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Moreira de Gouveia MI, Reuter A, Garrivier A, Daniel J, Bernalier-Donadille A, Jubelin G. Design and validation of a dual-fluorescence reporter system to monitor bacterial gene expression in the gut environment. Appl Microbiol Biotechnol 2023; 107:7301-7312. [PMID: 37750914 DOI: 10.1007/s00253-023-12788-7] [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: 06/22/2023] [Revised: 09/04/2023] [Accepted: 09/10/2023] [Indexed: 09/27/2023]
Abstract
Fluorescence-based reporter systems are valuable tools for studying gene expression dynamics in living cells. However, available strategies to follow gene expression in bacteria within their natural ecosystem that can be typically rich and complex are scarce. In this work, we designed a plasmid-based tool ensuring both the identification of a strain of interest in complex environments and the monitoring of gene expression through the combination of two distinct fluorescent proteins as reporter genes. The tool was validated in Escherichia coli to monitor the expression of eut genes involved in the catabolism of ethanolamine. We demonstrated that the constructed reporter strain gradually responds with a bimodal output to increasing ethanolamine concentrations during in vitro cultures. The reporter strain was next inoculated to mice, and flow cytometry was used to detect the reporter strain among the dense microbiota of intestinal samples and to analyze specifically the expression of eut genes. This novel dual-fluorescent reporter system would be helpful to evaluate transcriptional processes in bacteria within complex environments. KEY POINTS: • A reporter tool was developed to monitor bacterial gene expression in complex environments. • Ethanolamine utilization (eut) genes are expressed by commensal E. coli in the mouse gut. • Expression of eut genes follows a bimodal distribution.
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Affiliation(s)
| | - Audrey Reuter
- Université Clermont Auvergne, INRAE, MEDIS UMR454, F-63000, Clermont-Ferrand, France
| | - Annie Garrivier
- Université Clermont Auvergne, INRAE, MEDIS UMR454, F-63000, Clermont-Ferrand, France
| | - Julien Daniel
- Université Clermont Auvergne, INRAE, MEDIS UMR454, F-63000, Clermont-Ferrand, France
| | | | - Gregory Jubelin
- Université Clermont Auvergne, INRAE, MEDIS UMR454, F-63000, Clermont-Ferrand, France.
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2
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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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3
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Jiao C, Sharma S, Dugar G, Peeck NL, Bischler T, Wimmer F, Yu Y, Barquist L, Schoen C, Kurzai O, Sharma CM, Beisel CL. Noncanonical crRNAs derived from host transcripts enable multiplexable RNA detection by Cas9. Science 2021; 372:941-948. [PMID: 33906967 PMCID: PMC8224270 DOI: 10.1126/science.abe7106] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Accepted: 04/09/2021] [Indexed: 12/19/2022]
Abstract
CRISPR-Cas systems recognize foreign genetic material using CRISPR RNAs (crRNAs). In type II systems, a trans-activating crRNA (tracrRNA) hybridizes to crRNAs to drive their processing and utilization by Cas9. While analyzing Cas9-RNA complexes from Campylobacter jejuni, we discovered tracrRNA hybridizing to cellular RNAs, leading to formation of "noncanonical" crRNAs capable of guiding DNA targeting by Cas9. Our discovery inspired the engineering of reprogrammed tracrRNAs that link the presence of any RNA of interest to DNA targeting with different Cas9 orthologs. This capability became the basis for a multiplexable diagnostic platform termed LEOPARD (leveraging engineered tracrRNAs and on-target DNAs for parallel RNA detection). LEOPARD allowed simultaneous detection of RNAs from different viruses in one test and distinguished severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its D614G (Asp614→Gly) variant with single-base resolution in patient samples.
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Affiliation(s)
- Chunlei Jiao
- Helmholtz Institute for RNA-based Infection Research (HIRI)/Helmholtz-Centre for Infection Research (HZI), 97080 Würzburg, Germany
| | - Sahil Sharma
- Molecular Infection Biology II, Institute of Molecular Infection Biology, University of Würzburg. 97080 Würzburg, Germany
| | - Gaurav Dugar
- Molecular Infection Biology II, Institute of Molecular Infection Biology, University of Würzburg. 97080 Würzburg, Germany
| | - Natalia L Peeck
- Helmholtz Institute for RNA-based Infection Research (HIRI)/Helmholtz-Centre for Infection Research (HZI), 97080 Würzburg, Germany
| | - Thorsten Bischler
- Core Unit Systems Medicine, University of Würzburg, 97080 Würzburg, Germany
| | - Franziska Wimmer
- Helmholtz Institute for RNA-based Infection Research (HIRI)/Helmholtz-Centre for Infection Research (HZI), 97080 Würzburg, Germany
| | - Yanying Yu
- Helmholtz Institute for RNA-based Infection Research (HIRI)/Helmholtz-Centre for Infection Research (HZI), 97080 Würzburg, Germany
| | - Lars Barquist
- Helmholtz Institute for RNA-based Infection Research (HIRI)/Helmholtz-Centre for Infection Research (HZI), 97080 Würzburg, Germany
- Medical Faculty, University of Würzburg, 97080 Würzburg, Germany
| | - Christoph Schoen
- Institute for Hygiene and Microbiology, University of Würzburg, 97080 Würzburg, Germany
| | - Oliver Kurzai
- Institute for Hygiene and Microbiology, University of Würzburg, 97080 Würzburg, Germany
- Leibniz Institute for Natural Product Research and Infection Biology, Hans-Knoell-Institute, Jena, 07745 Germany
| | - Cynthia M Sharma
- Molecular Infection Biology II, Institute of Molecular Infection Biology, University of Würzburg. 97080 Würzburg, Germany.
| | - Chase L Beisel
- Helmholtz Institute for RNA-based Infection Research (HIRI)/Helmholtz-Centre for Infection Research (HZI), 97080 Würzburg, Germany.
- Medical Faculty, University of Würzburg, 97080 Würzburg, Germany
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4
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Collins SP, Rostain W, Liao C, Beisel CL. Sequence-independent RNA sensing and DNA targeting by a split domain CRISPR-Cas12a gRNA switch. Nucleic Acids Res 2021; 49:2985-2999. [PMID: 33619539 PMCID: PMC7968991 DOI: 10.1093/nar/gkab100] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 01/13/2021] [Accepted: 02/04/2021] [Indexed: 12/11/2022] Open
Abstract
CRISPR technologies increasingly require spatiotemporal and dosage control of nuclease activity. One promising strategy involves linking nuclease activity to a cell's transcriptional state by engineering guide RNAs (gRNAs) to function only after complexing with a ‘trigger’ RNA. However, standard gRNA switch designs do not allow independent selection of trigger and guide sequences, limiting gRNA switch application. Here, we demonstrate the modular design of Cas12a gRNA switches that decouples selection of these sequences. The 5′ end of the Cas12a gRNA is fused to two distinct and non-overlapping domains: one base pairs with the gRNA repeat, blocking formation of a hairpin required for Cas12a recognition; the other hybridizes to the RNA trigger, stimulating refolding of the gRNA repeat and subsequent gRNA-dependent Cas12a activity. Using a cell-free transcription-translation system and Escherichia coli, we show that designed gRNA switches can respond to different triggers and target different DNA sequences. Modulating the length and composition of the sensory domain altered gRNA switch performance. Finally, gRNA switches could be designed to sense endogenous RNAs expressed only under specific growth conditions, rendering Cas12a targeting activity dependent on cellular metabolism and stress. Our design framework thus further enables tethering of CRISPR activities to cellular states.
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Affiliation(s)
- Scott P Collins
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
| | - William Rostain
- Génomique Métabolique, Genoscope, Institut François Jacob, CEA, CNRS, Univ Evry, Université Paris-Saclay, 91057 Évry, France
| | - Chunyu Liao
- Helmholtz Institute for RNA-based Infection Research (HIRI)/Helmholtz Centre for Infection Research (HZI), Josef-Schneider-Str. 2/D15, 97080 Würzburg, Germany
| | - Chase L Beisel
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA.,Helmholtz Institute for RNA-based Infection Research (HIRI)/Helmholtz Centre for Infection Research (HZI), Josef-Schneider-Str. 2/D15, 97080 Würzburg, Germany.,Medical Faculty, University of Würzburg, 97080 Würzburg, Germany
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5
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Stargardt P, Striedner G, Mairhofer J. Tunable expression rate control of a growth-decoupled T7 expression system by L-arabinose only. Microb Cell Fact 2021; 20:27. [PMID: 33522916 PMCID: PMC7852362 DOI: 10.1186/s12934-021-01512-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Accepted: 01/07/2021] [Indexed: 02/07/2023] Open
Abstract
BACKGROUND Precise regulation of gene expression is of utmost importance for the production of complex membrane proteins (MP), enzymes or other proteins toxic to the host cell. In this article we show that genes under control of a normally Isopropyl β-D-1-thiogalactopyranoside (IPTG)-inducible PT7-lacO promoter can be induced solely with L-arabinose in a newly constructed Escherichia coli expression host BL21-AI<gp2>, a strain based on the recently published approach of bacteriophage inspired growth-decoupled recombinant protein production. RESULTS Here, we show that BL21-AI<gp2> is able to precisely regulate protein production rates on a cellular level in an L-arabinose concentration-dependent manner and simultaneously allows for reallocation of metabolic resources due to L-arabinose induced growth decoupling by the phage derived inhibitor peptide Gp2. We have successfully characterized the system under relevant fed-batch like conditions in microscale cultivation (800 µL) and generated data proofing a relevant increase in specific yields for 6 different Escherichia coli derived MP-GFP fusion proteins by using online-GFP signals, FACS analysis, SDS-PAGE and western blotting. CONCLUSIONS In all cases tested, BL21-AI<gp2> outperformed the parental strain BL21-AI, operated in growth-associated production mode. Specific MP-GFP fusion proteins yields have been improved up to 2.7-fold. Therefore, this approach allows for fine tuning of MP production or expression of multi-enzyme pathways where e.g. particular stoichiometries have to be met to optimize product flux.
