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Lin J, Wang X, Liu T, Teng Y, Cui W. Diffusion-Based Generative Network for de Novo Synthetic Promoter Design. ACS Synth Biol 2024; 13:1513-1522. [PMID: 38613497 DOI: 10.1021/acssynbio.4c00041] [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] [Indexed: 04/15/2024]
Abstract
Computer-aided promoter design is a major development trend in synthetic promoter engineering. Various deep learning models have been used to evaluate or screen synthetic promoters, but there have been few works on de novo promoter design. To explore the potential ability of generative models in promoter design, we established a diffusion-based generative model for promoter design in Escherichia coli. The model was completely driven by sequence data and could study the essential characteristics of natural promoters, thus generating synthetic promoters similar to natural promoters in structure and component. We also improved the calculation method of FID indicator, using a convolution layer to extract the feature matrix of the promoter sequence instead. As a result, we got an FID equal to 1.37, which meant synthetic promoters have a distribution similar to that of natural ones. Our work provides a fresh approach to de novo promoter design, indicating that a completely data-driven generative model is feasible for promoter design.
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Affiliation(s)
- Jianfeng Lin
- School of Automation Science and Engineering, South China University of Technology, Guangzhou 510641, China
| | - Xin Wang
- School of Automation Science and Engineering, South China University of Technology, Guangzhou 510641, China
| | - Tuoyu Liu
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Yue Teng
- State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China
| | - Wei Cui
- School of Automation Science and Engineering, South China University of Technology, Guangzhou 510641, China
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2
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Deal C, De Wannemaeker L, De Mey M. Towards a rational approach to promoter engineering: understanding the complexity of transcription initiation in prokaryotes. FEMS Microbiol Rev 2024; 48:fuae004. [PMID: 38383636 PMCID: PMC10911233 DOI: 10.1093/femsre/fuae004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 01/29/2024] [Accepted: 02/20/2024] [Indexed: 02/23/2024] Open
Abstract
Promoter sequences are important genetic control elements. Through their interaction with RNA polymerase they determine transcription strength and specificity, thereby regulating the first step in gene expression. Consequently, they can be targeted as elements to control predictability and tuneability of a genetic circuit, which is essential in applications such as the development of robust microbial cell factories. This review considers the promoter elements implicated in the three stages of transcription initiation, detailing the complex interplay of sequence-specific interactions that are involved, and highlighting that DNA sequence features beyond the core promoter elements work in a combinatorial manner to determine transcriptional strength. In particular, we emphasize that, aside from promoter recognition, transcription initiation is also defined by the kinetics of open complex formation and promoter escape, which are also known to be highly sequence specific. Significantly, we focus on how insights into these interactions can be manipulated to lay the foundation for a more rational approach to promoter engineering.
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Affiliation(s)
- Cara Deal
- Centre for Synthetic Biology, Ghent University. Coupure Links 653, BE-9000 Ghent, Belgium
| | - Lien De Wannemaeker
- Centre for Synthetic Biology, Ghent University. Coupure Links 653, BE-9000 Ghent, Belgium
| | - Marjan De Mey
- Centre for Synthetic Biology, Ghent University. Coupure Links 653, BE-9000 Ghent, Belgium
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3
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Milito A, Aschern M, McQuillan JL, Yang JS. Challenges and advances towards the rational design of microalgal synthetic promoters in Chlamydomonas reinhardtii. JOURNAL OF EXPERIMENTAL BOTANY 2023; 74:3833-3850. [PMID: 37025006 DOI: 10.1093/jxb/erad100] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 03/24/2023] [Indexed: 06/19/2023]
Abstract
Microalgae hold enormous potential to provide a safe and sustainable source of high-value compounds, acting as carbon-fixing biofactories that could help to mitigate rapidly progressing climate change. Bioengineering microalgal strains will be key to optimizing and modifying their metabolic outputs, and to render them competitive with established industrial biotechnology hosts, such as bacteria or yeast. To achieve this, precise and tuneable control over transgene expression will be essential, which would require the development and rational design of synthetic promoters as a key strategy. Among green microalgae, Chlamydomonas reinhardtii represents the reference species for bioengineering and synthetic biology; however, the repertoire of functional synthetic promoters for this species, and for microalgae generally, is limited in comparison to other commercial chassis, emphasizing the need to expand the current microalgal gene expression toolbox. Here, we discuss state-of-the-art promoter analyses, and highlight areas of research required to advance synthetic promoter development in C. reinhardtii. In particular, we exemplify high-throughput studies performed in other model systems that could be applicable to microalgae, and propose novel approaches to interrogating algal promoters. We lastly outline the major limitations hindering microalgal promoter development, while providing novel suggestions and perspectives for how to overcome them.
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Affiliation(s)
- Alfonsina Milito
- Centre for Research in Agricultural Genomics (CRAG), CSIC-IRTA-UAB-UB, Campus UAB, Bellaterra, Barcelona, Spain
| | - Moritz Aschern
- Centre for Research in Agricultural Genomics (CRAG), CSIC-IRTA-UAB-UB, Campus UAB, Bellaterra, Barcelona, Spain
| | - Josie L McQuillan
- Department of Chemical and Biological Engineering, University of Sheffield, Mappin Street, Sheffield, S1 3JD, UK
| | - Jae-Seong Yang
- Centre for Research in Agricultural Genomics (CRAG), CSIC-IRTA-UAB-UB, Campus UAB, Bellaterra, Barcelona, Spain
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4
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Zhang Y, Bailey TS, Kubiak AM, Lambin P, Theys J. Heterologous Gene Regulation in Clostridia: Rationally Designed Gene Regulation for Industrial and Medical Applications. ACS Synth Biol 2022; 11:3817-3828. [PMID: 36265075 PMCID: PMC9680021 DOI: 10.1021/acssynbio.2c00401] [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] [Indexed: 01/27/2023]
Abstract
Several species from the Clostridium genus show promise as industrial solvent producers and cancer therapeutic delivery vehicles. Previous development of shuttle plasmids and genome editing tools has aided the study of these species and enabled their exploitation in industrial and medical applications. Nevertheless, the precise control of gene expression is still hindered by the limited range of characterized promoters. To address this, libraries of promoters (native and synthetic), 5' UTRs, and alternative start codons were constructed. These constructs were tested in Escherichia coli K-12, Clostridium sporogenes NCIMB 10696, and Clostridium butyricum DSM 10702, using β-glucuronidase (gusA) as a gene reporter. Promoter activity was corroborated using a second gene reporter, nitroreductase (nmeNTR) from Neisseria meningitides. A strong correlation was observed between the two reporters. In C. sporogenes and C. butyricum, respectively, changes in GusA activity between the weakest and strongest expressing levels were 129-fold and 78-fold. Similar results were obtained with the nmeNTR. Using the GusA reporter, translation initiation from six alternative (non-AUG) start codons was measured in E. coli, C. sporogenes, and C. butyricum. Clearly, species-specific differences between clostridia and E. coli in translation initiation were observed, and the performance of the start codons was influenced by the upstream 5' UTR sequence. These results highlight a new opportunity for gene control in recombinant clostridia. To demonstrate the value of these results, expression of the sacB gene from Bacillus subtilis was optimized for use as a novel negative selection marker in C. butyricum. In summary, these results indicate improvements in the understanding of heterologous gene regulation in Clostridium species and E. coli cloning strains. This new knowledge can be utilized for rationally designed gene regulation in Clostridium-mediated industrial and medical applications, as well as fundamental research into the biology of Clostridium species.
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Affiliation(s)
- Yanchao Zhang
- The
M-Lab, Department of Precision Medicine, GROW - School of Oncology
and Reproduction, Maastricht University, 6229 ER Maastricht, The Netherlands,
| | - Tom S. Bailey
- The
M-Lab, Department of Precision Medicine, GROW - School of Oncology
and Reproduction, Maastricht University, 6229 ER Maastricht, The Netherlands
| | - Aleksandra M. Kubiak
- The
M-Lab, Department of Precision Medicine, GROW - School of Oncology
and Reproduction, Maastricht University, 6229 ER Maastricht, The Netherlands,Exomnis
Biotech BV, Oxfordlaan
55, 6229 EV Maastricht, The Netherlands
| | - Philippe Lambin
- The
M-Lab, Department of Precision Medicine, GROW - School of Oncology
and Reproduction, Maastricht University, 6229 ER Maastricht, The Netherlands
| | - Jan Theys
- The
M-Lab, Department of Precision Medicine, GROW - School of Oncology
and Reproduction, Maastricht University, 6229 ER Maastricht, The Netherlands
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5
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Jiang W, Gao H, Sun J, Yang X, Jiang Y, Zhang W, Jiang M, Xin F. Current status, challenges and prospects for lignin valorization by using Rhodococcus sp. Biotechnol Adv 2022; 60:108004. [PMID: 35690272 DOI: 10.1016/j.biotechadv.2022.108004] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Revised: 05/30/2022] [Accepted: 06/03/2022] [Indexed: 11/18/2022]
Abstract
Lignin represents the most abundant renewable aromatics in nature, which has complicated and heterogeneous structure. The rapid development of biotransformation technology has brought new opportunities to achieve the complete lignin valorization. Especially, Rhodococcus sp. possesses excellent capabilities to metabolize aromatic hydrocarbons degraded from lignin. Furthermore, it can convert these toxic compounds into high value added bioproducts, such as microbial lipids, polyhydroxyalkanoate and carotenoid et al. Accordingly, this review will discuss the potentials of Rhodococcus sp. as a cell factory for lignin biotransformation, including phenol tolerance, lignin depolymerization and lignin-derived aromatic hydrocarbon metabolism. The detailed metabolic mechanism for lignin biotransformation and bioproducts spectrum of Rhodococcus sp. will be comprehensively discussed. The available molecular tools for the conversion of lignin by Rhodococcus sp. will be reviewed, and the possible direction for lignin biotransformation in the future will also be proposed.
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Affiliation(s)
- Wankui Jiang
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, PR China
| | - Haiyan Gao
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, PR China
| | - Jingxiang Sun
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, PR China
| | - Xinyi Yang
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, PR China
| | - Yujia Jiang
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, PR China
| | - Wenming Zhang
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, PR China; Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University, Nanjing 211816, PR China.
| | - Min Jiang
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, PR China; Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University, Nanjing 211816, PR China.
| | - Fengxue Xin
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, PR China; Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University, Nanjing 211816, PR China.
