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Wilson CM, Yang S, Rodriguez M, Ma Q, Johnson CM, Dice L, Xu Y, Brown SD. Clostridium thermocellum transcriptomic profiles after exposure to furfural or heat stress. BIOTECHNOLOGY FOR BIOFUELS 2013; 6:131. [PMID: 24028713 PMCID: PMC3848806 DOI: 10.1186/1754-6834-6-131] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2012] [Accepted: 09/04/2013] [Indexed: 05/23/2023]
Abstract
BACKGROUND The thermophilic anaerobe Clostridium thermocellum is a candidate consolidated bioprocessing (CBP) biocatalyst for cellulosic ethanol production. It is capable of both cellulose solubilization and its fermentation to produce lignocellulosic ethanol. Intolerance to stresses routinely encountered during industrial fermentations may hinder the commercial development of this organism. A previous C. thermocellum ethanol stress study showed that the largest transcriptomic response was in genes and proteins related to nitrogen uptake and metabolism. RESULTS In this study, C. thermocellum was grown to mid-exponential phase and treated with furfural or heat to a final concentration of 3 g.L-1 or 68°C respectively to investigate general and specific physiological and regulatory stress responses. Samples were taken at 10, 30, 60 and 120 min post-shock, and from untreated control fermentations, for transcriptomic analyses and fermentation product determinations and compared to a published dataset from an ethanol stress study. Urea uptake genes were induced following furfural stress, but not to the same extent as ethanol stress and transcription from these genes was largely unaffected by heat stress. The largest transcriptomic response to furfural stress was genes for sulfate transporter subunits and enzymes in the sulfate assimilatory pathway, although these genes were also affected late in the heat and ethanol stress responses. Lactate production was higher in furfural treated culture, although the lactate dehydrogenase gene was not differentially expressed under this condition. Other redox related genes such as a copy of the rex gene, a bifunctional acetaldehyde-CoA/alcohol dehydrogenase and adjacent genes did show lower expression after furfural stress compared to the control, heat and ethanol fermentation profiles. Heat stress induced expression from chaperone related genes and overlap was observed with the responses to the other stresses. This study suggests the involvement of C. thermocellum genes with functions in oxidative stress protection, electron transfer, detoxification, sulfur and nitrogen acquisition, and DNA repair mechanisms in its stress responses and the use of different regulatory networks to coordinate and control adaptation. CONCLUSIONS This study has identified C. thermocellum gene regulatory motifs and aspects of physiology and gene regulation for further study. The nexus between future systems biology studies and recently developed genetic tools for C. thermocellum offers the potential for more rapid strain development and for broader insights into this organism's physiology and regulation.
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Affiliation(s)
- Charlotte M Wilson
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, 37831 TN, USA
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Shihui Yang
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, 37831 TN, USA
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
- Present address: National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO 80401, USA
| | - Miguel Rodriguez
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, 37831 TN, USA
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Qin Ma
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
- Department of Biochemistry and Molecular Biology and Institute of Bioinformatics, Computational Systems Biology Laboratory, University of Georgia, Athens, GA 30602, USA
| | - Courtney M Johnson
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, 37831 TN, USA
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Lezlee Dice
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, 37831 TN, USA
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Ying Xu
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
- Department of Biochemistry and Molecular Biology and Institute of Bioinformatics, Computational Systems Biology Laboratory, University of Georgia, Athens, GA 30602, USA
- College of Computer Science and Technology, Jilin University, Changchun, Jilin, China
| | - Steven D Brown
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, 37831 TN, USA
- BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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Xu Q, Ding SY, Brunecky R, Bomble YJ, Himmel ME, Baker JO. Improving activity of minicellulosomes by integration of intra- and intermolecular synergies. BIOTECHNOLOGY FOR BIOFUELS 2013; 6:126. [PMID: 23987588 PMCID: PMC3766687 DOI: 10.1186/1754-6834-6-126] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Accepted: 08/28/2013] [Indexed: 05/20/2023]
Abstract
BACKGROUND Complete hydrolysis of cellulose to glucose requires the synergistic action of three general types of glycoside hydrolases; endoglucanases, exoglucanases, and cellobiases. Cellulases that are found in Nature vary considerably in their modular diversity and architecture. They include: non-complexed enzymes with single catalytic domains, independent single peptide chains incorporating multiple catalytic modules, and complexed, scaffolded structures, such as the cellulosome. The discovery of the latter two enzyme architectures has led to a generally held hypothesis that these systems take advantage of intramolecular and intermolecular proximity synergies, respectively, to enhance cellulose degradation. We use domain engineering to exploit both of these concepts to improve cellulase activity relative to the activity of mixtures of the separate catalytic domains. RESULTS We show that engineered minicellulosomes can achieve high levels of cellulose conversion on crystalline cellulose by taking advantage of three types of synergism; (1) a complementary synergy produced by interaction of endo- and exo-cellulases, (2) an intramolecular synergy of multiple catalytic modules in a single gene product (this type of synergism being introduced for the first time to minicellulosomes targeting crystalline cellulose), and (3) an intermolecular proximity synergy from the assembly of these cellulases into larger multi-molecular structures called minicellulosomes. The binary minicellulosome constructed in this study consists of an artificial multicatalytic cellulase (CBM4-Ig-GH9-X11-X12-GH8-Doc) and one cellulase with a single catalytic domain (a modified Cel48S with the structure CBM4-Ig-GH48-Doc), connected by a non-catalytic scaffoldin protein. The high level endo-exo synergy and intramolecular synergies within the artificial multifunctional cellulase have been combined with an additional proximity-dependent synergy produced by incorporation into a minicellulosome demonstrating high conversion of crystalline cellulose (Avicel). Our minicellulosome is the first engineered enzyme system confirmed by test to be capable of both operating at temperatures as high as 60°C and converting over 60% of crystalline cellulose to fermentable sugars. CONCLUSION When compared to previously reported minicellulosomes assembled from cellulases containing only one catalytic module each, our novel minicellulosome demonstrates a method for substantial reduction in the number of peptide chains required, permitting improved heterologous expression of minicellulosomes in microbial hosts. In addition, it has been shown to be capable of substantial conversion of actual crystalline cellulose, as well as of the less-well-ordered and more easily digestible fraction of nominally crystalline cellulose.
