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Baghdasaryan O, Khan S, Lin JC, Lee-Kin J, Hsu CY, Hu CMJ, Tan C. Synthetic control of living cells by intracellular polymerization. Trends Biotechnol 2024; 42:241-252. [PMID: 37743158 PMCID: PMC11132853 DOI: 10.1016/j.tibtech.2023.08.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 08/21/2023] [Accepted: 08/23/2023] [Indexed: 09/26/2023]
Abstract
An emerging cellular engineering method creates synthetic polymer matrices inside cells. By contrast with classical genetic, enzymatic, or radioactive techniques, this materials-based approach introduces non-natural polymers inside cells, thus modifying cellular states and functionalities. Here, we cover various materials and chemistries that have been exploited to create intracellular polymer matrices. In addition, we discuss emergent cellular properties due to the intracellular polymerization, including nonreplicating but active metabolism, maintenance of membrane integrity, and resistance to environmental stressors. We also discuss past work and future opportunities for developing and applying synthetic cells that contain intracellular polymers. The materials-based approach will usher in new applications of synthetic cells for broad biotechnological applications.
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Affiliation(s)
- Ofelya Baghdasaryan
- Biomedical Engineering, University of California Davis, Davis, CA 95616-5270, USA
| | - Shahid Khan
- Biomedical Engineering, University of California Davis, Davis, CA 95616-5270, USA
| | - Jung-Chen Lin
- Institute of Biomedical Sciences, Academia Sinica, Nankang, Taipei 115, Taiwan
| | - Jared Lee-Kin
- Biomedical Engineering, University of California Davis, Davis, CA 95616-5270, USA
| | - Chung-Yao Hsu
- Institute of Biomedical Sciences, Academia Sinica, Nankang, Taipei 115, Taiwan
| | - Che-Ming Jack Hu
- Institute of Biomedical Sciences, Academia Sinica, Nankang, Taipei 115, Taiwan.
| | - Cheemeng Tan
- Biomedical Engineering, University of California Davis, Davis, CA 95616-5270, USA.
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2
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Contreras‐Llano LE, Liu Y, Henson T, Meyer CC, Baghdasaryan O, Khan S, Lin C, Wang A, Hu CJ, Tan C. Engineering Cyborg Bacteria Through Intracellular Hydrogelation. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2204175. [PMID: 36628538 PMCID: PMC10037956 DOI: 10.1002/advs.202204175] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 11/18/2022] [Indexed: 05/06/2023]
Abstract
Natural and artificial cells are two common chassis in synthetic biology. Natural cells can perform complex tasks through synthetic genetic constructs, but their autonomous replication often causes safety concerns for biomedical applications. In contrast, artificial cells based on nonreplicating materials, albeit possessing reduced biochemical complexity, provide more defined and controllable functions. Here, for the first time, the authors create hybrid material-cell entities termed Cyborg Cells. To create Cyborg Cells, a synthetic polymer network is assembled inside each bacterium, rendering them incapable of dividing. Cyborg Cells preserve essential functions, including cellular metabolism, motility, protein synthesis, and compatibility with genetic circuits. Cyborg Cells also acquire new abilities to resist stressors that otherwise kill natural cells. Finally, the authors demonstrate the therapeutic potential by showing invasion into cancer cells. This work establishes a new paradigm in cellular bioengineering by exploiting a combination of intracellular man-made polymers and their interaction with the protein networks of living cells.
