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Liu X, Wang H, Wang B, Pan L. High-level extracellular protein expression in Bacillus subtilis by optimizing strong promoters based on the transcriptome of Bacillus subtilis and Bacillus megaterium. Protein Expr Purif 2018; 151:72-77. [DOI: 10.1016/j.pep.2018.06.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 06/08/2018] [Accepted: 06/08/2018] [Indexed: 10/14/2022]
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Development of a potential stationary-phase specific gene expression system by engineering of SigB-dependent cg3141 promoter in Corynebacterium glutamicum. Appl Microbiol Biotechnol 2016; 100:4473-83. [PMID: 26782746 DOI: 10.1007/s00253-016-7297-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 12/27/2015] [Accepted: 12/28/2015] [Indexed: 02/03/2023]
Abstract
Corynebacterium glutamicum is a non-pathogenic, non-sporulating Gram-positive soil bacterium that has been used for the industrial production of various proteins and chemicals. To achieve enhanced and economical production of target molecules, the development of strong auto-inducible promoters is desired, which can be activated without expensive inducers and has significant advantages for industrial-scale use. Here, we developed a stationary-phase gene expression system by engineering a sigma factor B (SigB)-dependent promoter that can be activated during the transition phase between exponential and stationary growth phases in C. glutamicum. First, the inducibilities of three well-known SigB-dependent promoters were examined using super-folder green fluorescent protein as a reporter protein, and we found that promoter of cg3141 (P cg3141 ) exhibited the highest inducibility. Next, a synthetic promoter library was constructed by randomizing the flanking and space regions of P cg3141 , and the stationary-phase promoters exhibiting high strengths were isolated via FACS-based high-throughput screening. The isolated synthetic promoter (P4-N14) showed a 3.5-fold inducibility and up to 20-fold higher strength compared to those of the original cg3141 promoter. Finally, the use of the isolated P4-N14 for fed-batch cultivation was verified with the production of glutathione S-transferase as a model protein in a lab-scale (5-L) bioreactor.
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Nešvera J, Holátko J, Pátek M. Analysis of Corynebacterium glutamicum promoters and their applications. Subcell Biochem 2014; 64:203-21. [PMID: 23080252 DOI: 10.1007/978-94-007-5055-5_10] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Abstract
Promoters are DNA sequences which function as regulatory signals of transcription initiation catalyzed by RNA polymerase. Since promoters substantially influence levels of gene expression, they have become powerful tools in metabolic engineering. Methods for their localization used in Corynebacterium glutamicum and techniques for the analysis of their function are described in this review. C. glutamicum promoters can be classified according to the respective σ factors which direct RNA polymerase to these structures. C. glutamicum promoters are recognized by holo-RNA polymerase formed by subunits α(2)ββ'ω + σ. C. glutamicum codes for seven different sigma factors: the principal sigma factor σ(A) and alternative sigma factors σ(B), σ(C), σ(D), σ(E), σ(H) and σ(M), which recognize various classes of promoters. The promoters of housekeeping genes recognized by σ(A), which are active during the exponential growth, form the largest described group. These promoters and their mutant derivatives are the most frequently used elements in modulation of gene expression in C. glutamicum. Promoters recognized by alternative sigma factors and their consensus sequences are gradually emerging.
