the circadian output transcriptional regulator, RpaA (regulator of phycobilisome-associated A). Although RpaA activity is important for carbon degradation at night, KaiC is dispensable for those processes. Untargeted metabolomics analysis and glycogen kinetics suggest that functional KaiC is important for metabolite partitioning in the morning. Additionally, output from the oscillator functions to inhibit RpaA activity in the morning, and kaiC-null strains expressing a mutant KaiC phosphomimetic, KaiC-pST, in which the oscillator is locked in the most active output state, phenocopies a ΔrpaA strain. Inhibition of RpaA by the oscillator in the morning suppresses metabolic processes that normally are active at night, and kaiC-null strains show indications of oxidative pentose phosphate pathway activation as well as increased abundance of primary metabolites. Inhibitory clock output may serve to allow secondary metabolite biosynthesis in the morning, and some metabolites resulting from these processes may feed back to reinforce clock timing.
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20
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You L, Berla B, He L, Pakrasi HB, Tang YJ. 13C-MFA delineates the photomixotrophic metabolism of Synechocystis sp. PCC 6803 under light- and carbon-sufficient conditions. Biotechnol J 2014; 9:684-92. [PMID: 24659531 DOI: 10.1002/biot.201300477] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 02/08/2014] [Accepted: 03/19/2014] [Indexed: 11/07/2022]
Abstract
The central carbon metabolism of cyanobacteria is under debate. For over 50 years, the lack of α-ketoglutarate dehydrogenase has led to the belief that cyanobacteria have an incomplete TCA cycle. Recent in vitro enzymatic experiments suggest that this cycle may in fact be closed. The current study employed (13) C isotopomers to delineate pathways in the cyanobacterium Synechocystis sp. PCC 6803. By tracing the incorporation of supplemented glutamate into the downstream metabolites in the TCA cycle, we observed a direct in vivo transformation of α-ketoglutarate to succinate. Additionally, isotopic tracing of glyoxylate did not show a functional glyoxylate shunt and glyoxylate was used for glycine synthesis. The photomixotrophic carbon metabolism was then profiled with (13) C-MFA under light and carbon-sufficient conditions. We observed that: (i) the in vivo flux through the TCA cycle reactions (α-ketoglutarate → succinate) was minimal (<2%); (ii) the flux ratio of CO2 fixation was six times higher than that of glucose utilization; (iii) the relative flux through the oxidative pentose phosphate pathway was low (<2%); (iv) high flux through malic enzyme served as a main route for pyruvate synthesis. Our results improve the understanding of the versatile metabolism in cyanobacteria and shed light on their application for photo-biorefineries.
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Affiliation(s)
- Le You
- Department of Energy, Enviromental and Chemical Engineering, Washington University, St. Louis, MO, USA
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21
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D'Agostino PM, Song X, Neilan BA, Moffitt MC. Comparative proteomics reveals that a saxitoxin-producing and a nontoxic strain of Anabaena circinalis are two different ecotypes. J Proteome Res 2014; 13:1474-84. [PMID: 24460188 DOI: 10.1021/pr401007k] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
In Australia, saxitoxin production is restricted to the cyanobacterial species Anabaena circinalis and is strain-dependent. We aimed to characterize a saxitoxin-producing and nontoxic strain of A. circinalis at the proteomic level using iTRAQ. Seven proteins putatively involved in saxitoxin biosynthesis were identified within our iTRAQ experiment for the first time. The proteomic profile of the toxic A. circinalis was significantly different from the nontoxic strain, indicating that each is likely to inhabit a unique ecological niche. Under control growth conditions, the saxitoxin-producing A. circinalis displayed a higher abundance of photosynthetic, carbon fixation and nitrogen metabolic proteins. Differential abundance of these proteins suggests a higher intracellular C:N ratio and a higher concentration of intracellular 2-oxoglutarate in our toxic strain compared with the nontoxic strain. This may be a novel site for posttranslational regulation because saxitoxin biosynthesis putatively requires a 2-oxoglutarate-dependent dioxygenase. The nontoxic A. circinalis was more abundant in proteins, indicating cellular stress. Overall, our study has provided the first insight into fundamental differences between a toxic and nontoxic strain of A. circinalis, indicating that they are distinct ecotypes.
