1
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Elarabi NI, Abdelhadi AA, Nassrallah AA, Mohamed MSM, Abdelhaleem HAR. Biodegradation of isoproturon by Escherichia coli expressing a Pseudomonas putida catechol 1,2-dioxygenase gene. AMB Express 2023; 13:101. [PMID: 37751014 PMCID: PMC10522561 DOI: 10.1186/s13568-023-01609-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Accepted: 09/15/2023] [Indexed: 09/27/2023] Open
Abstract
The phenylurea herbicides are persistent in soil and water, necessitating the creation of methods for removing them from the environment. This study aimed to examine the soil microbial diversity, searching for local bacterial isolates able to efficiently degrade the phenylurea herbicide isoproturon, 3-(4-isopropylphenyl)-1, 1-dimethylurea (IPU). The best isolates able to effectively degrade IPU were selected, characterized, and identified as Pseudomonas putida and Acinetobacter johnsonii. The catechol 1, 2-dioxygenase enzyme's catA gene was amplified, cloned, and expressed in E. coli M15. The Expressed E. coli showed high degradation efficiency (44.80%) as analyzed by HPLC after 15 days of inoculation in comparison to P. putida (21.60%). The expression of the catA gene in P. putida and expressed E. coli was measured using quantitative polymerase chain reaction (qPCR). The results displayed a significant increase in the mRNA levels of the catA gene by increasing the incubation time with IPU. Hydrophilic interaction chromatography (HILIC) mass spectrometry analysis revealed that three intermediate metabolites, 1-(4-isopropylphenyl)-3-methylurea (MDIPU), 4-Isopropylaniline (4-IA) and 1-(4-isopropylphenyl) urea (DDIPU) were generated by both P. putida and expressed E. coli. In addition, IPU-induced catA activity was detected in both P. putida and expressed E. coli. The supernatant of both P. putida and expressed E. coli had a significant influence on weed growth. The study clearly exhibited that P. putida and expressed E. coli were capable of metabolizing IPU influentially and thus could be utilized for bioremediation and biodegradation technology development.
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Affiliation(s)
- Nagwa I Elarabi
- Department of Genetics, Faculty of Agriculture, Cairo University, Giza, 12613, Egypt
| | - Abdelhadi A Abdelhadi
- Department of Genetics, Faculty of Agriculture, Cairo University, Giza, 12613, Egypt.
| | - Amr A Nassrallah
- Department of Biochemistry, Faculty of Agriculture, Cairo University, Giza, 12613, Egypt
- Basic Applied Science institute, Egypt-Japan University of Science and Technology (E-JUST), P.O. Box 179, New Borg El- Arab City, 21934, Alexandria, Egypt
| | - Mahmoud S M Mohamed
- Botany and Microbiology Department, Faculty of Science, Cairo University, Giza, 12613, Egypt
| | - Heba A R Abdelhaleem
- College of Biotechnology, Misr University for Science and Technology (MUST), 6(th) October City, Egypt
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2
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Baugh AC, Momany C, Neidle EL. Versatility and Complexity: Common and Uncommon Facets of LysR-Type Transcriptional Regulators. Annu Rev Microbiol 2023; 77:317-339. [PMID: 37285554 DOI: 10.1146/annurev-micro-050323-040543] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
LysR-type transcriptional regulators (LTTRs) form one of the largest families of bacterial regulators. They are widely distributed and contribute to all aspects of metabolism and physiology. Most are homotetramers, with each subunit composed of an N-terminal DNA-binding domain followed by a long helix connecting to an effector-binding domain. LTTRs typically bind DNA in the presence or absence of a small-molecule ligand (effector). In response to cellular signals, conformational changes alter DNA interactions, contact with RNA polymerase, and sometimes contact with other proteins. Many are dual-function repressor-activators, although different modes of regulation may occur at multiple promoters. This review presents an update on the molecular basis of regulation, the complexity of regulatory schemes, and applications in biotechnology and medicine. The abundance of LTTRs reflects their versatility and importance. While a single regulatory model cannot describe all family members, a comparison of similarities and differences provides a framework for future study.
