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Mardoukhi MSY, Rapp J, Irisarri I, Gunka K, Link H, Marienhagen J, de Vries J, Stülke J, Commichau FM. Metabolic rewiring enables ammonium assimilation via a non-canonical fumarate-based pathway. Microb Biotechnol 2024; 17:e14429. [PMID: 38483038 PMCID: PMC10938345 DOI: 10.1111/1751-7915.14429] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Revised: 01/16/2024] [Accepted: 02/09/2024] [Indexed: 03/17/2024] Open
Abstract
Glutamate serves as the major cellular amino group donor. In Bacillus subtilis, glutamate is synthesized by the combined action of the glutamine synthetase and the glutamate synthase (GOGAT). The glutamate dehydrogenases are devoted to glutamate degradation in vivo. To keep the cellular glutamate concentration high, the genes and the encoded enzymes involved in glutamate biosynthesis and degradation need to be tightly regulated depending on the available carbon and nitrogen sources. Serendipitously, we found that the inactivation of the ansR and citG genes encoding the repressor of the ansAB genes and the fumarase, respectively, enables the GOGAT-deficient B. subtilis mutant to synthesize glutamate via a non-canonical fumarate-based ammonium assimilation pathway. We also show that the de-repression of the ansAB genes is sufficient to restore aspartate prototrophy of an aspB aspartate transaminase mutant. Moreover, in the presence of arginine, B. subtilis mutants lacking fumarase activity show a growth defect that can be relieved by aspB overexpression, by reducing arginine uptake and by decreasing the metabolic flux through the TCA cycle.
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Affiliation(s)
| | - Johanna Rapp
- Interfaculty Institute for Microbiology and Infection Medicine TübingenUniversity of TübingenTübingenGermany
| | - Iker Irisarri
- Department of Applied Bioinformatics, Institute of Microbiology and Genetics, GZMBGeorg‐August‐University GöttingenGöttingenGermany
- Campus Institute Data ScienceUniversity of GöttingenGöttingenGermany
| | - Katrin Gunka
- Department of General Microbiology, Institute for Microbiology and Genetics, GZMBGeorg‐August‐University GöttingenGöttingenGermany
| | - Hannes Link
- Interfaculty Institute for Microbiology and Infection Medicine TübingenUniversity of TübingenTübingenGermany
| | - Jan Marienhagen
- Institute of Bio‐ and Geosciences, IBG‐1: BiotechnologyForschungszentrum JülichJülichGermany
- Institut of BiotechnologyRWTH Aachen UniversityAachenGermany
| | - Jan de Vries
- Department of Applied Bioinformatics, Institute of Microbiology and Genetics, GZMBGeorg‐August‐University GöttingenGöttingenGermany
- Campus Institute Data ScienceUniversity of GöttingenGöttingenGermany
| | - Jörg Stülke
- Department of General Microbiology, Institute for Microbiology and Genetics, GZMBGeorg‐August‐University GöttingenGöttingenGermany
| | - Fabian M. Commichau
- FG Molecular Microbiology, Institute for BiologyUniversity of HohenheimStuttgartGermany
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2
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Shibamura-Fujiogi M, Wang X, Maisat W, Koutsogiannaki S, Li Y, Chen Y, Lee JC, Yuki K. GltS regulates biofilm formation in methicillin-resistant Staphylococcus aureus. Commun Biol 2022; 5:1284. [PMID: 36418899 PMCID: PMC9684512 DOI: 10.1038/s42003-022-04239-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 11/08/2022] [Indexed: 11/25/2022] Open
Abstract
Biofilm-based infection is a major healthcare burden. Methicillin-resistant Staphylococcus aureus (MRSA) is one of major organisms responsible for biofilm infection. Although biofilm is induced by a number of environmental signals, the molecule responsible for environmental sensing is not well delineated. Here we examined the role of ion transporters in biofilm formation and found that the sodium-glutamate transporter gltS played an important role in biofilm formation in MRSA. This was shown by gltS transposon mutant as well as its complementation. The lack of exogenous glutamate also enhanced biofilm formation in JE2 strain. The deficiency of exogenous glutamate intake accelerated endogenous glutamate/glutamine production, which led to the activation of the urea cycle. We also showed that urea cycle activation was critical for biofilm formation. In conclusion, we showed that gltS was a critical regulator of biofilm formation by controlling the intake of exogenous glutamate. An intervention to target glutamate intake may be a potential useful approach against biofilm.
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Affiliation(s)
- Miho Shibamura-Fujiogi
- Department of Anesthesiology, Critical Care and Pain Medicine, Cardiac Anesthesia Division, Boston Children's Hospital, Boston, MA, USA
- Department of Anaesthesia and Immunology, Harvard Medical School, Boston, MA, USA
| | - Xiaogang Wang
- Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Wiriya Maisat
- Department of Anesthesiology, Critical Care and Pain Medicine, Cardiac Anesthesia Division, Boston Children's Hospital, Boston, MA, USA
- Department of Anaesthesia and Immunology, Harvard Medical School, Boston, MA, USA
| | - Sophia Koutsogiannaki
- Department of Anesthesiology, Critical Care and Pain Medicine, Cardiac Anesthesia Division, Boston Children's Hospital, Boston, MA, USA
- Department of Anaesthesia and Immunology, Harvard Medical School, Boston, MA, USA
| | - Yunan Li
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - Yue Chen
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - Jean C Lee
- Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, USA
| | - Koichi Yuki
- Department of Anesthesiology, Critical Care and Pain Medicine, Cardiac Anesthesia Division, Boston Children's Hospital, Boston, MA, USA.
- Department of Anaesthesia and Immunology, Harvard Medical School, Boston, MA, USA.
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3
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Frank C, Hoffmann T, Zelder O, Felle MF, Bremer E. Enhanced Glutamate Synthesis and Export by the Thermotolerant Emerging Industrial Workhorse Bacillus methanolicus in Response to High Osmolarity. Front Microbiol 2021; 12:640980. [PMID: 33897645 PMCID: PMC8060640 DOI: 10.3389/fmicb.2021.640980] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2020] [Accepted: 03/01/2021] [Indexed: 11/13/2022] Open
Abstract
The thermotolerant methylotroph Bacillus methanolicus MGA3 was originally isolated from freshwater marsh soil. Due to its ability to use methanol as sole carbon and energy source, B. methanolicus is increasingly explored as a cell factory for the production of amino acids, fine chemicals, and proteins of biotechnological interest. During high cell density fermentation in industrial settings with the membrane-permeable methanol as the feed, the excretion of low molecular weight products synthesized from it will increase the osmotic pressure of the medium. This in turn will impair cell growth and productivity of the overall biotechnological production process. With this in mind, we have analyzed the core of the physiological adjustment process of B. methanolicus MGA3 to sustained high osmolarity surroundings. Through growth assays, we found that B. methanolicus MGA3 possesses only a restricted ability to cope with sustained osmotic stress. This finding is consistent with the ecophysiological conditions in the habitat from which it was originally isolated. None of the externally provided compatible solutes and proline-containing peptides affording osmostress protection for Bacillus subtilis were able to stimulate growth of B. methanolicus MGA3 at high salinity. B. methanolicus MGA3 synthesized the moderately effective compatible solute L-glutamate in a pattern such that the cellular pool increased concomitantly with increases in the external osmolarity. Counterintuitively, a large portion of the newly synthesized L-glutamate was excreted. The expression of the genes (gltAB and gltA2) for two L-glutamate synthases were upregulated in response to high salinity along with that of the gltC regulatory gene. Such a regulatory pattern of the system(s) for L-glutamate synthesis in Bacilli is new. Our findings might thus be generally relevant to understand the production of the osmostress protectant L-glutamate by those Bacilli that exclusively rely on this compatible solute for their physiological adjustment to high osmolarity surroundings.
