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You J, Du Y, Pan X, Zhang X, Yang T, Rao Z. Increased Production of Riboflavin by Coordinated Expression of Multiple Genes in Operons in Bacillus subtilis. ACS Synth Biol 2022; 11:1801-1810. [PMID: 35467340 DOI: 10.1021/acssynbio.1c00640] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Riboflavin is an essential vitamin widely used in the food, pharmaceutical, and feed industries. However, the insufficient supply of precursors caused by the imbalance of intracellular metabolic flow limits the riboflavin synthesis by industrial strains. Here, we increase riboflavin production by tuning multiple gene expression to balance intracellular metabolic flow. First, we tuned the expression of mCherry and egfp genes within operons by generating libraries of tunable intergenic regions (TIGRs) and confirmed the relative expression of the two reporter genes. The TIGR library can coordinate the expression ratio of reporter genes more than 180 times in Escherichia coli and more than 70 times in Bacillus subtilis. Next, we used this strategy to tune the expression of zwf, ribBA, and ywlf genes within operons through the TIGR library to increase the intracellular precursor pool for riboflavin biosynthesis. Based on the fluorescence characteristics of riboflavin, 96-well plates were used to screen the optimal combination mutants quickly. The best-engineered strain was selected from the library, which produced 2.7 g/L riboflavin, increasing by 64.35% in the shake flask. Finally, the riboflavin titer increased by 59.27% to 11.77 g/L in fed-batch fermentation. The strategy described here will contribute to the industrial production of riboflavin and related products by B. subtilis.
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Affiliation(s)
- Jiajia You
- Key Laboratory of Industrial Biotechnology of the Ministry of Education, Laboratory of Applied Microorganisms and Metabolic Engineering, School of Biotechnology, Jiangnan University, Wuxi 214122, China
| | - Yuxuan Du
- Key Laboratory of Industrial Biotechnology of the Ministry of Education, Laboratory of Applied Microorganisms and Metabolic Engineering, School of Biotechnology, Jiangnan University, Wuxi 214122, China
| | - Xuewei Pan
- Key Laboratory of Industrial Biotechnology of the Ministry of Education, Laboratory of Applied Microorganisms and Metabolic Engineering, School of Biotechnology, Jiangnan University, Wuxi 214122, China
| | - Xian Zhang
- Key Laboratory of Industrial Biotechnology of the Ministry of Education, Laboratory of Applied Microorganisms and Metabolic Engineering, School of Biotechnology, Jiangnan University, Wuxi 214122, China
| | - Taowei Yang
- Key Laboratory of Industrial Biotechnology of the Ministry of Education, Laboratory of Applied Microorganisms and Metabolic Engineering, School of Biotechnology, Jiangnan University, Wuxi 214122, China
| | - Zhiming Rao
- Key Laboratory of Industrial Biotechnology of the Ministry of Education, Laboratory of Applied Microorganisms and Metabolic Engineering, School of Biotechnology, Jiangnan University, Wuxi 214122, China
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Lozano Terol G, Gallego-Jara J, Sola Martínez RA, Martínez Vivancos A, Cánovas Díaz M, de Diego Puente T. Impact of the Expression System on Recombinant Protein Production in Escherichia coli BL21. Front Microbiol 2021; 12:682001. [PMID: 34234760 PMCID: PMC8257044 DOI: 10.3389/fmicb.2021.682001] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 05/18/2021] [Indexed: 12/13/2022] Open
Abstract
Recombinant protein production for medical, academic, or industrial applications is essential for our current life. Recombinant proteins are obtained mainly through microbial fermentation, with Escherichia coli being the host most used. In spite of that, some problems are associated with the production of recombinant proteins in E. coli, such as the formation of inclusion bodies, the metabolic burden, or the inefficient translocation/transport system of expressed proteins. Optimizing transcription of heterologous genes is essential to avoid these drawbacks and develop competitive biotechnological processes. Here, expression of YFP reporter protein is evaluated under the control of four promoters of different strength (PT7lac, Ptrc, Ptac, and PBAD) and two different replication origins (high copy number pMB1′ and low copy number p15A). In addition, the study has been carried out with the E. coli BL21 wt and the ackA mutant strain growing in a rich medium with glucose or glycerol as carbon sources. Results showed that metabolic burden associated with transcription and translation of foreign genes involves a decrease in recombinant protein expression. It is necessary to find a balance between plasmid copy number and promoter strength to maximize soluble recombinant protein expression. The results obtained represent an important advance on the most suitable expression system to improve both the quantity and quality of recombinant proteins in bioproduction engineering.