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Affiliation(s)
- Qi Xu
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, USA
| | - Shi-You Ding
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, USA
| | - Roman Brunecky
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, USA
| | - Yannick J Bomble
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, USA
| | - Michael E Himmel
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, USA
| | - John O Baker
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, USA
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Bae J, Morisaka H, Kuroda K, Ueda M. Cellulosome complexes: natural biocatalysts as arming microcompartments of enzymes. J Mol Microbiol Biotechnol 2013; 23:370-8. [PMID: 23920499 DOI: 10.1159/000351358] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Cellulose, a primary component of lignocellulosic biomass, is the most abundant carbohydrate polymer in nature. Only a limited number of microorganisms are known to degrade cellulose, which is highly recalcitrant due to its crystal structure. Anaerobic bacteria efficiently degrade cellulose by producing cellulosomes, which are complexes of cellulases bound to scaffoldins. The underlying mechanisms that are responsible for the assembly and efficiency of cellulosomes are not yet fully understood. The cohesin-dockerin specificity has been extensively studied to understand cellulosome assembly. Moreover, the recent progress in proteomics has enabled integral analyses of the growth-substrate-dependent variations in cellulosomal systems. Furthermore, the proximity and targeting effects of cellulosomal synergistic actions have been investigated using designed minicellulosomes. The recent findings about cellulosome assembly, strategies for optimal cellulosome production, and beneficial features of cellulosomes as an arming microcompartment on the microbial cell surface are summarized here.
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Affiliation(s)
- Jungu Bae
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
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Mohr G, Hong W, Zhang J, Cui GZ, Yang Y, Cui Q, Liu YJ, Lambowitz AM. A targetron system for gene targeting in thermophiles and its application in Clostridium thermocellum. PLoS One 2013; 8:e69032. [PMID: 23874856 PMCID: PMC3706431 DOI: 10.1371/journal.pone.0069032] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Accepted: 06/03/2013] [Indexed: 01/04/2023] Open
Abstract
Background Targetrons are gene targeting vectors derived from mobile group II introns. They consist of an autocatalytic intron RNA (a “ribozyme”) and an intron-encoded reverse transcriptase, which use their combined activities to achieve highly efficient site-specific DNA integration with readily programmable DNA target specificity. Methodology/Principal Findings Here, we used a mobile group II intron from the thermophilic cyanobacterium Thermosynechococcus elongatus to construct a thermotargetron for gene targeting in thermophiles. After determining its DNA targeting rules by intron mobility assays in Escherichia coli at elevated temperatures, we used this thermotargetron in Clostridium thermocellum, a thermophile employed in biofuels production, to disrupt six different chromosomal genes (cipA, hfat, hyd, ldh, pta, and pyrF). High integration efficiencies (67–100% without selection) were achieved, enabling detection of disruptants by colony PCR screening of a small number of transformants. Because the thermotargetron functions at high temperatures that promote DNA melting, it can recognize DNA target sequences almost entirely by base pairing of the intron RNA with less contribution from the intron-encoded protein than for mesophilic targetrons. This feature increases the number of potential targetron-insertion sites, while only moderately decreasing DNA target specificity. Phenotypic analysis showed that thermotargetron disruption of the genes encoding lactate dehydrogenase (ldh; Clo1313_1160) and phosphotransacetylase (pta; Clo1313_1185) increased ethanol production in C. thermocellum by decreasing carbon flux toward lactate and acetate. Conclusions/Significance Thermotargetron provides a new, rapid method for gene targeting and genetic engineering of C. thermocellum, an industrially important microbe, and should be readily adaptable for gene targeting in other thermophiles.
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Affiliation(s)
- Georg Mohr
- Section of Molecular Genetics and Microbiology, Department of Chemistry and Biochemistry, Institute for Cellular and Molecular Biology, School of Biological Sciences, University of Texas at Austin, Austin, Texas, United States of America
| | - Wei Hong
- Shandong Provincial Key Laboratory of Energy Genetics, and Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, People’s Republic of China
- University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Jie Zhang
- Shandong Provincial Key Laboratory of Energy Genetics, and Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, People’s Republic of China
- University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, People’s Republic of China
| | - Gu-zhen Cui
- Shandong Provincial Key Laboratory of Energy Genetics, and Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, People’s Republic of China
| | - Yunfeng Yang
- State Key Joint Laboratory of Environment, Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, People’s Republic of China
| | - Qiu Cui
- Shandong Provincial Key Laboratory of Energy Genetics, and Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, People’s Republic of China
| | - Ya-jun Liu
- Shandong Provincial Key Laboratory of Energy Genetics, and Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, People’s Republic of China
- * E-mail: (AL); (YL)
| | - Alan M. Lambowitz
- Section of Molecular Genetics and Microbiology, Department of Chemistry and Biochemistry, Institute for Cellular and Molecular Biology, School of Biological Sciences, University of Texas at Austin, Austin, Texas, United States of America
- * E-mail: (AL); (YL)
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Dykstra AB, Rodriguez M, Raman B, Cook KD, Hettich RL. Characterizing the Range of Extracellular Protein Post-Translational Modifications in a Cellulose-Degrading Bacteria Using a Multiple Proteolyic Digestion/Peptide Fragmentation Approach. Anal Chem 2013; 85:3144-51. [DOI: 10.1021/ac3032838] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Andrew B. Dykstra
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Miguel Rodriguez
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Babu Raman
- Dow AgroSciences, Indianapolis,
Indiana 46268, United States
| | - Kelsey D. Cook
- University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Robert L. Hettich
- Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
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56
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Abstract
Cofactor specificities of glycolytic enzymes in Clostridium thermocellum were studied with cellobiose-grown cells from batch cultures. Intracellular glucose was phosphorylated by glucokinase using GTP rather than ATP. Although phosphofructokinase typically uses ATP as a phosphoryl donor, we found only pyrophosphate (PPi)-linked activity. Phosphoglycerate kinase used both GDP and ADP as phosphoryl acceptors. In agreement with the absence of a pyruvate kinase sequence in the C. thermocellum genome, no activity of this enzyme could be detected. Also, the annotated pyruvate phosphate dikinase (ppdk) is not crucial for the generation of pyruvate from phosphoenolpyruvate (PEP), as deletion of the ppdk gene did not substantially change cellobiose fermentation. Instead pyruvate formation is likely to proceed via a malate shunt with GDP-linked PEP carboxykinase, NADH-linked malate dehydrogenase, and NADP-linked malic enzyme. High activities of these enzymes were detected in extracts of cellobiose-grown cells. Our results thus show that GTP is consumed while both GTP and ATP are produced in glycolysis of C. thermocellum. The requirement for PPi in this pathway can be satisfied only to a small extent by biosynthetic reactions, in contrast to what is generally assumed for a PPi-dependent glycolysis in anaerobic heterotrophs. Metabolic network analysis showed that most of the required PPi must be generated via ATP or GTP hydrolysis exclusive of that which happens during biosynthesis. Experimental proof for the necessity of an alternative mechanism of PPi generation was obtained by studying the glycolysis in washed-cell suspensions in which biosynthesis was absent. Under these conditions, cells still fermented cellobiose to ethanol.