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Affiliation(s)
- Paul M D'Agostino
- School of Science and Health, University of Western Sydney , Campbelltown, NSW 2560, Australia
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22
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Gao L, Shen C, Liao L, Huang X, Liu K, Wang W, Guo L, Jin W, Huang F, Xu W, Wang Y. Functional proteomic discovery of Slr0110 as a central regulator of carbohydrate metabolism in Synechocystis species PCC6803. Mol Cell Proteomics 2013; 13:204-19. [PMID: 24169622 DOI: 10.1074/mcp.m113.033803] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The unicellular photosynthetic model-organism cyanobacterium Synechocystis sp. PCC6803 can grow photoautotrophically using CO2 or heterotrophically using glucose as the sole carbon source. Several pathways are involved in carbon metabolism in Synechocystis, and the concerted regulation of these pathways by numerous known and unknown genes is critical for the survival and growth of the organism. Here, we report that a hypothetical protein encoded by the open reading frame slr0110 is necessary for heterotrophic growth of Synechocystis. The slr0110-deletion mutant is defective in glucose uptake, heterotrophic growth, and dark viability without detectable defects in autotrophic growth, whereas the level of photosystem II and the rate of oxygen evolution are increased in the mutant. Quantitative proteomic analysis revealed that several proteins in glycolysis and the oxidative pentose phosphate pathway are down-regulated, whereas proteins in photosystem II and phycobilisome are significantly up-regulated, in the mutant. Among the down-regulated proteins are glucose transporter, glucokinase, glucose-6-phosphate isomerase, and glucose-6-phosphate dehydrogenase and its assembly protein OpcA, suggesting that glycolysis, oxidative pentose phosphate, and glycogen synthesis pathways are significantly inhibited in the mutant, which was further confirmed by enzymatic assays and quantification of glycogen content. These findings establish Slr0110 as a novel central regulator of carbon metabolism in Synechocystis, and shed light on an intricate mechanism whereby photosynthesis and carbon metabolism are well concerted to survive the crisis when one or more pathways of the system are impaired.
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Affiliation(s)
- Liyan Gao
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, No. 1 West Beichen Rd., Beijing 100101, China
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23
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Analysis of glucose-6-phosphate dehydrogenase of the cyanobacterium Synechococcus sp. PCC 7942 in the zwf mutant Escherichia coli DF214 cells. ANN MICROBIOL 2012. [DOI: 10.1007/s13213-012-0591-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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24
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Young JD, Shastri AA, Stephanopoulos G, Morgan JA. Mapping photoautotrophic metabolism with isotopically nonstationary (13)C flux analysis. Metab Eng 2011; 13:656-65. [PMID: 21907300 DOI: 10.1016/j.ymben.2011.08.002] [Citation(s) in RCA: 261] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Revised: 08/18/2011] [Accepted: 08/23/2011] [Indexed: 11/25/2022]
Abstract
Understanding in vivo regulation of photoautotrophic metabolism is important for identifying strategies to improve photosynthetic efficiency or re-route carbon fluxes to desirable end products. We have developed an approach to reconstruct comprehensive flux maps of photoautotrophic metabolism by computational analysis of dynamic isotope labeling measurements and have applied it to determine metabolic pathway fluxes in the cyanobacterium Synechocystis sp. PCC6803. Comparison to a theoretically predicted flux map revealed inefficiencies in photosynthesis due to oxidative pentose phosphate pathway and malic enzyme activity, despite negligible photorespiration. This approach has potential to fill important gaps in our understanding of how carbon and energy flows are systemically regulated in cyanobacteria, plants, and algae.