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Affiliation(s)
- Gema Lozano Terol
- Department of Biochemistry and Molecular Biology and Immunology (B), Faculty of Chemistry, University of Murcia, Campus of Espinardo, Regional Campus of International Excellence "Campus Mare Nostrum", Murcia, Spain
| | - Julia Gallego-Jara
- Department of Biochemistry and Molecular Biology and Immunology (B), Faculty of Chemistry, University of Murcia, Campus of Espinardo, Regional Campus of International Excellence "Campus Mare Nostrum", Murcia, Spain
| | - Rosa Alba Sola Martínez
- Department of Biochemistry and Molecular Biology and Immunology (B), Faculty of Chemistry, University of Murcia, Campus of Espinardo, Regional Campus of International Excellence "Campus Mare Nostrum", Murcia, Spain
| | - Adrián Martínez Vivancos
- Department of Biochemistry and Molecular Biology and Immunology (B), Faculty of Chemistry, University of Murcia, Campus of Espinardo, Regional Campus of International Excellence "Campus Mare Nostrum", Murcia, Spain
| | - Manuel Cánovas Díaz
- Department of Biochemistry and Molecular Biology and Immunology (B), Faculty of Chemistry, University of Murcia, Campus of Espinardo, Regional Campus of International Excellence "Campus Mare Nostrum", Murcia, Spain
| | - Teresa de Diego Puente
- Department of Biochemistry and Molecular Biology and Immunology (B), Faculty of Chemistry, University of Murcia, Campus of Espinardo, Regional Campus of International Excellence "Campus Mare Nostrum", Murcia, Spain
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Schäfer L, Bühler K, Karande R, Bühler B. Rational Engineering of a Multi‐Step Biocatalytic Cascade for the Conversion of Cyclohexane to Polycaprolactone Monomers in
Pseudomonas taiwanensis. Biotechnol J 2020; 15:e2000091. [DOI: 10.1002/biot.202000091] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2020] [Revised: 07/13/2020] [Indexed: 02/03/2023]
Affiliation(s)
- Lisa Schäfer
- Department of Solar Materials Helmholtz‐Centre for Environmental Research ‐ UFZ Permoserstraße 15 Leipzig Saxony 04318 Germany
| | - Katja Bühler
- Department of Solar Materials Helmholtz‐Centre for Environmental Research ‐ UFZ Permoserstraße 15 Leipzig Saxony 04318 Germany
| | - Rohan Karande
- Department of Solar Materials Helmholtz‐Centre for Environmental Research ‐ UFZ Permoserstraße 15 Leipzig Saxony 04318 Germany
| | - Bruno Bühler
- Department of Solar Materials Helmholtz‐Centre for Environmental Research ‐ UFZ Permoserstraße 15 Leipzig Saxony 04318 Germany
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Eicher T, Patt A, Kautto E, Machiraju R, Mathé E, Zhang Y. Challenges in proteogenomics: a comparison of analysis methods with the case study of the DREAM proteogenomics sub-challenge. BMC Bioinformatics 2019; 20:669. [PMID: 31861998 PMCID: PMC6923881 DOI: 10.1186/s12859-019-3253-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Background Proteomic measurements, which closely reflect phenotypes, provide insights into gene expression regulations and mechanisms underlying altered phenotypes. Further, integration of data on proteome and transcriptome levels can validate gene signatures associated with a phenotype. However, proteomic data is not as abundant as genomic data, and it is thus beneficial to use genomic features to predict protein abundances when matching proteomic samples or measurements within samples are lacking. Results We evaluate and compare four data-driven models for prediction of proteomic data from mRNA measured in breast and ovarian cancers using the 2017 DREAM Proteogenomics Challenge data. Our results show that Bayesian network, random forests, LASSO, and fuzzy logic approaches can predict protein abundance levels with median ground truth-predicted correlation values between 0.2 and 0.5. However, the most accurately predicted proteins differ considerably between approaches. Conclusions In addition to benchmarking aforementioned machine learning approaches for predicting protein levels from transcript levels, we discuss challenges and potential solutions in state-of-the-art proteogenomic analyses.