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Affiliation(s)
| | - Gerald Striedner
- Department of Biotechnology, University of Natural Resources and Life Sciences (BOKU), Muthgasse 18, 1190, Vienna, Austria
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Availability of the Molecular Switch XylR Controls Phenotypic Heterogeneity and Lag Duration during Escherichia coli Adaptation from Glucose to Xylose. mBio 2020; 11:mBio.02938-20. [PMID: 33443125 PMCID: PMC8534289 DOI: 10.1128/mbio.02938-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The glucose-xylose metabolic transition is of growing interest as a model to explore cellular adaption since these molecules are the main substrates resulting from the deconstruction of lignocellulosic biomass. Here, we investigated the role of the XylR transcription factor in the length of the lag phases when the bacterium Escherichia coli needs to adapt from glucose- to xylose-based growth. First, a variety of lag times were observed when different strains of E. coli were switched from glucose to xylose. These lag times were shown to be controlled by XylR availability in the cells with no further effect on the growth rate on xylose. XylR titration provoked long lag times demonstrated to result from phenotypic heterogeneity during the switch from glucose to xylose, with a subpopulation unable to resume exponential growth, whereas the other subpopulation grew exponentially on xylose. A stochastic model was then constructed based on the assumption that XylR availability influences the probability of individual cells to switch to xylose growth. The model was used to understand how XylR behaves as a molecular switch determining the bistability set-up. This work shows that the length of lag phases in E. coli is controllable and reinforces the role of stochastic mechanism in cellular adaptation, paving the way for new strategies for the better use of sustainable carbon sources in bioeconomy.
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7
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Zeng L, Burne RA. Subpopulation behaviors in lactose metabolism by Streptococcus mutans. Mol Microbiol 2020; 115:58-69. [PMID: 32881164 DOI: 10.1111/mmi.14596] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 08/17/2020] [Accepted: 08/24/2020] [Indexed: 01/08/2023]
Abstract
When Streptococcus mutans is transferred from a preferred carbohydrate (glucose or fructose) to lactose, initiation of growth can take several hours, and substantial amounts of glucose are released during growth. Here, S. mutans strains UA159 and GS-5 were examined for stochastic behaviors in transcription of the lac operon. Using a gfp reporter fusion, we demonstrated that induction of the lac operon occurs in only a fraction of the population, with prior exposure to carbohydrate source and strain influencing the magniture of the sub-population response. Lower glucokinase activity in GS-5 was associated with release of substantially more glucose than UA159 and significantly lower lac expression. Mutants unable to use lactose grew on lactose as the sole carbohydrate when strains with an intact lac operon were also present in the cultures, indicative of the potential for population cheating. Utilizing a set of engineered obligate cheating and non-cheating strains, we confirmed that cheating can sustain a heterogeneous population. Futher, obligate cheaters of GS-5 competed well with the non-cheaters and showed a high degree of competitive fitness in a human-derived consortium biofilm model. The results show that bet-hedging behaviors in carbohydrate metabolism may substantially influence the composition and pathogenic potential of oral biofilms.
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Affiliation(s)
- Lin Zeng
- Department of Oral Biology, University of Florida College of Dentistry, Gainesville, FL, USA
| | - Robert A Burne
- Department of Oral Biology, University of Florida College of Dentistry, Gainesville, FL, USA
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Ogura M, Shindo K, Kanesaki Y. Bacillus subtilis Nucleoid-Associated Protein YlxR Is Involved in Bimodal Expression of the Fructoselysine Utilization Operon ( frlBONMD-yurJ) Promoter. Front Microbiol 2020; 11:2024. [PMID: 32983026 PMCID: PMC7475707 DOI: 10.3389/fmicb.2020.02024] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 07/30/2020] [Indexed: 11/13/2022] Open
Abstract
Bacteria must survive harsh environmental fluctuations at times and have evolved several strategies. “Collective” behaviors have been identified due to recent progress in single-cell analysis. Since most bacteria exist as single cells, bacterial populations are often considered clonal. However, accumulated evidence suggests this is not the case. Gene expression and protein expression are often not homogeneous, resulting in phenotypic heterogeneity. In extreme cases, this leads to bistability, the existence of two stable states. In many cases, expression of key master regulators is bimodal via positive feedback loops causing bimodal expression of the target genes. We observed bimodal expression of metabolic genes for alternative carbon sources. Expression profiles of the frlBONMD-yurJ operon driven by the frlB promoter (PfrlB), which encodes degradation enzymes and a transporter for amino sugars including fructoselysine, were investigated using transcriptional lacZ and gfp, and translational fluorescence reporter mCherry fusions. Disruption effects of genes encoding CodY, FrlR, RNaseY, and nucleoid-associated protein YlxR, four known regulatory factors for PfrlB, were examined for expression of each fusion construct. Expression of PfrlB-gfp and PfrlB-mCherry, which were located at amyE and its original locus, respectively, was bimodal; and disruption of ylxR resulted in the disappearance of the clear bimodal expression pattern in flow cytometric analyses. This suggested a role for YlxR on the bimodal expression of PfrlB. The data indicated that YlxR acted on the bimodal expression of PfrlB through both transcription and translation. YlxR regulates many genes, including those related to translation, supporting the above notion. Depletion of RNaseY abolished heterogenous expression of transcriptional PfrlB-gfp but not bimodal expression of translational PfrlB-mCherry, suggesting the role of RNaseY in regulation of the operon through mRNA stability control and regulatory mechanism for PfrlB-mCherry at the translational level. Based on these results, we discuss the meaning and possible cause of bimodal PfrlB expression.
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Affiliation(s)
- Mitsuo Ogura
- Institute of Oceanic Research and Development, Tokai University, Shizuoka, Japan
| | - Kazutoshi Shindo
- Department of Food and Nutrition, Japan Women's University, Tokyo, Japan
| | - Yu Kanesaki
- Research Institute of Green Science and Technology, Shizuoka University, Shizuoka, Japan
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Colarusso A, Lauro C, Calvanese M, Parrilli E, Tutino ML. Improvement of Pseudoalteromonas haloplanktis TAC125 as a Cell Factory: IPTG-Inducible Plasmid Construction and Strain Engineering. Microorganisms 2020; 8:microorganisms8101466. [PMID: 32987756 PMCID: PMC7598627 DOI: 10.3390/microorganisms8101466] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2020] [Revised: 09/19/2020] [Accepted: 09/22/2020] [Indexed: 02/06/2023] Open
Abstract
Our group has used the marine bacterium Pseudoalteromonas haloplanktis TAC125 (PhTAC125) as a platform for the successful recombinant production of “difficult” proteins, including eukaryotic proteins, at low temperatures. However, there is still room for improvement both in the refinement of PhTAC125 expression plasmids and in the bacterium’s intrinsic ability to accumulate and handle heterologous products. Here, we present an integrated approach of plasmid design and strain engineering finalized to increment the recombinant expression and optimize the inducer uptake in PhTAC125. To this aim, we developed the IPTG-inducible plasmid pP79 and an engineered PhTAC125 strain called KrPL LacY+. This mutant was designed to express the E. coli lactose permease and to produce only a truncated version of the endogenous Lon protease through an integration-deletion strategy. In the wild-type strain, pP79 assured a significantly better production of two reporters in comparison to the most recent expression vector employed in PhTAC125. Nevertheless, the use of KrPL LacY+ was crucial to achieving satisfying production levels using reasonable IPTG concentrations, even at 0 °C. Both the wild-type and the mutant recombinant strains are characterized by an average graded response upon IPTG induction and they will find different future applications depending on the desired levels of expression.
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10
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Schuller A, Cserjan-Puschmann M, Tauer C, Jarmer J, Wagenknecht M, Reinisch D, Grabherr R, Striedner G. Escherichia coli σ 70 promoters allow expression rate control at the cellular level in genome-integrated expression systems. Microb Cell Fact 2020; 19:58. [PMID: 32138729 PMCID: PMC7059391 DOI: 10.1186/s12934-020-01311-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 02/17/2020] [Indexed: 12/18/2022] Open
Abstract
Background The genome-integrated T7 expression system offers significant advantages, in terms of productivity and product quality, even when expressing the gene of interest (GOI) from a single copy. Compared to plasmid-based expression systems, this system does not incur a plasmid-mediated metabolic load, and it does not vary the dosage of the GOI during the production process. However, long-term production with T7 expression system leads to a rapidly growing non-producing population, because the T7 RNA polymerase (RNAP) is prone to mutations. The present study aimed to investigate whether two σ70 promoters, which were recognized by the Escherichia coli host RNAP, might be suitable in genome-integrated expression systems. We applied a promoter engineering strategy that allowed control of expressing the model protein, GFP, by introducing lac operators (lacO) into the constitutive T5 and A1 promoter sequences. Results We showed that, in genome-integrated E. coli expression systems that used σ70 promoters, the number of lacO sites must be well balanced. Promoters containing three and two lacO sites exhibited low basal expression, but resulted in a complete stop in recombinant protein production in partially induced cultures. In contrast, expression systems regulated by a single lacO site and the lac repressor element, lacIQ, on the same chromosome caused very low basal expression, were highly efficient in recombinant protein production, and enables fine-tuning of gene expression levels on a cellular level. Conclusions Based on our results, we hypothesized that this phenomenon was associated with the autoregulation of the lac repressor protein, LacI. We reasoned that the affinity of LacI for the lacO sites of the GOI must be lower than the affinity of LacI to the lacO sites of the endogenous lac operon; otherwise, LacI autoregulation could not take place, and the lack of LacI autoregulation would lead to a disturbance in lac repressor-mediated regulation of transcription. By exploiting the mechanism of LacI autoregulation, we created a novel E. coli expression system for use in recombinant protein production, synthetic biology, and metabolic engineering applications.