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Affiliation(s)
- Alyssa C Baugh
- Department of Microbiology, University of Georgia, Athens, Georgia, USA;
| | - Cory Momany
- Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, Georgia, USA
| | - Ellen L Neidle
- Department of Microbiology, University of Georgia, Athens, Georgia, USA;
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3
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Mayo-Pérez S, Gama-Martínez Y, Dávila S, Rivera N, Hernández-Lucas I. LysR-type transcriptional regulators: state of the art. Crit Rev Microbiol 2023:1-33. [PMID: 37635411 DOI: 10.1080/1040841x.2023.2247477] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 08/03/2023] [Accepted: 08/08/2023] [Indexed: 08/29/2023]
Abstract
The LysR-type transcriptional regulators (LTTRs) are DNA-binding proteins present in bacteria, archaea, and in algae. Knowledge about their distribution, abundance, evolution, structural organization, transcriptional regulation, fundamental roles in free life, pathogenesis, and bacteria-plant interaction has been generated. This review focuses on these aspects and provides a current picture of LTTR biology.
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Affiliation(s)
- S Mayo-Pérez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mexico
| | - Y Gama-Martínez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mexico
| | - S Dávila
- Centro de Investigación en Dinámica Celular, Universidad Autónoma del Estado de Morelos, Cuernavaca, Mexico
| | - N Rivera
- IPN: CICATA, Unidad Morelos del Instituto Politécnico Nacional, Atlacholoaya, Mexico
| | - I Hernández-Lucas
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Mexico
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4
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Oliver Huidobro M, Tica J, Wachter GKA, Isalan M. Synthetic spatial patterning in bacteria: advances based on novel diffusible signals. Microb Biotechnol 2022; 15:1685-1694. [PMID: 34843638 PMCID: PMC9151330 DOI: 10.1111/1751-7915.13979] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2021] [Revised: 11/14/2021] [Accepted: 11/14/2021] [Indexed: 12/22/2022] Open
Abstract
Engineering multicellular patterning may help in the understanding of some fundamental laws of pattern formation and thus may contribute to the field of developmental biology. Furthermore, advanced spatial control over gene expression may revolutionize fields such as medicine, through organoid or tissue engineering. To date, foundational advances in spatial synthetic biology have often been made in prokaryotes, using artificial gene circuits. In this review, engineered patterns are classified into four levels of increasing complexity, ranging from spatial systems with no diffusible signals to systems with complex multi-diffusor interactions. This classification highlights how the field was held back by a lack of diffusible components. Consequently, we provide a summary of both previously characterized and some new potential candidate small-molecule signals that can regulate gene expression in Escherichia coli. These diffusive signals will help synthetic biologists to successfully engineer increasingly intricate, robust and tuneable spatial structures.
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Affiliation(s)
| | - Jure Tica
- Department of Life SciencesImperial College LondonLondonSW7 2AZUK
| | | | - Mark Isalan
- Department of Life SciencesImperial College LondonLondonSW7 2AZUK
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5
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Shi S, Yang L, Yang C, Li S, Zhao H, Ren L, Wang X, Lu F, Li Y, Zhao H. Function and Molecular Ecology Significance of Two Catechol-Degrading Gene Clusters in Pseudomonas putida ND6. J Microbiol Biotechnol 2021; 31:259-271. [PMID: 33323670 PMCID: PMC9705993 DOI: 10.4014/jmb.2009.09026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 12/06/2020] [Accepted: 12/08/2020] [Indexed: 12/15/2022]
Abstract
Many bacteria metabolize aromatic compounds via catechol as a catabolic intermediate, and possess multiple genes or clusters encoding catechol-cleavage enzymes. The presence of multiple isozyme-encoding genes is a widespread phenomenon that seems to give the carrying strains a selective advantage in the natural environment over those with only a single copy. In the naphthalene-degrading strain Pseudomonas putida ND6, catechol can be converted into intermediates of the tricarboxylic acid cycle via either the ortho- or meta-cleavage pathways. In this study, we demonstrated that the catechol ortho-cleavage pathway genes (catBICIAI and catBIICIIAII) on the chromosome play an important role. The catI and catII operons are co-transcribed, whereas catAI and catAII are under independent transcriptional regulation. We examined the binding of regulatory proteins to promoters. In the presence of cis-cis-muconate, a well-studied inducer of the cat gene cluster, CatRI and CatRII occupy an additional downstream site, designated as the activation binding site. Notably, CatRI binds to both the catI and catII promoters with high affinity, while CatRII binds weakly. This is likely caused by a T to G mutation in the G/T-N11-A motif. Specifically, we found that CatRI and CatRII regulate catBICIAI and catBIICIIAII in a cooperative manner, which provides new insights into naphthalene degradation.