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Affiliation(s)
- Jamey D Young
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN 37235, USA
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25
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Tang KH, Tang YJ, Blankenship RE. Carbon metabolic pathways in phototrophic bacteria and their broader evolutionary implications. Front Microbiol 2011; 2:165. [PMID: 21866228 PMCID: PMC3149686 DOI: 10.3389/fmicb.2011.00165] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2011] [Accepted: 07/18/2011] [Indexed: 11/19/2022] Open
Abstract
Photosynthesis is the biological process that converts solar energy to biomass, bio-products, and biofuel. It is the only major natural solar energy storage mechanism on Earth. To satisfy the increased demand for sustainable energy sources and identify the mechanism of photosynthetic carbon assimilation, which is one of the bottlenecks in photosynthesis, it is essential to understand the process of solar energy storage and associated carbon metabolism in photosynthetic organisms. Researchers have employed physiological studies, microbiological chemistry, enzyme assays, genome sequencing, transcriptomics, and (13)C-based metabolomics/fluxomics to investigate central carbon metabolism and enzymes that operate in phototrophs. In this report, we review diverse CO(2) assimilation pathways, acetate assimilation, carbohydrate catabolism, the tricarboxylic acid cycle and some key, and/or unconventional enzymes in central carbon metabolism of phototrophic microorganisms. We also discuss the reducing equivalent flow during photoautotrophic and photoheterotrophic growth, evolutionary links in the central carbon metabolic network, and correlations between photosynthetic and non-photosynthetic organisms. Considering the metabolic versatility in these fascinating and diverse photosynthetic bacteria, many essential questions in their central carbon metabolism still remain to be addressed.
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Affiliation(s)
- Kuo-Hsiang Tang
- Department of Biology, Washington University in St. LouisSt. Louis, MO, USA
- Department of Chemistry, Washington University in St. LouisSt. Louis, MO, USA
| | - Yinjie J. Tang
- Department of Energy, Environment, and Chemical Engineering, Washington University in St. LouisSt. Louis, MO, USA
| | - Robert Eugene Blankenship
- Department of Biology, Washington University in St. LouisSt. Louis, MO, USA
- Department of Chemistry, Washington University in St. LouisSt. Louis, MO, USA
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26
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A Δzwf (glucose-6-phosphate dehydrogenase) mutant of the cyanobacteriumSynechocystis sp. PCC 6803 exhibits unimpaired dark viability. ANN MICROBIOL 2008. [DOI: 10.1007/bf03175330] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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27
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Lee S, Ryu JY, Kim SY, Jeon JH, Song JY, Cho HT, Choi SB, Choi D, de Marsac NT, Park YI. Transcriptional regulation of the respiratory genes in the cyanobacterium Synechocystis sp. PCC 6803 during the early response to glucose feeding. PLANT PHYSIOLOGY 2007; 145:1018-30. [PMID: 17827271 PMCID: PMC2048796 DOI: 10.1104/pp.107.105023] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The coordinated expression of the genes involved in respiration in the photosynthetic cyanobacterium Synechocystis sp. PCC 6803 during the early period of glucose (Glc) treatment is poorly understood. When photoautotrophically grown cells were supplemented with 10 mm Glc in the light or after a dark adaptation period of 14 h, significant increases in the respiratory activity, as determined by NAD(P)H turnover, respiratory O(2) uptake rate, and cytosolic alkalization, were observed. At the same time, the transcript levels of 18 genes coding for enzymes associated with respiration increased with differential induction kinetics; these genes were classified into three groups based on their half-rising times. Transcript levels of the four genes gpi, zwf, pdhB, and atpB started to increase along with a net increase in NAD(P)H, while the onset of net NAD(P)H consumption coincided with an increase in those of the genes tktA, ppc, pdhD, icd, ndhD2, ndbA, ctaD1, cydA, and atpE. In contrast, the expression of the atpI/G/D/A/C genes coding for ATP synthase subunits was the slowest among respiratory genes and their expression started to accumulate only after the establishment of cytosolic alkalization. These differential effects of Glc on the transcript levels of respiratory genes were not observed by inactivation of the genes encoding the Glc transporter or glucokinase. In addition, several Glc analogs could not mimic the effects of Glc. Our findings suggest that genes encoding some enzymes involved in central carbon metabolism and oxidative phosphorylation are coordinately regulated at the transcriptional level during the switch of nutritional mode.