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Affiliation(s)
- Tara Eicher
- Department of Computer Science and Engineering, The Ohio State University, Columbus, OH, 43210, USA
| | - Andrew Patt
- Department of Biomedical Informatics, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA
| | - Esko Kautto
- Department of Biomedical Informatics, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA
| | - Raghu Machiraju
- Department of Computer Science and Engineering, The Ohio State University, Columbus, OH, 43210, USA. .,Department of Biomedical Informatics, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA.
| | - Ewy Mathé
- Department of Biomedical Informatics, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA.
| | - Yan Zhang
- Department of Biomedical Informatics, College of Medicine, The Ohio State University, Columbus, OH, 43210, USA. .,The Ohio State University Comprehensive Cancer Center (OSUCCC - James), Columbus, OH, 43210, USA.
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Isolation and characterization of novel mutations in the pSC101 origin that increase copy number. Sci Rep 2018; 8:1590. [PMID: 29371642 PMCID: PMC5785507 DOI: 10.1038/s41598-018-20016-w] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 01/11/2018] [Indexed: 11/25/2022] Open
Abstract
pSC101 is a narrow host range, low-copy plasmid commonly used for genetically manipulating Escherichia coli. As a byproduct of a genetic screen for a more sensitive lactam biosensor, we identified multiple novel mutations that increase the copy number of plasmids with the pSC101 origin. All mutations identified in this study occurred on plasmids which also contained at least one mutation localized to the RepA protein encoded within the origin. Homology modelling predicts that many of these mutations occur within the dimerization interface of RepA. Mutant RepA resulted in plasmid copy numbers between ~31 and ~113 copies/cell, relative to ~5 copies/cell in wild-type pSC101 plasmids. Combining the mutations that were predicted to disrupt multiple contacts on the dimerization interface resulted in copy numbers of ~500 copies/cell, while also attenuating growth in host strains. Fluorescent protein production expressed from an arabinose-inducible promoter on mutant origin derived plasmids did correlate with copy number. Plasmids harboring RepA with one of two mutations, E83K and N99D, resulted in fluorescent protein production similar to that from p15a- (~20 copies/cell) and ColE1- (~31 copies/cell) based plasmids, respectively. The mutant copy number variants retained compatibility with p15a, pBBR, and ColE1 origins of replication. These pSC101 variants may be useful in future metabolic engineering efforts that require medium or high-copy vectors compatible with p15a- and ColE1-based plasmids.
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Felletti M, Bieber A, Hartig JS. The 3'-untranslated region of mRNAs as a site for ribozyme cleavage-dependent processing and control in bacteria. RNA Biol 2017; 14:1522-1533. [PMID: 27690736 DOI: 10.1080/15476286.2016.1240141] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
Besides its primary informational role, the sequence of the mRNA (mRNA) including its 5'- and 3'- untranslated regions (UTRs), contains important features that are relevant for post-transcriptional and translational regulation of gene expression. In this work a number of bacterial twister motifs are characterized both in vitro and in vivo. The analysis of their genetic contexts shows that these motifs have the potential of being transcribed as part of polycistronic mRNAs, thus we suggest the involvement of bacterial twister motifs in the processing of mRNA. Our data show that the ribozyme-mediated cleavage of the bacterial 3'-UTR has major effects on gene expression. While the observed effects correlate weakly with the kinetic parameters of the ribozymes, they show dependence on motif-specific structural features and on mRNA stabilization properties of the secondary structures that remain on the 3'-UTR after ribozyme cleavage. Using these principles, novel artificial twister-based riboswitches are developed that exert their activity via ligand-dependent cleavage of the 3'-UTR and the removal of the protective intrinsic terminator. Our results provide insights into possible biological functions of these recently discovered and widespread catalytic RNA motifs and offer new tools for applications in biotechnology, synthetic biology and metabolic engineering.