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6
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Tietze L, Lale R. Importance of the 5' regulatory region to bacterial synthetic biology applications. Microb Biotechnol 2021; 14:2291-2315. [PMID: 34171170 PMCID: PMC8601185 DOI: 10.1111/1751-7915.13868] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 06/03/2021] [Accepted: 06/04/2021] [Indexed: 01/02/2023] Open
Abstract
The field of synthetic biology is evolving at a fast pace. It is advancing beyond single-gene alterations in single hosts to the logical design of complex circuits and the development of integrated synthetic genomes. Recent breakthroughs in deep learning, which is increasingly used in de novo assembly of DNA components with predictable effects, are also aiding the discipline. Despite advances in computing, the field is still reliant on the availability of pre-characterized DNA parts, whether natural or synthetic, to regulate gene expression in bacteria and make valuable compounds. In this review, we discuss the different bacterial synthetic biology methodologies employed in the creation of 5' regulatory regions - promoters, untranslated regions and 5'-end of coding sequences. We summarize methodologies and discuss their significance for each of the functional DNA components, and highlight the key advances made in bacterial engineering by concentrating on their flaws and strengths. We end the review by outlining the issues that the discipline may face in the near future.
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Affiliation(s)
- Lisa Tietze
- PhotoSynLabDepartment of BiotechnologyFaculty of Natural SciencesNorwegian University of Science and TechnologyTrondheimN‐7491Norway
| | - Rahmi Lale
- PhotoSynLabDepartment of BiotechnologyFaculty of Natural SciencesNorwegian University of Science and TechnologyTrondheimN‐7491Norway
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7
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Round JW, Robeck LD, Eltis LD. An Integrative Toolbox for Synthetic Biology in Rhodococcus. ACS Synth Biol 2021; 10:2383-2395. [PMID: 34428025 DOI: 10.1021/acssynbio.1c00292] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The development of microbial cell factories requires robust synthetic biology tools to reduce design uncertainty and accelerate the design-build-test-learn process. Herein, we developed a suite of integrative genetic tools to facilitate the engineering of Rhodococcus, a genus of bacteria with considerable biocatalytic potential. We first created pRIME, a modular, copy-controlled integrative-vector, to provide a robust platform for strain engineering and characterizing genetic parts. This vector was then employed to benchmark a series of strong promoters. We found PM6 to be the strongest constitutive rhodococcal promoter, 2.5- to 3-fold stronger than the next in our study, while overall promoter activities ranged 23-fold between the weakest and strongest promoters during exponential growth. Next, we used an optimized variant of PM6 to develop hybrid-promoters and integrative vectors to allow for tetracycline-inducible gene expression in Rhodococcus. The best of the resulting hybrid-promoters maintained a maximal activity of ∼50% of PM6 and displayed an induction factor of ∼40-fold. Finally, we developed and implemented a uLoop-derived Golden Gate assembly strategy for high-throughput DNA assembly in Rhodococcus. To demonstrate the utility of our approaches, pRIME was used to engineer Rhodococcus jostii RHA1 to grow on vanillin at concentrations 10-fold higher than what the wild-type strain tolerated. Overall, this study provides a suite of tools that will accelerate the engineering of Rhodococcus for various biocatalytic applications, including the sustainable production of chemicals from lignin-derived aromatics.
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Affiliation(s)
- James W. Round
- Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Logan D. Robeck
- Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Lindsay D. Eltis
- Department of Microbiology and Immunology, Life Sciences Institute, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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8
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Delgado-Martín J, Velasco L. An efficient dsRNA constitutive expression system in Escherichia coli. Appl Microbiol Biotechnol 2021; 105:6381-6393. [PMID: 34415390 DOI: 10.1007/s00253-021-11494-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 07/22/2021] [Accepted: 08/03/2021] [Indexed: 11/24/2022]
Abstract
Synthetic dsRNA are valuable tools for reverse genetics research and virus silencing applications. Its synthesis can be performed both in vivo or in vitro. Whilst the latter presents the drawback of high production cost, the former has the advantage of being less expensive and suitable for scalable production. In general, dsRNAs are obtained in vivo from Escherichia coli heterologous systems that require the gene for the T7 RNA polymerase inducible by IPTG. The (ds)RNAs for gene of interest are then synthesized under the T7 promoter. In this work, we present a reliable vector system that includes the insulated promoter proD for the constitutive expression of dsRNA in E. coli that does not require any inducer and that renders elevated dsRNA yield. In tandem, the T7 and proD promoters render the highest dsRNA yield. The accumulation of dsRNA in this system entails a high metabolic cost for the cell. Bacterial RNA extractions that included dsRNAs homologous to the m5GFPer gene and derived from both the synthetic and constitutive promoters induce silencing of GFP expression in Nicotiana benthamiana 16c.Key points• A vector system that includes a constitutive promoter and a T7 promoter in tandem for maximizing dsRNA synthesis.• The metabolic cost for bacteria is maximum when the two promoters are operating simultaneously and results from the accumulation of dsRNA.• Bacterial RNA extractions from both the induced and constitutive systems that include a mGFP5er-derived dsRNA are capable of silencing the GFP expression in Nicotiana benthamiana 16c plants.
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Affiliation(s)
- Josemaría Delgado-Martín
- Plant Protection, Centro de Málaga, Instituto Andaluz de Investigación Y Formación Agraria (IFAPA), Churriana, 29140, Málaga, Spain
- Universidad de Málaga, Málaga, Spain
| | - Leonardo Velasco
- Plant Protection, Centro de Málaga, Instituto Andaluz de Investigación Y Formación Agraria (IFAPA), Churriana, 29140, Málaga, Spain.
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9
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Wilson EH, Groom JD, Sarfatis MC, Ford SM, Lidstrom ME, Beck DAC. A Computational Framework for Identifying Promoter Sequences in Nonmodel Organisms Using RNA-seq Data Sets. ACS Synth Biol 2021; 10:1394-1405. [PMID: 33988977 DOI: 10.1021/acssynbio.1c00017] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Engineering microorganisms into biological factories that convert renewable feedstocks into valuable materials is a major goal of synthetic biology; however, for many nonmodel organisms, we do not yet have the genetic tools, such as suites of strong promoters, necessary to effectively engineer them. In this work, we developed a computational framework that can leverage standard RNA-seq data sets to identify sets of constitutive, strongly expressed genes and predict strong promoter signals within their upstream regions. The framework was applied to a diverse collection of RNA-seq data measured for the methanotroph Methylotuvimicrobium buryatense 5GB1 and identified 25 genes that were constitutively, strongly expressed across 12 experimental conditions. For each gene, the framework predicted short (27-30 nucleotide) sequences as candidate promoters and derived -35 and -10 consensus promoter motifs (TTGACA and TATAAT, respectively) for strong expression in M. buryatense. This consensus closely matches the canonical E. coli sigma-70 motif and was found to be enriched in promoter regions of the genome. A subset of promoter predictions was experimentally validated in a XylE reporter assay, including the consensus promoter, which showed high expression. The pmoC, pqqA, and ssrA promoter predictions were additionally screened in an experiment that scrambled the -35 and -10 signal sequences, confirming that transcription initiation was disrupted when these specific regions of the predicted sequence were altered. These results indicate that the computational framework can make biologically meaningful promoter predictions and identify key pieces of regulatory systems that can serve as foundational tools for engineering diverse microorganisms for biomolecule production.
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Affiliation(s)
- Erin H. Wilson
- The Paul G. Allen School of Computer Science & Engineering, University of Washington, Seattle, Washington 98195, United States
| | - Joseph D. Groom
- Department of Chemical Engineering, University of Washington, Seattle, Washington 98195, United States
| | - M. Claire Sarfatis
- Department of Microbiology, University of Washington, Seattle, Washington 98195, United States
| | - Stephanie M. Ford
- Department of Chemical Engineering, University of Washington, Seattle, Washington 98195, United States
| | - Mary E. Lidstrom
- Department of Chemical Engineering, University of Washington, Seattle, Washington 98195, United States
- Department of Microbiology, University of Washington, Seattle, Washington 98195, United States
| | - David A. C. Beck
- Department of Chemical Engineering, University of Washington, Seattle, Washington 98195, United States
- eScience Institute, University of Washington, Seattle, Washington 98195, United States
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10
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Moore SJ, Hleba YB, Bischoff S, Bell D, Polizzi KM, Freemont PS. Refactoring of a synthetic raspberry ketone pathway with EcoFlex. Microb Cell Fact 2021; 20:116. [PMID: 34112158 PMCID: PMC8193874 DOI: 10.1186/s12934-021-01604-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Accepted: 05/31/2021] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND A key focus of synthetic biology is to develop microbial or cell-free based biobased routes to value-added chemicals such as fragrances. Originally, we developed the EcoFlex system, a Golden Gate toolkit, to study genes/pathways flexibly using Escherichia coli heterologous expression. In this current work, we sought to use EcoFlex to optimise a synthetic raspberry ketone biosynthetic pathway. Raspberry ketone is a high-value (~ £20,000 kg-1) fine chemical farmed from raspberry (Rubeus rubrum) fruit. RESULTS By applying a synthetic biology led design-build-test-learn cycle approach, we refactor the raspberry ketone pathway from a low level of productivity (0.2 mg/L), to achieve a 65-fold (12.9 mg/L) improvement in production. We perform this optimisation at the prototype level (using microtiter plate cultures) with E. coli DH10β, as a routine cloning host. The use of E. coli DH10β facilitates the Golden Gate cloning process for the screening of combinatorial libraries. In addition, we also newly establish a novel colour-based phenotypic screen to identify productive clones quickly from solid/liquid culture. CONCLUSIONS Our findings provide a stable raspberry ketone pathway that relies upon a natural feedstock (L-tyrosine) and uses only constitutive promoters to control gene expression. In conclusion we demonstrate the capability of EcoFlex for fine-tuning a model fine chemical pathway and provide a range of newly characterised promoter tools gene expression in E. coli.