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Affiliation(s)
- Sanghyeob Lee
- Laboratory of Plant Genomics, Korea Research Institute of Bioscience and Biotechnology, Daejeon 305-806, Korea
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28
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Osanai T, Azuma M, Tanaka K. Sugar catabolism regulated by light- and nitrogen-status in the cyanobacterium Synechocystis sp. PCC 6803. Photochem Photobiol Sci 2007; 6:508-14. [PMID: 17487300 DOI: 10.1039/b616219n] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In photosynthetic organisms, sugar catabolic pathways, such as glycolysis and the oxidative pentose phosphate pathway, are indispensable for survival in the absence of light. In this review, we will focus on the regulation of sugar catabolic gene expression in cyanobacteria, especially that of Synechocystis sp. PCC 6803 (Synechocystis). In Synechocystis, the expression of sugar catabolic genes is activated by the shift from light-to-dark and diurnally during the evening, and positively regulated by a histidine kinase, Hik8, and a RNA polymerase sigma factor, SigE. Mutants for these regulators are defective for survival in the dark and unable to carry out light-activated heterotrophic growth. It has also been shown that transcripts of sugar catabolic genes are increased by nitrogen depletion and a global nitrogen regulator NtcA is essential for the induction. These results indicate a regulatory connection between nitrogen status and sugar catabolism in cyanobacteria.
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Affiliation(s)
- Takashi Osanai
- Institute of Molecular and Cellular Biosciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
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29
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Abstract
To provide an insight into the heterotrophic metabolism of cyanobacteria, a proteomic approach has been employed with the model organism Synechocystis sp. PCC 6803. The soluble proteins from Synechocystis grown under photoautotrophic and light-activated heterotrophic conditions were separated by 2-DE and identified by MALDI-MS or LC-MS/MS analysis. 2-DE gels made using narrow- and micro-range IPG strips allowed quantitative comparison of more than 900 spots. Out of 67 abundant protein spots identified, 13 spots were increased and 9 decreased under heterotrophy, representing all the major fold changes. Proteomic alterations and activity levels of selected enzymes indicate a shift in the central carbon metabolism in response to trophic change. The significant reduction in light-saturated rate of photosynthesis as well as in the expression levels of rubisco and CO(2)-concentrating mechanism proteins under heterotrophy indicates the down-regulation of the photosynthetic machinery. Alterations in the expression level of proteins involved in carbon utilization pathways refer to enhanced glycolysis, oxidative pentose phosphate pathway as well as tricarboxylic acid cycle under heterotrophy. Proteomic evidences also suggest an enhanced biosynthesis of amino acids such as histidine and serine during heterotrophic growth.
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Affiliation(s)
- Dominic Kurian
- Laboratory of Plant Physiology and Molecular Biology, Department of Biology, University of Turku, Turku, Finland
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30
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Kahlon S, Beeri K, Ohkawa H, Hihara Y, Murik O, Suzuki I, Ogawa T, Kaplan A. A putative sensor kinase, Hik31, is involved in the response of Synechocystis sp. strain PCC 6803 to the presence of glucose. MICROBIOLOGY-SGM 2006; 152:647-655. [PMID: 16514145 DOI: 10.1099/mic.0.28510-0] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The reason(s) for glucose sensitivity in certain cyanobacterial strains is poorly understood. Inactivation of genes encoding the putative sensor kinase Hik31 in Synechocystis sp. strain PCC 6803 resulted in a mutant unable to grow in the presence of D-glucose. Sensitivities to D-glucose, its analogue 2-deoxy-D-glucose, and fructose, were alleviated in mutants in which glcP, encoding the glucose transporter, was inactivated. These data indicate that permeation of these substrates is required to inflict cell death. The mutant Deltahik31, and the glucose-sensitive strain of Synechocystis, do not possess glucokinase activity, although a transcript originating from glk, encoding glucokinase, is present. Inactivation of glk led to severe sensitivity to glucose, indicating that the presence of glucose itself, within the cells, inflicted this sensitivity. On the other hand, sensitivity to 2-deoxy-D-glucose was lower in Deltaglk, thus distinguishing between the effect of glucose itself and that of its analogue, which, in the absence of glucokinase activity, may not be phosphorylated. Addition of glucose led to a small rise in glucose-6-phosphate dehydrogenase activity in the wild type, but constitutive activity was observed in the Deltahik31 mutant regardless of the presence of glucose. Microarray analyses showed only small changes in the abundance of global transcripts in Synechocystis following glucose addition, but the transcription levels of several genes, including icfG, but not glk, were strongly affected by inactivation of hik31. The mechanism(s) whereby Hik31 is involved in glucose sensing and response is discussed.
