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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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Chen Y, Li J, Zhang S, Hu J, Chen X, Lin T, Dang D, Fan J. Controlling expression and inhibiting function of the toxin reporter for simple detection of the promoters’ activities in Escherichia coli. Enzyme Microb Technol 2022; 158:110051. [DOI: 10.1016/j.enzmictec.2022.110051] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Revised: 04/10/2022] [Accepted: 04/11/2022] [Indexed: 01/09/2023]
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3
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Ratner HK, Weiss DS. crRNA complementarity shifts endogenous CRISPR-Cas systems between transcriptional repression and DNA defense. RNA Biol 2021; 18:1560-1573. [PMID: 33733999 PMCID: PMC8583161 DOI: 10.1080/15476286.2021.1878335] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 01/10/2021] [Accepted: 01/13/2021] [Indexed: 12/26/2022] Open
Abstract
CRISPR-Cas systems are prokaryotic adaptive immune systems that recognize and cleave nucleic acid targets using small RNAs called CRISPR RNAs (crRNAs) to guide Cas protein(s). There is increasing evidence for the broader endogenous roles of these systems. The CRISPR-Cas9 system of Francisella novicida also represses endogenous transcription using a non-canonical small RNA (scaRNA). We examined whether the crRNAs of the native F. novicida CRISPR-Cas systems, Cas12a and Cas9, can guide transcriptional repression. Both systems repressed mRNA transcript levels when crRNA-target complementarity was limited, and led to target cleavage with extended complementarity. Using these parameters we engineered the CRISPR array of Cas12a to guide the transcriptional repression of a new and endogenous target. Since the majority of crRNA targets remain unidentified, this work suggests that a re-analysis of crRNAs for endogenous targets with limited complementarity could reveal new, diverse regulatory roles for CRISPR-Cas systems in prokaryotic biology.
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Affiliation(s)
- Hannah K. Ratner
- Microbiology and Molecular Genetics Program, Emory University, Atlanta, GA, USA
- Emory Vaccine Center, Emory University, Atlanta, GA, USA
- Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA
| | - David S. Weiss
- Emory Vaccine Center, Emory University, Atlanta, GA, USA
- Yerkes National Primate Research Center, Emory University, Atlanta, GA, USA
- Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA, USA
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4
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Bertram R, Neumann B, Schuster CF. Status quo of tet regulation in bacteria. Microb Biotechnol 2021; 15:1101-1119. [PMID: 34713957 PMCID: PMC8966031 DOI: 10.1111/1751-7915.13926] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 09/02/2021] [Accepted: 09/04/2021] [Indexed: 11/27/2022] Open
Abstract
The tetracycline repressor (TetR) belongs to the most popular, versatile and efficient transcriptional regulators used in bacterial genetics. In the tetracycline (Tc) resistance determinant tet(B) of transposon Tn10, tetR regulates the expression of a divergently oriented tetA gene that encodes a Tc antiporter. These components of Tn10 and of other natural or synthetic origins have been used for tetracycline‐dependent gene regulation (tet regulation) in at least 40 bacterial genera. Tet regulation serves several purposes such as conditional complementation, depletion of essential genes, modulation of artificial genetic networks, protein overexpression or the control of gene expression within cell culture or animal infection models. Adaptations of the promoters employed have increased tet regulation efficiency and have made this system accessible to taxonomically distant bacteria. Variations of TetR, different effector molecules and mutated DNA binding sites have enabled new modes of gene expression control. This article provides a current overview of tet regulation in bacteria.