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Affiliation(s)
- Christine Frank
- Laboratory for Microbiology, Department of Biology, Philipps-University Marburg, Marburg, Germany
| | - Tamara Hoffmann
- Laboratory for Microbiology, Department of Biology, Philipps-University Marburg, Marburg, Germany.,Center for Synthetic Microbiology (SYNMIKRO), Philipps-University Marburg, Marburg, Germany
| | - Oskar Zelder
- BASF SE, RWB/EC - A030 - L3/10, Ludwigshafen, Germany
| | - Max F Felle
- BASF SE, RWB/EC - A030 - L3/10, Ludwigshafen, Germany
| | - Erhard Bremer
- Laboratory for Microbiology, Department of Biology, Philipps-University Marburg, Marburg, Germany.,Center for Synthetic Microbiology (SYNMIKRO), Philipps-University Marburg, Marburg, Germany
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4
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Role of GlnR in Controlling Expression of Nitrogen Metabolism Genes in Listeria monocytogenes. J Bacteriol 2020; 202:JB.00209-20. [PMID: 32690554 DOI: 10.1128/jb.00209-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2020] [Accepted: 07/10/2020] [Indexed: 01/27/2023] Open
Abstract
Listeria monocytogenes is a fastidious bacterial pathogen that can utilize only a limited number of nitrogen sources for growth. Both glutamine and ammonium are common nitrogen sources used in listerial defined growth media, but little is known about the regulation of their uptake or utilization. The functional role of L. monocytogenes GlnR, the transcriptional regulator of nitrogen metabolism genes in low-G+C Gram-positive bacteria, was determined using transcriptome sequencing and real-time reverse transcription-PCR experiments. The GlnR regulon included transcriptional units involved in ammonium transport (amtB glnK) and biosynthesis of glutamine (glnRA) and glutamate (gdhA) from ammonium. As in other bacteria, GlnR proved to be an autoregulatory repressor of the glnRA operon. Unexpectedly, GlnR was most active during growth with ammonium as the nitrogen source and less active in the glutamine medium, apparently because listerial cells perceive growth with glutamine as a nitrogen-limiting condition. Therefore, paradoxically, expression of the glnA gene, encoding glutamine synthetase, was highest in the glutamine medium. For the amtB glnK operon, GlnR served as both a negative regulator in the presence of ammonium and a positive regulator in the glutamine medium. The gdhA gene was subject to a third mode of regulation that apparently required an elevated level of GlnR for repression. Finally, activity of glutamate dehydrogenase encoded by the gdhA gene appeared to correlate inversely with expression of gltAB, the operon that encodes the other major glutamate-synthesizing enzyme, glutamate synthase. Both gdhA and amtB were also regulated, in a negative manner, by the global transcriptional regulator CodY.IMPORTANCE L. monocytogenes is a widespread foodborne pathogen. Nitrogen-containing compounds, such as the glutamate-containing tripeptide, glutathione, and glutamine, have been shown to be important for expression of L. monocytogenes virulence genes. In this work, we showed that a transcriptional regulator, GlnR, controls expression of critical listerial genes of nitrogen metabolism that are involved in ammonium uptake and biosynthesis of glutamine and glutamate. A different mode of GlnR-mediated regulation was found for each of these three pathways.
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Dormeyer M, Lentes S, Richts B, Heermann R, Ischebeck T, Commichau FM. Variants of the Bacillus subtilis LysR-Type Regulator GltC With Altered Activator and Repressor Function. Front Microbiol 2019; 10:2321. [PMID: 31649652 PMCID: PMC6794564 DOI: 10.3389/fmicb.2019.02321] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 09/23/2019] [Indexed: 11/20/2022] Open
Abstract
The Gram-positive soil bacterium Bacillus subtilis relies on the glutamine synthetase and the glutamate synthase for glutamate biosynthesis from ammonium and 2-oxoglutarate. During growth with the carbon source glucose, the LysR-type transcriptional regulator GltC activates the expression of the gltAB glutamate synthase genes. With excess of intracellular glutamate, the gltAB genes are not transcribed because the glutamate-degrading glutamate dehydrogenases (GDHs) inhibit GltC. Previous in vitro studies revealed that 2-oxoglutarate and glutamate stimulate the activator and repressor function, respectively, of GltC. Here, we have isolated GltC variants with enhanced activator or repressor function. The majority of the GltC variants with enhanced activator function differentially responded to the GDHs and to glutamate. The GltC variants with enhanced repressor function were still capable of activating the PgltA promoter in the absence of a GDH. Using PgltA promoter variants (PgltA∗) that are active independent of GltC, we show that the wild type GltC and the GltC variants with enhanced repressor function inactivate PgltA∗ promoters in the presence of the native GDHs. These findings suggest that GltC may also act as a repressor of the gltAB genes in vivo. We discuss a model combining previous models that were derived from in vivo and in vitro experiments.
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Affiliation(s)
- Miriam Dormeyer
- Department of General Microbiology, Institute of Microbiology and Genetics, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Sabine Lentes
- Department of General Microbiology, Institute of Microbiology and Genetics, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Björn Richts
- Department of General Microbiology, Institute of Microbiology and Genetics, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Ralf Heermann
- Institut für Molekulare Physiologie, Mikrobiologie und Weinforschung, Johannes Gutenberg-Universität Mainz, Mainz, Germany
| | - Till Ischebeck
- Department for Plant Biochemistry, Albrecht-von-Haller-Institute for Plant Sciences, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Fabian M Commichau
- Department of General Microbiology, Institute of Microbiology and Genetics, Georg-August-Universität Göttingen, Göttingen, Germany
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6
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Randazzo P, Aucouturier A, Delumeau O, Auger S. Revisiting the in vivo GlnR-binding sites at the genome scale in Bacillus subtilis. BMC Res Notes 2017; 10:422. [PMID: 28835263 PMCID: PMC5569456 DOI: 10.1186/s13104-017-2703-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Accepted: 07/29/2017] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND In Bacillus subtilis, two major transcriptional factors, GlnR and TnrA, are involved in a sophisticated network of adaptive responses to nitrogen availability. GlnR was reported to repress the transcription of the glnRA, tnrA and ureABC operons under conditions of excess nitrogen. As GlnR and TnrA regulators share the same DNA binding motifs, a genome-wide mapping of in vivo GlnR-binding sites was still needed to clearly define the set of GlnR/TnrA motifs directly bound by GlnR. METHODS We used chromatin immunoprecipitation coupled with hybridization to DNA tiling arrays (ChIP-on-chip) to identify the GlnR DNA-binding sites, in vivo, at the genome scale. RESULTS We provide evidence that GlnR binds reproducibly to 61 regions on the chromosome. Among those, 20 regions overlap the previously defined in vivo TnrA-binding sites. In combination with real-time in vivo transcriptional profiling using firefly luciferase, we identified the alsT gene as a new member of the GlnR regulon. Additionally, we characterized the GlnR secondary regulon, which is composed of promoter regions harboring a GlnR/TnrA box and bound by GlnR in vivo. However, the growth conditions revealing a GlnR-dependent regulation for this second category of genes are still unknown. CONCLUSIONS Our findings show an extended overlap between the GlnR and TnrA in vivo binding sites. This could allow efficient and fine tuning of gene expression in response to nitrogen availability. GlnR appears to be part of complex transcriptional regulatory networks, which involves interactions between different regulatory proteins.
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Affiliation(s)
- Paola Randazzo
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350, Jouy-en-Josas, France
| | - Anne Aucouturier
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350, Jouy-en-Josas, France
| | - Olivier Delumeau
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350, Jouy-en-Josas, France
| | - Sandrine Auger
- Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay, 78350, Jouy-en-Josas, France.