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Affiliation(s)
- Jan Nešvera
- Institute of Microbiology, Academy of Sciences of the Czech Republic, Vídeňská 1083, CZ-14220, Prague 4, Czech Republic
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Barriuso-Iglesias M, Barreiro C, Sola-Landa A, Martín JF. Transcriptional control of the F0F1-ATP synthase operon of Corynebacterium glutamicum: SigmaH factor binds to its promoter and regulates its expression at different pH values. Microb Biotechnol 2013; 6:178-88. [PMID: 23298179 PMCID: PMC3917460 DOI: 10.1111/1751-7915.12022] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Accepted: 11/03/2012] [Indexed: 12/05/2022] Open
Abstract
Corynebacterium glutamicum used in the amino acid fermentation industries is an alkaliphilic microorganism. Its F0F1-ATPase operon (atpBEFHAGDC) is expressed optimally at pH 9.0 forming a polycistronic (7.5 kb) and a monocistronic (1.2 kb) transcripts both starting upstream of the atpB gene. Expression of this operon is controlled by the SigmaH factor. The sigmaH gene (sigH) was cloned and shown to be co-transcribed with a small gene, cg0877, encoding a putative anti-sigma factor. A mutant deleted in the sigH gene expressed the atpBEFHAGDC operon optimally at pH 7.0 at difference of the wild-type strain (optimal expression at pH 9.0). These results suggested that the SigmaH factor is involved in pH control of expression of the F0F1 ATPase operon. The SigmaH protein was expressed in Escherichia coli fused to the GST (glutathione-S-transferase) and purified to homogeneity by affinity chromatography on a GSTrap HP column. The fused protein was identified by immunodetection with anti-GST antibodies. DNA-binding studies by electrophoretic mobility shift assays showed that the SigH protein binds to a region of the atpB promoter containing the sigmaH recognition sequence (−35)TTGGAT…18nt…GTTA(−10). SigmaH plays an important role in the cascade of control of pH stress in Corynebacterium.
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Pátek M, Nešvera J. Promoters and Plasmid Vectors of Corynebacterium glutamicum. CORYNEBACTERIUM GLUTAMICUM 2013. [DOI: 10.1007/978-3-642-29857-8_2] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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6
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Sigma factors and promoters in Corynebacterium glutamicum. J Biotechnol 2011; 154:101-13. [DOI: 10.1016/j.jbiotec.2011.01.017] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Revised: 01/05/2011] [Accepted: 01/18/2011] [Indexed: 11/19/2022]
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Schröder J, Tauch A. Transcriptional regulation of gene expression inCorynebacterium glutamicum: the role of global, master and local regulators in the modular and hierarchical gene regulatory network. FEMS Microbiol Rev 2010; 34:685-737. [DOI: 10.1111/j.1574-6976.2010.00228.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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Ehira S, Teramoto H, Inui M, Yukawa H. Regulation of Corynebacterium glutamicum heat shock response by the extracytoplasmic-function sigma factor SigH and transcriptional regulators HspR and HrcA. J Bacteriol 2009; 191:2964-72. [PMID: 19270092 PMCID: PMC2681815 DOI: 10.1128/jb.00112-09] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Accepted: 02/24/2009] [Indexed: 11/20/2022] Open
Abstract
Heat shock response in Corynebacterium glutamicum was characterized by whole-genome expression analysis using a DNA microarray. It was indicated that heat shock response of C. glutamicum included not only upregulation of heat shock protein (HSP) genes encoding molecular chaperones and ATP-dependent proteases, but it also increased and decreased expression of more than 300 genes related to disparate physiological functions. An extracytoplasmic-function sigma factor, SigH, was upregulated by heat shock. The SigH regulon was defined by gene expression profiling using sigH-disrupted and overexpressing strains in conjunction with mapping of transcription initiation sites. A total of 45 genes, including HSP genes and genes involved in oxidative stress response, were identified as the SigH regulon. Expression of some HSP genes was also upregulated by deletion of the transcriptional regulators HspR and HrcA. HspR represses expression of the clpB and dnaK operons, and HrcA represses expression of groESL1 and groEL2. SigH was shown to play an important role in regulation of heat shock response in concert with HspR and HrcA, but its role is likely restricted to only a part of the regulation of C. glutamicum heat shock response. Upregulation of 18 genes encoding transcriptional regulators by heat shock suggests a complex regulatory network of heat shock response in C. glutamicum.