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Affiliation(s)
- Simon J Moore
- Centre for Synthetic Biology and Innovation, Imperial College London, South Kensington Campus, Exhibition Road, London, SW7 2AZ, UK.,Department Section of Structural and Synthetic Biology, Department of Infectious Disease, Imperial College London, South Kensington Campus, Exhibition Road, London, SW7 2AZ, UK.,School of Biosciences, University of Kent, CT2 7NJ, Canterbury, England
| | - Yonek B Hleba
- Centre for Synthetic Biology and Innovation, Imperial College London, South Kensington Campus, Exhibition Road, London, SW7 2AZ, UK.,Department Section of Structural and Synthetic Biology, Department of Infectious Disease, Imperial College London, South Kensington Campus, Exhibition Road, London, SW7 2AZ, UK
| | - Sarah Bischoff
- School of Biosciences, University of Kent, CT2 7NJ, Canterbury, England
| | - David Bell
- Centre for Synthetic Biology and Innovation, Imperial College London, South Kensington Campus, Exhibition Road, London, SW7 2AZ, UK.,Department Section of Structural and Synthetic Biology, Department of Infectious Disease, Imperial College London, South Kensington Campus, Exhibition Road, London, SW7 2AZ, UK
| | - Karen M Polizzi
- Centre for Synthetic Biology and Innovation, Imperial College London, South Kensington Campus, Exhibition Road, London, SW7 2AZ, UK. .,Department of Life Sciences, Imperial College London, South Kensington Campus, Exhibition Road, London, SW7 2AZ, UK. .,Department of Chemical Engineering, Imperial College London, South Kensington Campus, Exhibition Road, London, SW7 2AZ, UK.
| | - Paul S Freemont
- Centre for Synthetic Biology and Innovation, Imperial College London, South Kensington Campus, Exhibition Road, London, SW7 2AZ, UK. .,Department Section of Structural and Synthetic Biology, Department of Infectious Disease, Imperial College London, South Kensington Campus, Exhibition Road, London, SW7 2AZ, UK. .,The London Biofoundry, Imperial College Translation & Innovation Hub, White City Campus, 80 Wood Lane, London, W12 0BZ, UK. .,Dementia Research Institute Care Research and Technology Centre, Imperial College London, Hammersmith Campus, Du Cane Road, London, W12 0NN, UK.
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11
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Ma J, Ji Q, Wang S, Qiu J, Liu Q. Identification and evaluation of a panel of strong constitutive promoters in Listeria monocytogenes for improving the expression of foreign antigens. Appl Microbiol Biotechnol 2021; 105:5135-5145. [PMID: 34086117 PMCID: PMC8175932 DOI: 10.1007/s00253-021-11374-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 05/10/2021] [Accepted: 05/27/2021] [Indexed: 12/19/2022]
Abstract
Attenuated Listeria monocytogenes could be a potential vaccine vector for the immunotherapy of tumors or pathogens. However, the lack of reliable promoters has limited its ability to express foreign antigens. In the present study, 21 promoters were identified from Listeria monocytogenes through RNA-seq analysis under two pH conditions of pH 7.4 and pH 5.5. Based on the constructed fluorescence report system, 7 constitutive promoters exhibited higher strength than Phelp (1.8-fold to 5.4-fold), a previously reported strong promoter. Furthermore, the selected 5 constitutive promoters exhibited higher UreB production activity than Phelp (1.1-fold to 8.3-fold). Notably, a well-characterized constitutive promoter P18 was found with the highest activity of fluorescence intensity and UreB production. In summary, the study provides a panel of strong constitutive promoters for Listeria monocytogenes and offers a theoretical basis for mining constitutive promoters in other organisms. KEY POINTS: • Twenty-one promoters were identified from L. monocytogenes through RNA-seq. • Fluorescent tracer of L. monocytogenes (P18) was performed in vitro and in vivo. • A well-characterized constitutive promoter P18 could improve the expression level of a foreign antigen UreB in L. monocytogenes.
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Affiliation(s)
- Junfei Ma
- School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China
| | - Qianyu Ji
- School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China
| | - Shuying Wang
- School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China
| | - Jingxuan Qiu
- School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China
| | - Qing Liu
- School of Medical Instrument and Food Engineering, University of Shanghai for Science and Technology, Shanghai, 200093, China. .,Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266071, China.
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12
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Gilman J, Walls L, Bandiera L, Menolascina F. Statistical Design of Experiments for Synthetic Biology. ACS Synth Biol 2021; 10:1-18. [PMID: 33406821 DOI: 10.1021/acssynbio.0c00385] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The design and optimization of biological systems is an inherently complex undertaking that requires careful balancing of myriad synergistic and antagonistic variables. However, despite this complexity, much synthetic biology research is predicated on One Factor at A Time (OFAT) experimentation; the genetic and environmental variables affecting the activity of a system of interest are sequentially altered while all other variables are held constant. Beyond being time and resource intensive, OFAT experimentation crucially ignores the effect of interactions between factors. Given the ubiquity of interacting genetic and environmental factors in biology this failure to account for interaction effects in OFAT experimentation can result in the development of suboptimal systems. To address these limitations, an increasing number of studies have turned to Design of Experiments (DoE), a suite of methods that enable efficient, systematic exploration and exploitation of complex design spaces. This review provides an overview of DoE for synthetic biologists. Key concepts and commonly used experimental designs are introduced, and we discuss the advantages of DoE as compared to OFAT experimentation. We dissect the applicability of DoE in the context of synthetic biology and review studies which have successfully employed these methods, illustrating the potential of statistical experimental design to guide the design, characterization, and optimization of biological protocols, pathways, and processes.
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Affiliation(s)
- James Gilman
- Institute for Bioengineering, School of Engineering, University of Edinburgh, Edinburgh EH8 9YL, U.K
| | - Laura Walls
- Institute for Bioengineering, School of Engineering, University of Edinburgh, Edinburgh EH8 9YL, U.K
| | - Lucia Bandiera
- Institute for Bioengineering, School of Engineering, University of Edinburgh, Edinburgh EH8 9YL, U.K
| | - Filippo Menolascina
- Institute for Bioengineering, School of Engineering, University of Edinburgh, Edinburgh EH8 9YL, U.K
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13
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Gilman J, Zulkower V, Menolascina F. Using a Design of Experiments Approach to Inform the Design of Hybrid Synthetic Yeast Promoters. Methods Mol Biol 2021; 2189:1-17. [PMID: 33180289 DOI: 10.1007/978-1-0716-0822-7_1] [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] [Indexed: 06/11/2023]
Abstract
Hybrid promoter engineering takes advantage of the modular nature of eukaryotic promoters by combining discrete promoter motifs to confer novel regulatory function. By combinatorially screening sequence libraries for trans-acting transcriptional operators, activators, repressors and core promoter sequences, it is possible to derive constitutive or inducible promoter collections covering a broad range of expression strengths. However, combinatorial approaches to promoter design can result in highly complex, multidimensional design spaces, which can be experimentally costly to thoroughly explore in vivo. Here, we describe an in silico pipeline for the design of hybrid promoter libraries that employs a Design of Experiments (DoE) approach to reduce experimental burden and efficiently explore the promoter fitness landscape. We also describe a software pipeline to ensure that the designed promoter sequences are compatible with the YTK assembly standard.
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Affiliation(s)
- James Gilman
- Institute for Bioengineering, School of Engineering, University of Edinburgh, Edinburgh, UK
| | - Valentin Zulkower
- Edinburgh Genome Foundry, The University of Edinburgh, Edinburgh, UK
| | - Filippo Menolascina
- Institute for Bioengineering, School of Engineering, University of Edinburgh, Edinburgh, UK.
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14
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Lammens EM, Nikel PI, Lavigne R. Exploring the synthetic biology potential of bacteriophages for engineering non-model bacteria. Nat Commun 2020; 11:5294. [PMID: 33082347 PMCID: PMC7576135 DOI: 10.1038/s41467-020-19124-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Accepted: 09/25/2020] [Indexed: 12/26/2022] Open
Abstract
Non-model bacteria like Pseudomonas putida, Lactococcus lactis and other species have unique and versatile metabolisms, offering unique opportunities for Synthetic Biology (SynBio). However, key genome editing and recombineering tools require optimization and large-scale multiplexing to unlock the full SynBio potential of these bacteria. In addition, the limited availability of a set of characterized, species-specific biological parts hampers the construction of reliable genetic circuitry. Mining of currently available, diverse bacteriophages could complete the SynBio toolbox, as they constitute an unexplored treasure trove for fully adapted metabolic modulators and orthogonally-functioning parts, driven by the longstanding co-evolution between phage and host.
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Affiliation(s)
- Eveline-Marie Lammens
- Department of Biosystems, Laboratory of Gene Technology, KU Leuven, Kasteelpark Arenberg 21 box 2462, 3001, Leuven, BE, Belgium
| | - Pablo Ivan Nikel
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kemitorvet, Building 220, 2800 Kgs, Lyngby, DK, Denmark
| | - Rob Lavigne
- Department of Biosystems, Laboratory of Gene Technology, KU Leuven, Kasteelpark Arenberg 21 box 2462, 3001, Leuven, BE, Belgium.
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15
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Wang Y, Wang H, Wei L, Li S, Liu L, Wang X. Synthetic promoter design in Escherichia coli based on a deep generative network. Nucleic Acids Res 2020; 48:6403-6412. [PMID: 32424410 PMCID: PMC7337522 DOI: 10.1093/nar/gkaa325] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2019] [Revised: 04/05/2020] [Accepted: 04/22/2020] [Indexed: 01/11/2023] Open
Abstract
Promoter design remains one of the most important considerations in metabolic engineering and synthetic biology applications. Theoretically, there are 450 possible sequences for a 50-nt promoter, of which naturally occurring promoters make up only a small subset. To explore the vast number of potential sequences, we report a novel AI-based framework for de novo promoter design in Escherichia coli. The model, which was guided by sequence features learned from natural promoters, could capture interactions between nucleotides at different positions and design novel synthetic promoters in silico. We combined a deep generative model that guides the search for artificial sequences with a predictive model to preselect the most promising promoters. The AI-designed promoters were optimized based on the promoter activity in E. coli and the predictive model. After two rounds of optimization, up to 70.8% of the AI-designed promoters were experimentally demonstrated to be functional, and few of them shared significant sequence similarity with the E. coli genome. Our work provided an end-to-end approach to the de novo design of novel promoter elements, indicating the potential to apply deep learning methods to de novo genetic element design.
