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Improving growth of Cupriavidus necator H16 on formate using adaptive laboratory evolution-informed engineering. Metab Eng 2023; 75:78-90. [PMID: 36368470 DOI: 10.1016/j.ymben.2022.10.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Revised: 10/28/2022] [Accepted: 10/30/2022] [Indexed: 11/11/2022]
Abstract
Conversion of CO2 to value-added products presents an opportunity to reduce GHG emissions while generating revenue. Formate, which can be generated by the electrochemical reduction of CO2, has been proposed as a promising intermediate compound for microbial upgrading. Here we present progress towards improving the soil bacterium Cupriavidus necator H16, which is capable of growing on formate as its sole source of carbon and energy using the Calvin-Benson-Bassham (CBB) cycle, as a host for formate utilization. Using adaptive laboratory evolution, we generated several isolates that exhibited faster growth rates on formate. The genomes of these isolates were sequenced, and resulting mutations were systematically reintroduced by metabolic engineering, to identify those that improved growth. The metabolic impact of several mutations was investigated further using RNA-seq transcriptomics. We found that deletion of a transcriptional regulator implicated in quorum sensing, PhcA, reduced expression of several operons and led to improved growth on formate. Growth was also improved by deleting large genomic regions present on the extrachromosomal megaplasmid pHG1, particularly two hydrogenase operons and the megaplasmid CBB operon, one of two copies present in the genome. Based on these findings, we generated a rationally engineered ΔphcA and megaplasmid-deficient strain that exhibited a 24% faster maximum growth rate on formate. Moreover, this strain achieved a 7% growth rate improvement on succinate and a 19% increase on fructose, demonstrating the broad utility of microbial genome reduction. This strain has the potential to serve as an improved microbial chassis for biological conversion of formate to value-added products.
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Dynamic and single cell characterization of a CRISPR-interference toolset in Pseudomonas putida KT2440 for β-ketoadipate production from p-coumarate. Metab Eng Commun 2022; 15:e00204. [PMID: 36093381 PMCID: PMC9460563 DOI: 10.1016/j.mec.2022.e00204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 07/22/2022] [Accepted: 08/22/2022] [Indexed: 11/17/2022] Open
Abstract
Pseudomonas putida KT2440 is a well-studied bacterium for the conversion of lignin-derived aromatic compounds to bioproducts. The development of advanced genetic tools in P. putida has reduced the turnaround time for hypothesis testing and enabled the construction of strains capable of producing various products of interest. Here, we evaluate an inducible CRISPR-interference (CRISPRi) toolset on fluorescent, essential, and metabolic targets. Nuclease-deficient Cas9 (dCas9) expressed with the arabinose (8K)-inducible promoter was shown to be tightly regulated across various media conditions and when targeting essential genes. In addition to bulk growth data, single cell time lapse microscopy was conducted, which revealed intrinsic heterogeneity in knockdown rate within an isoclonal population. The dynamics of knockdown were studied across genomic targets in exponentially-growing cells, revealing a universal 1.75 ± 0.38 h quiescent phase after induction where 1.5 ± 0.35 doublings occur before a phenotypic response is observed. To demonstrate application of this CRISPRi toolset, β-ketoadipate, a monomer for performance-advantaged nylon, was produced at a 4.39 ± 0.5 g/L and yield of 0.76 ± 0.10 mol/mol from p-coumarate, a hydroxycinnamic acid that can be derived from grasses. These cultivation metrics were achieved by using the higher strength IPTG (1K)-inducible promoter to knockdown the pcaIJ operon in the βKA pathway during early exponential phase. This allowed the majority of the carbon to be shunted into the desired product while eliminating the need for a supplemental carbon and energy source to support growth and maintenance. Developed an inducible dCas9-based CRISPR interference toolset in Pseudomonas putida KT2440. Characterized single-cell dynamics of fluorescent and essential gene knockdown. Applied the toolset for glucose-free production of β-ketoadipate from p-coumarate. Produced β-ketoadipate at titer of 4.39 ± 0.5 g/L and 0.76 ± 0.10 mol/mol yield.