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Affiliation(s)
- Artur Schuller
- Christian Doppler Laboratory for Production of Next-level Biopharmaceuticals in E. coli, Department of Biotechnology, University of Natural Resources and Life Sciences, Muthgasse 18, 1190, Vienna, Austria
| | - Monika Cserjan-Puschmann
- Christian Doppler Laboratory for Production of Next-level Biopharmaceuticals in E. coli, Department of Biotechnology, University of Natural Resources and Life Sciences, Muthgasse 18, 1190, Vienna, Austria.
| | - Christopher Tauer
- Christian Doppler Laboratory for Production of Next-level Biopharmaceuticals in E. coli, Department of Biotechnology, University of Natural Resources and Life Sciences, Muthgasse 18, 1190, Vienna, Austria
| | - Johanna Jarmer
- Boehringer Ingelheim RCV GmbH & Co KG, Dr.-Boehringer-Gasse 5-11, 1120, Vienna, Austria
| | - Martin Wagenknecht
- Boehringer Ingelheim RCV GmbH & Co KG, Dr.-Boehringer-Gasse 5-11, 1120, Vienna, Austria
| | - Daniela Reinisch
- Boehringer Ingelheim RCV GmbH & Co KG, Dr.-Boehringer-Gasse 5-11, 1120, Vienna, Austria
| | - Reingard Grabherr
- Christian Doppler Laboratory for Production of Next-level Biopharmaceuticals in E. coli, Department of Biotechnology, University of Natural Resources and Life Sciences, Muthgasse 18, 1190, Vienna, Austria
| | - Gerald Striedner
- Christian Doppler Laboratory for Production of Next-level Biopharmaceuticals in E. coli, Department of Biotechnology, University of Natural Resources and Life Sciences, Muthgasse 18, 1190, Vienna, Austria
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11
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Modular one-pot assembly of CRISPR arrays enables library generation and reveals factors influencing crRNA biogenesis. Nat Commun 2019; 10:2948. [PMID: 31270316 PMCID: PMC6610086 DOI: 10.1038/s41467-019-10747-3] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 05/22/2019] [Indexed: 12/19/2022] Open
Abstract
CRISPR-Cas systems inherently multiplex through CRISPR arrays—whether to defend against different invaders or mediate multi-target editing, regulation, imaging, or sensing. However, arrays remain difficult to generate due to their reoccurring repeat sequences. Here, we report a modular, one-pot scheme called CRATES to construct CRISPR arrays and array libraries. CRATES allows assembly of repeat-spacer subunits using defined assembly junctions within the trimmed portion of spacers. Using CRATES, we construct arrays for the single-effector nucleases Cas9, Cas12a, and Cas13a that mediated multiplexed DNA/RNA cleavage and gene regulation in cell-free systems, bacteria, and yeast. CRATES further allows the one-pot construction of array libraries and composite arrays utilized by multiple Cas nucleases. Finally, array characterization reveals processing of extraneous CRISPR RNAs from Cas12a terminal repeats and sequence- and context-dependent loss of RNA-directed nuclease activity via global RNA structure formation. CRATES thus can facilitate diverse multiplexing applications and help identify factors impacting crRNA biogenesis. CRISPR array generation is difficult due to reoccurring repeat sequences. Here the authors present CRATES—a modular, one-pot assembly method—and demonstrate the creation of arrays for Cas9, Cas12a and Cas13a for cell-free, bacterial, yeast and mammalian systems.
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12
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Liao C, Slotkowski RA, Achmedov T, Beisel CL. The Francisella novicida Cas12a is sensitive to the structure downstream of the terminal repeat in CRISPR arrays. RNA Biol 2019; 16:404-412. [PMID: 30252595 PMCID: PMC6546362 DOI: 10.1080/15476286.2018.1526537] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Revised: 09/07/2018] [Accepted: 09/11/2018] [Indexed: 10/28/2022] Open
Abstract
The Class 2 Type V-A CRISPR effector protein Cas12a/Cpf1 has gained widespread attention in part because of the ease in achieving multiplexed genome editing, gene regulation, and DNA detection. Multiplexing derives from the ability of Cas12a alone to generate multiple guide RNAs from a transcribed CRISPR array encoding alternating conserved repeats and targeting spacers. While array design has focused on how to optimize guide-RNA sequences, little attention has been paid to sequences outside of the CRISPR array. Here, we show that a structured hairpin located immediately downstream of the 3' repeat interferes with utilization of the adjacent encoded guide RNA by Francisella novicida (Fn)Cas12a. We first observed that a synthetic Rho-independent terminator immediately downstream of an array impaired DNA cleavage based on plasmid clearance in E. coli and DNA cleavage in a cell-free transcription-translation (TXTL) system. TXTL-based cleavage assays further revealed that inhibition was associated with incomplete processing of the transcribed CRISPR array and could be attributed to the stable hairpin formed by the terminator. We also found that the inhibitory effect partially extended to upstream spacers in a multi-spacer array. Finally, we found that removing the terminal repeat from the array increased the inhibitory effect, while replacing this repeat with an unprocessable terminal repeat from a native FnCas12a array restored cleavage activity directed by the adjacent encoded guide RNA. Our study thus revealed that sequences surrounding a CRISPR array can interfere with the function of a CRISPR nuclease, with implications for the design and evolution of CRISPR arrays.
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Affiliation(s)
- Chunyu Liao
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC USA
- Helmholtz Institute for RNA-based Infection Research, Würzburg, Germany
| | - Rebecca A. Slotkowski
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC USA
| | - Tatjana Achmedov
- Helmholtz Institute for RNA-based Infection Research, Würzburg, Germany
| | - Chase L. Beisel
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC USA
- Helmholtz Institute for RNA-based Infection Research, Würzburg, Germany
- Faculty of Medicine, University of Würzburg, Würzburg, Germany
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13
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Kremling A, Geiselmann J, Ropers D, de Jong H. An ensemble of mathematical models showing diauxic growth behaviour. BMC SYSTEMS BIOLOGY 2018; 12:82. [PMID: 30241537 PMCID: PMC6151013 DOI: 10.1186/s12918-018-0604-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 08/20/2018] [Indexed: 11/17/2022]
Abstract
Background Carbon catabolite repression (CCR) controls the order in which different carbon sources are metabolised. Although this system is one of the paradigms of regulation in bacteria, the underlying mechanisms remain controversial. CCR involves the coordination of different subsystems of the cell - responsible for the uptake of carbon sources, their breakdown for the production of energy and precursors, and the conversion of the latter to biomass. The complexity of this integrated system, with regulatory mechanisms cutting across metabolism, gene expression, and signalling, has motivated important modelling efforts over the past four decades, especially in the enterobacterium Escherichia coli. Results Starting from a simple core model with only four intracellular metabolites, we develop an ensemble of model variants, all showing diauxic growth behaviour during a batch process. The model variants fall into one of the four categories: flux balance models, kinetic models with growth dilution, kinetic models with regulation, and resource allocation models. The model variants differ from one another in only a single aspect, each breaking the symmetry between the two substrate assimilation pathways in a different manner, and can be quantitatively compared using a so-called diauxic growth index. For each of the model variants, we predict the behaviour in two new experimental conditions, namely a glucose pulse for a culture growing in minimal medium with lactose and a batch culture with different initial concentrations of the components of the transport systems. When qualitatively comparing these predictions with experimental data for these two conditions, a number of models can be excluded while other model variants are still not discriminable. The best-performing model variants are based on inducer inclusion and activation of enzymatic genes by a global transcription factor, but the other proposed factors may complement these well-known regulatory mechanisms. Conclusions The model ensemble presented here offers a better understanding of the variety of mechanisms that have been proposed to play a role in CCR. In addition, it provides an educational resource for systems biology, as it gives an introduction to a broad range of modeling approaches in the context of a simple but biologically relevant example. Electronic supplementary material The online version of this article (10.1186/s12918-018-0604-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Andreas Kremling
- Systems Biotechnology, Technical University of Munich, Boltzmannstrasse 15, Garching b. München, 85748, Germany.
| | - Johannes Geiselmann
- Laboratoire Interdisciplinaire de Physique, Université Grenoble Alpes, 140 avenue de la Physique, Saint Martin d'Hères, 38402, France
| | - Delphine Ropers
- Inria, Université Grenoble Alpes, 655 avenue de l'Europe, Saint Ismier Cedex, 38334, France
| | - Hidde de Jong
- Inria, Université Grenoble Alpes, 655 avenue de l'Europe, Saint Ismier Cedex, 38334, France
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14
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Zong DM, Cinar S, Shis DL, Josić K, Ott W, Bennett MR. Predicting Transcriptional Output of Synthetic Multi-input Promoters. ACS Synth Biol 2018; 7:1834-1843. [PMID: 30040895 DOI: 10.1021/acssynbio.8b00165] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Recent advances in synthetic biology have led to a wealth of well-characterized genetic parts. As parts libraries grow, so too does the potential to create novel multi-input promoters that integrate disparate signals to determine transcriptional output. Our ability to construct such promoters will outpace our ability to characterize promoter performance, due to the vast number of input combinations. In this study, we examine the input-output relations of recently developed synthetic multi-input promoters and describe two methods for predicting their behavior. The first method uses 1-dimensional induction data obtained from experiments on single-input systems to predict the n-dimensional induction responses of systems with n inputs. We demonstrate that this approach accurately predicts Boolean (on/off) responses of multi-input systems consisting of novel chimeric transcription factors and hybrid promoters in Escherichia coli. The second method uses only a small amount of multi-input response data to accurately predict analog system response over the entire landscape of input combinations. Taken together, these methods facilitate the design of synthetic circuits that utilize multi-input promoters.