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Affiliation(s)
- Michele Felletti
- a Department of Chemistry , University of Konstanz , Konstanz , Germany.,b Konstanz Research School Chemical Biology (Kors-CB), University of Konstanz Konstanz , Germany
| | - Anna Bieber
- a Department of Chemistry , University of Konstanz , Konstanz , Germany
| | - Jörg S Hartig
- a Department of Chemistry , University of Konstanz , Konstanz , Germany.,b Konstanz Research School Chemical Biology (Kors-CB), University of Konstanz Konstanz , Germany
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Wu G, Yan Q, Jones JA, Tang YJ, Fong SS, Koffas MA. Metabolic Burden: Cornerstones in Synthetic Biology and Metabolic Engineering Applications. Trends Biotechnol 2016; 34:652-664. [DOI: 10.1016/j.tibtech.2016.02.010] [Citation(s) in RCA: 365] [Impact Index Per Article: 45.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 02/18/2016] [Accepted: 02/19/2016] [Indexed: 01/23/2023]
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8
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Meyer S, Chappell J, Sankar S, Chew R, Lucks JB. Improving fold activation of small transcription activating RNAs (STARs) with rational RNA engineering strategies. Biotechnol Bioeng 2015; 113:216-25. [PMID: 26134708 DOI: 10.1002/bit.25693] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Revised: 06/04/2015] [Accepted: 06/23/2015] [Indexed: 01/16/2023]
Abstract
Regulatory RNAs have become integral components of the synthetic biology and bioengineering toolbox for controlling gene expression. We recently expanded this toolbox by creating small transcription activating RNAs (STARs) that act by disrupting the formation of a target transcriptional terminator hairpin placed upstream of a gene. While STARs are a promising addition to the repertoire of RNA regulators, much work remains to be done to optimize the fold activation of these systems. Here we apply rational RNA engineering strategies to improve the fold activation of two STAR regulators. We demonstrate that a combination of promoter strength tuning and multiple RNA engineering strategies can improve fold activation from 5.4-fold to 13.4-fold for a STAR regulator derived from the pbuE riboswitch terminator. We then validate the generality of our approach and show that these same strategies improve fold activation from 2.1-fold to 14.6-fold for an unrelated STAR regulator, opening the door to creating a range of additional STARs to use in a broad array of biotechnologies. We also establish that the optimizations preserve the orthogonality of these STARs between themselves and a set of RNA transcriptional repressors, enabling these optimized STARs to be used in sophisticated circuits.
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Affiliation(s)
- Sarai Meyer
- School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853
| | - James Chappell
- School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853
| | - Sitara Sankar
- School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853
| | - Rebecca Chew
- School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853
| | - Julius B Lucks
- School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853.
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9
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Synthetic regulatory RNAs as tools for engineering biological systems: Design and applications. Chem Eng Sci 2013. [DOI: 10.1016/j.ces.2013.01.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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10
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Hochkoeppler A. Expanding the landscape of recombinant protein production in Escherichia coli. Biotechnol Lett 2013; 35:1971-81. [DOI: 10.1007/s10529-013-1396-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 06/26/2013] [Indexed: 12/11/2022]
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11
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Construction of a 5′-controllable stabilizing element (CoSE) for over-production of heterologous proteins at high levels in Bacillus subtilis. J Biotechnol 2013; 168:32-9. [DOI: 10.1016/j.jbiotec.2013.07.031] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 07/24/2013] [Accepted: 07/24/2013] [Indexed: 01/26/2023]
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12
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Flowers D, Thompson RA, Birdwell D, Wang T, Trinh CT. SMET: Systematic multiple enzyme targeting - a method to rationally design optimal strains for target chemical overproduction. Biotechnol J 2013; 8:605-18. [DOI: 10.1002/biot.201200233] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2012] [Revised: 03/26/2013] [Accepted: 04/03/2013] [Indexed: 01/07/2023]
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13
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Rationally designed families of orthogonal RNA regulators of translation. Nat Chem Biol 2012; 8:447-54. [DOI: 10.1038/nchembio.919] [Citation(s) in RCA: 144] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Accepted: 01/27/2012] [Indexed: 12/19/2022]
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A T7 RNA polymerase-based toolkit for the concerted expression of clustered genes. J Biotechnol 2012; 159:162-71. [PMID: 22285639 DOI: 10.1016/j.jbiotec.2012.01.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Revised: 12/16/2011] [Accepted: 01/10/2012] [Indexed: 11/21/2022]
Abstract
Bacterial genes whose enzymes are either assembled into complex multi-domain proteins or form biosynthetic pathways are frequently organized within large chromosomal clusters. The functional expression of clustered genes, however, remains challenging since it generally requires an expression system that facilitates the coordinated transcription of numerous genes irrespective of their natural promoters and terminators. Here, we report on the development of a novel expression system that is particularly suitable for the homologous expression of multiple genes organized in a contiguous cluster. The new expression toolkit consists of an Ω interposon cassette carrying a T7 RNA polymerase specific promoter which is designed for promoter tagging of clustered genes and a small set of broad-host-range plasmids providing the respective polymerase in different bacteria. The uptake hydrogenase gene locus of the photosynthetic non-sulfur purple bacterium Rhodobacter capsulatus which consists of 16 genes was used as an example to demonstrate functional expression only by T7 RNA polymerase but not by bacterial RNA polymerase. Our findings clearly indicate that due to its unique properties T7 RNA polymerase can be applied for overexpression of large and complex bacterial gene regions.
