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Pech-Canul A, Hammer SK, Ziegler SJ, Richardson ID, Sharma BD, Maloney MI, Bomble YJ, Lynd LR, Olson DG. The role of AdhE on ethanol tolerance and production in Clostridium thermocellum. J Biol Chem 2024; 300:107559. [PMID: 39002679 PMCID: PMC11365378 DOI: 10.1016/j.jbc.2024.107559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Revised: 07/01/2024] [Accepted: 07/02/2024] [Indexed: 07/15/2024] Open
Abstract
Many anaerobic microorganisms use the bifunctional aldehyde and alcohol dehydrogenase enzyme, AdhE, to produce ethanol. One such organism is Clostridium thermocellum, which is of interest for cellulosic biofuel production. In the course of engineering this organism for improved ethanol tolerance and production, we observed that AdhE was a frequent target of mutations. Here, we characterized those mutations to understand their effects on enzymatic activity, as well ethanol tolerance and product formation in the organism. We found that there is a strong correlation between NADH-linked alcohol dehydrogenase (ADH) activity and ethanol tolerance. Mutations that decrease NADH-linked ADH activity increase ethanol tolerance; correspondingly, mutations that increase NADH-linked ADH activity decrease ethanol tolerance. We also found that the magnitude of ADH activity did not play a significant role in determining ethanol titer. Increasing ADH activity had no effect on ethanol titer. Reducing ADH activity had indeterminate effects on ethanol titer, sometimes increasing and sometimes decreasing it. Finally, this study shows that the cofactor specificity of ADH activity was found to be the primary factor affecting ethanol yield. We expect that these results will inform efforts to use AdhE enzymes in metabolic engineering approaches.
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Affiliation(s)
- Angel Pech-Canul
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA; Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Sarah K Hammer
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA; Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Samantha J Ziegler
- Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA; Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado, USA
| | - Isaiah D Richardson
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA; Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Bishal D Sharma
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA; Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Marybeth I Maloney
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA; Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Yannick J Bomble
- Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA; Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado, USA
| | - Lee R Lynd
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA; Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
| | - Daniel G Olson
- Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA; Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA.
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2
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Dai K, Qu C, Li X, Lan Y, Fu H, Wang J. Cofactor engineering in Thermoanaerobacterium aotearoense SCUT27 for maximizing ethanol yield and revealing an enzyme complex with high ferredoxin-NAD + reductase activity. BIORESOURCE TECHNOLOGY 2024; 402:130784. [PMID: 38701976 DOI: 10.1016/j.biortech.2024.130784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Revised: 04/03/2024] [Accepted: 04/30/2024] [Indexed: 05/06/2024]
Abstract
Thermoanaerobacterium aotearoense SCUT27 is a prominent producer of biofuels from lignocellulosic materials. To provide sufficient NAD(P)H for ethanol production, redox-related genes, including lactate dehydrogenase (ldh), redox-sensing transcriptional repressor (rex), and hydrogenase (hfsB), were knocked out. However, the growth of strain PRH (Δldh/Δrex/ΔhfsB) was suppressed due to the intracellular redox state imbalance with the increased NADH concentration. Coincidentally, when the Bcd-EtfAB (BCD) complex was overexpressed, the resulting strain PRH-B3 (Δldh/Δrex/ΔhfsB::BCD) grew rapidly and produced ethanol with a high yield. With lignocellulosic hydrolysates, PRH-BA (Δldh/Δrex/ΔhfsB::BCD::adhE) demonstrated high ethanol productivity and yield, reaching levels of 0.45-0.51 g/L/h and 0.46-0.53 g/g sugars, respectively. The study results shed light on the cofactor balance for cell stability and the high ferredoxin-NAD+ reductase activity of the BCD complex under an intracellular low redox state. They also provide an essential reference for developing strains for improved biofuel production.
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Affiliation(s)
- Kaiqun Dai
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou 510006, China
| | - Chunyun Qu
- College of Light Industry and Food Science, Guangdong Provincial Key Laboratory of Science and Technology of Lingnan Special Food Science and Technology, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China
| | - Xin Li
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou 510006, China
| | - Yang Lan
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou 510006, China
| | - Hongxin Fu
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou 510006, China; Guangdong Provincial Key Laboratory of Fermentation and Enzyme Engineering, South China University of Technology, Guangzhou 510006, China; State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou 510006, China.
| | - Jufang Wang
- School of Biology and Biological Engineering, South China University of Technology, Guangzhou 510006, China; Guangdong Provincial Key Laboratory of Fermentation and Enzyme Engineering, South China University of Technology, Guangzhou 510006, China; State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou 510006, China.