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Affiliation(s)
| | - Yu‐Han Liu
- Institute of Biomedical SciencesAcademia SinicaTaipei11529Taiwan
| | - Tanner Henson
- Department of Biomedical EngineeringUniversity of CaliforniaDavisCA95616USA
- Department of SurgeryUniversity of CaliforniaDavis School of MedicineSacramentoCA95817USA
| | - Conary C. Meyer
- Department of Biomedical EngineeringUniversity of CaliforniaDavisCA95616USA
| | | | - Shahid Khan
- Department of Biomedical EngineeringUniversity of CaliforniaDavisCA95616USA
| | - Chi‐Long Lin
- Institute of Biomedical SciencesAcademia SinicaTaipei11529Taiwan
| | - Aijun Wang
- Department of Biomedical EngineeringUniversity of CaliforniaDavisCA95616USA
- Department of SurgeryUniversity of CaliforniaDavis School of MedicineSacramentoCA95817USA
| | - Che‐Ming J. Hu
- Institute of Biomedical SciencesAcademia SinicaTaipei11529Taiwan
| | - Cheemeng Tan
- Department of Biomedical EngineeringUniversity of CaliforniaDavisCA95616USA
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3
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Zhu X, Zhaoyang Zhang, Bin Jia, Yuan Y. Current advances of biocontainment strategy in synthetic biology. Chin J Chem Eng 2022. [DOI: 10.1016/j.cjche.2022.07.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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4
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A genetic toolkit and gene switches to limit Mycoplasma growth for biosafety applications. Nat Commun 2022; 13:1910. [PMID: 35393441 PMCID: PMC8991246 DOI: 10.1038/s41467-022-29574-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 03/24/2022] [Indexed: 12/18/2022] Open
Abstract
Mycoplasmas have exceptionally streamlined genomes and are strongly adapted to their many hosts, which provide them with essential nutrients. Owing to their relative genomic simplicity, Mycoplasmas have been used to develop chassis for biotechnological applications. However, the dearth of robust and precise toolkits for genomic manipulation and tight regulation has hindered any substantial advance. Herein we describe the construction of a robust genetic toolkit for M. pneumoniae, and its successful deployment to engineer synthetic gene switches that control and limit Mycoplasma growth, for biosafety containment applications. We found these synthetic gene circuits to be stable and robust in the long-term, in the context of a minimal cell. With this work, we lay a foundation to develop viable and robust biosafety systems to exploit a synthetic Mycoplasma chassis for live attenuated vectors for therapeutic applications. Mycoplasmas are minimal cell model organisms but lack genetic tools. Here the authors provide a robust genetic toolkit for Mycoplasma demonstrating gene circuit engineering applications.
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5
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Giachino A, Focarelli F, Marles-Wright J, Waldron KJ. Synthetic biology approaches to copper remediation: bioleaching, accumulation and recycling. FEMS Microbiol Ecol 2021; 97:6021318. [PMID: 33501489 DOI: 10.1093/femsec/fiaa249] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Accepted: 12/02/2020] [Indexed: 12/20/2022] Open
Abstract
One of the current aims of synthetic biology is the development of novel microorganisms that can mine economically important elements from the environment or remediate toxic waste compounds. Copper, in particular, is a high-priority target for bioremediation owing to its extensive use in the food, metal and electronic industries and its resulting common presence as an environmental pollutant. Even though microbe-aided copper biomining is a mature technology, its application to waste treatment and remediation of contaminated sites still requires further research and development. Crucially, any engineered copper-remediating chassis must survive in copper-rich environments and adapt to copper toxicity; they also require bespoke adaptations to specifically extract copper and safely accumulate it as a human-recoverable deposit to enable biorecycling. Here, we review current strategies in copper bioremediation, biomining and biorecycling, as well as strategies that extant bacteria use to enhance copper tolerance, accumulation and mineralization in the native environment. By describing the existing toolbox of copper homeostasis proteins from naturally occurring bacteria, we show how these modular systems can be exploited through synthetic biology to enhance the properties of engineered microbes for biotechnological copper recovery applications.
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Affiliation(s)
- Andrea Giachino
- Faculty of Medical Sciences, Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, United Kingdom
| | - Francesca Focarelli
- Faculty of Medical Sciences, Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, United Kingdom
| | - Jon Marles-Wright
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, United Kingdom
| | - Kevin J Waldron
- Faculty of Medical Sciences, Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, United Kingdom
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6
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7
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Del Valle I, Fulk EM, Kalvapalle P, Silberg JJ, Masiello CA, Stadler LB. Translating New Synthetic Biology Advances for Biosensing Into the Earth and Environmental Sciences. Front Microbiol 2021; 11:618373. [PMID: 33633695 PMCID: PMC7901896 DOI: 10.3389/fmicb.2020.618373] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 12/17/2020] [Indexed: 12/26/2022] Open
Abstract
The rapid diversification of synthetic biology tools holds promise in making some classically hard-to-solve environmental problems tractable. Here we review longstanding problems in the Earth and environmental sciences that could be addressed using engineered microbes as micron-scale sensors (biosensors). Biosensors can offer new perspectives on open questions, including understanding microbial behaviors in heterogeneous matrices like soils, sediments, and wastewater systems, tracking cryptic element cycling in the Earth system, and establishing the dynamics of microbe-microbe, microbe-plant, and microbe-material interactions. Before these new tools can reach their potential, however, a suite of biological parts and microbial chassis appropriate for environmental conditions must be developed by the synthetic biology community. This includes diversifying sensing modules to obtain information relevant to environmental questions, creating output signals that allow dynamic reporting from hard-to-image environmental materials, and tuning these sensors so that they reliably function long enough to be useful for environmental studies. Finally, ethical questions related to the use of synthetic biosensors in environmental applications are discussed.