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Affiliation(s)
- Shigeki Ehira
- Research Institute of Innovative Technology for the Earth, 9-2 Kizugawadai, Kizugawa, Kyoto 619-0292, Japan
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Ehira S, Shirai T, Teramoto H, Inui M, Yukawa H. Group 2 sigma factor SigB of Corynebacterium glutamicum positively regulates glucose metabolism under conditions of oxygen deprivation. Appl Environ Microbiol 2008; 74:5146-52. [PMID: 18567683 PMCID: PMC2519270 DOI: 10.1128/aem.00944-08] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2008] [Accepted: 06/16/2008] [Indexed: 11/20/2022] Open
Abstract
The sigB gene of Corynebacterium glutamicum encodes a group 2 sigma factor of RNA polymerase. Under conditions of oxygen deprivation, the sigB gene is upregulated and cells exhibit high productivity of organic acids as a result of an elevated glucose consumption rate. Using DNA microarray and quantitative reverse transcription-PCR (RT-PCR) analyses, we found that sigB disruption led to reduced transcript levels of genes involved in the metabolism of glucose into organic acids. This in turn resulted in retardation of glucose consumption by cells under conditions of oxygen deprivation. These results indicate that SigB is involved in positive regulation of glucose metabolism genes and enhances glucose consumption under conditions of oxygen deprivation. Moreover, sigB disruption reduced the transcript levels of genes involved in various cellular functions, including the glucose metabolism genes not only in the growth-arrested cells under conditions of oxygen deprivation but also in the cells during aerobic exponential growth, suggesting that SigB functions as another vegetative sigma factor.
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Affiliation(s)
- Shigeki Ehira
- Research Institute of Innovative Technology for the Earth, 9-2 Kizugawadai, Kizugawa, Kyoto 619-0292, Japan
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Brinkrolf K, Brune I, Tauch A. The transcriptional regulatory network of the amino acid producer Corynebacterium glutamicum. J Biotechnol 2007; 129:191-211. [PMID: 17227685 DOI: 10.1016/j.jbiotec.2006.12.013] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2006] [Revised: 11/14/2006] [Accepted: 12/04/2006] [Indexed: 11/18/2022]
Abstract
The complete nucleotide sequence of the Corynebacterium glutamicum ATCC 13032 genome was previously determined and allowed the reliable prediction of 3002 protein-coding genes within this genome. Using computational methods, we have defined 158 genes, which form the minimal repertoire for proteins that presumably act as transcriptional regulators of gene expression. Most of these regulatory proteins have a direct role as DNA-binding transcriptional regulator, while others either have less well-defined functions in transcriptional regulation or even more general functions, such as the sigma factors. Recent advances in genome-wide transcriptional profiling of C. glutamicum generated a huge amount of data on regulation of gene expression. To understand transcriptional regulation of gene expression from the perspective of systems biology, rather than from the analysis of an individual regulatory protein, we compiled the current knowledge on the defined DNA-binding transcriptional regulators and their physiological role in modulating transcription in response to environmental signals. This comprehensive data collection provides a solid basis for database-guided reconstructions of the gene regulatory network of C. glutamicum, currently comprising 56 transcriptional regulators that exert 411 regulatory interactions to control gene expression. A graphical reconstruction revealed first insights into the functional modularity, the hierarchical architecture and the topological design principles of the transcriptional regulatory network of C. glutamicum.