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7
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Sun Y, De Vos P, Willems A. Nitrogen assimilation in denitrifier Bacillus azotoformans LMG 9581 T. Antonie van Leeuwenhoek 2017; 110:1613-1626. [PMID: 28726125 DOI: 10.1007/s10482-017-0911-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 07/12/2017] [Indexed: 11/27/2022]
Abstract
Until recently, it has not been generally known that some bacteria can contain the gene inventory for both denitrification and dissimilatory nitrate (NO3-)/nitrite (NO2-) reduction to ammonium (NH4+) (DNRA). Detailed studies of these microorganisms could shed light on the differentiating environmental drivers of both processes without interference of organism-specific variation. Genome analysis of Bacillus azotoformans LMG 9581T shows a remarkable redundancy of dissimilatory nitrogen reduction, with multiple copies of each denitrification gene as well as DNRA genes nrfAH, but a reduced capacity for nitrogen assimilation, with no nas operon nor amtB gene. Here, we explored nitrogen assimilation in detail using growth experiments in media with different organic and inorganic nitrogen sources at different concentrations. Monitoring of growth, NO3- NO2-, NH4+ concentration and N2O production revealed that B. azotoformans LMG 9581T could not grow with NH4+ as sole nitrogen source and confirmed the hypothesis of reduced nitrogen assimilation pathways. However, NH4+ could be assimilated and contributed up to 50% of biomass if yeast extract was also provided. NH4+ also had a significant but concentration-dependent influence on growth rate. The mechanisms behind these observations remain to be resolved but hypotheses for this deficiency in nitrogen assimilation are discussed. In addition, in all growth conditions tested a denitrification phenotype was observed, with all supplied NO3- converted to nitrous oxide (N2O).
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Affiliation(s)
- Yihua Sun
- Laboratory of Microbiology, Ghent University, K.L. Ledeganckstraat 35, 9000, Ghent, Belgium
| | - Paul De Vos
- Laboratory of Microbiology, Ghent University, K.L. Ledeganckstraat 35, 9000, Ghent, Belgium
| | - Anne Willems
- Laboratory of Microbiology, Ghent University, K.L. Ledeganckstraat 35, 9000, Ghent, Belgium.
- Laboratory of Microbiology (LM-UGent), Department of Biochemistry and Microbiology, Ghent University, K.L. Ledeganckstraat 35, 9000, Ghent, Belgium.
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8
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Dormeyer M, Lübke AL, Müller P, Lentes S, Reuß DR, Thürmer A, Stülke J, Daniel R, Brantl S, Commichau FM. Hierarchical mutational events compensate for glutamate auxotrophy of a Bacillus subtilis gltC mutant. ENVIRONMENTAL MICROBIOLOGY REPORTS 2017; 9:279-289. [PMID: 28294562 DOI: 10.1111/1758-2229.12531] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Revised: 03/01/2017] [Accepted: 03/05/2017] [Indexed: 06/06/2023]
Abstract
Glutamate is the major donor of nitrogen for anabolic reactions. The Gram-positive soil bacterium Bacillus subtilis either utilizes exogenously provided glutamate or synthesizes it using the gltAB-encoded glutamate synthase (GOGAT). In the absence of glutamate, the transcription factor GltC activates expression of the GOGAT genes for glutamate production. Consequently, a gltC mutant strain is auxotrophic for glutamate. Using a genetic selection and screening system, we could isolate and differentiate between gltC suppressor mutants in one step. All mutants had acquired the ability to synthesize glutamate, independent of GltC. We identified (i) gain-of-function mutations in the gltR gene, encoding the transcription factor GltR, (ii) mutations in the promoter of the gltAB operon and (iii) massive amplification of the genomic locus containing the gltAB operon. The mutants belonging to the first two classes constitutively expressed the gltAB genes and produced sufficient glutamate for growth. By contrast, mutants that belong to the third class appeared most frequently and solved glutamate limitation by increasing the copy number of the poorly expressed gltAB genes. Thus, glutamate auxotrophy of a B. subtilis gltC mutant can be relieved in multiple ways. Moreover, recombination-dependent amplification of the gltAB genes is the predominant mutational event indicating a hierarchy of mutations.
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Affiliation(s)
- Miriam Dormeyer
- Department of General Microbiology, Georg August University Göttingen, Grisebachstr. 8, Göttingen, 37077, Germany
| | - Anastasia L Lübke
- Department of General Microbiology, Georg August University Göttingen, Grisebachstr. 8, Göttingen, 37077, Germany
| | - Peter Müller
- Department of Genetics, Bacterial Genetics, Friedrich Schiller University Jena, Philosophenweg 12, Jena, 07743, Germany
| | - Sabine Lentes
- Department of General Microbiology, Georg August University Göttingen, Grisebachstr. 8, Göttingen, 37077, Germany
| | - Daniel R Reuß
- Department of General Microbiology, Georg August University Göttingen, Grisebachstr. 8, Göttingen, 37077, Germany
| | - Andrea Thürmer
- Department of Genomic and Applied Microbiology, Georg August University Göttingen, Grisebachstr. 8, Göttingen, 37077, Germany
| | - Jörg Stülke
- Department of General Microbiology, Georg August University Göttingen, Grisebachstr. 8, Göttingen, 37077, Germany
| | - Rolf Daniel
- Department of Genomic and Applied Microbiology, Georg August University Göttingen, Grisebachstr. 8, Göttingen, 37077, Germany
| | - Sabine Brantl
- Department of Genetics, Bacterial Genetics, Friedrich Schiller University Jena, Philosophenweg 12, Jena, 07743, Germany
| | - Fabian M Commichau
- Department of General Microbiology, Georg August University Göttingen, Grisebachstr. 8, Göttingen, 37077, Germany
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A novel approach to improve poly-γ-glutamic acid production by NADPH Regeneration in Bacillus licheniformis WX-02. Sci Rep 2017; 7:43404. [PMID: 28230096 PMCID: PMC5322528 DOI: 10.1038/srep43404] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 01/24/2017] [Indexed: 01/15/2023] Open
Abstract
Poly-γ-glutamic acid (γ-PGA) is an important biochemical product with a variety of applications. This work reports a novel approach to improve γ-PGA through over expression of key enzymes in cofactor NADPH generating process for NADPH pool. Six genes encoding the key enzymes in NADPH generation were over-expressed in the γ-PGA producing strain B. licheniformis WX-02. Among various recombinants, the strain over-expressing zwf gene (coding for glucose-6-phosphate dehydrogenase), WX-zwf, produced the highest γ-PGA concentration (9.13 g/L), 35% improvement compared to the control strain WX-pHY300. However, the growth rates and glucose uptake rates of the mutant WX-zwf were decreased. The transcriptional levels of the genes pgsB and pgsC responsible for γ-PGA biosynthesis were increased by 8.21- and 5.26-fold, respectively. The Zwf activity of the zwf over expression strain increased by 9.28-fold, which led to the improvement of the NADPH generation, and decrease of accumulation of by-products acetoin and 2,3-butanediol. Collectively, these results demonstrated that NADPH generation via over-expression of Zwf is as an effective strategy to improve the γ-PGA production in B. licheniformis.
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10
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Peng Q, Wang G, Liu G, Zhang J, Song F. Identification of metabolism pathways directly regulated by sigma(54) factor in Bacillus thuringiensis. Front Microbiol 2015; 6:407. [PMID: 26029175 PMCID: PMC4428206 DOI: 10.3389/fmicb.2015.00407] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Accepted: 04/19/2015] [Indexed: 11/13/2022] Open
Abstract
Sigma(54) (σ(54)) regulates nitrogen and carbon utilization in bacteria. Promoters that are σ(54)-dependent are highly conserved and contain short sequences located at the -24 and -12 positions upstream of the transcription initiation site. σ(54) requires regulatory proteins known as bacterial enhancer-binding proteins (bEBPs) to activate gene transcription. We show that σ(54) regulates the capacity to grow on various nitrogen sources using a Bacillus thuringiensis HD73 mutant lacking the sigL gene encoding σ(54) (ΔsigL). A 2-fold-change cutoff and a false discovery rate cutoff of P < 0.05 were used to analyze the DNA microarray data, which revealed 255 genes that were downregulated and 121 that were upregulated in the ΔsigL mutant relative to the wild-type HD73 strain. The σ(54) regulon (stationary phase) was characterized by DNA microarray, bioinformatics, and functional assay; 16 operons containing 47 genes were identified whose promoter regions contain the conserved -12/-24 element and whose transcriptional activities were abolished or reduced in the ΔsigL mutant. Eight σ(54)-dependent transcriptional bEBPs were found in the Bt HD73 genome, and they regulated nine σ(54)-dependent promoters. The metabolic pathways activated by σ(54) in this process have yet to be identified in Bacillus thuringiensis; nonetheless, the present analysis of the σ(54) regulon provides a better understanding of the physiological roles of σ factors in bacteria.