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Affiliation(s)
- Sanyuan Shi
- Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P.R. China
| | - Liu Yang
- Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P.R. China
| | - Chen Yang
- Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P.R. China
| | - Shanshan Li
- Department of Environmental Science and Engineering, Xi'an Jiaotong University, Xi'an 710048, P.R. China
| | - Hong Zhao
- Tianjin Entry-Exit Inspection and Quarantine Bureau, Tianjin 00457, P.R. China
| | - Lu Ren
- Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P.R. China
| | - Xiaokang Wang
- Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P.R. China
| | - Fuping Lu
- Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P.R. China
| | - Ying Li
- China Animal Disease Control Center, Beijing 100000, P.R. China,Y. Li Phone: +86-10-59198969 Fax: +86-10-59198969 E-mail:
| | - Huabing Zhao
- Tianjin Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, P.R. China,Corresponding authors H. Zhao Phone: +86-22-60601958 Fax: +86-22-60602298 E-mail:
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6
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Giannopoulou EA, Senda M, Koentjoro MP, Adachi N, Ogawa N, Senda T. Crystal structure of the full-length LysR-type transcription regulator CbnR in complex with promoter DNA. FEBS J 2021; 288:4560-4575. [PMID: 33576566 DOI: 10.1111/febs.15764] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 02/03/2021] [Accepted: 02/11/2021] [Indexed: 12/01/2022]
Abstract
LysR-type transcription regulators (LTTRs) comprise one of the largest families of transcriptional regulators in bacteria. They are typically homo-tetrameric proteins and interact with promoter DNA of ~ 50-60 bp. Earlier biochemical studies have suggested that LTTR binding to promoter DNA bends the DNA and, upon inducer binding, the bend angle of the DNA is reduced through a quaternary structure change of the tetrameric LTTR, leading to the activation of transcription. To date, crystal structures of full-length LTTRs, DNA-binding domains (DBD) with their target DNAs, and the regulatory domains with and without inducer molecules have been reported. However, these crystal structures have not provided direct evidence of the quaternary structure changes of LTTRs or of the molecular mechanism underlying these changes. Here, we report the first crystal structure of a full-length LTTR, CbnR, in complex with its promoter DNA. The crystal structure showed that, in the absence of bound inducer molecules, the four DBDs of the tetrameric CbnR interact with the promoter DNA, bending the DNA by ~ 70°. Structural comparison between the DNA-free and DNA-bound forms demonstrates that the quaternary structure change of the tetrameric CbnR required for promoter region-binding arises from relative orientation changes of the three domains in each subunit. The mechanism of the quaternary structure change caused by inducer binding is also discussed based on the present crystal structure, affinity analysis between CbnR and the promoter DNA, and earlier mutational studies on CbnR. DATABASE: Atomic coordinates and structure factors for the full-length Cupriavidus necator NH9 CbnR in complex with promoter DNA are available in the Protein Data Bank under the accession code 7D98.