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Affiliation(s)
- Ilenne Del Valle
- Systems, Synthetic, and Physical Biology Graduate Program, Rice University, Houston, TX, United States
| | - Emily M. Fulk
- Systems, Synthetic, and Physical Biology Graduate Program, Rice University, Houston, TX, United States
| | - Prashant Kalvapalle
- Systems, Synthetic, and Physical Biology Graduate Program, Rice University, Houston, TX, United States
| | - Jonathan J. Silberg
- Department of BioSciences, Rice University, Houston, TX, United States
- Department of Bioengineering, Rice University, Houston, TX, United States
- Department of Chemical and Biomolecular Engineering, Rice University, Houston, TX, United States
| | - Caroline A. Masiello
- Department of BioSciences, Rice University, Houston, TX, United States
- Department of Earth, Environmental and Planetary Sciences, Rice University, Houston, TX, United States
- Department of Chemistry, Rice University, Houston, TX, United States
| | - Lauren B. Stadler
- Department of Civil and Environmental Engineering, Rice University, Houston, TX, United States
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Abstract
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Biocontainment is an essential feature
when deploying genetically
modified organisms (GMOs) in open system applications, as variants
escaping their intended operating environments could negatively impact
ecosystems and human health. To avoid breaches resulting from metabolic
cross-feeding, horizontal gene transfer, and/or genetic mutations,
synthetic auxotrophs have been engineered to become dependent on exogenously
supplied xenobiotics, such as noncanonical amino acids (ncAAs). The
incorporation of these abiological building blocks into essential
proteins constitutes a first step toward constructing xenobiological
barriers between GMOs and their environments. To transition synthetic
auxotrophs further away from familiar biology, we demonstrate how
bacterial growth can be confined by transition-metal complexes that
catalyze the formation of an essential ncAA through new-to-nature
reactions. Specifically, using a homogeneous ruthenium complex enabled
us to localize bacterial growth on solid media, while heterogeneous
palladium nanoparticles could be recycled and deployed up to five
consecutive times to ensure the survival of synthetic auxotrophs in
liquid cultures.
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Affiliation(s)
- Rudy Rubini
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Clemens Mayer
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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9
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Fok JA, Mayer C. Genetic-Code-Expansion Strategies for Vaccine Development. Chembiochem 2020; 21:3291-3300. [PMID: 32608153 PMCID: PMC7361271 DOI: 10.1002/cbic.202000343] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 06/29/2020] [Indexed: 12/16/2022]
Abstract
By providing long-term protection against infectious diseases, vaccinations have significantly reduced death and morbidity worldwide. In the 21st century, (bio)technological advances have paved the way for developing prophylactic vaccines that are safer and more effective as well as enabling the use of vaccines as therapeutics to treat human diseases. Here, we provide a focused review of the utility of genetic code expansion as an emerging tool for the development of vaccines. Specifically, we discuss how the incorporation of immunogenic noncanonical amino acids can aid in eliciting immune responses against adverse self-proteins and highlight the potential of an expanded genetic code for the construction of replication-incompetent viruses. We close the review by discussing the future prospects and remaining challenges for the application of these approaches in the development of both prophylactic and therapeutic vaccines in the near future.
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Affiliation(s)
- Jelle A. Fok
- Stratingh Institute for ChemistryUniversity of GroningenNijenborgh 49474 AGGroningen (TheNetherlands
| | - Clemens Mayer
- Stratingh Institute for ChemistryUniversity of GroningenNijenborgh 49474 AGGroningen (TheNetherlands
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10
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Goodfellow S, Zhang D, Wang MB, Zhang R. Bacterium-Mediated RNA Interference: Potential Application in Plant Protection. PLANTS (BASEL, SWITZERLAND) 2019; 8:E572. [PMID: 31817412 PMCID: PMC6963952 DOI: 10.3390/plants8120572] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 11/26/2019] [Accepted: 11/27/2019] [Indexed: 01/10/2023]
Abstract
RNAi has emerged as a promising tool for targeting agricultural pests and pathogens and could provide an environmentally friendly alternative to traditional means of control. However, the deployment of this technology is still limited by a lack of suitable exogenous- or externally applied delivery mechanisms. Numerous means of overcoming this limitation are being explored. One such method, bacterium-mediated RNA interference, or bmRNAi, has been explored in other systems and shows great potential for application to agriculture. Here, we review the current state of bmRNAi, examine the technical limitations and possible improvements, and discuss its potential applications in crop protection.