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Affiliation(s)
- Karina Brinkrolf
- Institut für Genomforschung, Centrum für Biotechnologie, Universität Bielefeld, Universitätsstrasse 25, D-33615 Bielefeld, Germany
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The alternative sigma factor SigB of Corynebacterium glutamicum modulates global gene expression during transition from exponential growth to stationary phase. BMC Genomics 2007; 8:4. [PMID: 17204139 PMCID: PMC1779776 DOI: 10.1186/1471-2164-8-4] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2006] [Accepted: 01/04/2007] [Indexed: 11/16/2022] Open
Abstract
Background Corynebacterium glutamicum is a gram-positive soil bacterium widely used for the industrial production of amino acids. There is great interest in the examination of the molecular mechanism of transcription control. One of these control mechanisms are sigma factors. C. glutamicum ATCC 13032 has seven putative sigma factor-encoding genes, including sigA and sigB. The sigA gene encodes the essential primary sigma factor of C. glutamicum and is responsible for promoter recognition of house-keeping genes. The sigB gene codes for the non-essential sigma factor SigB that has a proposed role in stress reponse. Results The sigB gene expression was highest at transition between exponential growth and stationary phase, when the amount of sigA mRNA was already decreasing. Genome-wide transcription profiles of the wild-type and the sigB mutant were recorded by comparative DNA microarray hybridizations. The data indicated that the mRNA levels of 111 genes are significantly changed in the sigB-proficient strain during the transition phase, whereas the expression profile of the sigB-deficient strain showed only minor changes (26 genes). The genes that are higher expressed during transition phase only in the sigB-proficient strain mainly belong to the functional categories amino acid metabolism, carbon metabolism, stress defense, membrane processes, and phosphorus metabolism. The transcription start points of six of these genes were determined and the deduced promoter sequences turned out to be indistinguishable from that of the consensus promoter recognized by SigA. Real-time reverse transcription PCR assays revealed that the expression profiles of these genes during growth were similar to that of the sigB gene itself. In the sigB mutant, however, the transcription profiles resembled that of the sigA gene encoding the house-keeping sigma factor. Conclusion During transition phase, the sigB gene showed an enhanced expression, while simultaneously the sigA mRNA decreased in abundance. This might cause a replacement of SigA by SigB at the RNA polymerase core enzyme and in turn results in increased expression of genes relevant for the transition and the stationary phase, either to cope with nutrient limitation or with the accompanying oxidative stress. The increased expression of genes encoding anti-oxidative or protection functions also prepares the cell for upcoming limitations and environmental stresses.
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Brockmann-Gretza O, Kalinowski J. Global gene expression during stringent response in Corynebacterium glutamicum in presence and absence of the rel gene encoding (p)ppGpp synthase. BMC Genomics 2006; 7:230. [PMID: 16961923 PMCID: PMC1578569 DOI: 10.1186/1471-2164-7-230] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2006] [Accepted: 09/08/2006] [Indexed: 12/01/2022] Open
Abstract
Background The stringent response is the initial reaction of microorganisms to nutritional stress. During stringent response the small nucleotides (p)ppGpp act as global regulators and reprogram bacterial transcription. In this work, the genetic network controlled by the stringent response was characterized in the amino acid-producing Corynebacterium glutamicum. Results The transcriptome of a C. glutamicum rel gene deletion mutant, unable to synthesize (p)ppGpp and to induce the stringent response, was compared with that of its rel-proficient parent strain by microarray analysis. A total of 357 genes were found to be transcribed differentially in the rel-deficient mutant strain. In a second experiment, the stringent response was induced by addition of DL-serine hydroxamate (SHX) in early exponential growth phase. The time point of the maximal effect on transcription was determined by real-time RT-PCR using the histidine and serine biosynthetic genes. Transcription of all of these genes reached a maximum at 10 minutes after SHX addition. Microarray experiments were performed comparing the transcriptomes of SHX-induced cultures of the rel-proficient strain and the rel mutant. The differentially expressed genes were grouped into three classes. Class A comprises genes which are differentially regulated only in the presence of an intact rel gene. This class includes the non-essential sigma factor gene sigB which was upregulated and a large number of genes involved in nitrogen metabolism which were downregulated. Class B comprises genes which were differentially regulated in response to SHX in both strains, independent of the rel gene. A large number of genes encoding ribosomal proteins fall into this class, all being downregulated. Class C comprises genes which were differentially regulated in response to SHX only in the rel mutant. This class includes genes encoding putative stress proteins and global transcriptional regulators that might be responsible for the complex transcriptional patterns detected in the rel mutant when compared directly with its rel-proficient parent strain. Conclusion In C. glutamicum the stringent response enfolds a fast answer to an induced amino acid starvation on the transcriptome level. It also showed some significant differences to the transcriptional reactions occuring in Escherichia coli and Bacillus subtilis. Notable are the rel-dependent regulation of the nitrogen metabolism genes and the rel-independent regulation of the genes encoding ribosomal proteins.