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57
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Weimann A, Trukhina Y, Pope PB, Konietzny SGA, McHardy AC. De novo prediction of the genomic components and capabilities for microbial plant biomass degradation from (meta-)genomes. BIOTECHNOLOGY FOR BIOFUELS 2013; 6:24. [PMID: 23414703 PMCID: PMC3585893 DOI: 10.1186/1754-6834-6-24] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 02/12/2013] [Indexed: 05/05/2023]
Abstract
BACKGROUND Understanding the biological mechanisms used by microorganisms for plant biomass degradation is of considerable biotechnological interest. Despite of the growing number of sequenced (meta)genomes of plant biomass-degrading microbes, there is currently no technique for the systematic determination of the genomic components of this process from these data. RESULTS We describe a computational method for the discovery of the protein domains and CAZy families involved in microbial plant biomass degradation. Our method furthermore accurately predicts the capability to degrade plant biomass for microbial species from their genome sequences. Application to a large, manually curated data set of microbial degraders and non-degraders identified gene families of enzymes known by physiological and biochemical tests to be implicated in cellulose degradation, such as GH5 and GH6. Additionally, genes of enzymes that degrade other plant polysaccharides, such as hemicellulose, pectins and oligosaccharides, were found, as well as gene families which have not previously been related to the process. For draft genomes reconstructed from a cow rumen metagenome our method predicted Bacteroidetes-affiliated species and a relative to a known plant biomass degrader to be plant biomass degraders. This was supported by the presence of genes encoding enzymatically active glycoside hydrolases in these genomes. CONCLUSIONS Our results show the potential of the method for generating novel insights into microbial plant biomass degradation from (meta-)genome data, where there is an increasing production of genome assemblages for uncultured microbes.
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Affiliation(s)
- Aaron Weimann
- Max-Planck Research Group for Computational Genomics and Epidemiology, Max-Planck Institute for Informatics, University Campus E1 4, Saarbrücken, 66123, Germany
- Department of Algorithmic Bioinformatics, Heinrich Heine University Düsseldorf, Düsseldorf, 40225, Germany
| | - Yulia Trukhina
- Max-Planck Research Group for Computational Genomics and Epidemiology, Max-Planck Institute for Informatics, University Campus E1 4, Saarbrücken, 66123, Germany
- Department of Algorithmic Bioinformatics, Heinrich Heine University Düsseldorf, Düsseldorf, 40225, Germany
| | - Phillip B Pope
- Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Post Office Box 5003, Ås, 1432, Norway
| | - Sebastian GA Konietzny
- Max-Planck Research Group for Computational Genomics and Epidemiology, Max-Planck Institute for Informatics, University Campus E1 4, Saarbrücken, 66123, Germany
- Department of Algorithmic Bioinformatics, Heinrich Heine University Düsseldorf, Düsseldorf, 40225, Germany
| | - Alice C McHardy
- Max-Planck Research Group for Computational Genomics and Epidemiology, Max-Planck Institute for Informatics, University Campus E1 4, Saarbrücken, 66123, Germany
- Department of Algorithmic Bioinformatics, Heinrich Heine University Düsseldorf, Düsseldorf, 40225, Germany
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Waller BH, Olson DG, Currie DH, Guss AM, Lynd LR. Exchange of type II dockerin-containing subunits of the Clostridium thermocellum cellulosome as revealed by SNAP-tags. FEMS Microbiol Lett 2013; 338:46-53. [PMID: 23082914 DOI: 10.1111/1574-6968.12029] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Revised: 10/09/2012] [Accepted: 10/10/2012] [Indexed: 11/30/2022] Open
Abstract
Clostridium thermocellum is a thermophilic anaerobic bacterium which efficiently hydrolyzes and metabolizes cellulose to ethanol through the action of its cellulosome, a multiprotein enzymatic complex. A fluorescent protein probe, consisting of a type II dockerin module fused to a SNAP-tag, was developed in order to gain insight into the quaternary configuration of the cellulosome and to investigate the effect of deleting cipA, the protein scaffold on which the cellulosome is built. Fluorescence microscopy suggested that the probe had localized to polycellulosomal protuberances on the cell surface. Surprisingly, fluorescence intensity did not substantially change in the cipA deletion mutants. Sequential labeling experiments suggested that this was a result of bound type II dockerins from CipA being replaced by unbound type II dockerins from the fluorophore-SNAP-XDocII probe. This mechanism of dockerin exchange could represent an efficient means for modifying cellulosome composition.