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Affiliation(s)
- Qi Peng
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences Beijing, China
| | - Guannan Wang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences Beijing, China
| | - Guiming Liu
- CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences Beijing, China
| | - Jie Zhang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences Beijing, China
| | - Fuping Song
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences Beijing, China
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11
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Stannek L, Thiele MJ, Ischebeck T, Gunka K, Hammer E, Völker U, Commichau FM. Evidence for synergistic control of glutamate biosynthesis by glutamate dehydrogenases and glutamate inBacillus subtilis. Environ Microbiol 2015; 17:3379-90. [DOI: 10.1111/1462-2920.12813] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 02/04/2015] [Accepted: 02/11/2015] [Indexed: 11/28/2022]
Affiliation(s)
- Lorena Stannek
- Department of General Microbiology; Institute of Microbiology and Genetics; Georg-August-University Göttingen; Grisebachstr. 8 Göttingen D-37077 Germany
| | - Martin J. Thiele
- Department of General Microbiology; Institute of Microbiology and Genetics; Georg-August-University Göttingen; Grisebachstr. 8 Göttingen D-37077 Germany
| | - Till Ischebeck
- Department for Plant Biochemistry; Albrecht-von-Haller-Institute for Plant Sciences; Georg-August-University Göttingen; Grisebachstr. 8 Göttingen D-37077 Germany
| | - Katrin Gunka
- Department of General Microbiology; Institute of Microbiology and Genetics; Georg-August-University Göttingen; Grisebachstr. 8 Göttingen D-37077 Germany
| | - Elke Hammer
- Interfaculty Institute for Genetics and Functional Genomics; University Medicine Greifswald; Friedrich-Ludwig-Jahnstr. 15a Greifswald D-17475 Germany
| | - Uwe Völker
- Interfaculty Institute for Genetics and Functional Genomics; University Medicine Greifswald; Friedrich-Ludwig-Jahnstr. 15a Greifswald D-17475 Germany
| | - Fabian M. Commichau
- Department of General Microbiology; Institute of Microbiology and Genetics; Georg-August-University Göttingen; Grisebachstr. 8 Göttingen D-37077 Germany
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12
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Hierarchical expression of genes controlled by the Bacillus subtilis global regulatory protein CodY. Proc Natl Acad Sci U S A 2014; 111:8227-32. [PMID: 24843172 DOI: 10.1073/pnas.1321308111] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Global regulators that bind strategic metabolites allow bacteria to adapt rapidly to dynamic environments by coordinating the expression of many genes. We report an approach for determining gene regulation hierarchy using the regulon of the Bacillus subtilis global regulatory protein CodY as proof of principle. In theory, this approach can be used to measure the dynamics of any bacterial transcriptional regulatory network that is affected by interaction with a ligand. In B. subtilis, CodY controls dozens of genes, but the threshold activities of CodY required to regulate each gene are unknown. We hypothesized that targets of CodY are differentially regulated based on varying affinity for the protein's many binding sites. We used RNA sequencing to determine the transcription profiles of B. subtilis strains expressing mutant CodY proteins with different levels of residual activity. In parallel, we quantified intracellular metabolites connected to central metabolism. Strains producing CodY variants F71Y, R61K, and R61H retained varying degrees of partial activity relative to the WT protein, leading to gene-specific, differential alterations in transcript abundance for the 223 identified members of the CodY regulon. Using liquid chromatography coupled to MS, we detected significant increases in branched-chain amino acids and intermediates of arginine, proline, and glutamate metabolism, as well as decreases in pyruvate and glycerate as CodY activity decreased. We conclude that a spectrum of CodY activities leads to programmed regulation of gene expression and an apparent rerouting of carbon and nitrogen metabolism, suggesting that during changes in nutrient availability, CodY prioritizes the expression of specific pathways.
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Functional characterization of key enzymes involved in L-glutamate synthesis and degradation in the thermotolerant and methylotrophic bacterium Bacillus methanolicus. Appl Environ Microbiol 2013; 79:5321-8. [PMID: 23811508 DOI: 10.1128/aem.01382-13] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Bacillus methanolicus wild-type strain MGA3 secretes 59 g/liter(-1) of l-glutamate in fed-batch methanol cultivations at 50°C. We recently sequenced the MGA3 genome, and we here characterize key enzymes involved in l-glutamate synthesis and degradation. One glutamate dehydrogenase (GDH) that is encoded by yweB and two glutamate synthases (GOGATs) that are encoded by the gltAB operon and by gltA2 were found, in contrast to Bacillus subtilis, which has two different GDHs and only one GOGAT. B. methanolicus has a glutamine synthetase (GS) that is encoded by glnA and a 2-oxoglutarate dehydrogenase (OGDH) that is encoded by the odhAB operon. The yweB, gltA, gltB, and gltA2 gene products were purified and characterized biochemically in vitro. YweB has a low Km value for ammonium (10 mM) and a high Km value for l-glutamate (250 mM), and the Vmax value is 7-fold higher for l-glutamate synthesis than for the degradation reaction. GltA and GltA2 displayed similar Km values (1 to 1.4 mM) and Vmax values (4 U/mg) for both l-glutamate and 2-oxoglutarate as the substrates, and GltB had no effect on the catalytic activities of these enzymes in vitro. Complementation assays indicated that GltA and not GltA2 is dependent on GltB for GOGAT activity in vivo. To our knowledge, this is the first report describing the presence of two active GOGATs in a bacterium. In vivo experiments indicated that OGDH activity and, to some degree, GOGAT activity play important roles in regulating l-glutamate production in this organism.
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Gunka K, Stannek L, Care RA, Commichau FM. Selection-driven accumulation of suppressor mutants in bacillus subtilis: the apparent high mutation frequency of the cryptic gudB gene and the rapid clonal expansion of gudB(+) suppressors are due to growth under selection. PLoS One 2013; 8:e66120. [PMID: 23785476 PMCID: PMC3681913 DOI: 10.1371/journal.pone.0066120] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Accepted: 05/01/2013] [Indexed: 11/25/2022] Open
Abstract
Soil bacteria like Bacillus subtilis can cope with many growth conditions by adjusting gene expression and metabolic pathways. Alternatively, bacteria can spontaneously accumulate beneficial mutations or shape their genomes in response to stress. Recently, it has been observed that a B. subtilis mutant lacking the catabolically active glutamate dehydrogenase (GDH), RocG, mutates the cryptic gudBCR gene at a high frequency. The suppressor mutants express the active GDH GudB, which can fully replace the function of RocG. Interestingly, the cryptic gudBCR allele is stably inherited as long as the bacteria synthesize the functional GDH RocG. Competition experiments revealed that the presence of the cryptic gudBCR allele provides the bacteria with a selective growth advantage when glutamate is scarce. Moreover, the lack of exogenous glutamate is the driving force for the selection of mutants that have inactivated the active gudB gene. In contrast, two functional GDHs are beneficial for the cells when glutamate was available. Thus, the amount of GDH activity strongly affects fitness of the bacteria depending on the availability of exogenous glutamate. At a first glance the high mutation frequency of the cryptic gudBCR allele might be attributed to stress-induced adaptive mutagenesis. However, other loci on the chromosome that could be potentially mutated during growth under the selective pressure that is exerted on a GDH-deficient mutant remained unaffected. Moreover, we show that a GDH-proficient B. subtilis strain has a strong selective growth advantage in a glutamate-dependent manner. Thus, the emergence and rapid clonal expansion of the active gudB allele can be in fact explained by spontaneous mutation and growth under selection without an increase of the mutation rate. Moreover, this study shows that the selective pressure that is exerted on a maladapted bacterium strongly affects the apparent mutation frequency of mutational hot spots.