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Affiliation(s)
- Ye Wang
- Ministry of Education Key Laboratory of Bioinformatics; Center for Synthetic and Systems Biology; Bioinformatics Division, Beijing National Research Center for Information Science and Technology; Department of Automation, Tsinghua University, Beijing 100084, China
| | - Haochen Wang
- Ministry of Education Key Laboratory of Bioinformatics; Center for Synthetic and Systems Biology; Bioinformatics Division, Beijing National Research Center for Information Science and Technology; Department of Automation, Tsinghua University, Beijing 100084, China
| | - Lei Wei
- Ministry of Education Key Laboratory of Bioinformatics; Center for Synthetic and Systems Biology; Bioinformatics Division, Beijing National Research Center for Information Science and Technology; Department of Automation, Tsinghua University, Beijing 100084, China
| | - Shuailin Li
- School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Liyang Liu
- Ministry of Education Key Laboratory of Bioinformatics; Center for Synthetic and Systems Biology; Bioinformatics Division, Beijing National Research Center for Information Science and Technology; Department of Automation, Tsinghua University, Beijing 100084, China
| | - Xiaowo Wang
- Ministry of Education Key Laboratory of Bioinformatics; Center for Synthetic and Systems Biology; Bioinformatics Division, Beijing National Research Center for Information Science and Technology; Department of Automation, Tsinghua University, Beijing 100084, China
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16
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Sengupta A, Madhu S, Wangikar PP. A Library of Tunable, Portable, and Inducer-Free Promoters Derived from Cyanobacteria. ACS Synth Biol 2020; 9:1790-1801. [PMID: 32551554 DOI: 10.1021/acssynbio.0c00152] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Cyanobacteria are emerging as hosts for various biotechnological applications. The ability to engineer these photosynthetic prokaryotes greatly depends on the availability of well-characterized promoters. Inducer-free promoters of a range of activities may be desirable for the eventual large-scale, outdoor cultivations. Further, several native promoters of cyanobacteria are repressed by high carbon dioxide or light, and it would be of interest to alter this property. We started with PrbcL and PcpcB, the well-characterized native promoters of the model cyanobacterium Synechococcus elongatus PCC 7942, found upstream of the two abundantly expressed genes, Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase, and phycocyanin β-1 subunit, respectively. The library of 48 promoters created via error-prone PCR of these 300-bp-long native promoters showed 2 orders of magnitude dynamic range with activities that were both lower and higher than those of the wild-type promoters. A few mutants of the PrbcL showed greater strength than PcpcB, which is widely considered a superstrong promoter. A number of mutant promoters did not show repression by high CO2 or light, typically found for PrbcL and PcpcB, respectively. Further, the wild-type and mutant promoters showed comparable activities in the fast-growing and stress-tolerant strains S. elongatus PCC 11801 and PCC 11802, suggesting that the library can be used in different cyanobacteria. Interestingly, the majority of the promoters showed strong expression in E. coli, thus adding to the repertoire of inducer-free promoters for this heterotrophic workhorse. Our results have implications in the metabolic engineering of cyanobacteria and E. coli.
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17
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Köbbing S, Blank LM, Wierckx N. Characterization of Context-Dependent Effects on Synthetic Promoters. Front Bioeng Biotechnol 2020; 8:551. [PMID: 32596224 PMCID: PMC7303508 DOI: 10.3389/fbioe.2020.00551] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2020] [Accepted: 05/07/2020] [Indexed: 11/13/2022] Open
Abstract
Understanding the composability of genetic elements is central to synthetic biology. Even for seemingly well-known elements such as a sigma 70 promoter the genetic context-dependent variability of promoter activity remains poorly understood. The lack of understanding of sequence to function results in highly limited de novo design of novel genetic element combinations. To address this issue, we characterized in detail concatenated "stacked" synthetic promoters including varying spacer sequence lengths and compared the transcription strength to the output of the individual promoters. The proxy for promoter activity, the msfGFP synthesis from stacked promoters was consistently lower than expected from the sum of the activities of the single promoters. While the spacer sequence itself had no activity, it drastically affected promoter activities when placed up- or downstream of a promoter. Single promoter-spacer combinations revealed a bivalent effect on msfGFP synthesis. By systematic analysis of promoter and spacer combinations, a semi-empirical correlation was developed to determine the combined activity of stacked promoters.
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Affiliation(s)
- Sebastian Köbbing
- Institute of Applied Microbiology - iAMB, Aachen Biology and Biotechnology - ABBt, RWTH Aachen University, Aachen, Germany
| | - Lars M Blank
- Institute of Applied Microbiology - iAMB, Aachen Biology and Biotechnology - ABBt, RWTH Aachen University, Aachen, Germany
| | - Nick Wierckx
- Institute of Applied Microbiology - iAMB, Aachen Biology and Biotechnology - ABBt, RWTH Aachen University, Aachen, Germany.,Institute of Bio- and Geosciences (IBG-1: Biotechnology), Forschungszentrum Jülich GmbH, Jülich, Germany
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18
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Jin L, Nawab S, Xia M, Ma X, Huo Y. Context-dependency of synthetic minimal promoters in driving gene expression: a case study. Microb Biotechnol 2019; 12:1476-1486. [PMID: 31578818 PMCID: PMC6801132 DOI: 10.1111/1751-7915.13489] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Accepted: 09/09/2019] [Indexed: 12/13/2022] Open
Abstract
Synthetic promoters are considered ideal candidates in driving robust gene expression. Most of the available synthetic promoters are minimal promoters, for which the upstream sequence of the 5' end of the core region is usually excluded. Although the upstream sequence has been shown to mediate transcription of natural promoters, its impact on synthetic promoters has not been widely studied. Here, a library of chromosomal DNA fragments is randomly fused with the 5' end of the J23119 synthetic promoter, and the transcriptional performance of the promoter is evaluated through β-galactosidase assay, fluorescence intensity and chemical biosynthesis. Results show that changes in the upstream sequence can induce significant variation in the promoter strength of up to 5.8-fold. The effect is independent of the length of the insertions and the number of potential transcription factor binding sites. Several DNA fragments that are able to enhance the transcription of both the natural and the synthetic promoters are identified. This study indicates that the synthetic minimal promoters are susceptible to the surrounding sequence context. Therefore, the upstream sequence should be treated as an indispensable component in the design and application of synthetic promoters, or as an independent genetic part for the fine-tuning of gene expression.
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Affiliation(s)
- Liyuan Jin
- Key Laboratory of Molecular Medicine and BiotherapySchool of Life ScienceBeijing Institute of Technology5 South Zhongguancun Street, Haidian DistrictBeijing100081China
| | - Said Nawab
- Key Laboratory of Molecular Medicine and BiotherapySchool of Life ScienceBeijing Institute of Technology5 South Zhongguancun Street, Haidian DistrictBeijing100081China
| | - Mengli Xia
- Key Laboratory of Molecular Medicine and BiotherapySchool of Life ScienceBeijing Institute of Technology5 South Zhongguancun Street, Haidian DistrictBeijing100081China
| | - Xiaoyan Ma
- Key Laboratory of Molecular Medicine and BiotherapySchool of Life ScienceBeijing Institute of Technology5 South Zhongguancun Street, Haidian DistrictBeijing100081China
| | - Yi‐Xin Huo
- Key Laboratory of Molecular Medicine and BiotherapySchool of Life ScienceBeijing Institute of Technology5 South Zhongguancun Street, Haidian DistrictBeijing100081China
- UCLA Institute for Technology Advancement (Suzhou)10 Yueliangwan Road, Suzhou Industrial ParkSuzhou215123China
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19
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Tschirhart T, Shukla V, Kelly EE, Schultzhaus Z, NewRingeisen E, Erickson JS, Wang Z, Garcia W, Curl E, Egbert RG, Yeung E, Vora GJ. Synthetic Biology Tools for the Fast-Growing Marine Bacterium Vibrio natriegens. ACS Synth Biol 2019; 8:2069-2079. [PMID: 31419124 DOI: 10.1021/acssynbio.9b00176] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The fast-growing nonmodel marine bacterium Vibrio natriegens has recently garnered attention as a host for molecular biology and biotechnology applications. In order to further its capabilities as a synthetic biology chassis, we have characterized a wide range of genetic parts and tools for use in V. natriegens. These parts include many commonly used resistance markers, promoters, ribosomal binding sites, reporters, terminators, degradation tags, origin of replication sequences, and plasmid backbones. We have characterized the behavior of these parts in different combinations and have compared their functionality in V. natriegens and Escherichia coli. Plasmid stability over time, plasmid copy numbers, and production load on the cells were also evaluated. Additionally, we tested constructs for chemical and optogenetic induction and characterized basic engineered circuit behavior in V. natriegens. The results indicate that, while most parts and constructs work similarly in the two organisms, some deviate significantly. Overall, these results will serve as a primer for anyone interested in engineering V. natriegens and will aid in developing more robust synthetic biology principles and approaches for this nonmodel chassis.
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Affiliation(s)
- Tanya Tschirhart
- American Society for Engineering Education, Postdoctoral Fellowship Program, US Naval Research Laboratory, Washington, DC 20375, United States of America
| | - Vrinda Shukla
- Center for Bio/Molecular Science and Engineering, US Naval Research Laboratory, Washington, DC 20375, United States of America
| | - Erin E. Kelly
- National Research Council, Postdoctoral Fellowship Program, US Naval Research Laboratory, Washington, DC 20375, United States of America
| | - Zachary Schultzhaus
- National Research Council, Postdoctoral Fellowship Program, US Naval Research Laboratory, Washington, DC 20375, United States of America
| | - Erin NewRingeisen
- Center for Bio/Molecular Science and Engineering, US Naval Research Laboratory, Washington, DC 20375, United States of America
| | - Jeffrey S. Erickson
- Center for Bio/Molecular Science and Engineering, US Naval Research Laboratory, Washington, DC 20375, United States of America
| | - Zheng Wang
- Center for Bio/Molecular Science and Engineering, US Naval Research Laboratory, Washington, DC 20375, United States of America
| | - Whitney Garcia
- Earth and Biological Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, United States of America
| | - Emaleigh Curl
- Biomolecular Science and Engineering, University of California Santa Barbara, Santa Barbara, California 93106, United States of America
| | - Robert G. Egbert
- Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, United States of America
| | - Enoch Yeung
- Department of Mechanical Engineering, University of California Santa Barbara, Santa Barbara, California 93106, United States of America
| | - Gary J. Vora
- Center for Bio/Molecular Science and Engineering, US Naval Research Laboratory, Washington, DC 20375, United States of America
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20
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Bervoets I, Charlier D. Diversity, versatility and complexity of bacterial gene regulation mechanisms: opportunities and drawbacks for applications in synthetic biology. FEMS Microbiol Rev 2019; 43:304-339. [PMID: 30721976 PMCID: PMC6524683 DOI: 10.1093/femsre/fuz001] [Citation(s) in RCA: 87] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Accepted: 01/21/2019] [Indexed: 12/15/2022] Open
Abstract
Gene expression occurs in two essential steps: transcription and translation. In bacteria, the two processes are tightly coupled in time and space, and highly regulated. Tight regulation of gene expression is crucial. It limits wasteful consumption of resources and energy, prevents accumulation of potentially growth inhibiting reaction intermediates, and sustains the fitness and potential virulence of the organism in a fluctuating, competitive and frequently stressful environment. Since the onset of studies on regulation of enzyme synthesis, numerous distinct regulatory mechanisms modulating transcription and/or translation have been discovered. Mostly, various regulatory mechanisms operating at different levels in the flow of genetic information are used in combination to control and modulate the expression of a single gene or operon. Here, we provide an extensive overview of the very diverse and versatile bacterial gene regulatory mechanisms with major emphasis on their combined occurrence, intricate intertwinement and versatility. Furthermore, we discuss the potential of well-characterized basal expression and regulatory elements in synthetic biology applications, where they may ensure orthogonal, predictable and tunable expression of (heterologous) target genes and pathways, aiming at a minimal burden for the host.