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Affiliation(s)
- Simon Goodfellow
- School of Chemistry and Molecular Bioscience, University of Wollongong, NSW 2522, Australia
- CSIRO Agriculture and Food, Canberra, ACT 2601, Australia
| | - Daai Zhang
- School of Chemistry and Molecular Bioscience, University of Wollongong, NSW 2522, Australia
- CSIRO Agriculture and Food, Canberra, ACT 2601, Australia
| | - Ming-Bo Wang
- CSIRO Agriculture and Food, Canberra, ACT 2601, Australia
| | - Ren Zhang
- School of Chemistry and Molecular Bioscience, University of Wollongong, NSW 2522, Australia
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11
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Mayer C. Selection, Addiction and Catalysis: Emerging Trends for the Incorporation of Noncanonical Amino Acids into Peptides and Proteins in Vivo. Chembiochem 2019; 20:1357-1364. [PMID: 30618145 PMCID: PMC6563710 DOI: 10.1002/cbic.201800733] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Indexed: 12/22/2022]
Abstract
Expanding the genetic code of organisms by incorporating noncanonical amino acids (ncAAs) into target proteins through the suppression of stop codons in vivo has profoundly impacted how we perform protein modification or detect proteins and their interaction partners in their native environment. Yet, with genetic code expansion strategies maturing over the past 15 years, new applications that make use—or indeed repurpose—these techniques are beginning to emerge. This Concept article highlights three of these developments: 1) The incorporation of ncAAs for the biosynthesis and selection of bioactive macrocyclic peptides with novel ring architectures, 2) synthetic biocontainment strategies based on the addiction of microorganisms to ncAAs, and 3) enzyme design strategies, in which ncAAs with unique functionalities enable the catalysis of new‐to‐nature reactions. Key advances in all three areas are presented and potential future applications discussed.
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Affiliation(s)
- Clemens Mayer
- Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
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12
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Whitford CM, Dymek S, Kerkhoff D, März C, Schmidt O, Edich M, Droste J, Pucker B, Rückert C, Kalinowski J. Auxotrophy to Xeno-DNA: an exploration of combinatorial mechanisms for a high-fidelity biosafety system for synthetic biology applications. J Biol Eng 2018; 12:13. [PMID: 30123321 PMCID: PMC6090650 DOI: 10.1186/s13036-018-0105-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 06/25/2018] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Biosafety is a key aspect in the international Genetically Engineered Machine (iGEM) competition, which offers student teams an amazing opportunity to pursue their own research projects in the field of Synthetic Biology. iGEM projects often involve the creation of genetically engineered bacterial strains. To minimize the risks associated with bacterial release, a variety of biosafety systems were constructed, either to prevent survival of bacteria outside the lab or to hinder horizontal or vertical gene transfer. MAIN BODY Physical containment methods such as bioreactors or microencapsulation are considered the first safety level. Additionally, various systems involving auxotrophies for both natural and synthetic compounds have been utilized by iGEM teams in recent years. Combinatorial systems comprising multiple auxotrophies have been shown to reduced escape frequencies below the detection limit. Furthermore, a number of natural toxin-antitoxin systems can be deployed to kill cells under certain conditions. Additionally, parts of naturally occurring toxin-antitoxin systems can be used for the construction of 'kill switches' controlled by synthetic regulatory modules, allowing control of cell survival. Kill switches prevent cell survival but do not completely degrade nucleic acids. To avoid horizontal gene transfer, multiple mechanisms to cleave nucleic acids can be employed, resulting in 'self-destruction' of cells. Changes in light or temperature conditions are powerful regulators of gene expression and could serve as triggers for kill switches or self-destruction systems. Xenobiology-based containment uses applications of Xeno-DNA, recoded codons and non-canonical amino acids to nullify the genetic information of constructed cells for wild type organisms. A 'minimal genome' approach brings the opportunity to reduce the genome of a cell to only genes necessary for survival under lab conditions. Such cells are unlikely to survive in the natural environment and are thus considered safe hosts. If suitable for the desired application, a shift to cell-free systems based on Xeno-DNA may represent the ultimate biosafety system. CONCLUSION Here we describe different containment approaches in synthetic biology, ranging from auxotrophies to minimal genomes, which can be combined to significantly improve reliability. Since the iGEM competition greatly increases the number of people involved in synthetic biology, we will focus especially on biosafety systems developed and applied in the context of the iGEM competition.