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3
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Payne N, Kpebe A, Guendon C, Baffert C, Maillot M, Haurogné T, Tranchida F, Brugna M, Shintu L. NMR-based metabolomic analysis of the physiological role of the electron-bifurcating FeFe-hydrogenase Hnd in Solidesulfovibrio fructosivorans under pyruvate fermentation. Microbiol Res 2023; 268:127279. [PMID: 36592576 DOI: 10.1016/j.micres.2022.127279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 12/09/2022] [Accepted: 12/12/2022] [Indexed: 12/24/2022]
Abstract
Solidesulfovibrio fructosivorans (formely Desulfovibrio fructosovorans), an anaerobic sulfate-reducing bacterium, possesses six gene clusters encoding six hydrogenases catalyzing the reversible oxidation of hydrogen gas (H2) into protons and electrons. One of these, named Hnd, was demonstrated to be an electron-bifurcating hydrogenase Hnd (Kpebe et al., 2018). It couples the exergonic reduction of NAD+ to the endergonic reduction of a ferredoxin with electrons derived from H2 and whose function has been recently shown to be involved in ethanol production under pyruvate fermentation (Payne 2022). To understand further the physiological role of Hnd in S. fructosivorans, we compared the mutant deleted of part of the hnd gene with the wild-type strain grown on pyruvate without sulfate using NMR-based metabolomics. Our results confirm that Hnd is profoundly involved in ethanol metabolism, but also indirectly intervenes in global carbon metabolism and additional metabolic processes such as the biosynthesis of branched-chain amino acids. We also highlight the metabolic reprogramming induced by the deletion of hndD that leads to the upregulation of several NADP-dependent pathways.
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Affiliation(s)
- Natalie Payne
- Aix Marseille Univ, CNRS, BIP, Marseille, France; Aix Marseille Univ, CNRS, Centrale Marseille, ISM2, Marseille, France
| | | | | | | | | | | | - Fabrice Tranchida
- Aix Marseille Univ, CNRS, Centrale Marseille, ISM2, Marseille, France
| | | | - Laetitia Shintu
- Aix Marseille Univ, CNRS, Centrale Marseille, ISM2, Marseille, France.
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4
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Herring CD, Ajie MP, Lynd LR. Growth-uncoupled propanediol production in a Thermoanaerobacterium thermosaccharolyticum strain engineered for high ethanol yield. Sci Rep 2023; 13:2394. [PMID: 36765076 PMCID: PMC9918460 DOI: 10.1038/s41598-023-29220-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 01/31/2023] [Indexed: 02/12/2023] Open
Abstract
Cocultures of engineered thermophilic bacteria can ferment lignocellulose without costly pretreatment or added enzymes, an ability that can be exploited for low cost biofuel production from renewable feedstocks. The hemicellulose-fermenting species Thermoanaerobacterium thermosaccharolyticum was engineered for high ethanol yield, but we found that the strains switched from growth-coupled production of ethanol to growth uncoupled production of acetate and 1,2-propanediol upon growth cessation, producing up to 6.7 g/L 1,2-propanediol from 60 g/L cellobiose. The unique capability of this species to make 1,2-propanediol from sugars was described decades ago, but the genes responsible were not identified. Here we deleted genes encoding methylglyoxal reductase, methylglyoxal synthase and glycerol dehydrogenase. Deletion of the latter two genes eliminated propanediol production. To understand how carbon flux is redirected in this species, we hypothesized that high ATP levels during growth cessation downregulate the activity of alcohol and aldehyde dehydrogenase activities. Measurements with cell free extracts show approximately twofold and tenfold inhibition of these activities by 10 mM ATP, supporting the hypothesized mechanism of metabolic redirection. This result may have implications for efforts to direct and maximize flux through alcohol dehydrogenase in other species.