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Biological and Molecular Components for Genetically Engineering Biosensors in Plants. BIODESIGN RESEARCH 2022; 2022:9863496. [PMID: 37850147 PMCID: PMC10521658 DOI: 10.34133/2022/9863496] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Accepted: 10/08/2022] [Indexed: 10/19/2023] Open
Abstract
Plants adapt to their changing environments by sensing and responding to physical, biological, and chemical stimuli. Due to their sessile lifestyles, plants experience a vast array of external stimuli and selectively perceive and respond to specific signals. By repurposing the logic circuitry and biological and molecular components used by plants in nature, genetically encoded plant-based biosensors (GEPBs) have been developed by directing signal recognition mechanisms into carefully assembled outcomes that are easily detected. GEPBs allow for in vivo monitoring of biological processes in plants to facilitate basic studies of plant growth and development. GEPBs are also useful for environmental monitoring, plant abiotic and biotic stress management, and accelerating design-build-test-learn cycles of plant bioengineering. With the advent of synthetic biology, biological and molecular components derived from alternate natural organisms (e.g., microbes) and/or de novo parts have been used to build GEPBs. In this review, we summarize the framework for engineering different types of GEPBs. We then highlight representative validated biological components for building plant-based biosensors, along with various applications of plant-based biosensors in basic and applied plant science research. Finally, we discuss challenges and strategies for the identification and design of biological components for plant-based biosensors.
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Precision genome editing in plants using gene targeting and prime editing: existing and emerging strategies. Biotechnol J 2022; 17:e2100673. [PMID: 35766313 DOI: 10.1002/biot.202100673] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 06/16/2022] [Accepted: 06/22/2022] [Indexed: 11/08/2022]
Abstract
Precise modification of plant genomes, such as seamless insertion, deletion, or replacement of DNA sequences at a predefined site, is a challenging task. Gene targeting (GT) and prime editing are currently the best approaches for this purpose. However, these techniques are inefficient in plants, which limits their applications for crop breeding programs. Recently, substantial developments have been made to improve the efficiency of these techniques in plants. Several strategies, such as RNA donor templating, chemically modified donor DNA template, and tandem-repeat homology-directed repair, are aimed at improving GT. Additionally, improved prime editing gRNA design, use of engineered reverse transcriptase enzymes, and splitting prime editing components have improved the efficacy of prime editing in plants. These emerging strategies and existing technologies are reviewed along with various perspectives on their future improvement and the development of robust precision genome editing technologies for plants.
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Editorial: Microorganisms for Consolidated 2nd Generation Biorefining. Front Microbiol 2022; 13:940610. [PMID: 35783433 PMCID: PMC9248810 DOI: 10.3389/fmicb.2022.940610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Accepted: 05/23/2022] [Indexed: 12/01/2022] Open
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Highly Efficient Libraries Design for Saturation Mutagenesis. Synth Biol (Oxf) 2022; 7:ysac006. [PMID: 35734540 PMCID: PMC9205323 DOI: 10.1093/synbio/ysac006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2021] [Revised: 04/24/2022] [Accepted: 05/11/2022] [Indexed: 11/30/2022] Open
Abstract
Saturation mutagenesis is a semi-rational approach for protein engineering where sites are saturated either entirely or partially to include amino acids of interest. We previously reported on a codon compression algorithm, where a set of minimal degenerate codons are selected according to user-defined parameters such as the target organism, type of saturation and usage levels. Here, we communicate an addition to our web tool that considers the distance between the wild-type codon and the library, depending on its purpose. These forms of restricted collections further reduce library size, lowering downstream screening efforts or, in turn, allowing more comprehensive saturation of multiple sites. The library design tool can be accessed via http://www.dynamcc.com/dynamcc_d/.
Graphical Abstract
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An Agrobacterium strain auxotrophic for methionine is useful for switchgrass transformation. Transgenic Res 2022; 31:661-676. [PMID: 36239844 PMCID: PMC9747830 DOI: 10.1007/s11248-022-00328-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2022] [Accepted: 09/26/2022] [Indexed: 01/20/2023]
Abstract
Auxotrophic strains of Agrobacterium tumefaciens can contribute to the development of more efficient transformation systems, especially for crops historically considered recalcitrant. Homologous recombination was used to derive methionine auxotrophs of two common A. tumefaciens strains, LBA4404 and EHA105. The EHA105 strains were more efficient for switchgrass transformation, while both the EHA105 and LBA4404 strains worked equally well for the rice control. Event quality, as measured by transgene copy number, was not affected by auxotrophy, but was higher for the LBA4404 strains than the EHA105 strains. Ultimately, the use of auxotrophs reduced bacterial overgrowth during co-cultivation and decreased the need for antibiotics.