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Affiliation(s)
- Katrin Gunka
- Department of General Microbiology, Georg-August-University Göttingen, Göttingen, Germany
| | - Lorena Stannek
- Department of General Microbiology, Georg-August-University Göttingen, Göttingen, Germany
| | - Rachel A. Care
- Department of General Microbiology, Georg-August-University Göttingen, Göttingen, Germany
| | - Fabian M. Commichau
- Department of General Microbiology, Georg-August-University Göttingen, Göttingen, Germany
- * E-mail:
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15
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Gunka K, Commichau FM. Control of glutamate homeostasis in Bacillus subtilis: a complex interplay between ammonium assimilation, glutamate biosynthesis and degradation. Mol Microbiol 2012; 85:213-24. [DOI: 10.1111/j.1365-2958.2012.08105.x] [Citation(s) in RCA: 100] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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16
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A high-frequency mutation in Bacillus subtilis: requirements for the decryptification of the gudB glutamate dehydrogenase gene. J Bacteriol 2011; 194:1036-44. [PMID: 22178973 DOI: 10.1128/jb.06470-11] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Common laboratory strains of Bacillus subtilis encode two glutamate dehydrogenases: the enzymatically active protein RocG and the cryptic enzyme GudB that is inactive due to a duplication of three amino acids in its active center. The inactivation of the rocG gene results in poor growth of the bacteria on complex media due to the accumulation of toxic intermediates. Therefore, rocG mutants readily acquire suppressor mutations that decryptify the gudB gene. This decryptification occurs by a precise deletion of one part of the 9-bp direct repeat that causes the amino acid duplication. This mutation occurs at the extremely high frequency of 10(-4). Mutations affecting the integrity of the direct repeat result in a strong reduction of the mutation frequency; however, the actual sequence of the repeat is not essential. The mutation frequency of gudB was not affected by the position of the gene on the chromosome. When the direct repeat was placed in the completely different context of an artificial promoter, the precise deletion of one part of the repeat was also observed, but the mutation frequency was reduced by 3 orders of magnitude. Thus, transcription of the gudB gene seems to be essential for the high frequency of the appearance of the gudB1 mutation. This idea is supported by the finding that the transcription-repair coupling factor Mfd is required for the decryptification of gudB. The Mfd-mediated coupling of transcription to mutagenesis might be a built-in precaution that facilitates the accumulation of mutations preferentially in transcribed genes.
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Combined effect of improved cell yield and increased specific productivity enhances recombinant enzyme production in genome-reduced Bacillus subtilis strain MGB874. Appl Environ Microbiol 2011; 77:8370-81. [PMID: 21965396 DOI: 10.1128/aem.06136-11] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Genome reduction strategies to create genetically improved cellular biosynthesis machineries for proteins and other products have been pursued by use of a wide range of bacteria. We reported previously that the novel Bacillus subtilis strain MGB874, which was derived from strain 168 and has a total genomic deletion of 874 kb (20.7%), exhibits enhanced production of recombinant enzymes. However, it was not clear how the genomic reduction resulted in elevated enzyme production. Here we report that deletion of the rocDEF-rocR region, which is involved in arginine degradation, contributes to enhanced enzyme production in strain MGB874. Deletion of the rocDEF-rocR region caused drastic changes in glutamate metabolism, leading to improved cell yields with maintenance of enzyme productivity. Notably, the specific enzyme productivity was higher in the reduced-genome strain, with or without the rocDEF-rocR region, than in wild-type strain 168. The high specific productivity in strain MGB874 is likely attributable to the higher expression levels of the target gene resulting from an increased promoter activity and plasmid copy number. Thus, the combined effects of the improved cell yield by deletion of the rocDEF-rocR region and the increased specific productivity by deletion of another gene(s) or the genomic reduction itself enhanced the production of recombinant enzymes in MGB874. Our findings represent a good starting point for the further improvement of B. subtilis reduced-genome strains as cell factories for the production of heterologous enzymes.
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18
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Belitsky BR. Indirect repression by Bacillus subtilis CodY via displacement of the activator of the proline utilization operon. J Mol Biol 2011; 413:321-36. [PMID: 21840319 DOI: 10.1016/j.jmb.2011.08.003] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2011] [Revised: 07/22/2011] [Accepted: 08/01/2011] [Indexed: 11/25/2022]
Abstract
Proline is an efficient source of both carbon and nitrogen for many bacterial species. In Bacillus subtilis, the proline utilization pathway, encoded by the putBCP operon, is inducible by proline. Here, we show that this induction is mediated by PutR, a proline-responsive transcriptional activator of the PucR family. When other amino acids are present in the medium, proline utilization is prioritized through transient repression by CodY, a global transcriptional regulator in Gram-positive bacteria that responds to amino acid availability. CodY-mediated repression of the putBCP operon has two novel features. First, repression requires the cooperative binding of CodY to at least two adjacent motifs. Second, though CodY binds to the region that overlaps the putB promoter, repression is due to displacement of PutR rather than competition with RNA polymerase.
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Affiliation(s)
- Boris R Belitsky
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111, USA.
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19
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Flórez LA, Gunka K, Polanía R, Tholen S, Stülke J. SPABBATS: A pathway-discovery method based on Boolean satisfiability that facilitates the characterization of suppressor mutants. BMC SYSTEMS BIOLOGY 2011; 5:5. [PMID: 21219666 PMCID: PMC3024933 DOI: 10.1186/1752-0509-5-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/04/2010] [Accepted: 01/11/2011] [Indexed: 01/25/2023]
Abstract
Background Several computational methods exist to suggest rational genetic interventions that improve the productivity of industrial strains. Nonetheless, these methods are less effective to predict possible genetic responses of the strain after the intervention. This problem requires a better understanding of potential alternative metabolic and regulatory pathways able to counteract the targeted intervention. Results Here we present SPABBATS, an algorithm based on Boolean satisfiability (SAT) that computes alternative metabolic pathways between input and output species in a reconstructed network. The pathways can be constructed iteratively in order of increasing complexity. SPABBATS allows the accumulation of intermediates in the pathways, which permits discovering pathways missed by most traditional pathway analysis methods. In addition, we provide a proof of concept experiment for the validity of the algorithm. We deleted the genes for the glutamate dehydrogenases of the Gram-positive bacterium Bacillus subtilis and isolated suppressor mutant strains able to grow on glutamate as single carbon source. Our SAT approach proposed candidate alternative pathways which were decisive to pinpoint the exact mutation of the suppressor strain. Conclusions SPABBATS is the first application of SAT techniques to metabolic problems. It is particularly useful for the characterization of metabolic suppressor mutants and can be used in a synthetic biology setting to design new pathways with specific input-output requirements.