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Affiliation(s)
- Ralph Bertram
- Institute of Clinical Hygiene, Medical Microbiology and Infectiology, Paracelsus Medical University, Prof.-Ernst-Nathan-Straße 1, Nuremberg, 90419, Germany
| | - Bernd Neumann
- Institute of Clinical Hygiene, Medical Microbiology and Infectiology, Paracelsus Medical University, Prof.-Ernst-Nathan-Straße 1, Nuremberg, 90419, Germany
| | - Christopher F Schuster
- Department of Infectious Diseases, Division of Nosocomial Pathogens and Antibiotic Resistances, Robert Koch Institute, Burgstraße 37, Wernigerode, 38855, Germany
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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: 3] [Impact Index Per Article: 1.0] [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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Kassinger SJ, van Hoek ML. Genetic Determinants of Antibiotic Resistance in Francisella. Front Microbiol 2021; 12:644855. [PMID: 34054749 PMCID: PMC8149597 DOI: 10.3389/fmicb.2021.644855] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 03/25/2021] [Indexed: 12/21/2022] Open
Abstract
Tularemia, caused by Francisella tularensis, is endemic to the northern hemisphere. This zoonotic organism has historically been developed into a biological weapon. For this Tier 1, Category A select agent, it is important to expand our understanding of its mechanisms of antibiotic resistance (AMR). Francisella is unlike many Gram-negative organisms in that it does not have significant plasmid mobility, and does not express AMR mechanisms on plasmids; thus plasmid-mediated resistance does not occur naturally. It is possible to artificially introduce plasmids with AMR markers for cloning and gene expression purposes. In this review, we survey both the experimental research on AMR in Francisella and bioinformatic databases which contain genomic and proteomic data. We explore both the genetic determinants of intrinsic AMR and naturally acquired or engineered antimicrobial resistance as well as phenotypic resistance in Francisella. Herein we survey resistance to beta-lactams, monobactams, carbapenems, aminoglycosides, tetracycline, polymyxins, macrolides, rifampin, fosmidomycin, and fluoroquinolones. We also highlight research about the phenotypic AMR difference between planktonic and biofilm Francisella. We discuss newly developed methods of testing antibiotics against Francisella which involve the intracellular nature of Francisella infection and may better reflect the eventual clinical outcomes for new antibiotic compounds. Understanding the genetically encoded determinants of AMR in Francisella is key to optimizing the treatment of patients and potentially developing new antimicrobials for this dangerous intracellular pathogen.
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Affiliation(s)
| | - Monique L. van Hoek
- School of Systems Biology, George Mason University, Manassas, VA, United States
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Bhattarai K, Bastola R, Baral B. Antibiotic drug discovery: Challenges and perspectives in the light of emerging antibiotic resistance. ADVANCES IN GENETICS 2020; 105:229-292. [PMID: 32560788 DOI: 10.1016/bs.adgen.2019.12.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Amid a rising threat of antimicrobial resistance in a global scenario, our huge investments and high-throughput technologies injected for rejuvenating the key therapeutic scaffolds to suppress these rising superbugs has been diminishing severely. This has grasped world-wide attention, with increased consideration being given to the discovery of new chemical entities. Research has now proven that the relatively tiny and simpler microbes possess enhanced capability of generating novel and diverse chemical constituents with huge therapeutic leads. The usage of these beneficial organisms could help in producing new chemical scaffolds that govern the power to suppress the spread of obnoxious superbugs. Here in this review, we have explicitly focused on several appealing strategies employed for the generation of new chemical scaffolds. Also, efforts on providing novel insights on some of the unresolved questions in the production of metabolites, metabolic profiling and also the serendipity of getting "hit molecules" have been rigorously discussed. However, we are highly aware that biosynthetic pathway of different classes of secondary metabolites and their biosynthetic route is a vast topic, thus we have avoided discussion on this topic.
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Affiliation(s)
- Keshab Bhattarai
- University of Tübingen, Tübingen, Germany; Center for Natural and Applied Sciences (CENAS), Kathmandu, Nepal
| | - Rina Bastola
- Spinal Cord Injury Association-Nepal (SCIAN), Pokhara, Nepal
| | - Bikash Baral
- Spinal Cord Injury Association-Nepal (SCIAN), Pokhara, Nepal.
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Ratner HK, Escalera-Maurer A, Le Rhun A, Jaggavarapu S, Wozniak JE, Crispell EK, Charpentier E, Weiss DS. Catalytically Active Cas9 Mediates Transcriptional Interference to Facilitate Bacterial Virulence. Mol Cell 2019; 75:498-510.e5. [PMID: 31256988 DOI: 10.1016/j.molcel.2019.05.029] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 01/14/2019] [Accepted: 05/21/2019] [Indexed: 12/26/2022]
Abstract
In addition to defense against foreign DNA, the CRISPR-Cas9 system of Francisella novicida represses expression of an endogenous immunostimulatory lipoprotein. We investigated the specificity and molecular mechanism of this regulation, demonstrating that Cas9 controls a highly specific regulon of four genes that must be repressed for bacterial virulence. Regulation occurs through a protospacer adjacent motif (PAM)-dependent interaction of Cas9 with its endogenous DNA targets, dependent on a non-canonical small RNA (scaRNA) and tracrRNA. The limited complementarity between scaRNA and the endogenous DNA targets precludes cleavage, highlighting the evolution of scaRNA to repress transcription without lethally targeting the chromosome. We show that scaRNA can be reprogrammed to repress other genes, and with engineered, extended complementarity to an exogenous target, the repurposed scaRNA:tracrRNA-FnoCas9 machinery can also direct DNA cleavage. Natural Cas9 transcriptional interference likely represents a broad paradigm of regulatory functionality, which is potentially critical to the physiology of numerous Cas9-encoding pathogenic and commensal organisms.