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Affiliation(s)
- Shira Kahlon
- Department of Plant and Environmental Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Karen Beeri
- Department of Plant and Environmental Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | | | - Yukako Hihara
- Department of Biochemistry and Molecular Biology, Saitama University, Saitama, Japan
| | - Omer Murik
- Department of Plant and Environmental Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Iwane Suzuki
- National Institute for Basic Biology, Okazaki, Japan
| | - Teruo Ogawa
- Bioscience Center, Nagoya University, Nagoya, Japan
| | - Aaron Kaplan
- Department of Plant and Environmental Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel
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31
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Osanai T, Imamura S, Asayama M, Shirai M, Suzuki I, Murata N, Tanaka K. Nitrogen Induction of Sugar Catabolic Gene Expression in Synechocystis sp. PCC 6803. DNA Res 2006; 13:185-95. [PMID: 17046957 DOI: 10.1093/dnares/dsl010] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Nitrogen starvation requires cells to change their transcriptome in order to cope with this essential nutrient limitation. Here, using microarray analysis, we investigated changes in transcript profiles following nitrogen depletion in the unicellular cyanobacterium Synechocystis sp. PCC 6803. Results revealed that genes for sugar catabolic pathways including glycolysis, oxidative pentose phosphate (OPP) pathway, and glycogen catabolism were induced by nitrogen depletion, and activities of glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD), two key enzymes of the OPP pathway, were demonstrated to increase under this condition. We recently showed that a group 2 sigma factor SigE, which is under the control of the global nitrogen regulator NtcA, positively regulated these sugar catabolic pathways. However, increases of transcript levels of these sugar catabolic genes under nitrogen starvation were still observed even in a sigE-deficient mutant, indicating the involvement of other regulatory element(s) in addition to SigE. Since these nitrogen activations were abolished in an ntcA mutant, and since these genes were not directly included in the NtcA regulon, we suggested that sugar catabolic genes were induced by nitrogen depletion under complex and redundant regulations including SigE and other unknown factor(s) under the control of NtcA.
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Affiliation(s)
- Takashi Osanai
- Institute of Molecular and Cellular Biosciences, The University of Tokyo 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
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Osanai T, Kanesaki Y, Nakano T, Takahashi H, Asayama M, Shirai M, Kanehisa M, Suzuki I, Murata N, Tanaka K. Positive Regulation of Sugar Catabolic Pathways in the Cyanobacterium Synechocystis sp. PCC 6803 by the Group 2 σ Factor SigE. J Biol Chem 2005; 280:30653-9. [PMID: 15944148 DOI: 10.1074/jbc.m505043200] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The sigE gene of Synechocystis sp. PCC 6803 encodes a group 2 sigma factor for RNA polymerase and has been proposed to function in transcriptional regulation of nitrogen metabolism. By using microarray and Northern analyses, we demonstrated that the abundance of transcripts derived from genes important for glycolysis, the oxidative pentose phosphate pathway, and glycogen catabolism is reduced in a sigE mutant of Synechocystis maintained under the normal growth condition. Furthermore, the activities of the two key enzymes of the oxidative pentose phosphate pathway, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, encoded by the zwf and gnd genes were also reduced in the sigE mutant. The dark enhancements in both enzyme activity and transcript abundance apparent in the wild type were eliminated by the mutation. In addition, the sigE mutant showed a reduced rate of glucose uptake and an increased intracellular level of glycogen. Moreover, it was unable to proliferate under the light-activated heterotrophic growth conditions. These results indicate that SigE functions in the transcriptional activation of sugar catabolic pathways in Synechocystis sp. PCC 6803.