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Gulevich AY, Skorokhodova AY, Ermishev VY, Krylov AA, Minaeva NI, Polonskaya ZM, Zimenkov DV, Biryukova IV, Mashko SV. A new method for the construction of translationally coupled operons in a bacterial chromosome. Mol Biol 2009; 43:505-11. [DOI: 10.1134/s0026893309030194] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Bahl MI, Hansen LH, Licht TR, Sørensen SJ. In vivo detection and quantification of tetracycline by use of a whole-cell biosensor in the rat intestine. Antimicrob Agents Chemother 2004; 48:1112-7. [PMID: 15047509 PMCID: PMC375317 DOI: 10.1128/aac.48.4.1112-1117.2004] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
An Escherichia coli biosensor strain, harboring the plasmid pTGFP2, was introduced into the gastrointestinal tract of gnotobiotic rats that continuously received drinking water containing tetracycline. Plasmid pTGFP2 contains a transcriptional fusion between a green fluorescent protein (GFP) gene and a tetracycline-regulated promoter and was shown to produce a proportional GFP signal in response to exposure to various tetracycline concentrations when harbored by an E. coli strain. The plasmid was highly unstable in the host bacteria colonizing the intestinal system of the animals, and rapid plasmid loss was observed. Reintroduction of the E. coli MC4100/pTGFP2 strain into animals already colonized by the plasmid-free E. coli strain the day before euthanasia made it possible to extract and analyze the biosensors from intestinal samples. The induction of GFP in the biosensor cells extracted from the animals was estimated on a single-cell basis by use of flow cytometry, and the mean induction of GFP in the samples was compared to a standard curve prepared from known tetracycline concentrations. The results showed that the bioavailable tetracycline concentration within the bacterial growth habitat of the intestine was proportional to the concentration of tetracycline in drinking water but represented only approximately 0.4% of the intake concentration. This is a significant finding which will help to clarify antimicrobial therapy in the intestinal environment.
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Affiliation(s)
- Martin Iain Bahl
- Department of Microbiology, University of Copenhagen, 1307 Copenhagen K, Denmark
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Murli S, Kennedy J, Dayem LC, Carney JR, Kealey JT. Metabolic engineering of Escherichia coli for improved 6-deoxyerythronolide B production. J Ind Microbiol Biotechnol 2003; 30:500-9. [PMID: 12898389 DOI: 10.1007/s10295-003-0073-x] [Citation(s) in RCA: 105] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2002] [Accepted: 04/13/2003] [Indexed: 10/26/2022]
Abstract
Escherichia coli is an attractive candidate as a host for polyketide production and has been engineered to produce the erythromycin precursor polyketide 6-deoxyerythronolide B (6dEB). In order to identify and optimize parameters that affect polyketide production in engineered E. coli, we first investigated the supply of the extender unit ( 2S)-methylmalonyl-CoA via three independent pathways. Expression of the Streptomyces coelicolor malonyl/methylmalonyl-CoA ligase ( matB) pathway in E. coli together with methylmalonate feeding resulted in the accumulation of intracellular methylmalonyl-CoA to as much as 90% of the acyl-CoA pool. Surprisingly, the methylmalonyl-CoA generated from the matB pathway was not converted into 6dEB. In strains expressing either the S. coelicolor propionyl-CoA carboxylase (PCC) pathway or the Propionibacteria shermanii methylmalonyl-CoA mutase/epimerase pathway, methylmalonyl-CoA accumulated up to 30% of the total acyl-CoA pools, and 6dEB was produced; titers were fivefold higher when strains contained the PCC pathway rather than the mutase pathway. When the PCC and mutase pathways were expressed simultaneously, the PCC pathway predominated, as indicated by greater flux of (13)C-propionate into 6dEB through the PCC pathway. To further optimize the E. coli production strain, we improved 6dEB titers by integrating the PCC and mutase pathways into the E. coli chromosome and by expressing the 6-deoxyerythronolide B synthase (DEBS) genes from a stable plasmid system.