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Affiliation(s)
| | - Selahittin Cinar
- Department of Mathematics, ⊥Department of Biology and Biochemistry, University of Houston, Houston, Texas 77004, United States
| | | | - Krešimir Josić
- Department of Mathematics, ⊥Department of Biology and Biochemistry, University of Houston, Houston, Texas 77004, United States
| | - William Ott
- Department of Mathematics, ⊥Department of Biology and Biochemistry, University of Houston, Houston, Texas 77004, United States
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15
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Biosynthesis of selenium nanoparticles and effects of selenite, selenate, and selenomethionine on cell growth and morphology in Rahnella aquatilis HX2. Appl Microbiol Biotechnol 2018; 102:6191-6205. [PMID: 29806064 DOI: 10.1007/s00253-018-9060-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Revised: 04/23/2018] [Accepted: 04/27/2018] [Indexed: 01/13/2023]
Abstract
Rahnella aquatilis HX2 (proteobacteria) shows tolerance to selenium (Se). The minimum inhibitory concentrations of selenomethionine (Se-Met), selenite [Se (IV)], and selenate [Se (VI)] to HX2 are 4.0, 85.0, and 590.0 mM, respectively. HX2 shows the ability to reduce Se (IV) and Se (VI) to elemental Se nanoparticles (SeNPs). The maximum production of SeNPs by HX2 strain is 1.99 and 3.85 mM in Luria-Bertani (LB) broth with 5 mM Se (IV) and 10 mM Se (VI), respectively. The morphology of SeNPs and cells were observed by transmission electron microscope, environmental scanning electron microscope, and selected area electric diffraction detector. Spherical SeNPs with amorphous structure were found in the cytoplasm, membrane, and exterior of cells. Morphological variations of the cell membrane were further confirmed by the release of cellular materials absorbed at 260 nm. Flagella were inhibited and cell sizes were 1.8-, 1.6-, and 1.2-fold increases with the Se-Met, Se (VI), and Se (IV) treatments, respectively. The real-time quantitative PCR analysis indicated that some of the genes controlling Se metabolism or cell morphology, including cysA, cysP, rodA, ZntA, and ada, were significantly upregulated, while grxA, fliO, flgE, and fliC genes were significantly downregulated in those Se treatments. This study provided novel valuable information concerning the cell morphology along with biological synthesis process of SeNPs in R. aquatilis and demonstrated that the strain HX2 could be applied in both biosynthesis of SeNPs and in management of environmental Se pollution.
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16
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Ammar EM, Wang X, Rao CV. Regulation of metabolism in Escherichia coli during growth on mixtures of the non-glucose sugars: arabinose, lactose, and xylose. Sci Rep 2018; 8:609. [PMID: 29330542 PMCID: PMC5766520 DOI: 10.1038/s41598-017-18704-0] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Accepted: 12/15/2017] [Indexed: 02/02/2023] Open
Abstract
Catabolite repression refers to the process where the metabolism of one sugar represses the genes involved in metabolizing another sugar. While glucose provides the canonical example, many other sugars are also known to induce catabolite repression. However, less is known about the mechanism for catabolite repression by these non-glucose sugars. In this work, we investigated the mechanism of catabolite repression in the bacterium Escherichia coli during growth on lactose, L-arabinose, and D-xylose. The metabolism of these sugars is regulated in a hierarchical manner, where lactose is the preferred sugar, followed by L-arabinose, and then D-xylose. Previously, the preferential utilization of L-arabinose over D-xylose was found to result from transcriptional crosstalk. However, others have proposed that cAMP governs the hierarchical regulation of many non-glucose sugars. We investigated whether lactose-induced repression of L-arabinose and D-xylose gene expression is due to transcriptional crosstalk or cAMP. Our results demonstrate that it is due to cAMP and not transcriptional crosstalk. In addition, we found that repression is reciprocal, where both L-arabinose and D-xylose also repress the lactose gene expression, albeit to a lesser extent and also through a mechanism involving cAMP. Collectively, the results further our understanding of metabolism during growth on multiple sugars.
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Affiliation(s)
- Ehab M Ammar
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.,Genetic Engineering and Biotechnology Research Institute, University of Sadat City, El-Sadat City, Egypt
| | - Xiaoyi Wang
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Christopher V Rao
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
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17
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Rodrigo G, Fares MA. Intrinsic adaptive value and early fate of gene duplication revealed by a bottom-up approach. eLife 2018; 7:29739. [PMID: 29303479 PMCID: PMC5771667 DOI: 10.7554/elife.29739] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Accepted: 01/04/2018] [Indexed: 02/06/2023] Open
Abstract
The population genetic mechanisms governing the preservation of gene duplicates, especially in the critical very initial phase, have remained largely unknown. Here, we demonstrate that gene duplication confers per se a weak selective advantage in scenarios of fitness trade-offs. Through a precise quantitative description of a model system, we show that a second gene copy serves to reduce gene expression inaccuracies derived from pervasive molecular noise and suboptimal gene regulation. We then reveal that such an accuracy in the phenotype yields a selective advantage in the order of 0.1% on average, which would allow the positive selection of gene duplication in populations with moderate/large sizes. This advantage is greater at higher noise levels and intermediate concentrations of the environmental molecule, when fitness trade-offs become more evident. Moreover, we discuss how the genome rearrangement rates greatly condition the eventual fixation of duplicates. Overall, our theoretical results highlight an original adaptive value for cells carrying new-born duplicates, broadly analyze the selective conditions that determine their early fates in different organisms, and reconcile population genetics with evolution by gene duplication.
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Affiliation(s)
- Guillermo Rodrigo
- Instituto de Biología Molecular y Celular de Plantas, CSIC - UPV, Valencia, Spain.,Instituto de Biología Integrativa y de Sistemas, CSIC - UV, Paterna, Spain
| | - Mario A Fares
- Instituto de Biología Molecular y Celular de Plantas, CSIC - UPV, Valencia, Spain.,Instituto de Biología Integrativa y de Sistemas, CSIC - UV, Paterna, Spain.,Trinity College Dublin, University of Dublin, Dublin, Ireland
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18
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Nikolic N, Schreiber F, Dal Co A, Kiviet DJ, Bergmiller T, Littmann S, Kuypers MMM, Ackermann M. Cell-to-cell variation and specialization in sugar metabolism in clonal bacterial populations. PLoS Genet 2017; 13:e1007122. [PMID: 29253903 PMCID: PMC5773225 DOI: 10.1371/journal.pgen.1007122] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Revised: 01/18/2018] [Accepted: 11/22/2017] [Indexed: 12/05/2022] Open
Abstract
While we have good understanding of bacterial metabolism at the population level, we know little about the metabolic behavior of individual cells: do single cells in clonal populations sometimes specialize on different metabolic pathways? Such metabolic specialization could be driven by stochastic gene expression and could provide individual cells with growth benefits of specialization. We measured the degree of phenotypic specialization in two parallel metabolic pathways, the assimilation of glucose and arabinose. We grew Escherichia coli in chemostats, and used isotope-labeled sugars in combination with nanometer-scale secondary ion mass spectrometry and mathematical modeling to quantify sugar assimilation at the single-cell level. We found large variation in metabolic activities between single cells, both in absolute assimilation and in the degree to which individual cells specialize in the assimilation of different sugars. Analysis of transcriptional reporters indicated that this variation was at least partially based on cell-to-cell variation in gene expression. Metabolic differences between cells in clonal populations could potentially reduce metabolic incompatibilities between different pathways, and increase the rate at which parallel reactions can be performed. This study addresses a fundamental question in bacterial metabolism: do all individuals in a clonal population express the same metabolic functions, or do individuals specialize on different metabolic functions and assimilate different substrates? Reports about stochastic gene expression in bacterial populations raise the possibility that transcriptional differences between individuals translate into different metabolic behaviors, but the prevalence and magnitude of such effects is currently not known. Here, we quantified the assimilation of two isotope-labeled sugars by single Escherichia coli cells using nanometer-scale secondary ion mass spectrometry, an analytical approach seldom used in systems biology. By comparing sugar assimilation and gene expression dynamics, we were able to differentiate the metabolic profiles of individual cells. We observed a previously hidden level of cell-to-cell variation in metabolism: cells differed both in the total amount of sugar they assimilated, as well as with respect to which of the two sugars they preferentially assimilated. Intriguingly, a cell’s preference in sugar assimilation was only partially based on specialization in gene expression. Taken together, this study is a step towards understanding the magnitude and the relevance of metabolic differences between genetically identical cells.