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Affiliation(s)
- Christopher D Herring
- Terragia Biofuel Incorporated, Hanover, New Hampshire, United States. .,Dartmouth College, Thayer School of Engineering, Hanover, New Hampshire, United States. .,Center for Bioenergy Innovation, Oak Ridge, Tennessee, United States.
| | - Maulana Permana Ajie
- Technical University of Munich, Munich, Germany.,Bioengineering, Rhine-Waal University of Applied Sciences, Kleve, Germany
| | - Lee R Lynd
- Terragia Biofuel Incorporated, Hanover, New Hampshire, United States.,Dartmouth College, Thayer School of Engineering, Hanover, New Hampshire, United States.,Center for Bioenergy Innovation, Oak Ridge, Tennessee, United States
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5
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Functional analysis of H +-pumping membrane-bound pyrophosphatase, ADP-glucose synthase, and pyruvate phosphate dikinase as pyrophosphate sources in Clostridium thermocellum. Appl Environ Microbiol 2021; 88:e0185721. [PMID: 34936842 PMCID: PMC8863071 DOI: 10.1128/aem.01857-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The atypical glycolysis of Clostridium thermocellum is characterized by the use of pyrophosphate (PPi) as phosphoryl donor for phosphofructokinase (Pfk) and pyruvate phosphate dikinase (Ppdk) reactions. Previously, biosynthetic PPi was calculated to be stoichiometrically insufficient to drive glycolysis. This study investigates the role of a H+-pumping membrane-bound pyrophosphatase, glycogen cycling, a predicted Ppdk-malate shunt cycle and acetate cycling in generating PPi. Knockout studies and enzyme assays confirmed that clo1313_0823 encodes a membrane-bound pyrophosphatase. Additionally, clo1313_0717-0718 was confirmed to encode ADP-glucose synthase by knockouts, glycogen measurements in C. thermocellum and heterologous expression in E. coli. Unexpectedly, individually-targeted gene deletions of the four putative PPi sources did not have a significant phenotypic effect. Although combinatorial deletion of all four putative PPi sources reduced the growth rate by 22% (0.30±0.01 h-1) and the biomass yield by 38% (0.18±0.00 gbiomass gsubstrate-1), this change was much smaller than what would be expected for stoichiometrically essential PPi-supplying mechanisms. Growth-arrested cells of the quadruple knockout readily fermented cellobiose indicating that the unknown PPi-supplying mechanisms are independent of biosynthesis. An alternative hypothesis that ATP-dependent Pfk activity circumvents a need for PPi altogether, was falsified by enzyme assays, heterologous expression of candidate genes and whole-genome sequencing. As a secondary outcome, enzymatic assays confirmed functional annotation of clo1313_1832 as ATP- and GTP-dependent fructokinase. These results indicate that the four investigated PPi sources individually and combined play no significant PPi-supplying role and the true source(s) of PPi, or alternative phosphorylating mechanisms, that drive glycolysis in C. thermocellum remain(s) elusive. IMPORTANCE Increased understanding of the central metabolism of C. thermocellum is important from a fundamental as well as from a sustainability and industrial perspective. In addition to showing that H+-pumping membrane-bound PPase, glycogen cycling, a Ppdk-malate shunt cycle, and acetate cycling are not significant sources of PPi supply, this study adds functional annotation of four genes and availability of an updated PPi stoichiometry from biosynthesis to the scientific domain. Together, this aids future metabolic engineering attempts aimed to improve C. thermocellum as a cell factory for sustainable and efficient production of ethanol from lignocellulosic material through consolidated bioprocessing with minimal pretreatment. Getting closer to elucidating the elusive source of PPi, or alternative phosphorylating mechanisms, for the atypical glycolysis is itself of fundamental importance. Additionally, the findings of this study directly contribute to investigations into trade-offs between thermodynamic driving force versus energy yield of PPi- and ATP-dependent glycolysis.
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Biorefinery Gets Hot: Thermophilic Enzymes and Microorganisms for Second-Generation Bioethanol Production. Processes (Basel) 2021. [DOI: 10.3390/pr9091583] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
To mitigate the current global energy and the environmental crisis, biofuels such as bioethanol have progressively gained attention from both scientific and industrial perspectives. However, at present, commercialized bioethanol is mainly derived from edible crops, thus raising serious concerns given its competition with feed production. For this reason, lignocellulosic biomasses (LCBs) have been recognized as important alternatives for bioethanol production. Because LCBs supply is sustainable, abundant, widespread, and cheap, LCBs-derived bioethanol currently represents one of the most viable solutions to meet the global demand for liquid fuel. However, the cost-effective conversion of LCBs into ethanol remains a challenge and its implementation has been hampered by several bottlenecks that must still be tackled. Among other factors related to the challenging and variable nature of LCBs, we highlight: (i) energy-demanding pretreatments, (ii) expensive hydrolytic enzyme blends, and (iii) the need for microorganisms that can ferment mixed sugars. In this regard, thermophiles represent valuable tools to overcome some of these limitations. Thus, the aim of this review is to provide an overview of the state-of-the-art technologies involved, such as the use of thermophilic enzymes and microorganisms in industrial-relevant conditions, and to propose possible means to implement thermophiles into second-generation ethanol biorefineries that are already in operation.