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Affiliation(s)
- Benjamin H Waller
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA
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Van Riper SK, de Jong EP, Carlis JV, Griffin TJ. Mass Spectrometry-Based Proteomics: Basic Principles and Emerging Technologies and Directions. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 990:1-35. [DOI: 10.1007/978-94-007-5896-4_1] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Letzel AC, Pidot SJ, Hertweck C. A genomic approach to the cryptic secondary metabolome of the anaerobic world. Nat Prod Rep 2012; 30:392-428. [PMID: 23263685 DOI: 10.1039/c2np20103h] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A total of 211 complete and published genomes from anaerobic bacteria are analysed for the presence of secondary metabolite biosynthesis gene clusters, in particular those tentatively coding for polyketide synthases (PKS) and non-ribosomal peptide synthetases (NRPS). We investigate the distribution of these gene clusters according to bacterial phylogeny and, if known, correlate these to the type of metabolic pathways they encode. The potential of anaerobes as secondary metabolite producers is highlighted.
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Affiliation(s)
- Anne-Catrin Letzel
- Leibniz Institute for Natural Product Research and Infection Biology HKI, Beutenbergstr. 11a, Jena, 07745, Germany
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61
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Role of the CipA scaffoldin protein in cellulose solubilization, as determined by targeted gene deletion and complementation in Clostridium thermocellum. J Bacteriol 2012. [PMID: 23204466 DOI: 10.1128/jb.02014-12] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The CipA scaffoldin protein plays a key role in the Clostridium thermocellum cellulosome. Previous studies have revealed that mutants deficient in binding or solubilizing cellulose also exhibit reduced expression of CipA. To confirm that CipA is, in fact, necessary for rapid solubilization of crystalline cellulose, the gene was deleted from the chromosome using targeted gene deletion technologies. The CipA deletion mutant exhibited a 100-fold reduction in cellulose solubilization rate, although it was eventually able to solubilize 80% of the 5 g/liter cellulose initially present. The deletion mutant was complemented by a copy of cipA expressed from a replicating plasmid. In this strain, Avicelase activity was restored, although the rate was 2-fold lower than that in the wild type and the duration of the lag phase was increased. The cipA coding sequence is located at the beginning of a gene cluster containing several other genes thought to be responsible for the structural organization of the cellulosome, including olpB, orf2p, and olpA. Tandem mass spectrometry revealed a 10-fold reduction in the expression of olpB, which may explain the lower growth rate. This deletion experiment adds further evidence that CipA plays a key role in cellulose solubilization by C. thermocellum, and it raises interesting questions about the differential roles of the anchor scaffoldin proteins OlpB, Orf2p, and SdbA.
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62
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Redirecting carbon flux through exogenous pyruvate kinase to achieve high ethanol yields in Clostridium thermocellum. Metab Eng 2012. [PMID: 23202749 DOI: 10.1016/j.ymben.2012.11.006] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In Clostridium thermocellum, a thermophilic anaerobic bacterium able to rapidly ferment cellulose to ethanol, pyruvate kinase (EC 2.7.1.40) is absent based on both the genome sequence and enzymatic assays. Instead, a new pathway converting phosphoenolpyruvate to pyruvate via a three-step pathway involving phosphoenolpyruvate carboxykinase, NADH-linked malate dehydrogenase, and NADP-dependent malic enzyme has been found. We examined the impact of targeted modification of enzymes associated with this pathway, termed the "malate shunt", including expression of the pyruvate kinase gene from Thermoanaerobacterium saccharolyticum, mutation of the phosphoenolpyruvate carboxykinase and deletion of malic enzyme gene. Strain YD01 with exogenous pyruvate kinase, in which phosphoenolpyruvate carboxykinase expression was diminished by modifying the start codon from ATG to GTG, exhibited 3.25-fold higher ethanol yield than the wild-type strain. A second strain, YD02 with exogenous pyruvate kinase, in which the gene for malic enzyme and part of malate dehydrogenase were deleted, had over 3-fold higher ethanol yield than the wild-type strain.
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63
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Smith MA, Rentmeister A, Snow CD, Wu T, Farrow MF, Mingardon F, Arnold FH. A diverse set of family 48 bacterial glycoside hydrolase cellulases created by structure-guided recombination. FEBS J 2012; 279:4453-65. [DOI: 10.1111/febs.12032] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2012] [Revised: 10/10/2012] [Accepted: 10/12/2012] [Indexed: 12/01/2022]
Affiliation(s)
- Matthew A. Smith
- Division of Chemistry and Chemical Engineering; California Institute of Technology; Pasadena; CA; USA
| | | | | | - Timothy Wu
- Division of Chemistry and Chemical Engineering; California Institute of Technology; Pasadena; CA; USA
| | - Mary F. Farrow
- Division of Chemistry and Chemical Engineering; California Institute of Technology; Pasadena; CA; USA
| | - Florence Mingardon
- Division of Chemistry and Chemical Engineering; California Institute of Technology; Pasadena; CA; USA
| | - Frances H. Arnold
- Division of Chemistry and Chemical Engineering; California Institute of Technology; Pasadena; CA; USA
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Sukharnikov LO, Alahuhta M, Brunecky R, Upadhyay A, Himmel ME, Lunin VV, Zhulin IB. Sequence, structure, and evolution of cellulases in glycoside hydrolase family 48. J Biol Chem 2012; 287:41068-77. [PMID: 23055526 DOI: 10.1074/jbc.m112.405720] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Currently, the cost of cellulase enzymes remains a key economic impediment to commercialization of biofuels. Enzymes from glycoside hydrolase family 48 (GH48) are a critical component of numerous natural lignocellulose-degrading systems. Although computational mining of large genomic data sets is a promising new approach for identifying novel cellulolytic activities, current computational methods are unable to distinguish between cellulases and enzymes with different substrate specificities that belong to the same protein family. We show that by using a robust computational approach supported by experimental studies, cellulases and non-cellulases can be effectively identified within a given protein family. Phylogenetic analysis of GH48 showed non-monophyletic distribution, an indication of horizontal gene transfer. Enzymatic function of GH48 proteins coded by horizontally transferred genes was verified experimentally, which confirmed that these proteins are cellulases. Computational and structural studies of GH48 enzymes identified structural elements that define cellulases and can be used to computationally distinguish them from non-cellulases. We propose that the structural element that can be used for in silico discrimination between cellulases and non-cellulases belonging to GH48 is an ω-loop located on the surface of the molecule and characterized by highly conserved rare amino acids. These markers were used to screen metagenomics data for "true" cellulases.