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Affiliation(s)
- Nela Nikolic
- Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland
- Department of Environmental Microbiology, Eawag, Duebendorf, Switzerland
- Institute of Science and Technology Austria (IST Austria), Klosterneuburg, Austria
- * E-mail: (NN); (MA)
| | - Frank Schreiber
- Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland
- Department of Environmental Microbiology, Eawag, Duebendorf, Switzerland
- Division of Biodeterioration and Reference Organisms, Department of Materials and Environment, Federal Institute for Materials Research and Testing (BAM), Berlin, Germany
| | - Alma Dal Co
- Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland
- Department of Environmental Microbiology, Eawag, Duebendorf, Switzerland
| | - Daniel J. Kiviet
- Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland
- Department of Environmental Microbiology, Eawag, Duebendorf, Switzerland
| | - Tobias Bergmiller
- Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland
- Department of Environmental Microbiology, Eawag, Duebendorf, Switzerland
- Institute of Science and Technology Austria (IST Austria), Klosterneuburg, Austria
| | - Sten Littmann
- Department of Biogeochemistry, Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Marcel M. M. Kuypers
- Department of Biogeochemistry, Max Planck Institute for Marine Microbiology, Bremen, Germany
| | - Martin Ackermann
- Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland
- Department of Environmental Microbiology, Eawag, Duebendorf, Switzerland
- * E-mail: (NN); (MA)
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19
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de Jong H, Casagranda S, Giordano N, Cinquemani E, Ropers D, Geiselmann J, Gouzé JL. Mathematical modelling of microbes: metabolism, gene expression and growth. J R Soc Interface 2017; 14:20170502. [PMID: 29187637 PMCID: PMC5721159 DOI: 10.1098/rsif.2017.0502] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 10/31/2017] [Indexed: 11/12/2022] Open
Abstract
The growth of microorganisms involves the conversion of nutrients in the environment into biomass, mostly proteins and other macromolecules. This conversion is accomplished by networks of biochemical reactions cutting across cellular functions, such as metabolism, gene expression, transport and signalling. Mathematical modelling is a powerful tool for gaining an understanding of the functioning of this large and complex system and the role played by individual constituents and mechanisms. This requires models of microbial growth that provide an integrated view of the reaction networks and bridge the scale from individual reactions to the growth of a population. In this review, we derive a general framework for the kinetic modelling of microbial growth from basic hypotheses about the underlying reaction systems. Moreover, we show that several families of approximate models presented in the literature, notably flux balance models and coarse-grained whole-cell models, can be derived with the help of additional simplifying hypotheses. This perspective clearly brings out how apparently quite different modelling approaches are related on a deeper level, and suggests directions for further research.
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Affiliation(s)
| | - Stefano Casagranda
- University Côte d'Azur, Inria, INRA, CNRS, UPMC University Paris 06, BIOCORE team, Sophia-Antipolis, France
| | - Nils Giordano
- University Grenoble-Alpes, Inria, Grenoble, France
- University Grenoble-Alpes, CNRS, LIPhy, Grenoble, France
| | | | | | - Johannes Geiselmann
- University Grenoble-Alpes, Inria, Grenoble, France
- University Grenoble-Alpes, CNRS, LIPhy, Grenoble, France
| | - Jean-Luc Gouzé
- University Côte d'Azur, Inria, INRA, CNRS, UPMC University Paris 06, BIOCORE team, Sophia-Antipolis, France
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20
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Kim SK, Kim H, Ahn WC, Park KH, Woo EJ, Lee DH, Lee SG. Efficient Transcriptional Gene Repression by Type V-A CRISPR-Cpf1 from Eubacterium eligens. ACS Synth Biol 2017; 6:1273-1282. [PMID: 28375596 DOI: 10.1021/acssynbio.6b00368] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Clustered regularly interspaced short palindromic repeats interference (CRISPRi) is an emerging technology for artificial gene regulation. Type II CRISPR-Cas endonuclease Cas9 is the most widely used protein for gene regulation with CRISPRi. Here, we present type V-A CRISPR-Cas endonuclease Cpf1-based CRISPRi. We constructed an l-rhamnose-inducible CRISPRi system with DNase-deactivated Cpf1 from Eubacterium eligens (EedCpf1) and compared its performance with catalytically deactivated Cas9 from Streptococcus pyogenes (SpdCas9). In contrast to SpdCas9, EedCpf1 showed stronger gene repression when it was targeted to the template strand than when it was targeted to the nontemplate strand of the 5' untranslated region or coding DNA sequences. EedCpf1 exhibited no strand bias when targeted to the promoter, and preferentially used the 5'-TTTV-3' (V = A, G, or C) protospacer adjacent motif. Multiplex repression of the EedCpf1-based CRISPRi system was demonstrated using episomal and chromosomal gene targets. Our findings will guide an efficient EedCpf1-mediated CRISPRi genetic control.
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Affiliation(s)
- Seong Keun Kim
- Synthetic
Biology and Bioengineering Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 34141, Republic of Korea
- Biosystems
and Bioengineering Program, University of Science and Technology (UST), Daejeon 34113, Republic of Korea
| | - Haseong Kim
- Synthetic
Biology and Bioengineering Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 34141, Republic of Korea
- Biosystems
and Bioengineering Program, University of Science and Technology (UST), Daejeon 34113, Republic of Korea
| | - Woo-Chan Ahn
- Disease
Target Structure Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 34141, Republic of Korea
| | - Kwang-Hyun Park
- Disease
Target Structure Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 34141, Republic of Korea
| | - Eui-Jeon Woo
- Disease
Target Structure Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 34141, Republic of Korea
- Bio-Analytical
Science Program, University of Science and Technology (UST), Daejeon 34113, Republic of Korea
| | - Dae-Hee Lee
- Synthetic
Biology and Bioengineering Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 34141, Republic of Korea
- Biosystems
and Bioengineering Program, University of Science and Technology (UST), Daejeon 34113, Republic of Korea
| | - Seung-Goo Lee
- Synthetic
Biology and Bioengineering Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 34141, Republic of Korea
- Biosystems
and Bioengineering Program, University of Science and Technology (UST), Daejeon 34113, Republic of Korea
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21
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Waller MC, Bober JR, Nair NU, Beisel CL. Toward a genetic tool development pipeline for host-associated bacteria. Curr Opin Microbiol 2017. [PMID: 28624690 DOI: 10.1016/j.mib.2017.05.006] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Bacteria reside in externally accessible niches on and in multicellular organisms, often forming mutualistic relationships with their host. Recent studies have linked the composition of these microbial communities with alterations in the host's health, behavior, and development, yet the causative mediators of host-microbiota interactions remain poorly understood. Advances in understanding and engineering these interactions require the development of genetic tools to probe the molecular interactions driving the structure and function of microbial communities as well as their interactions with their host. This review discusses the current challenges to rendering culturable, non-model members of microbial communities genetically tractable - including overcoming barriers to DNA delivery, achieving predictable gene expression, and applying CRISPR-based tools - and details recent efforts to create generalized pipelines that simplify and expedite the tool-development process. We use the bacteria present in the human gastrointestinal tract as representative microbiota to illustrate some of the recent achievements and future opportunities for genetic tool development.
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Affiliation(s)
- Matthew C Waller
- North Carolina State University, Department of Chemical and Biomolecular Engineering, Raleigh, NC 27695, United States
| | - Josef R Bober
- Tufts University, Department of Chemical and Biological Engineering, Medford, MA 02155, United States
| | - Nikhil U Nair
- Tufts University, Department of Chemical and Biological Engineering, Medford, MA 02155, United States
| | - Chase L Beisel
- North Carolina State University, Department of Chemical and Biomolecular Engineering, Raleigh, NC 27695, United States.
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22
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Bistability and Nonmonotonic Induction of the lac Operon in the Natural Lactose Uptake System. Biophys J 2017; 112:1984-1996. [PMID: 28494968 DOI: 10.1016/j.bpj.2017.03.038] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Revised: 02/22/2017] [Accepted: 03/31/2017] [Indexed: 11/23/2022] Open
Abstract
The Escherichia coli lac operon is regulated by a positive feedback loop whose potential to generate an all-or-none response in single cells has been a paradigm for bistable gene expression. However, so far bistable lac induction has only been observed using gratuitous inducers, raising the question about the biological relevance of bistable lac induction in the natural setting with lactose as the inducer. In fact, the existing experimental evidence points to a graded rather than an all-or-none response in the natural lactose uptake system. In contrast, predictions based on computational models of the lactose uptake pathway remain controversial. Although some argue in favor of bistability, others argue against it. Here, we reinvestigate lac operon expression in single cells using a combined experimental/modeling approach. To this end, we parameterize a well-supported mathematical model using transient measurements of LacZ activity upon induction with different amounts of lactose. The resulting model predicts a monostable induction curve for the wild-type system, but indicates that overexpression of the LacI repressor would drive the system into the bistable regime. Both predictions were confirmed experimentally supporting the view that the wild-type lac induction circuit generates a graded response rather than bistability. More interestingly, we find that the lac induction curve exhibits a pronounced maximum at intermediate lactose concentrations. Supported by our data, a model-based analysis suggests that the nonmonotonic response results from saturation of the LacI repressor at low inducer concentrations and dilution of Lac enzymes due to an increased growth rate beyond the saturation point. We speculate that the observed maximum in the lac expression level helps to save cellular resources by limiting Lac enzyme expression at high inducer concentrations.