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Affiliation(s)
- Indra Bervoets
- Research Group of Microbiology, Department of Bioengineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium
| | - Daniel Charlier
- Research Group of Microbiology, Department of Bioengineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium
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21
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Han L, Cui W, Suo F, Miao S, Hao W, Chen Q, Guo J, Liu Z, Zhou L, Zhou Z. Development of a novel strategy for robust synthetic bacterial promoters based on a stepwise evolution targeting the spacer region of the core promoter in Bacillus subtilis. Microb Cell Fact 2019; 18:96. [PMID: 31142347 PMCID: PMC6540529 DOI: 10.1186/s12934-019-1148-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Accepted: 05/22/2019] [Indexed: 01/06/2023] Open
Abstract
Background Promoter evolution by synthetic promoter library (SPL) is a powerful approach to development of functional synthetic promoters to synthetic biology. However, it requires much tedious and time-consuming screenings because of the plethora of different variants in SPL. Actually, a large proportion of mutants in the SPL are significantly lower in strength, which contributes only to fabrication of a promoter library with a continuum of strength. Thus, to effectively obtain the evolved synthetic promoter exhibiting higher strength, it is essential to develop novel strategies to construct mutant library targeting the pivotal region rather than the arbitrary region of the template promoter. In this study, a strategy termed stepwise evolution targeting the spacer of core promoter (SETarSCoP) was established in Bacillus subtilis to effectively evolve the strength of bacterial promoter. Results The native promoter, PsrfA, from B. subtilis, which exhibits higher strength than the strong promoter P43, was set as the parental template. According to the comparison of conservation of the spacer sequences between − 35 box and − 10 box among a set of strong and weak native promoter, it revealed that 7-bp sequence immediately upstream of the − 10 box featured in the regulation of promoter strength. Based on the conservative feature, two rounds of consecutive evolution were performed targeting the hot region of PsrfA. In the first round, a primary promoter mutation library (pPML) was constructed by mutagenesis targeting the 3-bp sequence immediately upstream of the − 10 box of the PsrfA. Subsequently, four evolved mutants from pPML were selected to construction of four secondary promoter mutation libraries (sPMLs) based on mutagenesis of the 4-bp sequence upstream of the first-round target. After the consecutive two-step evolution, the mutant PBH4 was identified and verified to be a highly evolved synthetic promoter. The strength of PBH4 was higher than PsrfA by approximately 3 times. Moreover, PBH4 also exhibited broad suitability for different cargo proteins, such as β-glucuronidase and nattokinase. The proof-of-principle test showed that SETarSCoP successfully evolved both constitutive and inducible promoters. Conclusion Comparing with the commonly used SPL strategy, SETarSCoP facilitates the evolution process to obtain strength-evolved synthetic bacterial promoter through fabrication and screening of small-scale mutation libraries. This strategy will be a promising method to evolve diverse bacterial promoters to expand the toolbox for synthetic biology. Electronic supplementary material The online version of this article (10.1186/s12934-019-1148-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Laichuang Han
- School of Biotechnology, Key Laboratory of Industrial Biotechnology (Ministry of Education), Jiangnan University, Wuxi, 214122, Jiangsu, China
| | - Wenjing Cui
- School of Biotechnology, Key Laboratory of Industrial Biotechnology (Ministry of Education), Jiangnan University, Wuxi, 214122, Jiangsu, China.
| | - Feiya Suo
- School of Biotechnology, Key Laboratory of Industrial Biotechnology (Ministry of Education), Jiangnan University, Wuxi, 214122, Jiangsu, China
| | - Shengnan Miao
- School of Biotechnology, Key Laboratory of Industrial Biotechnology (Ministry of Education), Jiangnan University, Wuxi, 214122, Jiangsu, China
| | - Wenliang Hao
- School of Biotechnology, Key Laboratory of Industrial Biotechnology (Ministry of Education), Jiangnan University, Wuxi, 214122, Jiangsu, China
| | - Qiaoqing Chen
- School of Biotechnology, Key Laboratory of Industrial Biotechnology (Ministry of Education), Jiangnan University, Wuxi, 214122, Jiangsu, China
| | - Junling Guo
- School of Biotechnology, Key Laboratory of Industrial Biotechnology (Ministry of Education), Jiangnan University, Wuxi, 214122, Jiangsu, China
| | - Zhongmei Liu
- School of Biotechnology, Key Laboratory of Industrial Biotechnology (Ministry of Education), Jiangnan University, Wuxi, 214122, Jiangsu, China
| | - Li Zhou
- School of Biotechnology, Key Laboratory of Industrial Biotechnology (Ministry of Education), Jiangnan University, Wuxi, 214122, Jiangsu, China
| | - Zhemin Zhou
- School of Biotechnology, Key Laboratory of Industrial Biotechnology (Ministry of Education), Jiangnan University, Wuxi, 214122, Jiangsu, China.
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22
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Gilman J, Singleton C, Tennant RK, James P, Howard TP, Lux T, Parker DA, Love J. Rapid, Heuristic Discovery and Design of Promoter Collections in Non-Model Microbes for Industrial Applications. ACS Synth Biol 2019; 8:1175-1186. [PMID: 30995831 DOI: 10.1021/acssynbio.9b00061] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Well-characterized promoter collections for synthetic biology applications are not always available in industrially relevant hosts. We developed a broadly applicable method for promoter identification in atypical microbial hosts that requires no a priori understanding of cis-regulatory element structure. This novel approach combines bioinformatic filtering with rapid empirical characterization to expand the promoter toolkit and uses machine learning to improve the understanding of the relationship between DNA sequence and function. Here, we apply the method in Geobacillus thermoglucosidasius, a thermophilic organism with high potential as a synthetic biology chassis for industrial applications. Bioinformatic screening of G. kaustophilus, G. stearothermophilus, G. thermodenitrificans, and G. thermoglucosidasius resulted in the identification of 636 100 bp putative promoters, encompassing the genome-wide design space and lacking known transcription factor binding sites. Eighty of these sequences were characterized in vivo, and activities covered a 2-log range of predictable expression levels. Seven sequences were shown to function consistently regardless of the downstream coding sequence. Partition modeling identified sequence positions upstream of the canonical -35 and -10 consensus motifs that were predicted to strongly influence regulatory activity in Geobacillus, and artificial neural network and partial least squares regression models were derived to assess if there were a simple, forward, quantitative method for in silico prediction of promoter function. However, the models were insufficiently general to predict pre hoc promoter activity in vivo, most probably as a result of the relatively small size of the training data set compared to the size of the modeled design space.
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Affiliation(s)
- James Gilman
- The BioEconomy Centre, Biosciences, College of Life and Environmental Sciences, Stocker Road, University of Exeter, Exeter EX4 4QD, U.K
| | - Chloe Singleton
- The BioEconomy Centre, Biosciences, College of Life and Environmental Sciences, Stocker Road, University of Exeter, Exeter EX4 4QD, U.K
| | - Richard K. Tennant
- The BioEconomy Centre, Biosciences, College of Life and Environmental Sciences, Stocker Road, University of Exeter, Exeter EX4 4QD, U.K
| | - Paul James
- The BioEconomy Centre, Biosciences, College of Life and Environmental Sciences, Stocker Road, University of Exeter, Exeter EX4 4QD, U.K
| | - Thomas P. Howard
- School of Natural and Environmental Sciences, Newcastle University, Devonshire Building, Newcastle-upon-Tyne NE1 7RU, U.K
| | - Thomas Lux
- Plant Genome and Systems Biology, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Munich 85764, Germany
| | - David A. Parker
- Biodomain, Shell Technology Center Houston, 3333 Highway 6 South, Houston, Texas 77082-3101, United States
| | - John Love
- The BioEconomy Centre, Biosciences, College of Life and Environmental Sciences, Stocker Road, University of Exeter, Exeter EX4 4QD, U.K
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23
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Uluşeker C, Torres-Bacete J, García JL, Hanczyc MM, Nogales J, Kahramanoğulları O. Quantifying dynamic mechanisms of auto-regulation in Escherichia coli with synthetic promoter in response to varying external phosphate levels. Sci Rep 2019; 9:2076. [PMID: 30765722 PMCID: PMC6376016 DOI: 10.1038/s41598-018-38223-w] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 12/13/2018] [Indexed: 12/16/2022] Open
Abstract
Escherichia coli have developed one of the most efficient regulatory response mechanisms to phosphate starvation. The machinery involves a cascade with a two-component system (TCS) that relays the external signal to the genetic circuit, resulting in a feedback response. Achieving a quantitative understanding of this system has implications in synthetic biology and biotechnology, for example, in applications for wastewater treatment. To this aim, we present a computational model and experimental results with a detailed description of the TCS, consisting of PhoR and PhoB, together with the mechanisms of gene expression. The model is parameterised within the feasible range, and fitted to the dynamic response of our experimental data on PhoB as well as PhoA, the product of this network that is used in alkaline phosphatase production. Deterministic and stochastic simulations with our model predict the regulation dynamics in higher external phosphate concentrations while reproducing the experimental observations. In a cycle of simulations and experimental verification, our model predicts and explores phenotypes with various synthetic promoter designs that can optimise the inorganic phosphate intake in E. coli. Sensitivity analysis demonstrates that the Pho-controlled genes have a significant influence over the phosphate response. Together with experimental findings, our model should thus provide insights for the investigations on engineering new sensors and regulators for living technologies.