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Affiliation(s)
- Olaf Brockmann-Gretza
- Institut für Genomforschung, Centrum für Biotechnologie, Universität Bielefeld, Universitätsstrasse 25, D-33615 Bielefeld, Germany
| | - Jörn Kalinowski
- Institut für Genomforschung, Centrum für Biotechnologie, Universität Bielefeld, Universitätsstrasse 25, D-33615 Bielefeld, Germany
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Oram DM, Jacobson AD, Holmes RK. Transcription of the contiguous sigB, dtxR, and galE genes in Corynebacterium diphtheriae: evidence for multiple transcripts and regulation by environmental factors. J Bacteriol 2006; 188:2959-73. [PMID: 16585757 PMCID: PMC1447015 DOI: 10.1128/jb.188.8.2959-2973.2006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The iron-dependent transcriptional regulator DtxR from Corynebacterium diphtheriae is the prototype for a family of metal-dependent regulators found in diverse bacterial species. The structure of DtxR and its action as a repressor have been extensively characterized, but little is known about expression of dtxR. In the current study, we investigated transcription of dtxR as well as the sigB and galE genes located immediately upstream and downstream from dtxR, respectively. We identified two promoters that determine transcription of dtxR. The first, located upstream of sigB, appears to be controlled by an extracytoplasmic function sigma factor. The second, located in the intergenic region between sigB and dtxR, is similar to promoters used by the primary vegetative sigma factors in other actinomycete species. Using quantitative real-time assays, we demonstrated that the number of transcripts initiated upstream from sigB is affected by several environmental factors. In contrast, the presence of sodium dodecyl sulfate was the only factor tested that conclusively affects the number of transcripts initiated in the sigB-dtxR intergenic region. Additionally, we provided evidence for the existence of transcripts that contain sigB, dtxR, and galE. Our studies provide the first quantitative transcriptional analysis of a gene encoding a DtxR family regulator and give new insights into transcriptional regulation in C. diphtheriae.
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Affiliation(s)
- Diana Marra Oram
- University of Colorado at Denver and Health Sciences Center, School of Medicine, Department of Microbiology, Mail Stop 8333, P.O. Box 6511, Aurora, CO 80045, USA
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Srivastava P, Deb JK. Gene expression systems in corynebacteria. Protein Expr Purif 2005; 40:221-9. [PMID: 15766862 DOI: 10.1016/j.pep.2004.06.017] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2004] [Revised: 06/13/2004] [Indexed: 11/29/2022]
Abstract
Corynebacterium belongs to a group of gram-positive bacteria having moderate to high G+C content, the other members being Mycobacterium, Nocardia, and Rhodococcus. Considerable information is now available on the plasmids, gene regulatory elements, and gene expression in corynebacteria, especially in soil corynebacteria such as Corynebacterium glutamicum. These bacteria are non-pathogenic and, unlike Bacillus and Streptomyces, are low in proteolytic activity and thus have the potential of becoming attractive systems for expression of heterologous proteins. This review discusses recent advances in our understanding of the organization of various regulatory elements, such as promoters, transcription terminators, and development of vectors for cloning and gene expression.