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23
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Sassu EL, Frömbling J, Duvigneau JC, Miller I, Müllebner A, Gutiérrez AM, Grunert T, Patzl M, Saalmüller A, von Altrock A, Menzel A, Ganter M, Spergser J, Hewicker-Trautwein M, Verspohl J, Ehling-Schulz M, Hennig-Pauka I. Host-pathogen interplay at primary infection sites in pigs challenged with Actinobacillus pleuropneumoniae. BMC Vet Res 2017; 13:64. [PMID: 28245826 PMCID: PMC5329957 DOI: 10.1186/s12917-017-0979-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2016] [Accepted: 02/16/2017] [Indexed: 01/06/2023] Open
Abstract
Background Actinobacillus (A.) pleuropneumoniae is the causative agent of porcine pleuropneumonia and causes significant losses in the pig industry worldwide. Early host immune response is crucial for further progression of the disease. A. pleuropneumoniae is either rapidly eliminated by the immune system or switches to a long-term persistent form. To gain insight into the host-pathogen interaction during the early stages of infection, pigs were inoculated intratracheally with A. pleuropneumoniae serotype 2 and humanely euthanized eight hours after infection. Gene expression studies of inflammatory cytokines and the acute phase proteins haptoglobin, serum amyloid A and C-reactive protein were carried out by RT-qPCR from the lung, liver, tonsils and salivary gland. In addition, the concentration of cytokines and acute phase proteins were measured by quantitative immunoassays in bronchoalveolar lavage fluid, serum and saliva. In parallel to the analyses of host response, the impact of the host on the bacterial pathogen was assessed on a metabolic level. For the latter, Fourier-Transform Infrared (FTIR-) spectroscopy was employed. Results Significant cytokine and acute phase protein gene expression was detected in the lung and the salivary gland however this was not observed in the tonsils. In parallel to the analyses of host response, the impact of the host on the bacterial pathogen was assessed on a metabolic level. For the latter investigations, Fourier-Transform Infrared (FTIR-) spectroscopy was employed. The bacteria isolated from the upper and lower respiratory tract showed distinct IR spectral patterns reflecting the organ-specific acute phase response of the host. Conclusions In summary, this study implies a metabolic adaptation of A. pleuropneumoniae to the porcine upper respiratory tract already during early infection, which might indicate a first step towards the persistence of A. pleuropneumoniae. Not only in lung, but also in the salivary gland an increased inflammatory gene expression was detectable during the acute stage of infection. Electronic supplementary material The online version of this article (doi:10.1186/s12917-017-0979-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Elena L Sassu
- University Clinic for Swine, Department of Farm Animals and Veterinary Public Health, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Janna Frömbling
- Department of Pathobiology, Functional Microbiology, Institute of Microbiology, University of Veterinary Medicine Vienna, Vienna, Austria
| | - J Catharina Duvigneau
- Department of Biomedical Sciences, Institute for Medical Biochemistry, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Ingrid Miller
- Department of Biomedical Sciences, Institute for Medical Biochemistry, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Andrea Müllebner
- Department of Biomedical Sciences, Institute for Medical Biochemistry, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Ana M Gutiérrez
- Department of Animal Medicine and Surgery, University of Murcia, Murcia, Spain
| | - Tom Grunert
- Department of Pathobiology, Functional Microbiology, Institute of Microbiology, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Martina Patzl
- Department of Pathobiology, Institute of Immunology, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Armin Saalmüller
- Department of Pathobiology, Institute of Immunology, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Alexandra von Altrock
- Forensic Medicine and Ambulatory Services, Clinic for Swine and Small Ruminants, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Anne Menzel
- Forensic Medicine and Ambulatory Services, Clinic for Swine and Small Ruminants, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Martin Ganter
- Forensic Medicine and Ambulatory Services, Clinic for Swine and Small Ruminants, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Joachim Spergser
- Department of Pathobiology, Functional Microbiology, Institute of Microbiology, University of Veterinary Medicine Vienna, Vienna, Austria
| | | | - Jutta Verspohl
- Institute for Microbiology, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Monika Ehling-Schulz
- Department of Pathobiology, Functional Microbiology, Institute of Microbiology, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Isabel Hennig-Pauka
- University Clinic for Swine, Department of Farm Animals and Veterinary Public Health, University of Veterinary Medicine Vienna, Vienna, Austria.
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Marschall L, Sagmeister P, Herwig C. Tunable recombinant protein expression in E. coli: promoter systems and genetic constraints. Appl Microbiol Biotechnol 2017; 101:501-512. [PMID: 27999902 PMCID: PMC5566544 DOI: 10.1007/s00253-016-8045-z] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2016] [Revised: 11/26/2016] [Accepted: 11/29/2016] [Indexed: 12/11/2022]
Abstract
Tuning of transcription is a promising strategy to overcome challenges associated with a non-suitable expression rate like outgrowth of segregants, inclusion body formation, metabolic burden and inefficient translocation. By adjusting the expression rate-even on line-to purposeful levels higher product titres and more cost-efficient production processes can be achieved by enabling culture long-term stability and constant product quality. Some tunable systems are registered for patents or already commercially available. Within this contribution, we discuss the induction mechanisms of various Escherichia coli inherent promoter systems with respect to their tunability and review studies using these systems for expression tuning. According to the current level of knowledge, some promoter systems were successfully used for expression tuning, and in some cases, analytical evidence on single-cell level is still pending. However, only a few studies using tunable strains apply a suitable process control strategy. So far, expression tuning has only gathered little attention, but we anticipate that expression tuning harbours great potential for enabling and optimizing the production of a broad spectrum of products in E. coli.
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Affiliation(s)
- Lukas Marschall
- Institute of Chemical Engineering, Research Area Biochemical Engineering, Vienna University of Technology, Vienna, Austria
| | | | - Christoph Herwig
- Institute of Chemical Engineering, Research Area Biochemical Engineering, Vienna University of Technology, Vienna, Austria.
- Christian Doppler Laboratory for Mechanistic and Physiological Methods for Improved Bioprocesses, Vienna University of Technology, Gumpendorferstrasse 1a/166-4, A-1060, Vienna, Austria.
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Spot 42 sRNA regulates arabinose-inducible araBAD promoter activity by repressing synthesis of the high-affinity low-capacity arabinose transporter. J Bacteriol 2016; 199:e00691-16. [PMID: 27849174 DOI: 10.1128/jb.00691-16] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The L-arabinose-inducible araBAD promoter (PBAD) allows tightly controlled and tunable expression of genes of interest in a broad range of bacterial species. It has been successfully used to study bacterial sRNA regulation, where PBAD drives expression of target mRNA translational fusions. Here we report that in Escherichia coli, Spot 42 sRNA can regulate PBAD promoter activity by affecting arabinose uptake. We demonstrate that Spot 42 sRNA represses araF, a gene encoding the AraF subunit of the high-affinity low-capacity arabinose transporter AraFGH, through direct base pairing interactions. We further show that endogenous Spot 42 sRNA is sufficient to repress araF expression under various growth conditions. Finally, we demonstrate this posttranscriptional repression has a biological consequence, decreasing the induction of PBAD at low levels of arabinose. This problem can be circumvented using strategies reported previously for avoiding all-or-none induction behavior, that is through constitutive expression of the low-affinity high-capacity arabinose transporter AraE or induction with higher concentration of inducers. This work adds araF to the set of Spot 42-regulated genes, in agreement with previous studies suggesting that Spot 42, itself negatively regulated by cAMP-CRP complex, reinforces the catabolite repression network. IMPORTANCE The bacterial arabinose inducible system is widely used for titratable control of gene expression. We demonstrate here that a post-transcriptional mechanism mediated by the Spot 42 sRNA contributes to the functionality of the PBAD system at subsaturating inducer concentrations by affecting inducer uptake. Our finding extends the inputs into the known transcriptional control for the PBAD system, and has implications for improving its usage for tunable gene expression.
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Marschall L, Sagmeister P, Herwig C. Tunable recombinant protein expression in E. coli: enabler for continuous processing? Appl Microbiol Biotechnol 2016; 100:5719-28. [PMID: 27170324 PMCID: PMC4957632 DOI: 10.1007/s00253-016-7550-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 04/11/2016] [Accepted: 04/13/2016] [Indexed: 02/06/2023]
Abstract
Tuning of transcription is a powerful process technological tool for efficient recombinant protein production in Escherichia coli. Many challenges such as product toxicity, formation of inclusion bodies, cell death, and metabolic burden are associated with non-suitable (too high or too low) levels of recombinant protein expression. Tunable expression systems allow adjusting the recombinant protein expression using process technological means. This enables to exploit the cell's metabolic capacities to a maximum. Within this article, we review genetic and process technological aspects of tunable expression systems in E. coli, providing a roadmap for the industrial exploitation of the reviewed technologies. We attempt to differentiate the term "expression tuning" from its inflationary use by providing a concise definition and highlight interesting fields of application for this versatile new technology. Dependent on the type of inducer (metabolizable or non-metabolizable), different process strategies are required in order to achieve tuning. To fully profit from the benefits of tunable systems, an independent control of growth rate and expression rate is indispensable. Being able to tackle problems such as long-term culture stability and constant product quality expression tuning is a promising enabler for continuous processing in biopharmaceutical production.
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Affiliation(s)
- Lukas Marschall
- Institute of Chemical Engineering, Research Area Biochemical Engineering, Vienna University of Technology, Vienna, Austria
| | | | - Christoph Herwig
- Exputec GmbH, Vienna, Austria. .,Christian Doppler Laboratory for Mechanistic and Physiological Methods for Improved Bioprocesses, Vienna University of Technology, Gumpendorferstraße 1a/166-4, 1060, Vienna, Austria.
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Abstract
Bacteria are known to consume some sugars over others, although recent work reported by Koirala and colleagues in this issue of the Journal of Bacteriology (S. Koirala, X. Wang, and C. V. Rao, J Bacteriol 198:386-393, 2016, http://dx.doi.org/10.1128/JB.00709-15) revealed that individual cells do not necessarily follow this hierarchy. By studying the preferential consumption of l-arabinose over d-xylose in Escherichia coli, those authors found that subpopulations consume one, the other, or both sugars through cross-repression between utilization pathways. Their findings challenge classic assertions about established hierarchies and can guide efforts to engineer the simultaneous utilization of multiple sugars.