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Affiliation(s)
- Leonid O Sukharnikov
- BioEnergy Science Center, University of Tennessee, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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Yang S, Giannone RJ, Dice L, Yang ZK, Engle NL, Tschaplinski TJ, Hettich RL, Brown SD. Clostridium thermocellum ATCC27405 transcriptomic, metabolomic and proteomic profiles after ethanol stress. BMC Genomics 2012; 13:336. [PMID: 22823947 PMCID: PMC3478167 DOI: 10.1186/1471-2164-13-336] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 07/01/2012] [Indexed: 01/12/2023] Open
Abstract
Background Clostridium thermocellum is a candidate consolidated bioprocessing biocatalyst, which is a microorganism that expresses enzymes for both cellulose hydrolysis and its fermentation to produce fuels such as lignocellulosic ethanol. However, C. thermocellum is relatively sensitive to ethanol compared to ethanologenic microorganisms such as yeast and Zymomonas mobilis that are used in industrial fermentations but do not possess native enzymes for industrial cellulose hydrolysis. Results In this study, C. thermocellum was grown to mid-exponential phase and then treated with ethanol to a final concentration of 3.9 g/L to investigate its physiological and regulatory responses to ethanol stress. Samples were taken pre-shock and 2, 12, 30, 60, 120, and 240 min post-shock, and from untreated control fermentations for systems biology analyses. Cell growth was arrested by ethanol supplementation with intracellular accumulation of carbon sources such as cellobiose, and sugar phosphates, including fructose-6-phosphate and glucose-6-phosphate. The largest response of C. thermocellum to ethanol shock treatment was in genes and proteins related to nitrogen uptake and metabolism, which is likely important for redirecting the cells physiology to overcome inhibition and allow growth to resume. Conclusion This study suggests possible avenues for metabolic engineering and provides comprehensive, integrated systems biology datasets that will be useful for future metabolic modeling and strain development endeavors.
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Affiliation(s)
- Shihui Yang
- Biosciences Division, Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831, USA
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66
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Characterization of a family 5 glycoside hydrolase isolated from the outer membrane of cellulolytic Cytophaga hutchinsonii. Appl Microbiol Biotechnol 2012; 97:3925-37. [DOI: 10.1007/s00253-012-4259-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Revised: 06/15/2012] [Accepted: 06/19/2012] [Indexed: 11/30/2022]
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67
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Olson DG, McBride JE, Joe Shaw A, Lynd LR. Recent progress in consolidated bioprocessing. Curr Opin Biotechnol 2012; 23:396-405. [DOI: 10.1016/j.copbio.2011.11.026] [Citation(s) in RCA: 370] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Revised: 11/08/2011] [Accepted: 11/23/2011] [Indexed: 12/30/2022]
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68
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Caldicellulosiruptor core and pangenomes reveal determinants for noncellulosomal thermophilic deconstruction of plant biomass. J Bacteriol 2012; 194:4015-28. [PMID: 22636774 DOI: 10.1128/jb.00266-12] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Extremely thermophilic bacteria of the genus Caldicellulosiruptor utilize carbohydrate components of plant cell walls, including cellulose and hemicellulose, facilitated by a diverse set of glycoside hydrolases (GHs). From a biofuel perspective, this capability is crucial for deconstruction of plant biomass into fermentable sugars. While all species from the genus grow on xylan and acid-pretreated switchgrass, growth on crystalline cellulose is variable. The basis for this variability was examined using microbiological, genomic, and proteomic analyses of eight globally diverse Caldicellulosiruptor species. The open Caldicellulosiruptor pangenome (4,009 open reading frames [ORFs]) encodes 106 GHs, representing 43 GH families, but only 26 GHs from 17 families are included in the core (noncellulosic) genome (1,543 ORFs). Differentiating the strongly cellulolytic Caldicellulosiruptor species from the others is a specific genomic locus that encodes multidomain cellulases from GH families 9 and 48, which are associated with cellulose-binding modules. This locus also encodes a novel adhesin associated with type IV pili, which was identified in the exoproteome bound to crystalline cellulose. Taking into account the core genomes, pangenomes, and individual genomes, the ancestral Caldicellulosiruptor was likely cellulolytic and evolved, in some cases, into species that lost the ability to degrade crystalline cellulose while maintaining the capacity to hydrolyze amorphous cellulose and hemicellulose.
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69
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Olson DG, Lynd LR. Computational design and characterization of a temperature-sensitive plasmid replicon for gram positive thermophiles. J Biol Eng 2012; 6:5. [PMID: 22578246 PMCID: PMC3464808 DOI: 10.1186/1754-1611-6-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Accepted: 04/27/2012] [Indexed: 11/24/2022] Open
Abstract
Background Temperature-sensitive (Ts) plasmids are useful tools for genetic engineering, but there are currently none compatible with the gram positive, thermophilic, obligate anaerobe, Clostridium thermocellum. Traditional mutagenesis techniques yield Ts mutants at a low frequency, and therefore requires the development of high-throughput screening protocols, which are also not available for this organism. Recently there has been progress in the development of computer algorithms which can predict Ts mutations. Most plasmids currently used for genetic modification of C. thermocellum are based on the replicon of plasmid pNW33N, which replicates using the RepB replication protein. To address this problem, we set out to create a Ts plasmid by mutating the gene coding for the RepB replication protein using an algorithm designed by Varadarajan et al. (1996) for predicting Ts mutants based on the amino-acid sequence of the protein. Results A library of 34 mutant plasmids was designed, synthesized and screened, resulting in 6 mutants which exhibited a Ts phenotype. Of these 6, the one with the most temperature-sensitive phenotype (M166A) was compared with the original plasmid. It exhibited lower stability at 48°C and was completely unable to replicate at 55°C. Conclusions The plasmid described in this work could be useful in future efforts to genetically engineer C. thermocellum, and the method used to generate this plasmid may be useful for others trying to make Ts plasmids.