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Affiliation(s)
- Evdokia-Anastasia Giannopoulou
- Structural Biology Research Center, Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Japan
| | - Miki Senda
- Structural Biology Research Center, Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Japan
| | - Maharani Pertiwi Koentjoro
- Structural Biology Research Center, Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Japan.,The United Graduate School of Agricultural Science, Gifu University, Japan
| | - Naruhiko Adachi
- Structural Biology Research Center, Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Japan
| | - Naoto Ogawa
- The United Graduate School of Agricultural Science, Gifu University, Japan.,Department of Applied Life Sciences, Faculty of Agriculture, Shizuoka University, Japan
| | - Toshiya Senda
- Structural Biology Research Center, Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Japan.,Department of Materials Structure Science, School of High Energy Accelerator Science, The Graduate University of Advanced Studies (Soken-dai), Tsukuba, Japan
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7
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Wang T, Qi Y, Wang Z, Zhao J, Ji L, Li J, Cai Z, Yang L, Wu M, Liang H. Coordinated regulation of anthranilate metabolism and bacterial virulence by the GntR family regulator MpaR inPseudomonas aeruginosa. Mol Microbiol 2020; 114:857-869. [PMID: 32748556 DOI: 10.1111/mmi.14584] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2020] [Revised: 07/23/2020] [Accepted: 07/27/2020] [Indexed: 12/22/2022]
Affiliation(s)
- Tietao Wang
- Key Laboratory of Resources Biology and Biotechnology in Western China Ministry of Education College of Life Sciences Northwest University Xi'an China
| | - Yihang Qi
- Key Laboratory of Resources Biology and Biotechnology in Western China Ministry of Education College of Life Sciences Northwest University Xi'an China
| | - Zhihan Wang
- West China School of Basic Medical Science & Forensic Medicine Sichuan University ChengDu China
| | - Jingru Zhao
- Key Laboratory of Resources Biology and Biotechnology in Western China Ministry of Education College of Life Sciences Northwest University Xi'an China
| | - Linxuan Ji
- Key Laboratory of Resources Biology and Biotechnology in Western China Ministry of Education College of Life Sciences Northwest University Xi'an China
| | - Jun Li
- College of Bioengineering and Biotechnology Zhejiang University of Technology Hangzhou China
| | - Zhao Cai
- School of Medicine Southern University of Science and Technology ShenZhen China
| | - Liang Yang
- School of Medicine Southern University of Science and Technology ShenZhen China
| | - Min Wu
- Department of Basic Science School of Medicine and Health Science University of North Dakota Grand Forks ND USA
| | - Haihua Liang
- Key Laboratory of Resources Biology and Biotechnology in Western China Ministry of Education College of Life Sciences Northwest University Xi'an China
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8
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Pozdnyakova-Filatova I, Petrikov K, Vetrova A, Frolova A, Streletskii R, Zakharova M. The Naphthalene Catabolic Genes of Pseudomonas putida BS3701: Additional Regulatory Control. Front Microbiol 2020; 11:1217. [PMID: 32582120 PMCID: PMC7291925 DOI: 10.3389/fmicb.2020.01217] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 05/13/2020] [Indexed: 11/13/2022] Open
Abstract
Pseudomonas microorganisms are used for bioremediation of soils contaminated with petroleum hydrocarbons. The overall remediation efficiency is largely dependent on the presence of macro- and micronutrients. Widely varying concentrations of available nitrogen and iron (Fe) in soils were shown to affect residual hydrocarbons in the course of biodegradation. The regulatory mechanisms of expression of hydrocarbon catabolic genes in low nitrogen/low iron conditions remain unclear. The catabolism of naphthalene, a two-ring polycyclic aromatic hydrocarbon, has been well studied in pseudomonads in terms of the involvement of specific transcriptional activators, thus making it useful in revealing additional regulatory control of the adaptation of hydrocarbon destructors to a low level of the essential nutrients. The Pseudomonas putida strain BS3701 is a component of the "MicroBak" preparation for soil remediation. Previously, this strain was shown to contain genes encoding the key enzymes for naphthalene catabolism: naphthalene 1,2-dioxygenase, salicylate hydroxylase, catechol 2,3-dioxygenase, and catechol 1,2-dioxygenase. Our study aimed to clarify whether the naphthalene catabolic gene expression is dependent on the amount of nitrogen and iron in the growth culture medium, and if so, at exactly which stages the expression is regulated. We cultivated the strain in low nitrogen/low iron conditions with the concurrent evaluation of the activity of the key enzymes and the mRNA level of genes encoding these enzymes. We are the first to report that naphthalene catabolic genes are subject not only to transcriptional but also post-transcriptional regulation.