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Affiliation(s)
| | - Saskia Dymek
- Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany
| | - Denise Kerkhoff
- Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany
| | - Camilla März
- Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany
| | - Olga Schmidt
- Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany
| | - Maximilian Edich
- Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany
| | - Julian Droste
- Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany
- Faculty of Biology, Bielefeld University, Bielefeld, Germany
| | - Boas Pucker
- Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany
- Faculty of Biology, Bielefeld University, Bielefeld, Germany
- Present address: Evolution and Diversity, Department of Plant Sciences, University of Cambridge, Cambridge, UK
| | - Christian Rückert
- Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany
- Faculty of Biology, Bielefeld University, Bielefeld, Germany
| | - Jörn Kalinowski
- Center for Biotechnology, Bielefeld University, 33615 Bielefeld, Germany
- Faculty of Biology, Bielefeld University, Bielefeld, Germany
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Abstract
Surrogate microorganisms, in short surrogates, are an essential part of pathogen research. Compared to surrogates used in controlled laboratory environments, surrogates for field release are restricted by concerns about human and environmental safety. For field research of food-borne pathogens, strains of an attenuated pathogen or strains of genetically close non-pathogenic species have been used as surrogates. Genetic modification is usually performed to attenuate virulence, through for examples deletion of genes of virulence and transcriptional regulators and removal of virulence plasmids, and to facilitate detection and monitoring through observing antibiotic resistance, fluorescence, and bioluminescence. For field research of a biological warfare agent Bacillus anthracis, strains of genetically close non-pathogenic species or strains of genetically distant non-pathogenic species have been used, mostly without any genetic modification. Recently, we constructed strains of Bacillus thuringiensis as surrogates for B. anthracis, demonstrating that strain engineering could significantly enhance the utility of surrogates, and that the application of a simple genetic circuit could significantly impact surrogate safety. Thus far, enormous potential of biotechnology has not been exploited enough due to safety concerns regarding the field release of genetically engineered microorganisms. However, synthetic biology is rapidly developing, providing new concepts for biocontainment as well as ingenious genetic circuits and devices, which should be applied in future research of field-use surrogates.
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Affiliation(s)
- Sangjin Park
- a Metabolic and Biomolecular Engineering National Research Laboratory, Department of Chemical and Biomolecular Engineering (BK21 Plus Program), Center for Systems and Synthetic Biotechnology , Institute for the BioCentury, Korea Advanced Institute of Science and Technology (KAIST) , Daejeon , Republic of Korea.,b The 5th R&D Institute, Agency for Defense Development (ADD) , Daejeon , Republic of Korea
| | - Chang-Hwan Kim
- b The 5th R&D Institute, Agency for Defense Development (ADD) , Daejeon , Republic of Korea
| | - Seong Tae Jeong
- b The 5th R&D Institute, Agency for Defense Development (ADD) , Daejeon , Republic of Korea
| | - Sang Yup Lee
- a Metabolic and Biomolecular Engineering National Research Laboratory, Department of Chemical and Biomolecular Engineering (BK21 Plus Program), Center for Systems and Synthetic Biotechnology , Institute for the BioCentury, Korea Advanced Institute of Science and Technology (KAIST) , Daejeon , Republic of Korea
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14
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Abstract
The standard genetic code is robust to mutations during transcription and translation. Point mutations are likely to be synonymous or to preserve the chemical properties of the original amino acid. Saturation mutagenesis experiments suggest that in some cases the best-performing mutant requires replacement of more than a single nucleotide within a codon. These replacements are essentially inaccessible to common error-based laboratory engineering techniques that alter a single nucleotide per mutation event, due to the extreme rarity of adjacent mutations. In this theoretical study, we suggest a radical reordering of the genetic code that maximizes the mutagenic potential of single nucleotide replacements. We explore several possible genetic codes that allow a greater degree of accessibility to the mutational landscape and may result in a hyperevolvable organism that could serve as an ideal platform for directed evolution experiments. We then conclude by evaluating the challenges of constructing such recoded organisms and their potential applications within the field of synthetic biology. The conservative nature of the genetic code prevents bioengineers from efficiently accessing the full mutational landscape of a gene via common error-prone methods. Here, we present two computational approaches to generate alternative genetic codes with increased accessibility. These new codes allow mutational transitions to a larger pool of amino acids and with a greater extent of chemical differences, based on a single nucleotide replacement within the codon, thus increasing evolvability both at the single-gene and at the genome levels. Given the widespread use of these techniques for strain and protein improvement, along with more fundamental evolutionary biology questions, the use of recoded organisms that maximize evolvability should significantly improve the efficiency of directed evolution, library generation, and fitness maximization.