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Engineering improved ethylene production: Leveraging systems biology and adaptive laboratory evolution. Metab Eng 2021; 67:308-320. [PMID: 34245888 DOI: 10.1016/j.ymben.2021.07.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 05/26/2021] [Accepted: 07/02/2021] [Indexed: 10/20/2022]
Abstract
Ethylene is a small hydrocarbon gas widely used in the chemical industry. Annual worldwide production currently exceeds 150 million tons, producing considerable amounts of CO2 contributing to climate change. The need for a sustainable alternative is therefore imperative. Ethylene is natively produced by several different microorganisms, including Pseudomonas syringae pv. phaseolicola via a process catalyzed by the ethylene-forming enzyme (EFE), subsequent heterologous expression of EFE has led to ethylene production in non-native bacterial hosts including Escherichia coli and cyanobacteria. However, solubility of EFE and substrate availability remain rate-limiting steps in biological ethylene production. We employed a combination of genome-scale metabolic modelling, continuous fermentation, and protein evolution to enable the accelerated development of a high efficiency ethylene producing E. coli strain, yielding a 49-fold increase in production, the most significant improvement reported to date. Furthermore, we have clearly demonstrated that this increased yield resulted from metabolic adaptations that were uniquely linked to EFE (wild type versus mutant). Our findings provide a novel solution to deregulate metabolic bottlenecks in key pathways, which can be readily applied to address other engineering challenges.
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Abstract
Alcohol toxicity significantly impacts the titer and productivity of industrially produced biofuels. To overcome this limitation, we must find and use strategies to improve stress tolerance in production strains. Previously, we developed a multiplex navigation of a global regulatory network (MINR) library that targeted 25 regulatory genes that are predicted to modify global regulation in yeast under different stress conditions. In this study, we expanded this concept to target the active sites of 47 transcriptional regulators using a saturation mutagenesis library. The 47 targeted regulators interact with more than half of all yeast genes. We then screened and selected for C3-C4 alcohol tolerance. We identified specific mutants that have resistance to isopropanol and isobutanol. Notably, the WAR1_K110N variant improved tolerance to both isopropanol and isobutanol. In addition, we investigated the mechanisms for improvement of isopropanol and isobutanol stress tolerance and found that genes related to glycolysis play a role in tolerance to isobutanol, while changes in ATP synthesis and mitochondrial respiration play a role in tolerance to both isobutanol and isopropanol. Overall, this work sheds light on basic mechanisms for isopropanol and isobutanol toxicity and demonstrates a promising strategy to improve tolerance to C3-C4 alcohols by perturbing the transcriptional regulatory network.
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High-Throughput Functional Genomics for Energy Production. Curr Opin Biotechnol 2020; 67:7-14. [PMID: 33152605 DOI: 10.1016/j.copbio.2020.09.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Revised: 09/14/2020] [Accepted: 09/21/2020] [Indexed: 10/23/2022]
Abstract
Functional genomics remains a foundational field for establishing genotype-phenotype relationships that enable strain engineering. High-throughput (HTP) methods accelerate the Design-Build-Test-Learn cycle that currently drives synthetic biology towards a forward engineering future. Trackable mutagenesis techniques including transposon insertion sequencing and CRISPR-Cas-mediated genome editing allow for rapid fitness profiling of a collection, or library, of mutants to discover beneficial mutations. Due to the relative speed of these experiments compared to adaptive evolution experiments, iterative rounds of mutagenesis can be implemented for next-generation metabolic engineering efforts to design complex production and tolerance phenotypes. Additionally, the expansion of these mutagenesis techniques to novel bacteria are opening up industrial microbes that show promise for establishing a bio-based economy.
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Abstract
Advances in high-throughput synthetic biology technologies based on the CRISPR/Cas9 system have enabled a comprehensive assessment of mutations conferring desired phenotypes, as well as a better understanding of genotype-phenotype correlations in protein engineering. Engineering antibodies to enhance properties such as binding affinity and stability plays an essential role in therapeutic applications. Here we report a method, multiplex navigation of antibody structure (MINAS), that combines a CRISPR/Cas9-based trackable editing method and fluorescent-activated cell sorting (FACS) of yeast-displayed libraries. We designed mutations in all of the complementarity-determining and framework regions of a well-characterized scFv antibody and mapped the contribution of these regions to enhanced properties. We identified specific mutants that showed higher binding affinities up to 100-fold compared to the wild-type. This study expands the applicability of CRISPR/Cas9-based trackable protein engineering by combining it with a surface display platform.