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Affiliation(s)
- Lope A Flórez
- Department of General Microbiology, Georg-August-University of Göttingen, Germany
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20
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Gunka K, Newman JA, Commichau FM, Herzberg C, Rodrigues C, Hewitt L, Lewis RJ, Stülke J. Functional dissection of a trigger enzyme: mutations of the bacillus subtilis glutamate dehydrogenase RocG that affect differentially its catalytic activity and regulatory properties. J Mol Biol 2010; 400:815-27. [PMID: 20630473 DOI: 10.1016/j.jmb.2010.05.055] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2010] [Revised: 05/20/2010] [Accepted: 05/22/2010] [Indexed: 11/12/2022]
Abstract
Any signal transduction requires communication between a sensory component and an effector. Some enzymes engage in signal perception and transduction, as well as in catalysis, and these proteins are known as "trigger" enzymes. In this report, we detail the trigger properties of RocG, the glutamate dehydrogenase of Bacillus subtilis. RocG not only deaminates the key metabolite glutamate to form alpha-ketoglutarate but also interacts directly with GltC, a LysR-type transcription factor that regulates glutamate biosynthesis from alpha-ketoglutarate, thus linking the two metabolic pathways. We have isolated mutants of RocG that separate the two functions. Several mutations resulted in permanent inactivation of GltC as long as a source of glutamate was present. These RocG proteins have lost their ability to catabolize glutamate due to a strongly reduced affinity for glutamate. The second class of mutants is exemplified by the replacement of aspartate residue 122 by asparagine. This mutant protein has retained enzymatic activity but has lost the ability to control the activity of GltC. Crystal structures of glutamate dehydrogenases that permit a molecular explanation of the properties of the various mutants are presented. Specifically, we may propose that D122N replacement affects the surface of RocG. Our data provide evidence for a correlation between the enzymatic activity of RocG and its ability to inactivate GltC, and thus give insights into the mechanism that couples the enzymatic activity of a trigger enzyme to its regulatory function.
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Affiliation(s)
- Katrin Gunka
- Abteilung für Allgemeine Mikrobiologie, Institut für Mikrobiologie und Genetik, Georg-August-Universität Göttingen, Grisebachstr. 8, D-37077 Göttingen, Germany
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21
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Amon J, Titgemeyer F, Burkovski A. Common patterns - unique features: nitrogen metabolism and regulation in Gram-positive bacteria. FEMS Microbiol Rev 2010; 34:588-605. [PMID: 20337720 DOI: 10.1111/j.1574-6976.2010.00216.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Gram-positive bacteria have developed elaborate mechanisms to control ammonium assimilation, at the levels of both transcription and enzyme activity. In this review, the common and specific mechanisms of nitrogen assimilation and regulation in Gram-positive bacteria are summarized and compared for the genera Bacillus, Clostridium, Streptomyces, Mycobacterium and Corynebacterium, with emphasis on the high G+C genera. Furthermore, the importance of nitrogen metabolism and control for the pathogenic lifestyle and virulence is discussed. In summary, the regulation of nitrogen metabolism in prokaryotes shows an impressive diversity. Virtually every phylum of bacteria evolved its own strategy to react to the changing conditions of nitrogen supply. Not only do the transcription factors differ between the phyla and sometimes even between families, but the genetic targets of a given regulon can also differ between closely related species.
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Affiliation(s)
- Johannes Amon
- Lehrstuhl für Mikrobiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
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22
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Acid and base stress and transcriptomic responses in Bacillus subtilis. Appl Environ Microbiol 2008; 75:981-90. [PMID: 19114526 DOI: 10.1128/aem.01652-08] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Acid and base environmental stress responses were investigated in Bacillus subtilis. B. subtilis AG174 cultures in buffered potassium-modified Luria broth were switched from pH 8.5 to pH 6.0 and recovered growth rapidly, whereas cultures switched from pH 6.0 to pH 8.5 showed a long lag time. Log-phase cultures at pH 6.0 survived 60 to 100% at pH 4.5, whereas cells grown at pH 7.0 survived <15%. Cells grown at pH 9.0 survived 40 to 100% at pH 10, whereas cells grown at pH 7.0 survived <5%. Thus, growth in a moderate acid or base induced adaptation to a more extreme acid or base, respectively. Expression indices from Affymetrix chip hybridization were obtained for 4,095 protein-encoding open reading frames of B. subtilis grown at external pH 6, pH 7, and pH 9. Growth at pH 6 upregulated acetoin production (alsDS), dehydrogenases (adhA, ald, fdhD, and gabD), and decarboxylases (psd and speA). Acid upregulated malate metabolism (maeN), metal export (czcDO and cadA), oxidative stress (catalase katA; OYE family namA), and the SigX extracytoplasmic stress regulon. Growth at pH 9 upregulated arginine catabolism (roc), which generates organic acids, glutamate synthase (gltAB), polyamine acetylation and transport (blt), the K(+)/H(+) antiporter (yhaTU), and cytochrome oxidoreductases (cyd, ctaACE, and qcrC). The SigH, SigL, and SigW regulons were upregulated at high pH. Overall, greater genetic adaptation was seen at pH 9 than at pH 6, which may explain the lag time required for growth shift to high pH. Low external pH favored dehydrogenases and decarboxylases that may consume acids and generate basic amines, whereas high external pH favored catabolism-generating acids.
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Glutamate metabolism in Bacillus subtilis: gene expression and enzyme activities evolved to avoid futile cycles and to allow rapid responses to perturbations of the system. J Bacteriol 2008; 190:3557-64. [PMID: 18326565 DOI: 10.1128/jb.00099-08] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Glutamate is a central metabolite in all organisms since it provides the link between carbon and nitrogen metabolism. In Bacillus subtilis, glutamate is synthesized exclusively by the glutamate synthase, and it can be degraded by the glutamate dehydrogenase. In B. subtilis, the major glutamate dehydrogenase RocG is expressed only in the presence of arginine, and the bacteria are unable to utilize glutamate as the only carbon source. In addition to rocG, a second cryptic gene (gudB) encodes an inactive glutamate dehydrogenase. Mutations in rocG result in the rapid accumulation of gudB1 suppressor mutations that code for an active enzyme. In this work, we analyzed the physiological significance of this constellation of genes and enzymes involved in glutamate metabolism. We found that the weak expression of rocG in the absence of the inducer arginine is limiting for glutamate utilization. Moreover, we addressed the potential ability of the active glutamate dehydrogenases of B. subtilis to synthesize glutamate. Both RocG and GudB1 were unable to catalyze the anabolic reaction, most probably because of their very high K(m) values for ammonium. In contrast, the Escherichia coli glutamate dehydrogenase is able to produce glutamate even in the background of a B. subtilis cell. B. subtilis responds to any mutation that interferes with glutamate metabolism with the rapid accumulation of extragenic or intragenic suppressor mutations, bringing the glutamate supply into balance. Similarly, with the presence of a cryptic gene, the system can flexibly respond to changes in the external glutamate supply by the selection of mutations.
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Herzberg C, Weidinger LAF, Dörrbecker B, Hübner S, Stülke J, Commichau FM. SPINE: a method for the rapid detection and analysis of protein-protein interactions in vivo. Proteomics 2008; 7:4032-5. [PMID: 17994626 DOI: 10.1002/pmic.200700491] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The detection and analysis of protein-protein interactions is one of the central tasks of proteomics in the postgenomic era. For this purpose, we present a procedure, the Strep-protein interaction experiment (SPINE) that combines the advantages of the Strep-tag protein purification system with those of reversible in vivo protein crosslinking by formaldehyde. Using two Bacillus subtilis regulator proteins, we demonstrate that this method is well suited to isolate protein complexes with high purity and virtually no background. Plasmids allowing the high-level expression of proteins carrying an N- or C-terminal Strep-tag in B. subtilis were constructed.
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Affiliation(s)
- Christina Herzberg
- Department of General Microbiology, Georg-August-University Göttingen, Göttingen, Germany
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25
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Abstract
The remarkable ability of bacteria to adapt efficiently to a wide range of nutritional environments reflects their use of overlapping regulatory systems that link gene expression to intracellular pools of a small number of key metabolites. By integrating the activities of global regulators, such as CcpA, CodY and TnrA, Bacillus subtilis manages traffic through two metabolic intersections that determine the flow of carbon and nitrogen to and from crucial metabolites, such as pyruvate, 2-oxoglutarate and glutamate. Here, the latest knowledge on the control of these key intersections in B. subtilis is reviewed.