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Affiliation(s)
- Cansu Uluşeker
- University of Trento, Centre for Integrative Biology, Trento, 38123, Italy.,The Microsoft Research - University of Trento Centre for Computational and Systems Biology, Rovereto, 38068, Italy
| | - Jesús Torres-Bacete
- Centro Nacional de Biotecnología (CNB-CSIC), Systems Biology Department, Madrid, 28049, Spain
| | - José L García
- Centro de Investigaciones Biológicas (CIB-CSIC), Microbial and Plant Biotechnology Department, Madrid, 28040, Spain.,Institute for Integrative Systems Biology (I2Sysbio-CSIC-UV), Applied Systems Biology and Synthetic Biology Department, Paterna, 46980, Spain
| | - Martin M Hanczyc
- University of Trento, Centre for Integrative Biology, Trento, 38123, Italy.,Chemical and Biological Engineering, University of New Mexico, Albuquerque, NM, 87131, USA
| | - Juan Nogales
- Centro Nacional de Biotecnología (CNB-CSIC), Systems Biology Department, Madrid, 28049, Spain
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24
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Anthony WE, Carr RR, DeLorenzo DM, Campbell TP, Shang Z, Foston M, Moon TS, Dantas G. Development of Rhodococcus opacus as a chassis for lignin valorization and bioproduction of high-value compounds. BIOTECHNOLOGY FOR BIOFUELS 2019; 12:192. [PMID: 31404385 PMCID: PMC6683499 DOI: 10.1186/s13068-019-1535-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 07/24/2019] [Indexed: 05/09/2023]
Abstract
The current extraction and use of fossil fuels has been linked to extensive negative health and environmental outcomes. Lignocellulosic biomass-derived biofuels and bioproducts are being actively considered as renewable alternatives to the fuels, chemicals, and materials produced from fossil fuels. A major challenge limiting large-scale, economic deployment of second-generation biorefineries is the insufficient product yield, diversity, and value that current conversion technologies can extract from lignocellulose, in particular from the underutilized lignin fraction. Rhodococcus opacus PD630 is an oleaginous gram-positive bacterium with innate catabolic pathways and tolerance mechanisms for the inhibitory aromatic compounds found in depolymerized lignin, as well as native or engineered pathways for hexose and pentose sugars found in the carbohydrate fractions of biomass. As a result, R. opacus holds potential as a biological chassis for the conversion of lignocellulosic biomass into biodiesel precursors and other value-added products. This review begins by examining the important role that lignin utilization will play in the future of biorefineries and by providing a concise survey of the current lignin conversion technologies. The genetic machinery and capabilities of R. opacus that allow the bacterium to tolerate and metabolize aromatic compounds and depolymerized lignin are also discussed, along with a synopsis of the genetic toolbox and synthetic biology methods now available for engineering this organism. Finally, we summarize the different feedstocks that R. opacus has been demonstrated to consume, and the high-value products that it has been shown to produce. Engineered R. opacus will enable lignin valorization over the coming years, leading to cost-effective conversion of lignocellulose into fuels, chemicals, and materials.
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Affiliation(s)
- Winston E. Anthony
- The Edison Family Center for Genome Sciences and Systems Biology, Washington University in St. Louis School of Medicine, St. Louis, MO 63110 USA
| | - Rhiannon R. Carr
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO 63130 USA
| | - Drew M. DeLorenzo
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO 63130 USA
| | - Tayte P. Campbell
- The Edison Family Center for Genome Sciences and Systems Biology, Washington University in St. Louis School of Medicine, St. Louis, MO 63110 USA
| | - Zeyu Shang
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO 63130 USA
| | - Marcus Foston
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO 63130 USA
| | - Tae Seok Moon
- Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, MO 63130 USA
| | - Gautam Dantas
- The Edison Family Center for Genome Sciences and Systems Biology, Washington University in St. Louis School of Medicine, St. Louis, MO 63110 USA
- Department of Pathology and Immunology, Washington University in St. Louis School of Medicine, St. Louis, MO 63108 USA
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130 USA
- Department of Molecular Microbiology, Washington University in St. Louis School of Medicine, St. Louis, MO 63108 USA
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25
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Wang Y, Liu Q, Weng H, Shi Y, Chen J, Du G, Kang Z. Construction of Synthetic Promoters by Assembling the Sigma Factor Binding -35 and -10 Boxes. Biotechnol J 2018; 14:e1800298. [PMID: 30457214 DOI: 10.1002/biot.201800298] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Revised: 10/24/2018] [Indexed: 12/12/2022]
Abstract
Promoter is one of the key elements in regulating gene expression. Many natural or synthetic promoters have been modulated by their cis- or tans-regulatory elements to confer instant gene expression change in responding to designated stimuli. In addition, bacterial cells also engage different sigma factors to control the gene expression network at different growth phases or in response to the changing environment and external stresses. In this study, a set of promoters that assimilate the endogenous regulation of different sigma factors σ70 , σ38 , σ32 , and σ24 are synthesized. Promoters are designed to contain two or more kinds of interlocking sigma factor binding sites. The most competitive sigma factors will be automatically selected by the cell to take over the synthetic promoters during the cell growth course. Some of the synthetic promoters exhibit very strong strengths under different conditions, including stationary phase, low temperature, acidic pH, and high osmotic pressure. Comparing to the T7 promoter, synthetic promoter P21285 achieved higher yields of L-asparaginase and acid urease in Escherichia coli. The research not only expands the synthetic biology toolbox but also provide another strategy to design and construct synthetic promoters in prokaryotes.
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Affiliation(s)
- Yang Wang
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, China.,The Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi, 214122, China
| | - Qingtao Liu
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, China.,The Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi, 214122, China
| | - Huanjiao Weng
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, China.,The Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi, 214122, China
| | - Yanan Shi
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, China.,The Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi, 214122, China
| | - Jian Chen
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, China.,The Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi, 214122, China
| | - Guocheng Du
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, China.,The Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi, 214122, China
| | - Zhen Kang
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, China.,The Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi, 214122, China
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26
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Dong ZQ, Hu ZG, Li HQ, Jiang YM, Cao MY, Chen P, Lu C, Pan MH. Construction and characterization of a synthetic Baculovirus-inducible 39K promoter. J Biol Eng 2018; 12:30. [PMID: 30534200 PMCID: PMC6280533 DOI: 10.1186/s13036-018-0121-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 11/19/2018] [Indexed: 01/27/2023] Open
Abstract
Background Silkworm genetic engineering is widely used in gene function, silk engineering and disease-resistant engineering in most of Asia. Some of the earliest promoter elements are used to control the development of silkworm transgenic expression and gene therapy. However, the low expression and specificity of natural promoters limit the applications of genetic engineering. To construct a highly efficient synthetic inducible promoter in the Bombyx mori (Lepidoptera), we analyzed the regulatory elements and functional regions of the B. mori nucleopolyhedrovirus 39 K promoter. Results Truncated mutation analysis of the 39 K promoter showed that the transcriptional regulatory region spanning positions - 573 to - 274 and + 1 to + 62 are essential for virus-inducible promoter activity. Further investigations using the electrophoretic mobility shift assay revealed that the baculovirus IE-1 protein binds to the 39 K promoter at the - 310 to - 355 region, and transcription activates the expression of 39 K promoter assay. Finally, we successfully constructed a synthetic inducible promoter that increased the virus-inducing activity of other promoters using the baculovirus-inducible transcriptional activation region that binds to specific core elements of 39 K (i.e., spanning the region - 310 to - 355). Conclusions In summary, we constructed a novel, synthetic, and highly efficient biological tool, namely, a virus-inducible 39 K promoter, which provides endless possibilities for future research on gene function, gene therapy, and pest control in genetic engineering.
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Affiliation(s)
- Zhan-Qi Dong
- 1State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716 China
| | - Zhi-Gang Hu
- 1State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716 China
| | - Hai-Qing Li
- 1State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716 China
| | - Ya-Ming Jiang
- 1State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716 China
| | - Ming-Ya Cao
- 3Joint National Laboratory for Antibody Drug Engineering, Institute of Immunology, Henan University School of Medicine, Kaifeng, 475004 China
| | - Peng Chen
- 1State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716 China
| | - Cheng Lu
- 1State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716 China.,2Key Laboratory for Sericulture Functional Genomics and Biotechnology of Agricultural Ministry, Southwest University, Chongqing, 400716 China
| | - Min-Hui Pan
- 1State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716 China.,2Key Laboratory for Sericulture Functional Genomics and Biotechnology of Agricultural Ministry, Southwest University, Chongqing, 400716 China
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27
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Brown AJ, Gibson SJ, Hatton D, Arnall CL, James DC. Whole synthetic pathway engineering of recombinant protein production. Biotechnol Bioeng 2018; 116:375-387. [DOI: 10.1002/bit.26855] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 09/14/2018] [Accepted: 10/18/2018] [Indexed: 12/13/2022]
Affiliation(s)
- Adam J. Brown
- Department of Chemical and Biological EngineeringUniversity of SheffieldSheffield UK
| | | | - Diane Hatton
- Biopharmaceutical Development, MedImmuneCambridge UK
| | - Claire L. Arnall
- Department of Chemical and Biological EngineeringUniversity of SheffieldSheffield UK
| | - David C. James
- Department of Chemical and Biological EngineeringUniversity of SheffieldSheffield UK
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An Iterative, Synthetic Approach To Engineer a High-Performance PhoB-Specific Reporter. Appl Environ Microbiol 2018; 84:AEM.00603-18. [PMID: 29752265 DOI: 10.1128/aem.00603-18] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 05/03/2018] [Indexed: 11/20/2022] Open
Abstract
Transcriptional reporters are common tools for analyzing either the transcription of a gene of interest or the activity of a specific transcriptional regulator. Unfortunately, the latter application has the shortcoming that native promoters did not evolve as optimal readouts for the activity of a particular regulator. We sought to synthesize an optimized transcriptional reporter for assessing PhoB activity, aiming for maximal "on" expression when PhoB is active, minimal background in the "off" state, and no control elements for other regulators. We designed specific sequences for promoter elements with appropriately spaced PhoB-binding sites, and at 19 additional intervening nucleotide positions for which we did not predict sequence-specific effects, the bases were randomized. Eighty-three such constructs were screened in Vibrio fischeri, enabling us to identify bases at particular randomized positions that significantly correlated with high-level "on" or low-level "off" expression. A second round of promoter design rationally constrained 13 additional positions, leading to a reporter with high-level PhoB-dependent expression, essentially no background, and no other known regulatory elements. As expressed reporters, we used both stable and destabilized variants of green fluorescent protein (GFP), the latter of which has a half-life of 81 min in V. fischeri In culture, PhoB induced the reporter when phosphate was depleted to a concentration below 10 μM. During symbiotic colonization of its host squid, Euprymna scolopes, the reporter indicated heterogeneous phosphate availability in different light-organ microenvironments. Finally, testing this construct in other members of the Proteobacteria demonstrated its broader utility. The results illustrate how a limited ability to predict synthetic promoter-reporter performance can be overcome through iterative screening and reengineering.IMPORTANCE Transcriptional reporters can be powerful tools for assessing when a particular regulator is active; however, native promoters may not be ideal for this purpose. Optimal reporters should be specific to the regulator being examined and should maximize the difference between the "on" and "off" states; however, these properties are distinct from the selective pressures driving the evolution of natural promoters. Synthetic promoters offer a promising alternative, but our understanding often does not enable fully predictive promoter design, and the large number of alternative sequence possibilities can be intractable. In a synthetic promoter region with over 34 billion sequence variants, we identified bases correlated with favorable performance by screening only 83 candidates, allowing us to rationally constrain our design. We thereby generated an optimized reporter that is induced by PhoB and used it to explore the low-phosphate response of V. fischeri This promoter design strategy will facilitate the engineering of other regulator-specific reporters.