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Qu C, Chen L, Li Y, Fu H, Wang J. The redox-sensing transcriptional repressor Rex is important for regulating the products distribution in Thermoanaerobacterium aotearoense SCUT27. Appl Microbiol Biotechnol 2020; 104:5605-5617. [DOI: 10.1007/s00253-020-10554-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2019] [Revised: 02/28/2020] [Accepted: 03/16/2020] [Indexed: 01/06/2023]
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8
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Mazzoli R, Olson D. Clostridium thermocellum: A microbial platform for high-value chemical production from lignocellulose. ADVANCES IN APPLIED MICROBIOLOGY 2020; 113:111-161. [PMID: 32948265 DOI: 10.1016/bs.aambs.2020.07.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Second generation biorefining, namely fermentation processes based on lignocellulosic feedstocks, has attracted tremendous interest (owing to the large availability and low cost of this biomass) as a strategy to produce biofuels and commodity chemicals that is an alternative to oil refining. However, the innate recalcitrance of lignocellulose has slowed progress toward economically viable processes. Consolidated bioprocessing (CBP), i.e., single-step fermentation of lignocellulose may dramatically reduce the current costs of 2nd generation biorefining. Metabolic engineering has been used as a tool to develop improved microbial strains supporting CBP. Clostridium thermocellum is among the most efficient cellulose degraders isolated so far and one of the most promising host organisms for application of CBP. The development of efficient and reliable genetic tools has allowed significant progress in metabolic engineering of this strain aimed at expanding the panel of growth substrates and improving the production of a number of commodity chemicals of industrial interest such as ethanol, butanol, isobutanol, isobutyl acetate and lactic acid. The present review aims to summarize recent developments in metabolic engineering of this organism which currently represents a reference model for the development of biocatalysts for 2nd generation biorefining.
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9
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Holwerda EK, Olson DG, Ruppertsberger NM, Stevenson DM, Murphy SJL, Maloney MI, Lanahan AA, Amador-Noguez D, Lynd LR. Metabolic and evolutionary responses of Clostridium thermocellum to genetic interventions aimed at improving ethanol production. BIOTECHNOLOGY FOR BIOFUELS 2020; 13:40. [PMID: 32175007 PMCID: PMC7063780 DOI: 10.1186/s13068-020-01680-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 02/10/2020] [Indexed: 05/06/2023]
Abstract
BACKGROUND Engineering efforts targeted at increasing ethanol by modifying the central fermentative metabolism of Clostridium thermocellum have been variably successful. Here, we aim to understand this variation by a multifaceted approach including genomic and transcriptomic analysis combined with chemostat cultivation and high solids cellulose fermentation. Three strain lineages comprising 16 strains total were examined. Two strain lineages in which genes involved in pathways leading to organic acids and/or sporulation had been knocked out resulted in four end-strains after adaptive laboratory evolution (ALE). A third strain lineage recapitulated mutations involving adhE that occurred spontaneously in some of the engineered strains. RESULTS Contrary to lactate dehydrogenase, deleting phosphotransacetylase (pta, acetate) negatively affected steady-state biomass concentration and caused increased extracellular levels of free amino acids and pyruvate, while no increase in ethanol was detected. Adaptive laboratory evolution (ALE) improved growth and shifted elevated levels of amino acids and pyruvate towards ethanol, but not for all strain lineages. Three out of four end-strains produced ethanol at higher yield, and one did not. The occurrence of a mutation in the adhE gene, expanding its nicotinamide-cofactor compatibility, enabled two end-strains to produce more ethanol. A disruption in the hfsB hydrogenase is likely the reason why a third end-strain was able to make more ethanol. RNAseq analysis showed that the distribution of fermentation products was generally not regulated at the transcript level. At 120 g/L cellulose loadings, deletions of spo0A, ldh and pta and adaptive evolution did not negatively influence cellulose solubilization and utilization capabilities. Strains with a disruption in hfsB or a mutation in adhE produced more ethanol, isobutanol and 2,3-butanediol under these conditions and the highest isobutanol and ethanol titers reached were 5.1 and 29.9 g/L, respectively. CONCLUSIONS Modifications in the organic acid fermentative pathways in Clostridium thermocellum caused an increase in extracellular pyruvate and free amino acids. Adaptive laboratory evolution led to improved growth, and an increase in ethanol yield and production due a mutation in adhE or a disruption in hfsB. Strains with deletions in ldh and pta pathways and subjected to ALE demonstrated undiminished cellulolytic capabilities when cultured on high cellulose loadings.