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Affiliation(s)
- Irina Pozdnyakova-Filatova
- Laboratory of Molecular Microbiology, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Federal Research Center, G.K. Skryabin Institute of Biochemistry and Physiology of Microorganisms, Pushchino, Russia
| | - Kirill Petrikov
- Laboratory of Plasmid Biology, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Federal Research Center, G.K. Skryabin Institute of Biochemistry and Physiology of Microorganisms, Pushchino, Russia
| | - Anna Vetrova
- Laboratory of Plasmid Biology, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Federal Research Center, G.K. Skryabin Institute of Biochemistry and Physiology of Microorganisms, Pushchino, Russia
| | - Alina Frolova
- Laboratory of Bacteriophage Biology, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Federal Research Center, G.K. Skryabin Institute of Biochemistry and Physiology of Microorganisms, Pushchino, Russia
| | - Rostislav Streletskii
- Laboratory of Ecological Soil Science, Lomonosov Moscow State University, Moscow, Russia
| | - Marina Zakharova
- Laboratory of Molecular Microbiology, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences, Federal Research Center, G.K. Skryabin Institute of Biochemistry and Physiology of Microorganisms, Pushchino, Russia
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9
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Lubbers RJM, Dilokpimol A, Visser J, Mäkelä MR, Hildén KS, de Vries RP. A comparison between the homocyclic aromatic metabolic pathways from plant-derived compounds by bacteria and fungi. Biotechnol Adv 2019; 37:107396. [PMID: 31075306 DOI: 10.1016/j.biotechadv.2019.05.002] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 04/18/2019] [Accepted: 05/03/2019] [Indexed: 12/13/2022]
Abstract
Aromatic compounds derived from lignin are of great interest for renewable biotechnical applications. They can serve in many industries e.g. as biochemical building blocks for bioplastics or biofuels, or as antioxidants, flavor agents or food preservatives. In nature, lignin is degraded by microorganisms, which results in the release of homocyclic aromatic compounds. Homocyclic aromatic compounds can also be linked to polysaccharides, tannins and even found freely in plant biomass. As these compounds are often toxic to microbes already at low concentrations, they need to be degraded or converted to less toxic forms. Prior to ring cleavage, the plant- and lignin-derived aromatic compounds are converted to seven central ring-fission intermediates, i.e. catechol, protocatechuic acid, hydroxyquinol, hydroquinone, gentisic acid, gallic acid and pyrogallol through complex aromatic metabolic pathways and used as energy source in the tricarboxylic acid cycle. Over the decades, bacterial aromatic metabolism has been described in great detail. However, the studies on fungal aromatic pathways are scattered over different pathways and species, complicating a comprehensive view of fungal aromatic metabolism. In this review, we depicted the similarities and differences of the reported aromatic metabolic pathways in fungi and bacteria. Although both microorganisms share the main conversion routes, many alternative pathways are observed in fungi. Understanding the microbial aromatic metabolic pathways could lead to metabolic engineering for strain improvement and promote valorization of lignin and related aromatic compounds.
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Affiliation(s)
- Ronnie J M Lubbers
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands.
| | - Adiphol Dilokpimol
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands.
| | - Jaap Visser
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands.
| | - Miia R Mäkelä
- Department of Microbiology, University of Helsinki, Viikinkaari 9, Helsinki, Finland.
| | - Kristiina S Hildén
- Department of Microbiology, University of Helsinki, Viikinkaari 9, Helsinki, Finland.
| | - Ronald P de Vries
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands; Department of Microbiology, University of Helsinki, Viikinkaari 9, Helsinki, Finland.