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29
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Fang Y, Zhu C, Chen X, Wang Y, Xu M, Sun G, Guo J, Yoo J, Tie C, Jiang X, Li X. Copy number of ArsR reporter plasmid determines its arsenite response and metal specificity. Appl Microbiol Biotechnol 2018; 102:5753-5761. [PMID: 29766244 DOI: 10.1007/s00253-018-9042-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Revised: 04/19/2018] [Accepted: 04/19/2018] [Indexed: 10/16/2022]
Abstract
The key component in bacteria-based biosensors is a transcriptional reporter employed to monitor induction or repression of a reporter gene corresponding to environmental change. In this study, we made a series of reporters in order to achieve highly sensitive detection of arsenite. From these reporters, two biosensors were developed by transformation of Escherichia coli DH5α with pLHPars9 and pLLPars9, consisting of either a high or low copy number plasmid, along with common elements of ArsR-luciferase fusion and addition of two binding sequences, one each from E. coli and Acidithiobacillus ferrooxidans chromosome, in front of the R773 ArsR operon. Both of them were highly sensitive to arsenite, with a low detection limit of 0.04 μM arsenite (~ 5 μg/L). They showed a wide dynamic range of detection up to 50 μM using high copy number pLHPars9 and 100 μM using low copy number pLLPars9. Significantly, they differ in metal specificity, pLLPars9 more specific to arsenite, while pLHPars9 to both arsenite and antimonite. The only difference between pLHPars9 and pLLPars9 is their copy numbers of plasmid and corresponding ratios of ArsR to its binding promoter/operator sequence. Therefore, we propose a working model in which DNA bound-ArsR is different from its free form in metal specificity.
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Affiliation(s)
- Yun Fang
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Institute of Microbiology, 100 Central Xianlie Road, Guangzhou, 510070, Guangdong, China.,State Key Laboratory of Applied Microbiology Southern China, Guangzhou, China
| | - Chunjie Zhu
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Institute of Microbiology, 100 Central Xianlie Road, Guangzhou, 510070, Guangdong, China.,State Key Laboratory of Applied Microbiology Southern China, Guangzhou, China
| | - Xingjuan Chen
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Institute of Microbiology, 100 Central Xianlie Road, Guangzhou, 510070, Guangdong, China.,State Key Laboratory of Applied Microbiology Southern China, Guangzhou, China
| | - Yan Wang
- Science and Technology Library of Guangdong Province, Guangdong Institute of Science and Technology Information and Development Strategy, Guangzhou, China
| | - Meiying Xu
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Institute of Microbiology, 100 Central Xianlie Road, Guangzhou, 510070, Guangdong, China. .,State Key Laboratory of Applied Microbiology Southern China, Guangzhou, China.
| | - Guoping Sun
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Institute of Microbiology, 100 Central Xianlie Road, Guangzhou, 510070, Guangdong, China.,State Key Laboratory of Applied Microbiology Southern China, Guangzhou, China
| | - Jun Guo
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Institute of Microbiology, 100 Central Xianlie Road, Guangzhou, 510070, Guangdong, China.,State Key Laboratory of Applied Microbiology Southern China, Guangzhou, China
| | - Jinnon Yoo
- Signosis Inc., 1700 Wyatt Drive, suite10-12, Santa Clara, CA, USA
| | - Cuijuan Tie
- Signosis Inc., 1700 Wyatt Drive, suite10-12, Santa Clara, CA, USA
| | - Xin Jiang
- Signosis Inc., 1700 Wyatt Drive, suite10-12, Santa Clara, CA, USA
| | - Xianqiang Li
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangdong Institute of Microbiology, 100 Central Xianlie Road, Guangzhou, 510070, Guangdong, China. .,State Key Laboratory of Applied Microbiology Southern China, Guangzhou, China. .,Signosis Inc., 1700 Wyatt Drive, suite10-12, Santa Clara, CA, USA.
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30
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Hwang HJ, Lee SY, Lee PC. Engineering and application of synthetic nar promoter for fine-tuning the expression of metabolic pathway genes in Escherichia coli. BIOTECHNOLOGY FOR BIOFUELS 2018; 11:103. [PMID: 29636821 PMCID: PMC5889552 DOI: 10.1186/s13068-018-1104-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 04/02/2018] [Indexed: 05/23/2023]
Abstract
BACKGROUND Promoters regulate the expression of metabolic pathway genes to control the flux of metabolism. Therefore, fine-tuning of metabolic pathway gene expression requires an applicable promoter system. In this study, a dissolved oxygen-dependent nar promoter was engineered for fine-tuning the expression levels of biosynthetic pathway enzymes in Escherichia coli. To demonstrate the feasibility of using the synthetic nar promoters in production of biochemicals in E. coli, the d-lactate pathway consisting of one enzyme and the 2,3-butanediol (BDO) pathway consisting of three enzymes were investigated. RESULTS The spacer sequence of 15 bp between the - 35 and - 10 elements of the upstream region of the wild-type nar promoter was randomized, fused to the GFP gene, transduced into E. coli, and screened by flow cytometry. The sorted synthetic nar promoters were divided into three groups according to fluorescence intensity levels: strong, intermediate, and weak. The selected three representative nar promoters of strong, intermediate, and weak intensities were used to control the expression level of the d-lactate and 2,3-BDO biosynthetic pathway enzymes in E. coli. When the ldhD gene encoding d-lactate dehydrogenase was expressed under the control of the strong synthetic nar promoter in fed-batch cultures of E. coli, the d-lactate titers were 105.6 g/L, 34% higher than those using the wild-type promoter (79.0 g/L). When the three 2,3-BDO pathway genes (ilvBN, aldB, and bdh1) were expressed under the control of combinational synthetic nar promoters (strong-weak-strong) in fed-batch cultures of E. coli, the titers of 2,3-BDO were 88.0 g/L, 72% higher than those using the wild-type promoter (51.1 g/L). CONCLUSIONS The synthetic nar promoters, which were engineered to have strong, intermediate, and weak intensities, were successfully applied to metabolic engineering of d-lactate and 2,3-BDO pathways in E. coli. By controlling expression levels of d-lactate and 2,3-BDO pathway enzymes using the synthetic nar promoters, the production of d-lactate and 2,3-BDO was increased over that using the wild-type promoter by 34 and 72%, respectively. Thus, this synthetic promoter module system will support the improved production of biochemicals and biofuels through fine-tuning of gene expression levels.
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Affiliation(s)
- Hee Jin Hwang
- Department of Molecular Science and Technology, Ajou University, Woncheon-dong, Yeongtong-gu, Suwon, 16944 South Korea
| | - Sang Yup Lee
- Department of Chemical and Biomolecular Engineering, KAIST, Daejeon, 34141 South Korea
| | - Pyung Cheon Lee
- Department of Molecular Science and Technology, Ajou University, Woncheon-dong, Yeongtong-gu, Suwon, 16944 South Korea
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31
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Małachowska A, Olszewski P. TECS: a toxin expression control strategy as a tool for optimization of inducible promoters. Microb Cell Fact 2018. [PMID: 29534758 PMCID: PMC5851080 DOI: 10.1186/s12934-018-0891-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Background Transcriptional control of gene expression is a widely utilized regulatory mechanism in synthetic biology, biotechnology and recombinant protein production. It is achieved by utilization of naturally occurring promoters responding to nutrients or chemicals. Despite their regulatory properties, these promoters often possess features which diminish their utility for biotechnology. High basal expression level and low induction ratio can be removed using genetic engineering techniques, although this process is often laborious and time-consuming. Results In order to facilitate optimization process for inducible promoters, we developed a simple method based on a conditional toxin expression which we abbreviate as toxin expression control strategy (TECS). In the presence of sucrose, SacB enzyme from Bacillus subtilis synthesizes levans which cause Eschericha coli cell lysis. However, in the absence of sucrose the enzyme does not affect the growth of the host. We utilized this feature to develop a two-step protocol allowing for efficient selection of inducible promoter variants. Using TECS we were able to modify the well-described pBAD promoter to decrease its leakage while maintaining high activity upon induction. Furthermore, we used the method to test transcriptional interference of lambda phage-derived sequence and optimize it for higher induction levels through random mutagenesis. Conclusions We show that TECS is an efficient tool for optimization and development of inducible promoter systems in E. coli. Our strategy is very effective in the selection of promoter variants with improved properties. Its simplicity and short hands-on time make it an attractive method to optimize existing promoters and to construct novel, engineered genetic elements which improve properties of an inducible promoter system. Electronic supplementary material The online version of this article (10.1186/s12934-018-0891-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Aleksandra Małachowska
- Department of Genetics and Biosystematics, University of Gdańsk, ul. Wita Stwosza 59, 80-308, Gdańsk, Poland
| | - Paweł Olszewski
- Department of Genetics and Biosystematics, University of Gdańsk, ul. Wita Stwosza 59, 80-308, Gdańsk, Poland.
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32
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DeLorenzo DM, Rottinghaus AG, Henson WR, Moon TS. Molecular Toolkit for Gene Expression Control and Genome Modification in Rhodococcus opacus PD630. ACS Synth Biol 2018; 7:727-738. [PMID: 29366319 DOI: 10.1021/acssynbio.7b00416] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Rhodococcus opacus PD630 is a non-model Gram-positive bacterium that possesses desirable traits for lignocellulosic biomass conversion. In particular, it has a relatively rapid growth rate, exhibits genetic tractability, produces high quantities of lipids, and can tolerate and consume toxic lignin-derived aromatic compounds. Despite these unique, industrially relevant characteristics, R. opacus has been underutilized because of a lack of reliable genetic parts and engineering tools. In this work, we developed a molecular toolbox for reliable gene expression control and genome modification in R. opacus. To facilitate predictable gene expression, a constitutive promoter library spanning ∼45-fold in output was constructed. To improve the characterization of available plasmids, the copy numbers of four heterologous and nine endogenous plasmids were determined using quantitative PCR. The molecular toolbox was further expanded by screening a previously unreported antibiotic resistance marker (HygR) and constructing a curable plasmid backbone for temporary gene expression (pB264). Furthermore, a system for genome modification was devised, and three neutral integration sites were identified using a novel combination of transcriptomic data, genomic architecture, and growth rate analysis. Finally, the first reported system for targeted, tunable gene repression in Rhodococcus was developed by utilizing CRISPR interference (CRISPRi). Overall, this work greatly expands the ability to manipulate and engineer R. opacus, making it a viable new chassis for bioproduction from renewable feedstocks.