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Engineering regulatory networks for complex phenotypes in E. coli. Nat Commun 2020; 11:4050. [PMID: 32792485 PMCID: PMC7426931 DOI: 10.1038/s41467-020-17721-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Accepted: 07/07/2020] [Indexed: 12/11/2022] Open
Abstract
Regulatory networks describe the hierarchical relationship between transcription factors, associated proteins, and their target genes. Regulatory networks respond to environmental and genetic perturbations by reprogramming cellular metabolism. Here we design, construct, and map a comprehensive regulatory network library containing 110,120 specific mutations in 82 regulators expected to perturb metabolism. We screen the library for different targeted phenotypes, and identify mutants that confer strong resistance to various inhibitors, and/or enhanced production of target compounds. These improvements are identified in a single round of selection, showing that the regulatory network library is universally applicable and is convenient and effective for engineering targeted phenotypes. The facile construction and mapping of the regulatory network library provides a path for developing a more detailed understanding of global regulation in E. coli, with potential for adaptation and use in less-understood organisms, expanding toolkits for future strain engineering, synthetic biology, and broader efforts.
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Synthetic Biology and Metabolic Engineering Employing Escherichia coli for C2-C6 Bioalcohol Production. Front Bioeng Biotechnol 2020; 8:710. [PMID: 32719784 PMCID: PMC7347752 DOI: 10.3389/fbioe.2020.00710] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 06/08/2020] [Indexed: 12/18/2022] Open
Abstract
Biofuel production from renewable and sustainable resources is playing an increasingly important role within the fuel industry. Among biofuels, bioethanol has been most widely used as an additive for gasoline. Higher alcohols can be blended at a higher volume compared to ethanol and generate lower greenhouse gas (GHG) emissions without a need to change current fuel infrastructures. Thus, these fuels have the potential to replace fossil fuels in support of more environmentally friendly processes. This review summarizes the efforts to enhance bioalcohol production in engineered Escherichia coli over the last 5 years and analyzes the current challenges for increasing productivities for industrial applications.
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Development of both type I-B and type II CRISPR/Cas genome editing systems in the cellulolytic bacterium Clostridium thermocellum. Metab Eng Commun 2020; 10:e00116. [PMID: 31890588 PMCID: PMC6926293 DOI: 10.1016/j.mec.2019.e00116] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Revised: 11/13/2019] [Accepted: 11/25/2019] [Indexed: 12/21/2022] Open
Abstract
The robust lignocellulose-solubilizing activity of C. thermocellum makes it a top candidate for consolidated bioprocessing for biofuel production. Genetic techniques for C. thermocellum have lagged behind model organisms thus limiting attempts to improve biofuel production. To improve our ability to engineer C. thermocellum, we characterized a native Type I-B and heterologous Type II Clustered Regularly-Interspaced Short Palindromic Repeat (CRISPR)/cas (CRISPR associated) systems. We repurposed the native Type I-B system for genome editing. We tested three thermophilic Cas9 variants (Type II) and found that GeoCas9, isolated from Geobacillus stearothermophilus, is active in C. thermocellum. We employed CRISPR-mediated homology directed repair to introduce a nonsense mutation into pyrF. For both editing systems, homologous recombination between the repair template and the genome appeared to be the limiting step. To overcome this limitation, we tested three novel thermophilic recombinases and demonstrated that exo/beta homologs, isolated from Acidithiobacillus caldus, are functional in C. thermocellum. For the Type I-B system an engineered strain, termed LL1586, yielded 40% genome editing efficiency at the pyrF locus and when recombineering machinery was expressed this increased to 71%. For the Type II GeoCas9 system, 12.5% genome editing efficiency was observed and when recombineering machinery was expressed, this increased to 94%. By combining the thermophilic CRISPR system (either Type I-B or Type II) with the recombinases, we developed a new tool that allows for efficient CRISPR editing. We are now poised to enable CRISPR technologies to better engineer C. thermocellum for both increased lignocellulose degradation and biofuel production.