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10
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Biodegradation of Tetralin: Genomics, Gene Function and Regulation. Genes (Basel) 2019; 10:genes10050339. [PMID: 31064110 PMCID: PMC6563040 DOI: 10.3390/genes10050339] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Revised: 04/26/2019] [Accepted: 04/30/2019] [Indexed: 01/18/2023] Open
Abstract
Tetralin (1,2,3,4-tetrahydonaphthalene) is a recalcitrant compound that consists of an aromatic and an alicyclic ring. It is found in crude oils, produced industrially from naphthalene or anthracene, and widely used as an organic solvent. Its toxicity is due to the alteration of biological membranes by its hydrophobic character and to the formation of toxic hydroperoxides. Two unrelated bacteria, Sphingopyxis granuli strain TFA and Rhodococcus sp. strain TFB were isolated from the same niche as able to grow on tetralin as the sole source of carbon and energy. In this review, we provide an overview of current knowledge on tetralin catabolism at biochemical, genetic and regulatory levels in both strains. Although they share the same biodegradation strategy and enzymatic activities, no evidences of horizontal gene transfer between both bacteria have been found. Moreover, the regulatory elements that control the expression of the gene clusters are completely different in each strain. A special consideration is given to the complex regulation discovered in TFA since three regulatory systems, one of them involving an unprecedented communication between the catabolic pathway and the regulatory elements, act together at transcriptional and posttranscriptional levels to optimize tetralin biodegradation gene expression to the environmental conditions.
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11
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Filatova IY, Kazakov AS, Muzafarov EN, Zakharova MV. Protein SgpR of Pseudomonas putida strain AK5 is a LysR-type regulator of salicylate degradation through gentisate. FEMS Microbiol Lett 2017; 364:3924860. [DOI: 10.1093/femsle/fnx112] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Accepted: 06/03/2017] [Indexed: 11/13/2022] Open
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12
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Characterisation of a 3-hydroxypropionic acid-inducible system from Pseudomonas putida for orthogonal gene expression control in Escherichia coli and Cupriavidus necator. Sci Rep 2017; 7:1724. [PMID: 28496205 PMCID: PMC5431877 DOI: 10.1038/s41598-017-01850-w] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Accepted: 04/13/2017] [Indexed: 12/22/2022] Open
Abstract
3-hydroxypropionic acid (3-HP) is an important platform chemical used as a precursor for production of added-value compounds such as acrylic acid. Metabolically engineered yeast, Escherichia coli, cyanobacteria and other microorganisms have been developed for the biosynthesis of 3-HP. Attempts to overproduce this compound in recombinant Pseudomonas denitrificans revealed that 3-HP is consumed by this microorganism using the catabolic enzymes encoded by genes hpdH, hbdH and mmsA. 3-HP-inducible systems controlling the expression of these genes have been predicted in proteobacteria and actinobacteria. In this study, we identify and characterise 3-HP-inducible promoters and their corresponding LysR-type transcriptional regulators from Pseudomonas putida KT2440. A newly-developed modular reporter system proved possible to demonstrate that PpMmsR/PmmsA and PpHpdR/PhpdH are orthogonal and highly inducible by 3-HP in E. coli (12.3- and 23.3-fold, respectively) and Cupriavidus necator (51.5- and 516.6-fold, respectively). Bioinformatics and mutagenesis analyses revealed a conserved 40-nucleotide sequence in the hpdH promoter, which plays a key role in HpdR-mediated transcription activation. We investigate the kinetics and dynamics of the PpHpdR/PhpdH switchable system in response to 3-HP and show that it is also induced by both enantiomers of 3-hydroxybutyrate. These findings pave the way for use of the 3-HP-inducible system in synthetic biology and biotechnology applications.