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Affiliation(s)
- Takashi Osanai
- Institute of Molecular and Cellular Biosciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
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33
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Singh AK, Sherman LA. Pleiotropic effect of a histidine kinase on carbohydrate metabolism in Synechocystis sp. strain PCC 6803 and its requirement for heterotrophic growth. J Bacteriol 2005; 187:2368-76. [PMID: 15774880 PMCID: PMC1065225 DOI: 10.1128/jb.187.7.2368-2376.2005] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The deletion of a gene coding for a histidine kinase (sll0750, Hik8) in the unicellular cyanobacterium Synechocystis sp. strain PCC 6803 resulted in a conditional lethal phenotype with a pleiotropic effect on the expression of genes involved in glucose metabolism. This mutant had comparable doubling times to wild type (WT) in continuous-light-grown photoautotrophic and mixotrophic cultures, whereas it grew poorly under mixotrophic conditions with different light and dark cycles. Growth was completely stopped, and cells eventually died, when the light duration was less than 6 h on a 24-h regimen. Northern blot analysis demonstrated that steady-state transcript levels of genes encoding key enzymes of glycolysis, gluconeogenesis, the oxidative pentose phosphate pathway, and glycogen metabolism were significantly altered in a strain with mutant hik8 (Deltahik8) grown with or without glucose. In some cases, differential expression was dependent on growth conditions (photoautotrophic versus mixotrophic). The enzyme activities of glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and phosphofructokinase were significantly reduced in Deltahik8 compared to WT. Glycogen determination indicated that Deltahik8 accumulated glycogen under mixotrophic conditions but was unable to utilize these reserves for heterotrophic growth. The results suggest that the loss of gap1 transcription in the absence of Hik8 was the key factor that rendered cells unable to catabolize glucose and grow heterotrophically. Additionally, the transcript levels of the phytochrome gene (cph1) and its cotranscribed response regulator gene (rcp1) were significantly reduced and its dark inducibility was lost in Deltahik8. The results demonstrated that Hik8 plays an important role in glucose metabolism and is necessary for heterotrophic growth.
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Affiliation(s)
- Abhay K Singh
- Department of Biological Sciences, Purdue University, 1392 Lilly Hall of Life Sciences, West Lafayette, IN 47907, USA
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Min H, Golden SS. A new circadian class 2 gene, opcA, whose product is important for reductant production at night in Synechococcus elongatus PCC 7942. J Bacteriol 2000; 182:6214-21. [PMID: 11029444 PMCID: PMC94758 DOI: 10.1128/jb.182.21.6214-6221.2000] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Gene expression in the cyanobacterium Synechococcus elongatus PCC 7942 is under the control of a circadian oscillator, such that peaks and troughs of expression recur with a periodicity of about 24 h in the absence of environmental cues. This can be monitored easily as light production from luciferase gene fusions to S. elongatus promoters. All promoters seem to exhibit circadian oscillation of expression, but the phasing of peak and trough times differs among different genes. The majority of genes are designated class 1, with expression peaks near dusk or subjective dusk (the time corresponding to dusk in the absence of a diurnal cycle). A minority, of which purF is an example, have expression peaks approximately 12 h out of phase with class 1 genes. A screen of Tn5 mutants for those in which purF phasing is altered revealed a mutant that carries an insertion in the opcA gene, previously identified as essential for glucose-6-phosphate dehydrogenase function. However, a different enzymatic reporter and in vitro luciferase assays revealed that the expression pattern of the purF promoter is not altered by opcA inactivation, but rather the reduced flavin mononucleotide substrate of luciferase is limiting at the time of the natural circadian peak. The results suggest that OpcA is involved in temporally separated reductant-generating pathways in S. elongatus and that it has a role outside of its function in activating glucose-6-phosphate dehydrogenase. The opcA gene, expected to be cotranscribed with fbp and zwf, was shown to have its own class 2 promoter, whereas the fbp promoter was determined to be in class 1. Thus, opcA expression is likely to be constitutive by virtue of the activity of two promoters in nearly opposite circadian phases.