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Affiliation(s)
- Daniel G Olson
- Thayer School of Engineering at Dartmouth College, Hanover, NH, 03755, USA.
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70
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Guss AM, Olson DG, Caiazza NC, Lynd LR. Dcm methylation is detrimental to plasmid transformation in Clostridium thermocellum. BIOTECHNOLOGY FOR BIOFUELS 2012; 5:30. [PMID: 22559230 PMCID: PMC3536630 DOI: 10.1186/1754-6834-5-30] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2012] [Accepted: 03/29/2012] [Indexed: 05/18/2023]
Abstract
BACKGROUND Industrial production of biofuels and other products by cellulolytic microorganisms is of interest but hindered by the nascent state of genetic tools. Although a genetic system for Clostridium thermocellum DSM1313 has recently been developed, available methods achieve relatively low efficiency and similar plasmids can transform C. thermocellum at dramatically different efficiencies. RESULTS We report an increase in transformation efficiency of C. thermocellum for a variety of plasmids by using DNA that has been methylated by Escherichia coli Dam but not Dcm methylases. When isolated from a dam+dcm+E. coli strain, pAMG206 transforms C. thermocellum 100-fold better than the similar plasmid pAMG205, which contains an additional Dcm methylation site in the pyrF gene. Upon removal of Dcm methylation, transformation with pAMG206 showed a four- to seven-fold increase in efficiency; however, transformation efficiency of pAMG205 increased 500-fold. Removal of the Dcm methylation site from the pAMG205 pyrF gene via silent mutation resulted in increased transformation efficiencies equivalent to that of pAMG206. Upon proper methylation, transformation efficiency of plasmids bearing the pMK3 and pB6A origins of replication increased ca. three orders of magnitude. CONCLUSIONS E. coli Dcm methylation decreases transformation efficiency in C. thermocellum DSM1313. The use of properly methylated plasmid DNA should facilitate genetic manipulation of this industrially relevant bacterium.
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Affiliation(s)
- Adam M Guss
- Thayer School of Engineering, Dartmouth College, 8000 Cummings Hall, Hanover, NH 03755, USA
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Daniel G Olson
- Thayer School of Engineering, Dartmouth College, 8000 Cummings Hall, Hanover, NH 03755, USA
- Mascoma Corporation, 67 Etna Rd, Suite 300, Lebanon, NH 03755, USA
| | - Nicky C Caiazza
- Mascoma Corporation, 67 Etna Rd, Suite 300, Lebanon, NH 03755, USA
- Current address: Synthetic Genomics Inc, La Jolla, CA 92037, USA
| | - Lee R Lynd
- Thayer School of Engineering, Dartmouth College, 8000 Cummings Hall, Hanover, NH 03755, USA
- Mascoma Corporation, 67 Etna Rd, Suite 300, Lebanon, NH 03755, USA
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71
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Direct conversion of xylan to ethanol by recombinant Saccharomyces cerevisiae strains displaying an engineered minihemicellulosome. Appl Environ Microbiol 2012; 78:3837-45. [PMID: 22447594 DOI: 10.1128/aem.07679-11] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Arabinoxylan is a heteropolymeric chain of a β-1,4-linked xylose backbone substituted with arabinose residues, representing a principal component of plant cell walls. Here we developed recombinant Saccharomyces cerevisiae strains as whole-cell biocatalysts capable of combining hemicellulase production, xylan hydrolysis, and hydrolysate fermentation into a single step. These strains displayed a series of uni-, bi-, and trifunctional minihemicellulosomes that consisted of a miniscaffoldin (CipA3/CipA1) and up to three chimeric enzymes. The miniscaffoldin derived from Clostridium thermocellum contained one or three cohesin modules and was tethered to the cell surface through the S. cerevisiae a-agglutinin adhesion receptor. Up to three types of hemicellulases, an endoxylanase (XynII), an arabinofuranosidase (AbfB), and a β-xylosidase (XlnD), each bearing a C-terminal dockerin, were assembled onto the miniscaffoldin by high-affinity cohesin-dockerin interactions. Compared to uni- and bifunctional minihemicellulosomes, the resulting quaternary trifunctional complexes exhibited an enhanced rate of hydrolysis of arabinoxylan. Furthermore, with an integrated d-xylose-utilizing pathway, the recombinant yeast displaying the bifunctional minihemicellulosome CipA3-XynII-XlnD could simultaneously hydrolyze and ferment birchwood xylan to ethanol with a yield of 0.31 g per g of sugar consumed.
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72
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Abstract
Cellulolytic enzymes have been the subject of renewed interest owing to their potential role in the conversion of plant lignocellulose to sustainable biofuels. An analysis of ∼1,500 complete bacterial genomes, presented here, reveals that ∼40% of the genomes of sequenced bacteria encode at least one cellulase gene. Most of the bacteria that encode cellulases are soil and marine saprophytes, many of which encode a range of enzymes for cellulose hydrolysis and also for the breakdown of the other constituents of plant cell walls (hemicelluloses and pectins). Intriguingly, cellulases are present in organisms that are usually considered as non-saprophytic, such as Mycobacterium tuberculosis, Legionella pneumophila, Yersinia pestis and even Escherichia coli. We also discuss newly emerging roles of cellulases in such non-saprophytic organisms.