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Affiliation(s)
- Drew M. DeLorenzo
- Department of Energy, Environmental
and Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Austin G. Rottinghaus
- Department of Energy, Environmental
and Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - William R. Henson
- Department of Energy, Environmental
and Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
| | - Tae Seok Moon
- Department of Energy, Environmental
and Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
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33
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Mordaka PM, Heap JT. Stringency of Synthetic Promoter Sequences in Clostridium Revealed and Circumvented by Tuning Promoter Library Mutation Rates. ACS Synth Biol 2018; 7:672-681. [PMID: 29320851 DOI: 10.1021/acssynbio.7b00398] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Collections of characterized promoters of different strengths are key resources for synthetic biology, but are not well established for many important organisms, including industrially relevant Clostridium spp. When generating promoters, reporter constructs are used to measure expression, but classical fluorescent reporter proteins are oxygen-dependent and hence inactive in anaerobic bacteria like Clostridium. We directly compared oxygen-independent reporters of different types in Clostridium acetobutylicum and found that glucuronidase (GusA) from E. coli performed best. Using GusA, a library of synthetic promoters was first generated by a typical approach entailing complete randomization of a constitutive thiolase gene promoter (Pthl) except for the consensus -35 and -10 elements. In each synthetic promoter, the chance of each degenerate position matching Pthl was 25%. Surprisingly, none of the tested synthetic promoters from this library were functional in C. acetobutylicum, even though they functioned as expected in E. coli. Next, instead of complete randomization, we specified lower promoter mutation rates using oligonucleotide primers synthesized using custom mixtures of nucleotides. Using these primers, two promoter libraries were constructed in which the chance of each degenerate position matching Pthl was 79% or 58%, instead of 25% as before. Synthetic promoters from these "stringent" libraries functioned well in C. acetobutylicum, covering a wide range of strengths. The promoters functioned similarly in the distantly related species Clostridium sporogenes, and allowed predictable metabolic engineering of C. acetobutylicum for acetoin production. Besides generating the desired promoters and demonstrating their useful properties, this work indicates an unexpected "stringency" of promoter sequences in Clostridium, not reported previously.
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Affiliation(s)
- Paweł M. Mordaka
- Imperial College Centre for
Synthetic Biology, Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - John T. Heap
- Imperial College Centre for
Synthetic Biology, Department of Life Sciences, Imperial College London, London SW7 2AZ, United Kingdom
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34
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Kotopka BJ, Li Y, Smolke CD. Synthetic biology strategies toward heterologous phytochemical production. Nat Prod Rep 2018; 35:902-920. [DOI: 10.1039/c8np00028j] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
This review summarizes the recent progress in heterologous phytochemical biosynthetic pathway reconstitution in plant, bacteria, and yeast, with a focus on the synthetic biology strategies applied in these engineering efforts.
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Affiliation(s)
| | - Yanran Li
- Department of Chemical and Environmental Engineering
- Riverside
- USA
| | - Christina D. Smolke
- Department of Bioengineering
- Stanford University
- Stanford
- USA
- Chan Zuckerberg Biohub
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35
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Tekel SJ, Haynes KA. Molecular structures guide the engineering of chromatin. Nucleic Acids Res 2017; 45:7555-7570. [PMID: 28609787 PMCID: PMC5570049 DOI: 10.1093/nar/gkx531] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Accepted: 06/07/2017] [Indexed: 12/28/2022] Open
Abstract
Chromatin is a system of proteins, RNA, and DNA that interact with each other to organize and regulate genetic information within eukaryotic nuclei. Chromatin proteins carry out essential functions: packing DNA during cell division, partitioning DNA into sub-regions within the nucleus, and controlling levels of gene expression. There is a growing interest in manipulating chromatin dynamics for applications in medicine and agriculture. Progress in this area requires the identification of design rules for the chromatin system. Here, we focus on the relationship between the physical structure and function of chromatin proteins. We discuss key research that has elucidated the intrinsic properties of chromatin proteins and how this information informs design rules for synthetic systems. Recent work demonstrates that chromatin-derived peptide motifs are portable and in some cases can be customized to alter their function. Finally, we present a workflow for fusion protein design and discuss best practices for engineering chromatin to assist scientists in advancing the field of synthetic epigenetics.
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Affiliation(s)
- Stefan J Tekel
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ 85287, USA
| | - Karmella A Haynes
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ 85287, USA
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Han L, Suo F, Jiang C, Gu J, Li N, Zhang N, Cui W, Zhou Z. Fabrication and characterization of a robust and strong bacterial promoter from a semi-rationally engineered promoter library in Bacillus subtilis. Process Biochem 2017. [DOI: 10.1016/j.procbio.2017.06.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Decoene T, De Paepe B, Maertens J, Coussement P, Peters G, De Maeseneire SL, De Mey M. Standardization in synthetic biology: an engineering discipline coming of age. Crit Rev Biotechnol 2017; 38:647-656. [PMID: 28954542 DOI: 10.1080/07388551.2017.1380600] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
BACKGROUND Leaping DNA read-and-write technologies, and extensive automation and miniaturization are radically transforming the field of biological experimentation by providing the tools that enable the cost-effective high-throughput required to address the enormous complexity of biological systems. However, standardization of the synthetic biology workflow has not kept abreast with dwindling technical and resource constraints, leading, for example, to the collection of multi-level and multi-omics large data sets that end up disconnected or remain under- or even unexploited. PURPOSE In this contribution, we critically evaluate the various efforts, and the (limited) success thereof, in order to introduce standards for defining, designing, assembling, characterizing, and sharing synthetic biology parts. The causes for this success or the lack thereof, as well as possible solutions to overcome these, are discussed. CONCLUSION Akin to other engineering disciplines, extensive standardization will undoubtedly speed-up and reduce the cost of bioprocess development. In this respect, further implementation of synthetic biology standards will be crucial for the field in order to redeem its promise, i.e. to enable predictable forward engineering.
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Affiliation(s)
- Thomas Decoene
- a Centre for Synthetic Biology, Ghent University , Ghent , Belgium
| | - Brecht De Paepe
- a Centre for Synthetic Biology, Ghent University , Ghent , Belgium
| | - Jo Maertens
- a Centre for Synthetic Biology, Ghent University , Ghent , Belgium
| | | | - Gert Peters
- a Centre for Synthetic Biology, Ghent University , Ghent , Belgium
| | - Sofie L De Maeseneire
- b InBio.be, Centre for Industrial Biotechnology and Biocatalysis, Ghent University , Ghent , Belgium
| | - Marjan De Mey
- a Centre for Synthetic Biology, Ghent University , Ghent , Belgium
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Jensen TØ, Pogrebnyakov I, Falkenberg KB, Redl S, Nielsen AT. Application of the thermostable β-galactosidase, BgaB, from Geobacillus stearothermophilus as a versatile reporter under anaerobic and aerobic conditions. AMB Express 2017; 7:169. [PMID: 28875485 PMCID: PMC5585113 DOI: 10.1186/s13568-017-0469-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Accepted: 08/29/2017] [Indexed: 11/10/2022] Open
Abstract
Use of thermophilic organisms has a range of advantages, but the significant lack of engineering tools limits their applications. Here we show that β-galactosidase from Geobacillus stearothermophilus (BgaB) can be applicable in a range of conditions, including different temperatures and oxygen concentrations. This protein functions both as a marker, promoting colony color development in the presence of a lactose analogue S-gal, and as a reporter enabling quantitative measurement by a simple colorimetric assay. Optimal performance was observed at 70 °C and pH 6.4. The gene was introduced into G. thermoglucosidans. The combination of BgaB expressed from promoters of varying strength with S-gal produced distinct black colonies in aerobic and anaerobic conditions at temperatures ranging from 37 to 60 °C. It showed an important advantage over the conventional β-galactosidase (LacZ) and substrate X-gal, which were inactive at high temperature and under anaerobic conditions. To demonstrate the versatility of the reporter, a promoter library was constructed by randomizing sequences around −35 and −10 regions in a wild type groES promoter from Geobacillus sp. GHH01. The library contained 28 promoter variants and encompassed fivefold variation. The experimental pipeline allowed construction and measurement of expression levels of the library in just 4 days. This β-galactosidase provides a promising tool for engineering of aerobic, anaerobic, and thermophilic production organisms such as Geobacillus species.
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Synthetic metabolic bypass for a metabolic toggle switch enhances acetyl-CoA supply for isopropanol production by Escherichia coli. J Biosci Bioeng 2017; 123:625-633. [PMID: 28214243 DOI: 10.1016/j.jbiosc.2016.12.009] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Accepted: 12/15/2016] [Indexed: 01/04/2023]
Abstract
Almost all synthetic pathways for biofuel production are designed to require endogenous metabolites in glycolysis, such as phosphoenolpyruvate, pyruvate, and acetyl-CoA. However, such metabolites are also required for bacterial cell growth. To reduce the metabolic imbalance between cell growth and target chemical production, we previously constructed a metabolic toggle switch (MTS) as a conditional flux redirection tool controlling metabolic flux of TCA cycle toward isopropanol production. This approach succeeded to improve the isopropanol production titer and yield while ensuring sufficient cell growth. However, excess accumulation of pyruvate, the precursor for acetyl-CoA synthesis, was also observed. In this study, for efficient conversation of pyruvate to acetyl-CoA (pyruvate oxidation), we designed a synthetic metabolic bypass composed of poxB and acs with the MTS for acetyl-CoA supply from the excess pyruvate. When this designed bypass was expressed at the appropriate expression level associated with the conditional metabolic flux redirection, pyruvate accumulation was prevented, and the isopropanol production titer and yield were improved. Final isopropanol production titer of strain harboring MTS with the synthetic metabolic bypass improved 4.4-fold compared with strain without metabolic flux regulation, and it was 1.3-fold higher than that of strain harboring the conventional MTS alone. Additionally, glucose consumption was also improved 1.7-fold compared with strain without metabolic flux regulation. On the other hand, introduction of the synthetic metabolic bypass alone showed no improvement in isopropanol production and glucose consumption. These results showed that the improvement in bio-production process caused by synergy between the MTS and the synthetic metabolic bypass.
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