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Reciprocal Regulation of l-Arabinose and d-Xylose Metabolism in Escherichia coli. J Bacteriol 2015; 198:386-93. [PMID: 26527647 DOI: 10.1128/jb.00709-15] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Accepted: 10/28/2015] [Indexed: 01/17/2023] Open
Abstract
UNLABELLED Glucose is known to inhibit the transport and metabolism of many sugars in Escherichia coli. This mechanism leads to its preferential consumption. Far less is known about the preferential utilization of nonglucose sugars in E. coli. Two exceptions are l-arabinose and d-xylose. Previous studies have shown that l-arabinose inhibits d-xylose metabolism in Escherichia coli. This repression results from l-arabinose-bound AraC binding to the promoter of the d-xylose metabolic genes and inhibiting their expression. This mechanism, however, has not been explored in single cells. Both the l-arabinose and d-xylose utilization systems are known to exhibit a bimodal induction response to their cognate sugar, where mixed populations of cells either expressing the metabolic genes or not are observed at intermediate sugar concentrations. This suggests that l-arabinose can only inhibit d-xylose metabolism in l-arabinose-induced cells. To understand how cross talk between these systems affects their response, we investigated E. coli during growth on mixtures of l-arabinose and d-xylose at single-cell resolution. Our results showed that mixed, multimodal populations of l-arabinose- and d-xylose-induced cells occurred at intermediate sugar concentrations. We also found that d-xylose inhibited the expression of the l-arabinose metabolic genes and that this repression was due to XylR. These results demonstrate that a strict hierarchy does not exist between l-arabinose and d-xylose as previously thought. The results may also aid in the design of E. coli strains capable of simultaneous sugar consumption. IMPORTANCE Glucose, d-xylose, and l-arabinose are the most abundant sugars in plant biomass. Developing efficient fermentation processes that convert these sugars into chemicals and fuels will require strains capable of coutilizing these sugars. Glucose has long been known to repress the expression of the l-arabinose and d-xylose metabolic genes in Escherichia coli. Recent studies found that l-arabinose also represses the expression of the d-xylose metabolic genes. In the present study, we found that d-xylose also represses the expression of the l-arabinose metabolic genes, leading to mixed populations of cells capable of utilizing l-arabinose and d-xylose. These results further our understanding of mixed-sugar utilization and may aid in strain design.
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AraR, an l-Arabinose-Responsive Transcriptional Regulator in Corynebacterium glutamicum ATCC 31831, Exerts Different Degrees of Repression Depending on the Location of Its Binding Sites within the Three Target Promoter Regions. J Bacteriol 2015; 197:3788-96. [PMID: 26416832 DOI: 10.1128/jb.00314-15] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2015] [Accepted: 09/21/2015] [Indexed: 12/18/2022] Open
Abstract
UNLABELLED In Corynebacterium glutamicum ATCC 31831, a LacI-type transcriptional regulator AraR, represses the expression of l-arabinose catabolism (araBDA), uptake (araE), and the regulator (araR) genes clustered on the chromosome. AraR binds to three sites: one (BSB) between the divergent operons (araBDA and galM-araR) and two (BSE1 and BSE2) upstream of araE. L-Arabinose acts as an inducer of the AraR-mediated regulation. Here, we examined the roles of these AraR-binding sites in the expression of the AraR regulon. BSB mutation resulted in derepression of both araBDA and galM-araR operons. The effects of BSE1 and/or BSE2 mutation on araE expression revealed that the two sites independently function as the cis elements, but BSE1 plays the primary role. However, AraR was shown to bind to these sites with almost the same affinity in vitro. Taken together, the expression of araBDA and araE is strongly repressed by binding of AraR to a single site immediately downstream of the respective transcriptional start sites, whereas the binding site overlapping the -10 or -35 region of the galM-araR and araE promoters is less effective in repression. Furthermore, downregulation of araBDA and araE dependent on l-arabinose catabolism observed in the BSB mutant and the AraR-independent araR promoter identified within galM-araR add complexity to regulation of the AraR regulon derepressed by L-arabinose. IMPORTANCE Corynebacterium glutamicum has a long history as an industrial workhorse for large-scale production of amino acids. An important aspect of industrial microorganisms is the utilization of the broad range of sugars for cell growth and production process. Most C. glutamicum strains are unable to use a pentose sugar L-arabinose as a carbon source. However, genes for L-arabinose utilization and its regulation have been recently identified in C. glutamicum ATCC 31831. This study elucidates the roles of the multiple binding sites of the transcriptional repressor AraR in the derepression by L-arabinose and thereby highlights the complex regulatory feedback loops in combination with l-arabinose catabolism-dependent repression of the AraR regulon in an AraR-independent manner.
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Afroz T, Luo ML, Beisel CL. Impact of Residual Inducer on Titratable Expression Systems. PLoS One 2015; 10:e0137421. [PMID: 26348036 PMCID: PMC4562711 DOI: 10.1371/journal.pone.0137421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Accepted: 08/17/2015] [Indexed: 11/19/2022] Open
Abstract
Inducible expression systems are widely employed for the titratable control of gene expression, yet molecules inadvertently present in the growth medium or synthesized by the host cells can alter the response profile of some of these systems. Here, we explored the quantitative impact of these residual inducers on the apparent response properties of inducible systems. Using a simple mathematical model, we found that the presence of residual inducer shrinks the apparent dynamic range and causes the apparent Hill coefficient to converge to one. We also found that activating systems were more sensitive than repressing systems to the presence of residual inducer and the response parameters were most heavily dependent on the original Hill coefficient. Experimental interrogation of common titratable systems based on an L-arabinose inducible promoter or a thiamine pyrophosphate-repressing riboswitch in Escherichia coli confirmed the predicted trends. We finally found that residual inducer had a distinct effect on "all-or-none" systems, which exhibited increased sensitivity to the added inducer until becoming fully induced. Our findings indicate that residual inducer or repressor alters the quantitative response properties of titratable systems, impacting their utility for scientific discovery and pathway engineering.
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Affiliation(s)
- Taliman Afroz
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Michelle L Luo
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Chase L Beisel
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina, United States of America
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Boyle KE, Monaco H, van Ditmarsch D, Deforet M, Xavier JB. Integration of Metabolic and Quorum Sensing Signals Governing the Decision to Cooperate in a Bacterial Social Trait. PLoS Comput Biol 2015; 11:e1004279. [PMID: 26102206 PMCID: PMC4477906 DOI: 10.1371/journal.pcbi.1004279] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 04/11/2015] [Indexed: 01/18/2023] Open
Abstract
Many unicellular organisms live in multicellular communities that rely on cooperation between cells. However, cooperative traits are vulnerable to exploitation by non-cooperators (cheaters). We expand our understanding of the molecular mechanisms that allow multicellular systems to remain robust in the face of cheating by dissecting the dynamic regulation of cooperative rhamnolipids required for swarming in Pseudomonas aeruginosa. We combine mathematical modeling and experiments to quantitatively characterize the integration of metabolic and population density signals (quorum sensing) governing expression of the rhamnolipid synthesis operon rhlAB. The combined computational/experimental analysis reveals that when nutrients are abundant, rhlAB promoter activity increases gradually in a density dependent way. When growth slows down due to nutrient limitation, rhlAB promoter activity can stop abruptly, decrease gradually or even increase depending on whether the growth-limiting nutrient is the carbon source, nitrogen source or iron. Starvation by specific nutrients drives growth on intracellular nutrient pools as well as the qualitative rhlAB promoter response, which itself is modulated by quorum sensing. Our quantitative analysis suggests a supply-driven activation that integrates metabolic prudence with quorum sensing in a non-digital manner and allows P. aeruginosa cells to invest in cooperation only when the population size is large enough (quorum sensing) and individual cells have enough metabolic resources to do so (metabolic prudence). Thus, the quantitative description of rhlAB regulatory dynamics brings a greater understating to the regulation required to make swarming cooperation stable. Although bacteria are not multicellular organisms, they commonly live in large communities and engage in many cooperative behaviors. Cooperation can allow bacteria to access additional nutrients, but it requires the secretion of products that will be shared by the community. How bacteria make the molecular decision to cooperate within a community is still not completely understood. The bacterium Pseudomonas aeruginosa regulates the secretion of one of these shared products, rhamnolipids, using information about population density and nutrient availability in its environment. Expression of the operon rhlAB is required for the bacteria to produce rhamnolipids. We use a combined computational and experimental approach to investigate how P. aeruginosa continually combines current information of population density and nutrient availability to determine if it should express rhlAB. We find that when conditions are nutrient rich, P. aeruginosa uses population density to modulate the amount rhlAB expression, however when the bacteria are starved for nutrients the starvation condition largely determines how the bacteria will express rhlAB. Because the bacteria continually adjust expression based on the current conditions, the molecular decision to produce rhamnolipids can be adjusted if either population density or nutrient conditions change. Our combined computational and experimental approach sheds new light on the rich regulatory dynamics that govern a cellular decision to cooperate.