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Affiliation(s)
- H Min
- Department of Biology, Texas A&M University, College Station, Texas 77843-3258, USA
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35
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Sundaram S, Karakaya H, Scanlan DJ, Mann NH. Multiple oligomeric forms of glucose-6-phosphate dehydrogenase in cyanobacteria and the role of OpcA in the assembly process. MICROBIOLOGY (READING, ENGLAND) 1998; 144 ( Pt 6):1549-1556. [PMID: 9639925 DOI: 10.1099/00221287-144-6-1549] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Multiple molecular forms of glucose-6-phosphate dehydrogenase (G6PDH) were detected by activity staining in non-denaturing polyacrylamide gels of cell-free extracts from a range of cyanobacteria including Anabaena sp. PCC 7120, Synechococcus sp. PCC 7942, Plectonema boryanum PCC 73110, Synechocystis sp. PCC 6803, Nostoc sp. MAC PCC 8009 and the marine strain Synechococcus sp. WH7803. In most of the species tested, the profile of G6PDH activities was modulated by the growth of the cells in the presence of exogenous 10 mM glucose. Using an antiserum raised against a fragment of G6PDH from Anabaena sp. PCC 7120, it was shown that the different molecular forms of G6PDH all contained an antigenically related subunit, suggesting that the different forms arose from different quaternary structures involving the same monomer. An insertion mutant of Synechococcus sp. PCC 7942 was constructed in which the opcA gene, adjacent to zwf (encoding G6PDH), was disrupted. Although no reduction in the amount of G6PDH monomers (Zwf) was observed in the opcA mutant, activity staining of native gels indicated that most of this protein is not assembled into one of the active oligomeric forms. The oligomerization of G6PDH in extracts of the opcA mutant was stimulated in vitro by a factor present in crude extracts of the wild-type, suggesting that the product of the opcA gene is involved in the oligomerization and activation of G6PDH.
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Affiliation(s)
- Shanthy Sundaram
- Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK
| | - Haydar Karakaya
- Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK
| | - David J Scanlan
- Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK
| | - Nicholas H Mann
- Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, UK
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36
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Anderson LE, Li D, Muslin EH, Stevens FJ, Schiffer M. Predicting redox-sensitive cysteines in plant enzymes by homology modeling. ACTA ACUST UNITED AC 1997. [DOI: 10.1016/s0764-4469(97)85012-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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37
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Yoshida Y, Nakano Y, Yamashita Y, Koga T. The gnd gene encoding a novel 6-phosphogluconate dehydrogenase and its adjacent region of Actinobacillus actinomycetemcomitans chromosomal DNA. Biochem Biophys Res Commun 1997; 230:220-5. [PMID: 9020051 DOI: 10.1006/bbrc.1996.5917] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A 10-kb DNA fragment containing the gnd gene from Actinobacillus actinomy-cetemcomitans Y4 was isolated and sequenced. The structural gnd gene codes for 6-phosphogluconate dehydrogenase that consists of 484 amino acids. In contrast to the gnd gene in Escherichia coli, Salmonella typhimurium, or Klebsiella pneumoniae, the gnd gene of A. actinomycetemcomitans was not located in the rfb or cps operon. The zwf gene encoding glucose 6-phosphate dehydrogenase, which is another enzyme consisting of pentose-phosphate pathway, sided at 3.8-kb upstream from the gnd gene. A phylogenetic tree based on sequence analyses showed higher homology of 6-phospho-gluconate dehydrogenase of A. actinomycetemcomitans with the eucaryotic enzymes rather than with bacterial enzymes.