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Affiliation(s)
- Sumati Murli
- Kosan Biosciences, 3832 Bay Center Place, Hayward, CA 94545, USA
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Vazquez G, Wedel BJ, Trebak M, St John Bird G, Putney JW. Expression level of the canonical transient receptor potential 3 (TRPC3) channel determines its mechanism of activation. J Biol Chem 2003; 278:21649-54. [PMID: 12686562 DOI: 10.1074/jbc.m302162200] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Studies on the mechanism of activation of canonical transient receptor potential (TRPC) channels have often yielded conflicting results. In the current study, we have investigated the influence of expression level on the mode of regulation of TRPC3 channels. At relatively low levels of expression in DT40 chicken B-lymphocytes, TRPC3 was activated by the depletion of Ca2+ stores. Expression was increased by either transfecting with a 10-fold greater concentration of plasmid or transfecting with TRPC3 under control of a more efficient avian beta-actin promoter. At higher levels of expression, TRPC3 was no longer store-operated but could be activated through receptor-coupled phospholipase C. Under these expression conditions, TRPC3 was efficiently activated in DT40 cells lacking inositol 1,4,5-trisphosphate receptors. The Ca2+ store-operated channels formed upon expression of TRPC3 at limited levels were blocked by gadolinium; the receptor-activated channels formed upon expression of higher levels of TRPC3 were insensitive to gadolinium. These findings indicate that a single ion channel protein can form or contribute to the formation of channels regulated in two very distinct ways, i.e. either by phospholipase C-derived messengers or Ca2+ store-depletion. The mechanism of regulation of the channels depends on their level of expression.
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Affiliation(s)
- Guillermo Vazquez
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health/DHHS, Research Triangle Park, NC 27709, USA
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Smolke CD, Keasling JD. Effect of gene location, mRNA secondary structures, and RNase sites on expression of two genes in an engineered operon. Biotechnol Bioeng 2002; 80:762-76. [PMID: 12402322 DOI: 10.1002/bit.10434] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The effects of endoribonuclease sites, secondary structures in mRNA, and gene placement on protein production and mRNA stability and steady-state levels were tested in a dual-gene operon containing the genes encoding beta-galactosidase (lacZ) from Escherichia coli and green fluorescent protein (gfp) from Aequorea victoria. Two previously identified RNase E sites were placed separately between the coding regions to direct cleavage in this area and produce two secondary transcripts, each containing a single-gene coding region. Novel secondary structures were engineered into the 3' and 5' ends of each of the coding regions to protect the transcript from inactivation by endoribonucleases (5' hairpins) and degradation by exoribonucleases (3' hairpins). In addition, the effects of relative gene placement were examined by switching the locations of the two coding regions. Depending on the particular secondary structures and RNase E sites placed between the genes the relative steady-state transcript and protein levels encoded by the two reporter genes could be changed up to 2.5-fold and 4-fold, respectively. By changing gene location and incorporating secondary structures and RNase E sites the relative steady-state transcript and protein levels encoded by the two reporter genes could be changed up to 100-fold and 750-fold, respectively.
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Affiliation(s)
- Christina D Smolke
- Department of Chemical Engineering, University of California, Berkeley 94720-1462, USA
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