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Affiliation(s)
- Evert K. Holwerda
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Daniel G. Olson
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | | | - David M. Stevenson
- Department of Bacteriology, University of Wisconsin, Madison, WI 53706 USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Sean J. L. Murphy
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA
| | - Marybeth I. Maloney
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Anthony A. Lanahan
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Daniel Amador-Noguez
- Department of Bacteriology, University of Wisconsin, Madison, WI 53706 USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Lee R. Lynd
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA
- The Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
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10
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Sander K, Yeary M, Mahan K, Whitham J, Giannone RJ, Brown SD, Rodriguez M, Graham DE, Hankoua B. Expression of benzoyl-CoA metabolism genes in the lignocellulolytic host Caldicellulosiruptor bescii. AMB Express 2019; 9:59. [PMID: 31055784 PMCID: PMC6500515 DOI: 10.1186/s13568-019-0783-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Accepted: 04/25/2019] [Indexed: 11/18/2022] Open
Abstract
Genes responsible for the anaerobic catabolism of benzoate in the thermophilic archaeon Ferroglobus placidus were expressed in the thermophilic lignocellulose-degrading bacterium Caldicellulosiruptor bescii, as a first step to engineering this bacterium to degrade this lignin metabolite. The benzoyl-CoA ligase gene was expressed individually, and in combination with benzoyl-CoA reductase and a putative benzoate transporter. This effort also assessed heterologous expression from a synthetically designed operon whereby each coding sequence was proceeded by a unique C. bescii ribosome binding site sequence. The F. placidicus benzoyl-CoA ligase gene was expressed in C. bescii to produce a full-length protein with catalytic activity. A synthetic 6-gene operon encoding three enzymes involved in benzoate degradation was also successfully expressed in C. bescii as determined by RNA analysis, though the protein products of only four of the genes were detected. The discord between the mRNA and protein measurements, especially considering the two genes lacking apparent protein abundance, suggests variable effectiveness of the ribosome binding site sequences utilized in this synthetic operon. The engineered strains did not degrade benzoate. Although the heterologously expressed gene encoding benzoyl-CoA ligase yielded a protein that was catalytically active in vitro, expression in C. bescii of six benzoate catabolism-related genes combined in a synthetic operon yielded mixed results. More effective expression and in vivo activity might be brought about by validating and using different ribosome binding sites and different promoters. Expressing additional pathway components may alleviate any pathway inhibition and enhance benzoyl-CoA reductase activity.
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11
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Baffert C, Kpebe A, Avilan L, Brugna M. Hydrogenases and H 2 metabolism in sulfate-reducing bacteria of the Desulfovibrio genus. Adv Microb Physiol 2019; 74:143-189. [PMID: 31126530 DOI: 10.1016/bs.ampbs.2019.03.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Hydrogen metabolism plays a central role in sulfate-reducing bacteria of the Desulfovibrio genus and is based on hydrogenases that catalyze the reversible conversion of protons into dihydrogen. These metabolically versatile microorganisms possess a complex hydrogenase system composed of several enzymes of both [FeFe]- and [NiFe]-type that can vary considerably from one Desulfovibrio species to another. This review covers the molecular and physiological aspects of hydrogenases and H2 metabolism in Desulfovibrio but focuses particularly on our model bacterium Desulfovibrio fructosovorans. The search of hydrogenase genes in more than 30 sequenced genomes provides an overview of the distribution of these enzymes in Desulfovibrio. Our discussion will consider the significance of the involvement of electron-bifurcation in H2 metabolism.