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Affiliation(s)
- Preeti Srivastava
- Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology, Delhi, New Delhi 110 016, India
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Abstract
Regulation of gene expression in Corynebacterium glutamicum represents an important issue since this Gram-positive bacterium is a notable industrial amino acid producer. Transcription initiation, beginning by binding of RNA polymerase to the promoter DNA sequence, is one of the main points at which bacterial gene expression is regulated. More than 50 transcriptional promoters have so far been experimentally localized in C. glutamicum. Most of them are assumed to be promoters of vegetative genes recognized by the main sigma factor. Although transcription initiation rate defined by many of these promoters may be affected by transcription factors, which activate or repress their function, the promoter regions share common sequence features, which may be generalized in a consensus sequence. In the consensus C. glutamicum promoter, the prominent feature is a conserved extended -10 region tgngnTA(c/t)aaTgg, while the -35 region is much less conserved. Some commonly utilized heterologous promoters were shown to drive strong gene expression in C. glutamicum. Conversely, some C. glutamicum promoters were found to function in Escherichia coli and in other bacteria. These observations suggest that C. glutamicum promoters functionally conform with the common bacterial promoter scheme, although they differ in some sequence structures.
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Affiliation(s)
- Miroslav Pátek
- Institute of Microbiology, Academy of Sciences of the Czech Republic, Vídenská 1083, CZ-14220 Prague 4, Czech Republic.
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Halgasova N, Bukovska G, Ugorcakova J, Timko J, Kormanec J. The Brevibacterium flavum sigma factor SigB has a role in the environmental stress response. FEMS Microbiol Lett 2002; 216:77-84. [PMID: 12423756 DOI: 10.1111/j.1574-6968.2002.tb11418.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
We have previously cloned a gene encoding a SigB, a principal-like sigma factor in Brevibacterium flavum, which was induced by several stress conditions. To clarify the in vivo function of this sigma factor, the sigB gene was disrupted by a homologous recombination, replacing the internal essential coding region in B. flavum chromosome by a kanamycin resistance marker gene. This mutation dramatically decreased vegetative growth rates of B. flavum. Studies of the effect of the sigB mutation on growth and viability of the cells under conditions of stress showed that the sigB mutant had increased susceptibility to acid, salt, alcohol, heat and cold stress. The plasmid-born wild-type sigB gene complemented the mutation. Based on the results, we propose that SigB has a role in vegetative growth and in response to various environmental stresses.
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Affiliation(s)
- Nora Halgasova
- Institute of Molecular Biology, Slovak Academy of Sciences, Bratislava, Slovak Republic
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Hu Y, Coates AR. Transcription of two sigma 70 homologue genes, sigA and sigB, in stationary-phase Mycobacterium tuberculosis. J Bacteriol 1999; 181:469-76. [PMID: 9882660 PMCID: PMC93400 DOI: 10.1128/jb.181.2.469-476.1999] [Citation(s) in RCA: 93] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The sigA and sigB genes of Mycobacterium tuberculosis encode two sigma 70-like sigma factors of RNA polymerase. While transcription of the sigA gene is growth rate independent, sigB transcription is increased during entry into stationary phase. The sigA gene transcription is unresponsive to environmental stress but that of sigB is very responsive, more so in stationary-phase growth than in log-phase cultures. These data suggest that SigA is a primary sigma factor which, like sigma70, controls the transcription of the housekeeping type of promoters. In contrast, SigB, although showing some overlap in function with SigA, is more like the alternative sigma factor, sigmaS, which controls the transcription of the gearbox type of promoters. Primer extension analysis identified the RNA start sites for both genes as 129 nucleotides upstream to the GTG start codon of sigA and 27 nucleotides from the ATG start codon of sigB. The -10 promoter of sigA but not that of sigB was similar to the sigma70 promoter. The half-life of the sigA transcript was very long, and this is likely to play an important part in its regulation. In contrast, the half-life of the sigB transcript was short, about 2 min. These results demonstrate that the sigB gene may control the regulons of stationary phase and general stress resistance, while sigA may be involved in the housekeeping regulons.
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Affiliation(s)
- Y Hu
- Department of Medical Microbiology, St. George's Hospital Medical School, London SW17 ORE, United Kingdom
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