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13
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Ledesma-García L, Sánchez-Azqueta A, Medina M, Reyes-Ramírez F, Santero E. Redox proteins of hydroxylating bacterial dioxygenases establish a regulatory cascade that prevents gratuitous induction of tetralin biodegradation genes. Sci Rep 2016; 6:23848. [PMID: 27030382 PMCID: PMC4814904 DOI: 10.1038/srep23848] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 03/09/2016] [Indexed: 11/21/2022] Open
Abstract
Bacterial dioxygenase systems are multicomponent enzymes that catalyze the initial degradation of many environmentally hazardous compounds. In Sphingopyxis granuli strain TFA tetralin dioxygenase hydroxylates tetralin, an organic contaminant. It consists of a ferredoxin reductase (ThnA4), a ferredoxin (ThnA3) and a oxygenase (ThnA1/ThnA2), forming a NAD(P)H–ThnA4–ThnA3–ThnA1/ThnA2 electron transport chain. ThnA3 has also a regulatory function since it prevents expression of tetralin degradation genes (thn) in the presence of non-metabolizable substrates of the catabolic pathway. This role is of physiological relevance since avoids gratuitous and wasteful production of catabolic enzymes. Our hypothesis for thn regulation implies that ThnA3 exerts its action by diverting electrons towards the regulator ThnY, an iron-sulfur flavoprotein that together with the transcriptional activator ThnR is necessary for thn gene expression. Here we analyze electron transfer among ThnA4, ThnA3 and ThnY by using stopped-flow spectrophotometry and determination of midpoint reduction potentials. Our results indicate that when accumulated in its reduced form ThnA3 is able to fully reduce ThnY. In addition, we have reproduced in vitro the regulatory circuit in the proposed physiological direction, NAD(P)H–ThnA4–ThnA3–ThnY. ThnA3 represents an unprecedented way of communication between a catabolic pathway and its regulatory system to prevent gratuitous induction.
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Affiliation(s)
- Laura Ledesma-García
- Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide/Consejo Superior de Investigaciones Científicas/Junta de Andalucía, and Departamento de Biología Molecular e Ingeniería Bioquímica, Seville, Spain
| | - Ana Sánchez-Azqueta
- Departamento de Bioquímica y Biología Molecular y Celular, and Instituto de Biocomputación y Física de Sistemas Complejos (BIFI), Universidad de Zaragoza, Zaragoza, Spain
| | - Milagros Medina
- Departamento de Bioquímica y Biología Molecular y Celular, and Instituto de Biocomputación y Física de Sistemas Complejos (BIFI), Universidad de Zaragoza, Zaragoza, Spain
| | - Francisca Reyes-Ramírez
- Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide/Consejo Superior de Investigaciones Científicas/Junta de Andalucía, and Departamento de Biología Molecular e Ingeniería Bioquímica, Seville, Spain
| | - Eduardo Santero
- Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide/Consejo Superior de Investigaciones Científicas/Junta de Andalucía, and Departamento de Biología Molecular e Ingeniería Bioquímica, Seville, Spain
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Martí-Arbona R, Mu F, Nowak-Lovato KL, Wren MS, Unkefer CJ, Unkefer PJ. Automated genomic context analysis and experimental validation platform for discovery of prokaryote transcriptional regulator functions. BMC Genomics 2014; 15:1142. [PMID: 25523622 PMCID: PMC4349456 DOI: 10.1186/1471-2164-15-1142] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Accepted: 12/12/2014] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND The clustering of genes in a pathway and the co-location of functionally related genes is widely recognized in prokaryotes. We used these characteristics to predict the metabolic involvement for a Transcriptional Regulator (TR) of unknown function, identified and confirmed its biological activity. RESULTS A software tool that identifies the genes encoded within a defined genomic neighborhood for the subject TR and its homologs was developed. The output lists of genes in the genetic neighborhoods, their annotated functions, the reactants/products, and identifies the metabolic pathway in which the encoded-proteins function. When a set of TRs of known function was analyzed, we observed that their homologs frequently had conserved genomic neighborhoods that co-located the metabolically related genes regulated by the subject TR. We postulate that TR effectors are metabolites in the identified pathways; indeed the known effectors were present. We analyzed Bxe_B3018 from Burkholderia xenovorans, a TR of unknown function and predicted that this TR was related to the glycine, threonine and serine degradation. We tested the binding of metabolites in these pathways and for those that bound, their ability to modulate TR binding to its specific DNA operator sequence. Using rtPCR, we confirmed that methylglyoxal was an effector of Bxe_3018. CONCLUSION These studies provide the proof of concept and validation of a systematic approach to the discovery of the biological activity for proteins of unknown function, in this case a TR. Bxe_B3018 is a methylglyoxal responsive TR that controls the expression of an operon composed of a putative efflux system.