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73
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74
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High ethanol titers from cellulose by using metabolically engineered thermophilic, anaerobic microbes. Appl Environ Microbiol 2011; 77:8288-94. [PMID: 21965408 DOI: 10.1128/aem.00646-11] [Citation(s) in RCA: 191] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
This work describes novel genetic tools for use in Clostridium thermocellum that allow creation of unmarked mutations while using a replicating plasmid. The strategy employed counter-selections developed from the native C. thermocellum hpt gene and the Thermoanaerobacterium saccharolyticum tdk gene and was used to delete the genes for both lactate dehydrogenase (Ldh) and phosphotransacetylase (Pta). The Δldh Δpta mutant was evolved for 2,000 h, resulting in a stable strain with 40:1 ethanol selectivity and a 4.2-fold increase in ethanol yield over the wild-type strain. Ethanol production from cellulose was investigated with an engineered coculture of organic acid-deficient engineered strains of both C. thermocellum and T. saccharolyticum. Fermentation of 92 g/liter Avicel by this coculture resulted in 38 g/liter ethanol, with acetic and lactic acids below detection limits, in 146 h. These results demonstrate that ethanol production by thermophilic, cellulolytic microbes is amenable to substantial improvement by metabolic engineering.
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75
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Abo-Hashesh M, Wang R, Hallenbeck PC. Metabolic engineering in dark fermentative hydrogen production; theory and practice. BIORESOURCE TECHNOLOGY 2011; 102:8414-8422. [PMID: 21470849 DOI: 10.1016/j.biortech.2011.03.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Revised: 03/03/2011] [Accepted: 03/07/2011] [Indexed: 05/26/2023]
Abstract
Dark fermentation is an attractive option for hydrogen production since it could use already existing reactor technology and readily available substrates without requiring a direct input of solar energy. However, a number of improvements are required before the rates and yields of such a process approach those required for a practical process. Among the options for achieving the required advances, metabolic engineering offers some powerful tools for remodeling microbes to increase product production rates and molar yields. Here we review the current metabolic engineering tool box that is available, discuss the current status of engineering efforts as applied to dark hydrogen production, and suggest areas for future improvements.
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Affiliation(s)
- Mona Abo-Hashesh
- Département de Microbiologie et Immunologie, Université de Montréal, CP 6128 Succursale Centre-ville, Montréal, Québec, Canada H3C 3J7
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76
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Brown SD, Guss AM, Karpinets TV, Parks JM, Smolin N, Yang S, Land ML, Klingeman DM, Bhandiwad A, Rodriguez M, Raman B, Shao X, Mielenz JR, Smith JC, Keller M, Lynd LR. Mutant alcohol dehydrogenase leads to improved ethanol tolerance in Clostridium thermocellum. Proc Natl Acad Sci U S A 2011; 108:13752-7. [PMID: 21825121 PMCID: PMC3158198 DOI: 10.1073/pnas.1102444108] [Citation(s) in RCA: 141] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Clostridium thermocellum is a thermophilic, obligately anaerobic, gram-positive bacterium that is a candidate microorganism for converting cellulosic biomass into ethanol through consolidated bioprocessing. Ethanol intolerance is an important metric in terms of process economics, and tolerance has often been described as a complex and likely multigenic trait for which complex gene interactions come into play. Here, we resequence the genome of an ethanol-tolerant mutant, show that the tolerant phenotype is primarily due to a mutated bifunctional acetaldehyde-CoA/alcohol dehydrogenase gene (adhE), hypothesize based on structural analysis that cofactor specificity may be affected, and confirm this hypothesis using enzyme assays. Biochemical assays confirm a complete loss of NADH-dependent activity with concomitant acquisition of NADPH-dependent activity, which likely affects electron flow in the mutant. The simplicity of the genetic basis for the ethanol-tolerant phenotype observed here informs rational engineering of mutant microbial strains for cellulosic ethanol production.
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Affiliation(s)
- Steven D Brown
- Biosciences Division and BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
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77
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Liao H, Zhang XZ, Rollin JA, Zhang YHP. A minimal set of bacterial cellulases for consolidated bioprocessing of lignocellulose. Biotechnol J 2011; 6:1409-18. [PMID: 21751395 DOI: 10.1002/biot.201100157] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Revised: 05/04/2011] [Accepted: 06/06/2011] [Indexed: 11/06/2022]
Abstract
Cost-effective release of fermentable sugars from non-food biomass through biomass pretreatment/enzymatic hydrolysis is still the largest obstacle to second-generation biorefineries. Therefore, the hydrolysis performance of 21 bacterial cellulase mixtures containing the glycoside hydrolase family 5 Bacillus subtilis endoglucanase (BsCel5), family 9 Clostridium phytofermentans processive endoglucanase (CpCel9), and family 48 C. phytofermentans cellobiohydrolase (CpCel48) was studied on partially ordered low-accessibility microcrystalline cellulose (Avicel) and disordered high-accessibility regenerated amorphous cellulose (RAC). Faster hydrolysis rates and higher digestibilities were obtained on RAC than on Avicel. The optimal ratios for maximum cellulose digestibility were dynamic for Avicel but nearly fixed for RAC. Processive endoglucanase CpCel9 was the most important for high cellulose digestibility regardless of substrate type. This study provides important information for the construction of a minimal set of bacterial cellulases for the consolidated bioprocessing bacteria, such as Bacillus subtilis, for converting lignocellulose to biocommodities in a single step.
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Affiliation(s)
- Hehuan Liao
- Biological Systems Engineering Department, Virginia Tech, Blacksburg, VA 24061, USA
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78
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Determination of the catalytic base in family 48 glycosyl hydrolases. Appl Environ Microbiol 2011; 77:6274-6. [PMID: 21764975 DOI: 10.1128/aem.05532-11] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The catalytic base in family 48 glycosyl hydrolases has not been previously established experimentally. Based on structural and modeling data published to date, we used site-directed mutagenesis and azide rescue activity assays to show definitively that the catalytic base in Thermobifida fusca Cel48A is aspartic acid 225. Of the tested mutants, only Cel48A with the D225E mutation retained partial activity on soluble and insoluble substrates. In azide rescue experiments, only the D225G mutation, in the smallest residue tested, showed an increase in activity with added azide.
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79
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Complete genome sequence of the cellulolytic thermophile Clostridium thermocellum DSM1313. J Bacteriol 2011; 193:2906-7. [PMID: 21460082 DOI: 10.1128/jb.00322-11] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Clostridium thermocellum DSM1313 is a thermophilic, anaerobic bacterium with some of the highest rates of cellulose hydrolysis reported. The complete genome sequence reveals a suite of carbohydrate-active enzymes and demonstrates a level of diversity at the species level distinguishing it from the type strain ATCC 27405.