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15
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Brophy JAN, LaRue T, Dinneny JR. Understanding and engineering plant form. Semin Cell Dev Biol 2017; 79:68-77. [PMID: 28864344 DOI: 10.1016/j.semcdb.2017.08.051] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 08/25/2017] [Accepted: 08/28/2017] [Indexed: 11/18/2022]
Abstract
A plant's form is an important determinant of its fitness and economic value. Here, we review strategies for producing plants with altered forms. Historically, the process of changing a plant's form has been slow in agriculture, requiring iterative rounds of growth and selection. We discuss modern techniques for identifying genes involved in the development of plant form and tools that will be needed to effectively design and engineer plants with altered forms. Synthetic genetic circuits are highlighted for their potential to generate novel plant forms. We emphasize understanding development as a prerequisite to engineering and discuss the potential role of computer models in translating knowledge about single genes or pathways into a more comprehensive understanding of development.
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Affiliation(s)
- Jennifer A N Brophy
- Carnegie Institution for Science, Department of Plant Biology, Stanford, CA 94305, USA
| | - Therese LaRue
- Stanford University, Department of Biology, Stanford, CA 94305, USA
| | - José R Dinneny
- Carnegie Institution for Science, Department of Plant Biology, Stanford, CA 94305, USA.
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16
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Wang Y, Li J, Xiong K, Chen Z, Zheng C, Tan Y, Cong Y. Elimination of persistent vaccine bacteria of Salmonella enterica serovar Typhimurium in the guts of immunized mice by inducible expression of truncated YncE. PLoS One 2017; 12:e0179649. [PMID: 28628661 PMCID: PMC5476278 DOI: 10.1371/journal.pone.0179649] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 06/01/2017] [Indexed: 12/23/2022] Open
Abstract
Orally administered vaccine bacteria usually persist for a period of time in the intestinal tracts of immunized individuals, and are excreted in feces to the environment resulting in a potential biosafety issue. The releasing risk can be minimized by immediate elimination of the persistent vaccine bacteria once adequate protective immune responses have been elicited by the vaccine bacteria. In a previous study, inducible expression of truncated yncE gene (yncE*) was found lethal to host bacteria. This feature has an application potential in biosafety control. Here, we assessed the efficacy of YncE* in eliminating an attenuated strain of Salmonella enterica serovar Typhimurium in a mouse model. To this end, a pBAD-derived plasmid containing yncE* under the control of the Ara promoter was transformed into a ΔphoPQ mutant of S. Typhimurium. Our data show that the induced expression of yncE* in the presence of arabinose eliminated the vaccine bacteria both in vitro and in vivo. BALB/c mice with or without streptomycin-pretreatment were used to assess the efficacy of YncE* in vivo. Oral administration of 500 μl of 20% arabinose at 24 h postvaccination removed the vaccine bacteria from the guts of the tested mice without streptomycin-pretreatment. For streptomycin-pretreated mice, which were colonized with higher levels of Salmonella, an additional gavage of arabinose was required to completely eliminate the vaccine bacteria in the guts of the tested mice. The orally administered arabinose did not affect the persistence of bacteria that had penetrated the intestinal mucosa of the immunized mice. Furthermore, there was no significant difference in the protection rate between the routine immunization and the immunization with the arabinose treatment. The results indicate that the yncE* element improves the biosafety of the bacterial vaccine, and can be taken in consideration in future design of live bacterial vaccines.
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Affiliation(s)
- Yiran Wang
- Department of Microbiology, Third Military Medical University, Chongqing, China
| | - Jianhua Li
- The Orthopaedic Center of PLA, 88th Hospital of PLA, Tai’an, Shandong Province, China
| | - Kun Xiong
- Department of Microbiology, Third Military Medical University, Chongqing, China
| | - Zhijin Chen
- Department of Microbiology, Third Military Medical University, Chongqing, China
| | - Chunping Zheng
- Department of Microbiology, Third Military Medical University, Chongqing, China
| | - Yong Tan
- Department of Microbiology, Third Military Medical University, Chongqing, China
| | - Yanguang Cong
- Department of Microbiology, Third Military Medical University, Chongqing, China
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