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Affiliation(s)
- Abraham L Sonenshein
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, Massachusetts 02111, USA.
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26
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Commichau FM, Herzberg C, Tripal P, Valerius O, Stülke J. A regulatory protein-protein interaction governs glutamate biosynthesis in Bacillus subtilis: the glutamate dehydrogenase RocG moonlights in controlling the transcription factor GltC. Mol Microbiol 2007; 65:642-54. [PMID: 17608797 DOI: 10.1111/j.1365-2958.2007.05816.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Glutamate synthesis is the link between carbon and nitrogen metabolism. In Bacillus subtilis, glutamate is exclusively synthesized by the glutamate synthase encoded by the gltAB operon. The glutamate dehydrogenase RocG from B. subtilis is exclusively devoted to glutamate degradation rather than to its synthesis. The expression of the gltAB operon is induced by glucose and ammonium and strongly repressed by arginine. Regulation by glucose and arginine depends on the transcriptional activator protein GltC. The gltAB operon is constitutively expressed in a rocG mutant strain, but the molecular mechanism of negative control of gltAB expression by RocG has so far remained unknown. We studied the role of RocG in the intracellular accumulation of GltC. Furthermore, we considered the possibility that RocG might act as a transcription factor and be able to inhibit the expression of gltAB either by binding to the mRNA or to the promoter region of the gltAB operon. Finally, we asked whether a direct binding of RocG to GltC could be responsible for the inhibition of GltC. The genetic and biochemical data presented here show that the glutamate dehydrogenase RocG is able to bind to and concomitantly inactivate the activator protein GltC. This regulatory mechanism by the bifunctional enzyme RocG allows the tight control of glutamate metabolism by the availability of carbon and nitrogen sources.
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Affiliation(s)
- Fabian M Commichau
- Department of General Microbiology, Geor-August - University Göttingen, Göttingen, Germany
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27
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Tam LT, Eymann C, Antelmann H, Albrecht D, Hecker M. Global Gene Expression Profiling of Bacillus subtilis in Response to Ammonium and Tryptophan Starvation as Revealed by Transcriptome and Proteome Analysis. J Mol Microbiol Biotechnol 2006; 12:121-30. [PMID: 17183219 DOI: 10.1159/000096467] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The global gene expression profile of Bacillus subtilis in response to ammonium and tryptophan starvation was analyzed using transcriptomics and proteomics which gained novel insights into these starvation responses. The results demonstrate that both starvation conditions induce specific, overlapping and general starvation responses. The TnrA regulon, the glutamine synthetase (glnA) as well as the sigma(L)-dependent bkd and roc operons were most strongly and specifically induced after ammonium starvation. These are involved in the uptake and utilization of ammonium and alternative nitrogen sources such as amino acids, gamma-aminobutyrate, nitrate/nitrite, uric acid/urea and oligopeptides. In addition, several carbon catabolite-controlled genes (e.g. acsA, citB), the alpha-acetolactate synthase/-decarboxylase alsSD operon and several aminotransferase genes were specifically induced after ammonium starvation. The induction of sigma(F)- and sigma(E)-dependent sporulation proteins at later time points in ammonium-starved cells was accompanied by an increased sporulation frequency. The specific response to tryptophan starvation includes the TRAP-regulated tryptophan biosynthesis genes, some RelA-dependent genes (e.g. adeC, ald) as well as spo0E. Furthermore, we recognized overlapping responses between ammonium and tryptophan starvation (e.g. dat, maeN) as well as the common induction of the CodY and sigma(H) general starvation regulons and the RelA-dependent stringent response. Many genes encoding proteins of so far unknown functions could be assigned to specifically or commonly induced genes.
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Affiliation(s)
- Le Thi Tam
- Institut für Mikrobiologie, Ernst-Moritz-Arndt-Universität Greifswald, Greifswald, Germany
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28
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Commichau FM, Wacker I, Schleider J, Blencke HM, Reif I, Tripal P, Stülke J. Characterization of Bacillus subtilis Mutants with Carbon Source-Independent Glutamate Biosynthesis. J Mol Microbiol Biotechnol 2006; 12:106-13. [PMID: 17183217 DOI: 10.1159/000096465] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Bacillus subtilis synthesizes glutamate from 2-oxoglutarate and glutamine using the glutamate synthase, encoded by the gltAB operon. Glutamate degradation involves the catabolic glutamate dehydrogenase (GDH) RocG. Expression of both gltAB and rocG is controlled by the carbon and nitrogen sources. In the absence of glucose or other well-metabolizable carbon sources, B. subtilis is unable to grow unless provided with external glutamate. In this work, we isolated mutations that suppressed this growth defect of B. subtilis on minimal media (sgd mutants). All mutations enabled the cells to express the gltAB operon even in the absence of glucose. The mutations were all identified in the rocG gene suggesting that the catabolic GDH is essential for controlling gltAB expression in response to the availability of sugars.
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Affiliation(s)
- Fabian M Commichau
- Abteilung für Allgemeine Mikrobiologie, Georg-August-Universität Göttingen, Göttingen, Germany
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29
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Liu D, Swiatlo E, Austin FW, Lawrence ML. Use of a putative transcriptional regulator gene as target for specific identification of Staphylococcus epidermidis. Lett Appl Microbiol 2006; 43:325-30. [PMID: 16910940 DOI: 10.1111/j.1472-765x.2006.01948.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIMS To investigate the use of a Staphylococcus epidermidis transcriptional regulator gene as target for species-specific determination. METHODS AND RESULTS Staph. epidermidis genes encoding putative transcriptional regulators were retrieved from GenBank and those showing no homology with other bacterial sequences were selected. Of the four PCR primer sets analysed, the primers Serp0107F/R from serp0107 amplified a specific product of 581 bp from Staph. epidermidis DNA only, and they did not cross-react in PCR with nonepidermidis staphylococci and other common bacteria. CONCLUSION Being uniquely present in Staph. epidermidis, putative transcriptional regulator gene serp0107 offers a valuable target for specific identification of Staph. epidermidis. SIGNIFICANCE AND IMPACT OF THE STUDY As a member of a specialized gene group, putative transcriptional regulator gene serp0107 may be important to Staph. epidermidis adaptation to its niche environment. Further analysis of serp0107 and its related protein may help reveal new insights on the molecular regulation of Staph. epidermidis survival and virulence.
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Affiliation(s)
- D Liu
- College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762, USA.
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30
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Picossi S, Belitsky BR, Sonenshein AL. Molecular mechanism of the regulation of Bacillus subtilis gltAB expression by GltC. J Mol Biol 2006; 365:1298-313. [PMID: 17134717 PMCID: PMC1794623 DOI: 10.1016/j.jmb.2006.10.100] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2006] [Revised: 10/25/2006] [Accepted: 10/27/2006] [Indexed: 11/18/2022]
Abstract
In Bacillus subilis, glutamate synthase, a major enzyme of nitrogen metabolism, is encoded by the gltAB operon. Significant expression of this operon requires the activity of GltC, a LysR-family protein, encoded by the divergently transcribed gene. We purified a soluble, active form of GltC and found that it requires alpha-ketoglutarate, a substrate of glutamate synthase, to fully activate gltA transcription in vitro, and that its activity is inhibited by glutamate, the product of glutamate synthase. GltC regulated gltAB transcription through binding to three dyad-symmetry elements, Box I, Box II and Box III, located in the intergenic region of gltC and gltA. Free GltC bound almost exclusively to Box I and activated gltAB transcription only marginally. Glutamate-bound GltC bound to Box I and Box III, and repressed gltAB transcription. In the presence of alpha-ketoglutarate, GltC bound to Box I and Box II, stabilized binding of RNA polymerase to the gltA promoter, and activated gltAB transcription. The binding of GltC to Box II, which partially overlaps the -35 region of the gltA promoter, seems to be essential for activation of the gltAB operon. Due to the high concentration of glutamate in B. subtilis cells grown under most conditions, alterations of the concentration of alpha-ketoglutarate seem to be crucial for modulation of GltC activity and gltAB expression.