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Affiliation(s)
- Y Yoshida
- Department of Preventive Dentistry, Kyushu University Faculty of Dentistry, Maidashi, Higashi-ku, Japan
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38
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Summers ML, Wallis JG, Campbell EL, Meeks JC. Genetic evidence of a major role for glucose-6-phosphate dehydrogenase in nitrogen fixation and dark growth of the cyanobacterium Nostoc sp. strain ATCC 29133. J Bacteriol 1995; 177:6184-94. [PMID: 7592384 PMCID: PMC177459 DOI: 10.1128/jb.177.21.6184-6194.1995] [Citation(s) in RCA: 136] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Heterocysts, sites of nitrogen fixation in certain filamentous cyanobacteria, are limited to a heterotrophic metabolism, rather than the photoautotrophic metabolism characteristic of cyanobacterial vegetative cells. The metabolic route of carbon catabolism in the supply of reductant to nitrogenase and for respiratory electron transport in heterocysts is unresolved. The gene (zwf) encoding glucose-6-phosphate dehydrogenase (G6PD), the initial enzyme of the oxidative pentose phosphate pathway, was inactivated in the heterocyst-forming, facultatively heterotrophic cyanobacterium, Nostoc sp. strain ATCC 29133. The zwf mutant strain had less than 5% of the wild-type apparent G6PD activity, while retaining wild-type rates of photoautotrophic growth with NH4+ and of dark O2 uptake, but it failed to grow either under N2-fixing conditions or in the dark with organic carbon sources. A wild-type copy of zwf in trans in the zwf mutant strain restored only 25% of the G6PD specific activity, but the defective N2 fixation and dark growth phenotypes were nearly completely complemented. Transcript analysis established that zwf is in an operon also containing genes encoding two other enzymes of the oxidative pentose phosphate cycle, fructose-1,6-bisphosphatase and transaldolase, as well as a previously undescribed gene (designated opcA) that is cotranscribed with zwf. Inactivation of opcA yielded a growth phenotype identical to that of the zwf mutant, including a 98% decrease, relative to the wild type, in apparent G6PD specific activity. The growth phenotype and lesion of G6PD activity in the opcA mutant were complemented in trans with a wild-type copy of opcA. In addition, placement in trans of a multicopy plasmid containing the wild-type copies of both zwf and opcA in the zwf mutant resulted in an approximately 20-fold stimulation of G6PD activity, relative to the wild type, complete restoration of nitrogenase activity, and a slight stimulation of N2-dependent photoautotrophic growth and fructose-supported dark growth. These results unequivocally establish that G6PD, and most likely the oxidative pentose phosphate pathway, represents the essential catabolic route for providing reductant for nitrogen fixation and respiration in differentiated heterocysts and for dark growth of vegetative cells. Moreover, the opcA gene product is involved by an as yet unknown mechanism in G6PD synthesis or catalytic activity.
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Affiliation(s)
- M L Summers
- Section of Microbiology, University of California, Davis 95616, USA
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Newman J, Karakaya H, Scanlan DJ, Mann NH. A comparison of gene organization in the zwf region of the genomes of the cyanobacteria Synechococcus sp. PCC 7942 and Anabaena sp. PCC 7120. FEMS Microbiol Lett 1995; 133:187-93. [PMID: 8566707 DOI: 10.1111/j.1574-6968.1995.tb07882.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The region of the genome encoding the glucose-6-phosphate dehydrogenase gene zwf was analysed in a unicellular cyanobacterium, Synechococcus sp. PCC 7942, and a filamentous, heterocystous cyanobacterium, Anabaena sp. PCC 7120. Comparison of cyanobacterial zwf sequences revealed the presence of two absolutely conserved cysteine residues which may be implicated in the light/dark control of enzyme activity. The presence in both strains of a gene fbp, encoding fructose-1,6-bisphosphatase, upstream from zwf strongly suggests that the oxidative pentose phosphate pathway in these organisms may function to completely oxidize glucose 6-phosphate to CO2. The amino acid sequence of fructose-1,6-bisphosphatase does not support the idea of its light activation by a thiol/disulfide exchange mechanism. In the case of Anabaena sp. PCC 7120, the tal gene, encoding transaldolase, lies between zwf and fbp.
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Affiliation(s)
- J Newman
- Department of Biological Sciences, University of Warwick, Coventry, UK
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