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Key Words
- 5-FOA, 5-fluoroorotic acid
- CFU, colony forming unit
- CRISPR
- CRISPR/Cas, Clustered Regularly-Interspaced Short Palindromic Repeat/CRISPR associated
- Cas9
- Cas9n, nickase Cas9
- Clostridium thermocellum
- HDR, homology-directed repair
- HR, homologous recombination
- PAM, protospacer adjacent motif
- RNP, Cas9-sgRNA ribonucleoprotein
- Thermophilic recombineering
- Tm, thiamphenicol
- Type I–B
- sgRNA, single guide RNA
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Predicting Drug Resistance Using Deep Mutational Scanning. Molecules 2020; 25:E2265. [PMID: 32403408 PMCID: PMC7248951 DOI: 10.3390/molecules25092265] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2020] [Revised: 05/05/2020] [Accepted: 05/05/2020] [Indexed: 12/12/2022] Open
Abstract
Drug resistance is a major healthcare challenge, resulting in a continuous need to develop new inhibitors. The development of these inhibitors requires an understanding of the mechanisms of resistance for a critical mass of occurrences. Recent genome editing technologies based on high-throughput DNA synthesis and sequencing may help to predict mutations resulting in resistance by testing large mutagenesis libraries. Here we describe the rationale of this approach, with examples and relevance to drug development and resistance in malaria.
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Synthetic chimeric nucleases function for efficient genome editing. Nat Commun 2019; 10:5524. [PMID: 31797930 PMCID: PMC6892893 DOI: 10.1038/s41467-019-13500-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Accepted: 11/04/2019] [Indexed: 12/26/2022] Open
Abstract
CRISPR-Cas systems have revolutionized genome editing across a broad range of biotechnological endeavors. Many CRISPR-Cas nucleases have been identified and engineered for improved capabilities. Given the modular structure of such enzymes, we hypothesized that engineering chimeric sequences would generate non-natural variants that span the kinetic parameter landscape, and thus provide for the rapid selection of nucleases fit for a particular editing system. Here, we design a chimeric Cas12a-type library with approximately 560 synthetic chimeras, and select several functional variants. We demonstrate that certain nuclease domains can be recombined across distantly related nuclease templates to produce variants that function in bacteria, yeast, and human cell lines. We further characterize selected chimeric nucleases and find that they have different protospacer adjacent motif (PAM) preferences and the M44 chimera has higher specificity relative to wild-type (WT) sequences. This demonstration opens up the possibility of generating nuclease sequences with implications across biotechnology.
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Multiplex navigation of global regulatory networks (MINR) in yeast for improved ethanol tolerance and production. Metab Eng 2019; 51:50-58. [DOI: 10.1016/j.ymben.2018.07.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 06/29/2018] [Accepted: 07/16/2018] [Indexed: 01/24/2023]
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Genomic Deoxyxylulose Phosphate Reductoisomerase (DXR) Mutations Conferring Resistance to the Antimalarial Drug Fosmidomycin in E. coli. ACS Synth Biol 2018; 7:2824-2832. [PMID: 30462485 DOI: 10.1021/acssynbio.8b00219] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Sequence to activity mapping technologies are rapidly developing, enabling the generation and isolation of mutations conferring novel phenotypes. Here we used the CRISPR enabled trackable genome engineering (CREATE) technology to investigate the inhibition of the essential ispC gene in its native genomic context in Escherichia coli. We created a full saturation library of 33 sites proximal to the ligand binding pocket and challenged this library with the antimalarial drug fosmidomycin, which targets the ispC gene product, DXR. This selection is especially challenging since it is relatively weak in E. coli, with multiple naturally occurring pathways for resistance. We identified several previously unreported mutations that confer fosmidomycin resistance, in highly conserved sites that also exist in pathogens including the malaria-inducing Plasmodium falciparum. This approach may have implications for the isolation of resistance-conferring mutations and may affect the design of future generations of fosmidomycin-based drugs.