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Affiliation(s)
- Silvia Picossi
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111, USA
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31
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Wei Y, Deikus G, Powers B, Shelden V, Krulwich TA, Bechhofer DH. Adaptive gene expression in Bacillus subtilis strains deleted for tetL. J Bacteriol 2006; 188:7090-100. [PMID: 17015648 PMCID: PMC1636236 DOI: 10.1128/jb.00885-06] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2006] [Accepted: 07/25/2006] [Indexed: 11/20/2022] Open
Abstract
The growth properties of a new panel of Bacillus subtilis tetL deletion strains and of a derivative set of strains in which tetL is restored to the chromosome support earlier indications that deletion of tetL results in a range of phenotypes that are unrelated to tetracycline resistance. These phenotypes were not reversed by restoration of a tetL gene to its native locus and were hypothesized to result from secondary mutations that arise when multifunctional tetL is deleted. Such genetic changes would temper the alkali sensitivity and Na(+) sensitivity that accompany loss of the monovalent cation/proton activity of TetL. Microarray comparisons of the transcriptomes of wild-type B. subtilis, a tetL deletion strain, and its tetL-restored derivative showed that 37 up-regulated genes and 13 down-regulated genes in the deletion strain did not change back to wild-type expression patterns after tetL was returned to the chromosome. Up-regulation of the citM gene, which encodes a divalent metal ion-coupled citrate transporter, was shown to account for the Co(2+)-sensitive phenotype of tetL mutants. The changes in expression of citM and genes encoding other ion-coupled solute transporters appear to be adaptive to loss of TetL functions in alkali and Na(+) tolerance, because they reduce Na(+)-coupled solute uptake and enhance solute uptake that is coupled to H(+) entry.
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Affiliation(s)
- Yi Wei
- Department of Pharmacology and Biological Chemistry, Box 1603, Mount Sinai School of Medicine of New York University, New York, NY 10029, USA
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32
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Choi SK, Saier MH. Regulation of pho regulon gene expression by the carbon control protein A, CcpA, in Bacillus subtilis. J Mol Microbiol Biotechnol 2006; 10:40-50. [PMID: 16491025 DOI: 10.1159/000090347] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Bacterial regulons involved in carbon, nitrogen and phosphorus metabolism must interact for purposes of coordination, but the mechanisms involved are not understood. We here report that the carbon control pro-tein-A (CcpA) of Bacillus subtilis, primarily concerned with carbon metabolism, influences expression of various phosphorus (pho) regulon genes including the two alkaline phosphatase structural genes, phoA and phoB. The directions and magnitudes of the effects of glucose and the loss of CcpA on these two genes depend on growth conditions, but they always correlate inversely. Absolute expression levels of phoA and phoB depend on a rich nitrogen source, and gene activation by a fermentable substrate such as glucose depends on the presence of a respiratory substrate such as succinate. We show that these CcpA-dependent glucose effects can be explained by the effects of glucose and CcpA acting on the phoPR operon. Although a good CcpA-binding site (CRE) is found in the control region of the phoPR operon, direct regulation of phoPR gene expression by CcpA via this CRE could not account for the effects of glucose and CcpA on phoA and phoB gene expression. We conclude that CcpA exerts indirect control over the pho regulon by a mechanism that involves CcpA and PhoRP but does not involve the phoPR operon CRE.
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Affiliation(s)
- Soo-Keun Choi
- Korea Research Institute of Bioscience and Biotechnology (KRIBB), Yusong, Taejon, Korea
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33
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Commichau FM, Forchhammer K, Stülke J. Regulatory links between carbon and nitrogen metabolism. Curr Opin Microbiol 2006; 9:167-72. [PMID: 16458044 DOI: 10.1016/j.mib.2006.01.001] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2005] [Accepted: 01/20/2006] [Indexed: 10/25/2022]
Abstract
The metabolism of carbon- and nitrogen-containing compounds is fundamental to all forms of life. To cope with changing environmental conditions, bacteria have to sense the nutrient supply and adapt their metabolism accordingly. In addition to nutrient- and pathway-specific responses, they integrate information from the different branches of metabolism to coordinate the control of the expression of many metabolic genes. Two major players interconnecting carbon and nitrogen regulation are the PII proteins and the phosphotransferase system. Moreover, several DNA-binding transcription regulators sense signals are derived from both carbon and nitrogen metabolism. The regulatory networks enable the bacteria to make the appropriate metabolic responses to changing nutrient availabilities in the environment.
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Affiliation(s)
- Fabian M Commichau
- Department of General Microbiology, Institute of Microbiology and Genetics, Georg-August University Göttingen, Grisebachstr. 8, D-37077 Göttingen, Germany
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34
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Blencke HM, Reif I, Commichau FM, Detsch C, Wacker I, Ludwig H, Stülke J. Regulation of citB expression in Bacillus subtilis: integration of multiple metabolic signals in the citrate pool and by the general nitrogen regulatory system. Arch Microbiol 2006; 185:136-46. [PMID: 16395550 DOI: 10.1007/s00203-005-0078-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2005] [Revised: 11/14/2005] [Accepted: 12/13/2005] [Indexed: 10/25/2022]
Abstract
The tricarboxylic acid (TCA) cycle is one of the major routes of carbon catabolism in Bacillus subtilis. The syntheses of the enzymes performing the initial reactions of the cycle, citrate synthase, and aconitase, are synergistically repressed by rapidly metabolizable carbon sources and glutamine. This regulation involves the general transcription factor CcpA and the specific repressor CcpC. In this study, we analyzed the expression and intracellular localization of CcpC. The synthesis of citrate, the effector of CcpC, requires acetyl-CoA. This metabolite is located at a branching point in metabolism. It can be converted to acetate in overflow metabolism or to citrate. Manipulations of the fate of acetyl-CoA revealed that efficient citrate synthesis is required for the expression of the citB gene encoding aconitase and that control of the two pathways utilizing acetyl-CoA converges in the control of citrate synthesis for the induction of the TCA cycle. The citrate pool seems also to be controlled by arginine catabolism. The presence of arginine results in a severe CcpC-dependent repression of citB. In addition to regulators involved in sensing the carbon status of the cell, the pleiotropic nitrogen-related transcription factor, TnrA, activates citB transcription in the absence of glutamine.
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Affiliation(s)
- Hans-Matti Blencke
- Abteilung für Allgemeine Mikrobiologie, Institut für Mikrobiologie und Genetik, Georg-August-Universität Göttingen, Grisebachstr. 8, 37077, Göttingen, Germany
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35
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Belitsky BR, Kim HJ, Sonenshein AL. CcpA-dependent regulation of Bacillus subtilis glutamate dehydrogenase gene expression. J Bacteriol 2004; 186:3392-8. [PMID: 15150224 PMCID: PMC415767 DOI: 10.1128/jb.186.11.3392-3398.2004] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Bacillus subtilis rocG gene, encoding catabolic glutamate dehydrogenase, was found to be subject to direct CcpA-dependent glucose repression. The effect of CcpA required the presence of both the HPr and Crh proteins. The primary CcpA binding site was identified by mutational analysis and DNase I footprinting. In the absence of inducers of the Roc pathway, rocG was still expressed at a low level due to readthrough transcription. CcpA-dependent repression of rocG readthrough transcription proved to contribute to the slow growth rate of B. subtilis cells in glucose-glutamate medium. Increased readthrough expression of rocG was shown to be partially responsible for the growth defect of ccpA strains in glucose-ammonium medium.
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Affiliation(s)
- Boris R Belitsky
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
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