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Affiliation(s)
- Kerry E. Boyle
- Program in Immunology and Microbial Pathogenesis, Weill Cornell Graduate School of Medical Sciences, New York, New York, United States of America
- Program in Computational Biology, Memorial Sloan Kettering Cancer Center, New York, New York, United States of America
| | - Hilary Monaco
- Program in Computational Biology, Memorial Sloan Kettering Cancer Center, New York, New York, United States of America
- Tri-Institutional Training Program in Computational Biology and Medicine, New York, New York, United States of America
| | - Dave van Ditmarsch
- Program in Computational Biology, Memorial Sloan Kettering Cancer Center, New York, New York, United States of America
| | - Maxime Deforet
- Program in Computational Biology, Memorial Sloan Kettering Cancer Center, New York, New York, United States of America
| | - Joao B. Xavier
- Program in Immunology and Microbial Pathogenesis, Weill Cornell Graduate School of Medical Sciences, New York, New York, United States of America
- Program in Computational Biology, Memorial Sloan Kettering Cancer Center, New York, New York, United States of America
- Tri-Institutional Training Program in Computational Biology and Medicine, New York, New York, United States of America
- * E-mail:
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32
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The glycerol-dependent metabolic persistence of Pseudomonas putida KT2440 reflects the regulatory logic of the GlpR repressor. mBio 2015; 6:mBio.00340-15. [PMID: 25827416 PMCID: PMC4453509 DOI: 10.1128/mbio.00340-15] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The growth of the soil bacterium Pseudomonas putida KT2440 on glycerol as the sole carbon source is characterized by a prolonged lag phase, not observed with other carbon substrates. We examined the bacterial growth in glycerol cultures while monitoring the metabolic activity of individual cells. Fluorescence microscopy and flow cytometry, as well as the analysis of the temporal start of growth in single-cell cultures, revealed that adoption of a glycerol-metabolizing regime was not the result of a gradual change in the whole population but rather reflected a time-dependent bimodal switch between metabolically inactive (i.e., nongrowing) and fully active (i.e., growing) bacteria. A transcriptional Φ(glpD-gfp) fusion (a proxy of the glycerol-3-phosphate [G3P] dehydrogenase activity) linked the macroscopic phenotype to the expression of the glp genes. Either deleting glpR (encoding the G3P-responsive transcriptional repressor that controls the expression of the glpFKRD gene cluster) or altering G3P formation (by overexpressing glpK, encoding glycerol kinase) abolished the bimodal glpD expression. These manipulations eliminated the stochastic growth start by shortening the otherwise long lag phase. Provision of glpR in trans restored the phenotypes lost in the ΔglpR mutant. The prolonged nongrowth regime of P. putida on glycerol could thus be traced to the regulatory device controlling the transcription of the glp genes. Since the physiological agonist of GlpR is G3P, the arrangement of metabolic and regulatory components at this checkpoint merges a positive feedback loop with a nonlinear transcriptional response, a layout fostering the observed time-dependent shift between two alternative physiological states. Phenotypic variation is a widespread attribute of prokaryotes that leads, inter alia, to the emergence of persistent bacteria, i.e., live but nongrowing members within a genetically clonal population. Persistence allows a fraction of cells to avoid the killing caused by conditions or agents that destroy most growing bacteria (e.g., some antibiotics). Known molecular mechanisms underlying the phenomenon include genetic changes, epigenetic variations, and feedback-based multistability. We show that a prolonged nongrowing state of the bacterial population can be brought about by a distinct regulatory architecture of metabolic genes when cells face specific nutrients (e.g., glycerol). Pseudomonas putida may have adopted the resulting carbon source-dependent metabolic bet hedging as an advantageous trait for exploring new chemical and nutritional landscapes. Defeating such naturally occurring adaptive features of environmental bacteria is instrumental in improving the performance of these microorganisms as whole-cell catalysts in a bioreactor setup.
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Abstract
No organism lives in a constant environment. Based on classical studies in molecular biology, many have viewed microbes as following strict rules for shifting their metabolic activities when prevailing conditions change. For example, students learn that the bacterium Escherichia coli makes proteins for digesting lactose only when lactose is available and glucose, a better sugar, is not. However, recent studies, including three PLOS Biology papers examining sugar utilization in the budding yeast Saccharomyces cerevisiae, show that considerable heterogeneity in response to complex environments exists within and between populations. These results join similar recent results in other organisms that suggest that microbial populations anticipate predictable environmental changes and hedge their bets against unpredictable ones. The classical view therefore represents but one special case in a range of evolutionary adaptations to environmental changes that all organisms face. This Primer explores three recent PLOS Biology papers that increase our understanding of how microbes respond optimally to the changing availability of nutrients in their environment. Read the Research Articles.
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Affiliation(s)
- Mark L. Siegal
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, New York, United States of America
- * E-mail:
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34
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Grunert T, Monahan A, Lassnig C, Vogl C, Müller M, Ehling-Schulz M. Deciphering host genotype-specific impacts on the metabolic fingerprint of Listeria monocytogenes by FTIR spectroscopy. PLoS One 2014; 9:e115959. [PMID: 25541972 PMCID: PMC4277405 DOI: 10.1371/journal.pone.0115959] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Accepted: 11/28/2014] [Indexed: 01/19/2023] Open
Abstract
Bacterial pathogens are known for their wide range of strategies to specifically adapt to host environments and infection sites. An in-depth understanding of these adaptation mechanisms is crucial for the development of effective therapeutics and new prevention measures. In this study, we assessed the suitability of Fourier Transform Infrared (FTIR) spectroscopy for monitoring metabolic adaptations of the bacterial pathogen Listeria monocytogenes to specific host genotypes and for exploring the potential of FTIR spectroscopy to gain novel insights into the host-pathogen interaction. Three different mouse genotypes, showing different susceptibility to L. monocytogenes infections, were challenged with L. monocytogenes and re-isolated bacteria were subjected to FTIR spectroscopy. The bacteria from mice with different survival characteristics showed distinct IR spectral patterns, reflecting specific changes in the backbone conformation and the hydrogen-bonding pattern of the protein secondary structure in the bacterial cell. Coupling FTIR spectroscopy with chemometrics allowed us to link bacterial metabolic fingerprints with host infection susceptibility and to decipher longtime memory effects of the host on the bacteria. After prolonged cultivation of host-passaged bacteria under standard laboratory conditions, the host's imprint on bacterial metabolism vanished, which suggests a revertible metabolic adaptation of bacteria to host environment and loss of host environment triggered memory effects over time. In summary, our work demonstrates the potential and power of FTIR spectroscopy to be used as a fast, simple and highly discriminatory tool to investigate the mechanism of bacterial host adaptation on a macromolar and metabolic level.
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Affiliation(s)
- Tom Grunert
- Functional Microbiology, Institute of Microbiology, Department of Pathobiology, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Avril Monahan
- Institute of Animal Breeding and Genetics, Department for Biomedical Sciences, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Caroline Lassnig
- Institute of Animal Breeding and Genetics, Department for Biomedical Sciences, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Claus Vogl
- Institute of Animal Breeding and Genetics, Department for Biomedical Sciences, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Mathias Müller
- Institute of Animal Breeding and Genetics, Department for Biomedical Sciences, University of Veterinary Medicine Vienna, Vienna, Austria
| | - Monika Ehling-Schulz
- Functional Microbiology, Institute of Microbiology, Department of Pathobiology, University of Veterinary Medicine Vienna, Vienna, Austria
- * E-mail:
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35
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Luo ML, Mullis AS, Leenay RT, Beisel CL. Repurposing endogenous type I CRISPR-Cas systems for programmable gene repression. Nucleic Acids Res 2014. [PMID: 25326321 DOI: 10.1093/nar/gku971.] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
CRISPR-Cas systems have shown tremendous promise as heterologous tools for genome editing and transcriptional regulation. Because these RNA-directed immune systems are found in most prokaryotes, an opportunity exists to harness the endogenous systems as convenient tools in these organisms. Here, we report that the Type I-E CRISPR-Cas system in Escherichia coli can be co-opted for programmable transcriptional repression. We found that deletion of the signature cas3 gene converted this immune system into a programmable gene regulator capable of reversible gene silencing of heterologous and endogenous genes. Targeting promoter regions yielded the strongest repression, whereas targeting coding regions showed consistent strand bias. Furthermore, multi-targeting CRISPR arrays could generate complex phenotypes. This strategy offers a simple approach to convert many endogenous Type I systems into transcriptional regulators, thereby expanding the available toolkit for CRISPR-mediated genetic control while creating new opportunities for genome-wide screens and pathway engineering.
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Affiliation(s)
- Michelle L Luo
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
| | - Adam S Mullis
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
| | - Ryan T Leenay
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
| | - Chase L Beisel
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
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36
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Luo ML, Mullis AS, Leenay RT, Beisel CL. Repurposing endogenous type I CRISPR-Cas systems for programmable gene repression. Nucleic Acids Res 2014; 43:674-81. [PMID: 25326321 PMCID: PMC4288209 DOI: 10.1093/nar/gku971] [Citation(s) in RCA: 174] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
CRISPR-Cas systems have shown tremendous promise as heterologous tools for genome editing and transcriptional regulation. Because these RNA-directed immune systems are found in most prokaryotes, an opportunity exists to harness the endogenous systems as convenient tools in these organisms. Here, we report that the Type I-E CRISPR-Cas system in Escherichia coli can be co-opted for programmable transcriptional repression. We found that deletion of the signature cas3 gene converted this immune system into a programmable gene regulator capable of reversible gene silencing of heterologous and endogenous genes. Targeting promoter regions yielded the strongest repression, whereas targeting coding regions showed consistent strand bias. Furthermore, multi-targeting CRISPR arrays could generate complex phenotypes. This strategy offers a simple approach to convert many endogenous Type I systems into transcriptional regulators, thereby expanding the available toolkit for CRISPR-mediated genetic control while creating new opportunities for genome-wide screens and pathway engineering.
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Affiliation(s)
- Michelle L Luo
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
| | - Adam S Mullis
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
| | - Ryan T Leenay
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
| | - Chase L Beisel
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
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