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Affiliation(s)
- Carole Baffert
- Aix-Marseille University, CNRS, BIP, 31 Chemin Joseph Aiguier, 13402 Marseille, France
| | - Arlette Kpebe
- Aix-Marseille University, CNRS, BIP, 31 Chemin Joseph Aiguier, 13402 Marseille, France
| | - Luisana Avilan
- Aix-Marseille University, CNRS, BIP, 31 Chemin Joseph Aiguier, 13402 Marseille, France
| | - Myriam Brugna
- Aix-Marseille University, CNRS, BIP, 31 Chemin Joseph Aiguier, 13402 Marseille, France
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12
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Marcano-Velazquez JG, Lo J, Nag A, Maness PC, Chou KJ. Developing Riboswitch-Mediated Gene Regulatory Controls in Thermophilic Bacteria. ACS Synth Biol 2019; 8:633-640. [PMID: 30943368 DOI: 10.1021/acssynbio.8b00487] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Thermophilic bacteria are attractive hosts to produce bio-based chemicals. While various genetic manipulations have been employed in the metabolic engineering of thermophiles, a robust means to regulate gene expression in these bacteria (∼55 °C) is missing. Our bioinformatic search for various riboswitches in thermophilic bacteria revealed that major classes of riboswitches are present, suggesting riboswitches' regulatory roles in these bacteria. By building synthetic constructs incorporating natural and engineered purine riboswitch sequences originated from foreign species, we quantified respective riboswitches activities in repressing and up-regulating gene expression in Geobacillus thermoglucosidasius using a green fluorescence protein. The elicited regulatory response was ligand-concentration-dependent. We further demonstrated that riboswitch-mediated gene expression of adhE (responsible for ethanol production) in Clostridium thermocellum can modulate ethanol production, redirect metabolites, and control cell growth in the adhE knockout mutant. This work has made tunable gene expression feasible across different thermophiles for broad applications including biofuels production and gene-to-trait mapping.
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Affiliation(s)
| | - Jonathan Lo
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United states
| | - Ambarish Nag
- Computational Science Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United states
| | - Pin-Ching Maness
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United states
| | - Katherine J. Chou
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United states
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13
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Chongdar N, Birrell JA, Pawlak K, Sommer C, Reijerse EJ, Rüdiger O, Lubitz W, Ogata H. Unique Spectroscopic Properties of the H-Cluster in a Putative Sensory [FeFe] Hydrogenase. J Am Chem Soc 2018; 140:1057-1068. [PMID: 29251926 DOI: 10.1021/jacs.7b11287] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Sensory type [FeFe] hydrogenases are predicted to play a role in transcriptional regulation by detecting the H2 level of the cellular environment. These hydrogenases contain the hydrogenase domain with distinct modifications in the active site pocket, followed by a Per-Arnt-Sim (PAS) domain. As yet, neither the physiological function nor the biochemical or spectroscopic properties of these enzymes have been explored. Here, we present the characterization of an artificially maturated, putative sensory [FeFe] hydrogenase from Thermotoga maritima (HydS). This enzyme shows lower hydrogen conversion activity than prototypical [FeFe] hydrogenases and a reduced inhibition by CO. Using FTIR spectroelectrochemistry and EPR spectroscopy, three redox states of the active site were identified. The spectroscopic signatures of the most oxidized state closely resemble those of the Hox state from the prototypical [FeFe] hydrogenases, while the FTIR spectra of both singly and doubly reduced states show large differences. The FTIR bands of both the reduced states are strongly red-shifted relative to the Hox state, indicating reduction at the diiron site, but with retention of the bridging CO ligand. The unique functional and spectroscopic features of HydS are discussed with regard to the possible role of altered amino acid residues influencing the electronic properties of the H-cluster.
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Affiliation(s)
- Nipa Chongdar
- Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, D45470 Mülheim an der Ruhr, Germany
| | - James A Birrell
- Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, D45470 Mülheim an der Ruhr, Germany
| | - Krzysztof Pawlak
- Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, D45470 Mülheim an der Ruhr, Germany
| | - Constanze Sommer
- Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, D45470 Mülheim an der Ruhr, Germany
| | - Edward J Reijerse
- Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, D45470 Mülheim an der Ruhr, Germany
| | - Olaf Rüdiger
- Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, D45470 Mülheim an der Ruhr, Germany
| | - Wolfgang Lubitz
- Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, D45470 Mülheim an der Ruhr, Germany
| | - Hideaki Ogata
- Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, D45470 Mülheim an der Ruhr, Germany.,Institute of Low Temperature Science, Hokkaido University , Kita19 Nishi8, Kita-ku, 060-0819 Sapporo, Japan
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