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Affiliation(s)
- Hannah K Ratner
- Microbiology and Molecular Genetics Program, Emory University, Atlanta, GA 30329, USA; Emory Vaccine Center, Emory University, Atlanta, GA 30329, USA; Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA
| | - Andrés Escalera-Maurer
- Max Planck Unit for the Science of Pathogens, 10117 Berlin, Germany; Helmholtz Centre for Infection Research, Department of Regulation in Infection Biology, 38124 Braunschweig, Germany; Institute for Biology, Humboldt University, 10115 Berlin, Germany
| | - Anaïs Le Rhun
- Max Planck Unit for the Science of Pathogens, 10117 Berlin, Germany; Helmholtz Centre for Infection Research, Department of Regulation in Infection Biology, 38124 Braunschweig, Germany
| | - Siddharth Jaggavarapu
- Emory Vaccine Center, Emory University, Atlanta, GA 30329, USA; Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA; Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30329, USA
| | - Jessie E Wozniak
- Microbiology and Molecular Genetics Program, Emory University, Atlanta, GA 30329, USA; Emory Vaccine Center, Emory University, Atlanta, GA 30329, USA; Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA
| | - Emily K Crispell
- Microbiology and Molecular Genetics Program, Emory University, Atlanta, GA 30329, USA; Emory Vaccine Center, Emory University, Atlanta, GA 30329, USA; Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA
| | - Emmanuelle Charpentier
- Max Planck Unit for the Science of Pathogens, 10117 Berlin, Germany; Helmholtz Centre for Infection Research, Department of Regulation in Infection Biology, 38124 Braunschweig, Germany; Institute for Biology, Humboldt University, 10115 Berlin, Germany
| | - David S Weiss
- Microbiology and Molecular Genetics Program, Emory University, Atlanta, GA 30329, USA; Emory Vaccine Center, Emory University, Atlanta, GA 30329, USA; Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA; Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30329, USA.
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9
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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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10
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Wegelius A, Li X, Turco F, Stensjö K. Design and characterization of a synthetic minimal promoter for heterocyst-specific expression in filamentous cyanobacteria. PLoS One 2018; 13:e0203898. [PMID: 30204806 PMCID: PMC6133370 DOI: 10.1371/journal.pone.0203898] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Accepted: 08/29/2018] [Indexed: 11/25/2022] Open
Abstract
Short and well defined promoters are essential for advancing cyanobacterial biotechnology. The heterocyst of Nostoc sp. is suggested as a microbial cell factory for oxygen sensitive catalysts, such as hydrogenases for hydrogen production, due to its microoxic environment. We identified and predicted promoter elements of possible significance through a consensus strategy using a pool of heterocyst-induced DIF+ promoters known from Anabaena sp. PCC 7120. To test if these conserved promoter elements were crucial for heterocyst-specific expression, promoter-yfp reporter constructs were designed. The characterization was accomplished by replacing, -35 and -10 regions and the upstream element, with well described elements from the trc promoter of Escherichia coli, which is also functional in Nostoc sp. From the in vivo spatial fluorescence of the different promoter-yfp reporters in Nostoc punctiforme ATCC 29133, we concluded that both the consensus -35 and extended -10 regions were important for heterocyst-specific expression. Further that the promoter strength could be improved by the addition of an upstream element. We designed a short synthetic promoter of 48 nucleotides, PsynDIF, including a consensus DIF1 sequence, a 17 base pair stretch of random nucleotides and an extended consensus -10 region, and thus generated the shortest promoter for heterocyst-specific expression to date.