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80
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Brás JLA, Cartmell A, Carvalho ALM, Verzé G, Bayer EA, Vazana Y, Correia MAS, Prates JAM, Ratnaparkhe S, Boraston AB, Romão MJ, Fontes CMGA, Gilbert HJ. Structural insights into a unique cellulase fold and mechanism of cellulose hydrolysis. Proc Natl Acad Sci U S A 2011; 108:5237-42. [PMID: 21393568 PMCID: PMC3069175 DOI: 10.1073/pnas.1015006108] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Clostridium thermocellum is a well-characterized cellulose-degrading microorganism. The genome sequence of C. thermocellum encodes a number of proteins that contain type I dockerin domains, which implies that they are components of the cellulose-degrading apparatus, but display no significant sequence similarity to known plant cell wall-degrading enzymes. Here, we report the biochemical properties and crystal structure of one of these proteins, designated CtCel124. The protein was shown to be an endo-acting cellulase that displays a single displacement mechanism and acts in synergy with Cel48S, the major cellulosomal exo-cellulase. The crystal structure of CtCel124 in complex with two cellotriose molecules, determined to 1.5 Å, displays a superhelical fold in which a constellation of α-helices encircle a central helix that houses the catalytic apparatus. The catalytic acid, Glu96, is located at the C-terminus of the central helix, but there is no candidate catalytic base. The substrate-binding cleft can be divided into two discrete topographical domains in which the bound cellotriose molecules display twisted and linear conformations, respectively, suggesting that the enzyme may target the interface between crystalline and disordered regions of cellulose.
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Affiliation(s)
- Joana L. A. Brás
- Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Pólo Universitário do Alto da Ajuda, Avenida da Universidade Técnica, 1300-477 Lisbon, Portugal
| | - Alan Cartmell
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602-4712
| | - Ana Luísa M. Carvalho
- Rede de Química e Tecnologia, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - Genny Verzé
- Rede de Química e Tecnologia, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
- Biocrystallography Laboratory, Department of Biotechnology, University of Verona, 37129 Verona, Italy
| | - Edward A. Bayer
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100 Israel; and
| | - Yael Vazana
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100 Israel; and
| | - Márcia A. S. Correia
- Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Pólo Universitário do Alto da Ajuda, Avenida da Universidade Técnica, 1300-477 Lisbon, Portugal
| | - José A. M. Prates
- Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Pólo Universitário do Alto da Ajuda, Avenida da Universidade Técnica, 1300-477 Lisbon, Portugal
| | - Supriya Ratnaparkhe
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602-4712
| | - Alisdair B. Boraston
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, Canada V8W 3P6
| | - Maria J. Romão
- Rede de Química e Tecnologia, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - Carlos M. G. A. Fontes
- Centro de Investigação Interdisciplinar em Sanidade Animal, Faculdade de Medicina Veterinária, Pólo Universitário do Alto da Ajuda, Avenida da Universidade Técnica, 1300-477 Lisbon, Portugal
| | - Harry J. Gilbert
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602-4712
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Dam P, Kataeva I, Yang SJ, Zhou F, Yin Y, Chou W, Poole FL, Westpheling J, Hettich R, Giannone R, Lewis DL, Kelly R, Gilbert HJ, Henrissat B, Xu Y, Adams MWW. Insights into plant biomass conversion from the genome of the anaerobic thermophilic bacterium Caldicellulosiruptor bescii DSM 6725. Nucleic Acids Res 2011; 39:3240-54. [PMID: 21227922 PMCID: PMC3082886 DOI: 10.1093/nar/gkq1281] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Caldicellulosiruptor bescii DSM 6725 utilizes various polysaccharides and grows efficiently on untreated high-lignin grasses and hardwood at an optimum temperature of ∼80°C. It is a promising anaerobic bacterium for studying high-temperature biomass conversion. Its genome contains 2666 protein-coding sequences organized into 1209 operons. Expression of 2196 genes (83%) was confirmed experimentally. At least 322 genes appear to have been obtained by lateral gene transfer (LGT). Putative functions were assigned to 364 conserved/hypothetical protein (C/HP) genes. The genome contains 171 and 88 genes related to carbohydrate transport and utilization, respectively. Growth on cellulose led to the up-regulation of 32 carbohydrate-active (CAZy), 61 sugar transport, 25 transcription factor and 234 C/HP genes. Some C/HPs were overproduced on cellulose or xylan, suggesting their involvement in polysaccharide conversion. A unique feature of the genome is enrichment with genes encoding multi-modular, multi-functional CAZy proteins organized into one large cluster, the products of which are proposed to act synergistically on different components of plant cell walls and to aid the ability of C. bescii to convert plant biomass. The high duplication of CAZy domains coupled with the ability to acquire foreign genes by LGT may have allowed the bacterium to rapidly adapt to changing plant biomass-rich environments.
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Affiliation(s)
- Phuongan Dam
- Institute of Bioinformatics, Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
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Abstract
Cellulose macro- and nanofibers have gained increasing attention due to the high strength and stiffness, biodegradability and renewability, and their production and application in development of composites. Application of cellulose nanofibers for the development of composites is a relatively new research area. Cellulose macro- and nanofibers can be used as reinforcement in composite materials because of enhanced mechanical, thermal, and biodegradation properties of composites. Cellulose fibers are hydrophilic in nature, so it becomes necessary to increase their surface roughness for the development of composites with enhanced properties. In the present paper, we have reviewed the surface modification of cellulose fibers by various methods. Processing methods, properties, and various applications of nanocellulose and cellulosic composites are also discussed in this paper.
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83
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Demonstration of the importance for cellulose hydrolysis of CelS, the most abundant cellulosomal cellulase in Clostridium thermocellum [corrected]. Proc Natl Acad Sci U S A 2010; 107:17855-6. [PMID: 20921379 DOI: 10.1073/pnas.1012746107] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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