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CRISPR-Enabled Tools for Engineering Microbial Genomes and Phenotypes. Biotechnol J 2018; 13:e1700586. [DOI: 10.1002/biot.201700586] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2017] [Revised: 05/09/2018] [Indexed: 12/26/2022]
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Building a genome engineering toolbox in nonmodel prokaryotic microbes. Biotechnol Bioeng 2018; 115:2120-2138. [PMID: 29750332 DOI: 10.1002/bit.26727] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Revised: 04/02/2018] [Accepted: 03/10/2018] [Indexed: 12/26/2022]
Abstract
The realization of a sustainable bioeconomy requires our ability to understand and engineer complex design principles for the development of platform organisms capable of efficient conversion of cheap and sustainable feedstocks (e.g., sunlight, CO2 , and nonfood biomass) into biofuels and bioproducts at sufficient titers and costs. For model microbes, such as Escherichia coli, advances in DNA reading and writing technologies are driving the adoption of new paradigms for engineering biological systems. Unfortunately, microbes with properties of interest for the utilization of cheap and renewable feedstocks, such as photosynthesis, autotrophic growth, and cellulose degradation, have very few, if any, genetic tools for metabolic engineering. Therefore, it is important to develop "design rules" for building a genetic toolbox for novel microbes. Here, we present an overview of our current understanding of these rules for the genetic manipulation of prokaryotic microbes and the available genetic tools to expand our ability to genetically engineer nonmodel systems.
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Trackable Multiplex Recombineering (TRMR) and Next-Generation Genome Design Technologies: Modifying Gene Expression inE. coliby Inserting Synthetic DNA Cassettes and Molecular Barcodes. Synth Biol (Oxf) 2018. [DOI: 10.1002/9783527688104.ch2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/19/2023] Open
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The enhancement of pericentromeric cohesin association by conserved kinetochore components promotes high-fidelity chromosome segregation and is sensitive to microtubule-based tension. Genes Dev 2007; 21:278-91. [PMID: 17242156 PMCID: PMC1785119 DOI: 10.1101/gad.1498707] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2006] [Accepted: 12/05/2006] [Indexed: 02/02/2023]
Abstract
Sister chromatid cohesion, conferred by the evolutionarily conserved cohesin complex, is essential for proper chromosome segregation. Cohesin binds to discrete sites along chromosome arms, and is especially enriched surrounding centromeres, but past studies have not clearly defined the roles of arm and pericentromeric cohesion in chromosome segregation. To address this issue, we developed a technique that specifically reduced pericentromeric cohesin association on a single chromosome without affecting arm cohesin binding. Under these conditions, we observed more extensive stretching of centromeric chromatin and elevated frequencies of chromosome loss, suggesting that pericentromeric cohesin enrichment is essential for high-fidelity chromosome transmission. The magnitude of pericentromeric cohesin association was negatively correlated with tension between sister kinetochores, with the highest levels of association in cells lacking kinetochore-microtubule attachments. Pericentromeric cohesin recruitment required evolutionarily conserved components of the inner and central kinetochore. Together, these observations suggest that pericentromeric cohesin levels reflect the balance of opposing forces: the kinetochore-mediated enhancement of cohesin binding and the disruption of binding by mechanical tension at kinetochores. The involvement of conserved kinetochore components suggests that this pathway for pericentromeric cohesin enrichment may have been retained in higher eukaryotes to promote chromosome biorientation and accurate sister chromatid segregation.
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Abstract
The properties and uses of piperylene sulfone as a new, recyclable dipolar, aprotic solvent for conducting organic reactions are presented.
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24
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Asymmetric hydrogenation and catalyst recycling using ionic liquid and supercritical carbon dioxide. J Am Chem Soc 2001; 123:1254-5. [PMID: 11456690 DOI: 10.1021/ja005718t] [Citation(s) in RCA: 306] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Abstract
The journey to holism is the result of a grounded theory study of 18 members of the American Holistic Nurses' Association. Participants were prompted to "Tell me about holistic nursing" and replies revealed a seven-step process to becoming a holistic nurse. The process is an expansion of Van Gennep's three-stage theory of rites of passage, which involves separation, marginality/liminality, and reintegration. The expanded process begins with separation from mainstream nursing and concludes with reintegration into nursing as a holistic nurse. The marginality/liminality step shows five active steps: gathering information to quell the distress of the separation, applying that information to others, changing focus to self-care, applying the information to self, and increasing self-knowledge. This article describes the process and presents data to support the conclusion that the growth of a holistic nurse follows a recognizable course.
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Undergraduate training in occupational health. OCCUPATIONAL HEALTH & SAFETY (WACO, TEX.) 1980; 49:43-8. [PMID: 7352097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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