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Affiliation(s)
- Adam Wegelius
- Department of Chemistry– Ångström Laboratory, Uppsala University, Uppsala, Sweden
| | - Xin Li
- Department of Chemistry– Ångström Laboratory, Uppsala University, Uppsala, Sweden
| | - Federico Turco
- Department of Chemistry– Ångström Laboratory, Uppsala University, Uppsala, Sweden
| | - Karin Stensjö
- Department of Chemistry– Ångström Laboratory, Uppsala University, Uppsala, Sweden
- * E-mail:
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11
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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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12
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Abstract
The judicious choice of promoter to drive gene expression remains one of the most important considerations for synthetic biology applications. Constitutive promoter sequences isolated from nature are often used in laboratory settings or small-scale commercial production streams, but unconventional microbial chassis for new synthetic biology applications require well-characterized, robust and orthogonal promoters. This review provides an overview of the opportunities and challenges for synthetic promoter discovery and design, including molecular methodologies, such as saturation mutagenesis of flanking regions and mutagenesis by error-prone PCR, as well as the less familiar use of computational and statistical analyses for de novo promoter design.
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13
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Pearce SC, McWhinnie RL, Nano FE. Synthetic temperature-inducible lethal gene circuits in Escherichia coli. MICROBIOLOGY-SGM 2017; 163:462-471. [PMID: 28430101 DOI: 10.1099/mic.0.000446] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Temperature sensitivity is often used as a way to attenuate micro-organisms to convert them into live vaccines. In this work, we explore the use of temperature-sensitive (TS) genetic circuits that express lethal genes as a widely applicable approach to TS attenuation. We tested different combinations of TS repressors and cognate promoters controlling the expression of genes encoding restriction endonucleases inserted at four different non-essential sites in the Escherichia coli chromosome. We found that the presence of the restriction endonuclease genes did not affect the viability of the host strains at the permissive temperature, but that expression of the genes at elevated temperatures killed the strains to varying extents. The chromosomal insertion site of the lethal cassettes affected their functionality, and insertion at one site, ycgH, rendered them ineffective at inducing death at high temperature. Induction of a TS circuit in a growing culture led to a reduced cell mass and a reduction of the number of cells that could exclude a dye that indicated viability. Incubation of cells carrying a TS lethal gene circuit initially grown at low temperature and then suspended in phosphate buffered saline at high temperature led to about 100-fold loss of cell viability per day, compared to a minimal loss of viability for the parental strain. Strains carrying either one or two TS lethal circuits could generate mutants that survived at high temperature. These mutants included complete deletions of the lethal gene circuits.
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Affiliation(s)
- Stephanie C Pearce
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC V8W 3P6, Canada
| | - Ralph L McWhinnie
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC V8W 3P6, Canada
| | - Francis E Nano
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC V8W 3P6, Canada
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14
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Zhou S, Du G, Kang Z, Li J, Chen J, Li H, Zhou J. The application of powerful promoters to enhance gene expression in industrial microorganisms. World J Microbiol Biotechnol 2017; 33:23. [DOI: 10.1007/s11274-016-2184-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Accepted: 11/24/2016] [Indexed: 01/01/2023]
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15
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Robinson CM, Kobe BN, Schmitt DM, Phair B, Gilson T, Jung JY, Roberts L, Liao J, Camerlengo C, Chang B, Davis M, Figurski L, Sindeldecker D, Horzempa J. Genetic engineering of Francisella tularensis LVS for use as a novel live vaccine platform against Pseudomonas aeruginosa infections. Bioengineered 2016; 6:82-8. [PMID: 25617059 PMCID: PMC4601302 DOI: 10.1080/21655979.2015.1011033] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Francisella tularensis LVS (Live Vaccine Strain) is an attenuated bacterium that has been used as a live vaccine. Patients immunized with this organism show a very long-term memory response (over 30 years post vaccination) evidenced by the presence of indicators of robust cell-mediated immunity. Because F. tularensis LVS is such a potent vaccine, we hypothesized that this organism would be an effective vaccine platform. First, we sought to determine if we could genetically modify this strain to produce protective antigens of a heterologous pathogen. Currently, there is not a licensed vaccine against the important opportunistic bacterial pathogen, Pseudomonas aeruginosa. Because many P. aeruginosa strains are also drug resistant, the need for effective vaccines is magnified. Here, F. tularensis LVS was genetically modified to express surface proteins PilAPa, OprFPa, and FliCPa of P. aeruginosa. Immunization of mice with LVS expressing the recombinant FliCPa led to a significant production of antibodies specific for P. aeruginosa. However, mice that had been immunized with LVS expressing PilAPa or OprFPa did not produce high levels of antibodies specific for P. aerugionsa. Therefore, the recombinant LVS strain engineered to produce FliCPa may be able to provide immune protection against a P. aeruginosa challenge. However for future use of this vaccine platform, selection of the appropriate recombinant antigen is critical as not all recombinant antigens expressed in this strain were immunogenic.
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Affiliation(s)
- Cory M Robinson
- a Biomedical Sciences Department ; West Virginia School of Osteopathic Medicine ; Lewisburg , WV USA
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Temperature Sensitivity Conferred by ligA Alleles from Psychrophilic Bacteria upon Substitution in Mesophilic Bacteria and a Yeast Species. Appl Environ Microbiol 2016; 82:1924-1932. [PMID: 26773080 DOI: 10.1128/aem.03890-15] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 01/08/2016] [Indexed: 11/20/2022] Open
Abstract
We have assembled a collection of 13 psychrophilic ligA alleles that can serve as genetic elements for engineering mesophiles to a temperature-sensitive (TS) phenotype. When these ligA alleles were substituted into Francisella novicida, they conferred a TS phenotype with restrictive temperatures between 33 and 39°C. When the F. novicida ligA hybrid strains were plated above their restrictive temperatures, eight of them generated temperature-resistant variants. For two alleles, the mutations that led to temperature resistance clustered near the 5' end of the gene, and the mutations increased the predicted strength of the ribosome binding site at least 3-fold. Four F. novicida ligA hybrid strains generated no temperature-resistant variants at a detectable level. These results suggest that multiple mutations are needed to create temperature-resistant variants of these ligA gene products. One ligA allele was isolated from a Colwellia species that has a maximal growth temperature of 12°C, and this allele supported growth of F. novicida only as a hybrid between the psychrophilic and the F. novicida ligA genes. However, the full psychrophilic gene alone supported the growth of Salmonella enterica, imparting a restrictive temperature of 27°C. We also tested two ligA alleles from two Pseudoalteromonas strains for their ability to support the viability of a Saccharomyces cerevisiae strain that lacked its essential gene, CDC9, encoding an ATP-dependent DNA ligase. In both cases, the psychrophilic bacterial alleles supported yeast viability and their expression generated TS phenotypes. This collection of ligA alleles should be useful in engineering bacteria, and possibly eukaryotic microbes, to predictable TS phenotypes.
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Sahoo DK, Sarkar S, Maiti IB, Dey N. Novel Synthetic Promoters from the Cestrum Yellow Leaf Curling Virus. Methods Mol Biol 2016; 1482:111-38. [PMID: 27557764 DOI: 10.1007/978-1-4939-6396-6_8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Constitutive promoters direct gene expression uniformly in most tissues and cells at all stages of plant growth and development; they confer steady levels of transgene expression in plant cells and hence their demand is high in plant biology. The gene silencing due to promoter homology can be avoided by either using diverse promoters isolated from different plant and viral genomes or by designing synthetic promoters. The aim of this chapter was to describe the basic protocols needed to develop and analyze novel, synthetic, nearly constitutive promoters from Cestrum yellow leaf curling virus (CmYLCV) through promoter/leader deletion and activating cis-sequence analysis. We also describe the methods to evaluate the strength of the promoters efficiently in various transient expression systems like agroinfiltration assay, gene-gun method, and assay in tobacco protoplasts. Besides, the detailed methods for developing transgenic plants (tobacco and Arabidopsis) for evaluation of the promoter using the GUS reporter gene are also described. The detailed procedure for electrophoretic mobility shift assay (EMSA) coupled with super-shift EMSA analysis are also described for showing the binding of tobacco transcription factor, TGA1a to cis-elements in the CmYLCV distal promoter region.
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Affiliation(s)
- Dipak Kumar Sahoo
- KTRDC, College of Agriculture, Food and Environment, University of Kentucky, Lexington, KY, 40546, USA
- Department of Agronomy, Iowa State University, Ames, IA, 50011, USA
| | - Shayan Sarkar
- Department of Gene Function and Regulation, Institute of Life Sciences, Chandrasekharpur, Bhubaneswar, Odisha, India
| | - Indu B Maiti
- KTRDC, College of Agriculture, Food and Environment, University of Kentucky, Lexington, KY, 40546, USA
| | - Nrisingha Dey
- Department of Gene Function and Regulation, Institute of Life Sciences, Chandrasekharpur, Bhubaneswar, Odisha, India.
- Department of Biotechnology, Government of India, Chandrasekharpur, Bhubaneswar, Odisha, India.
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