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Affiliation(s)
- Ricardo Martí-Arbona
- Bioscience Division, Los Alamos National Laboratory, PO Box 1663, Los Alamos, NM 87545, USA.
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15
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Structural and functional characterization of Pseudomonas aeruginosa global regulator AmpR. J Bacteriol 2014; 196:3890-902. [PMID: 25182487 DOI: 10.1128/jb.01997-14] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa is a dreaded pathogen in many clinical settings. Its inherent and acquired antibiotic resistance thwarts therapy. In particular, derepression of the AmpC β-lactamase is a common mechanism of β-lactam resistance among clinical isolates. The inducible expression of ampC is controlled by the global LysR-type transcriptional regulator (LTTR) AmpR. In the present study, we investigated the genetic and structural elements that are important for ampC induction. Specifically, the ampC (PampC) and ampR (PampR) promoters and the AmpR protein were characterized. The transcription start sites (TSSs) of the divergent transcripts were mapped using 5' rapid amplification of cDNA ends-PCR (RACE-PCR), and strong σ(54) and σ(70) consensus sequences were identified at PampR and PampC, respectively. Sigma factor RpoN was found to negatively regulate ampR expression, possibly through promoter blocking. Deletion mapping revealed that the minimal PampC extends 98 bp upstream of the TSS. Gel shifts using membrane fractions showed that AmpR binds to PampC in vitro whereas in vivo binding was demonstrated using chromatin immunoprecipitation-quantitative PCR (ChIP-qPCR). Additionally, site-directed mutagenesis of the AmpR helix-turn-helix (HTH) motif identified residues critical for binding and function (Ser38 and Lys42) and critical for function but not binding (His39). Amino acids Gly102 and Asp135, previously implicated in the repression state of AmpR in the enterobacteria, were also shown to play a structural role in P. aeruginosa AmpR. Alkaline phosphatase fusion and shaving experiments suggest that AmpR is likely to be membrane associated. Lastly, an in vivo cross-linking study shows that AmpR dimerizes. In conclusion, a potential membrane-associated AmpR dimer regulates ampC expression by direct binding.
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Kumar A, Trefault N, Olaniran AO. Microbial degradation of 2,4-dichlorophenoxyacetic acid: Insight into the enzymes and catabolic genes involved, their regulation and biotechnological implications. Crit Rev Microbiol 2014; 42:194-208. [DOI: 10.3109/1040841x.2014.917068] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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17
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The Salmonella enterica serovar Typhi LeuO global regulator forms tetramers: residues involved in oligomerization, DNA binding, and transcriptional regulation. J Bacteriol 2014; 196:2143-54. [PMID: 24659766 DOI: 10.1128/jb.01484-14] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
LeuO is a LysR-type transcriptional regulator (LTTR) that has been described to be a global regulator in Escherichia coli and Salmonella enterica, since it positively and negatively regulates the expression of genes involved in multiple biological processes. LeuO is comprised of an N-terminal DNA-binding domain (DBD) with a winged helix-turn-helix (wHTH) motif and of a long linker helix (LH) involved in dimerization that connects the DBD with the C-terminal effector-binding domain (EBD) or regulatory domain (RD; which comprises subdomains RD-I and RD-II). Here we show that the oligomeric structure of LeuO is a tetramer that binds with high affinity to DNA. A collection of single amino acid substitutions in the LeuO DBD indicated that this region is involved in oligomerization, in positive and negative regulation, as well as in DNA binding. Mutants with point mutations in the central and C-terminal regions of RD-I were affected in transcriptional activation. Deletion of the RD-II and RD-I C-terminal subdomains affected not only oligomerization but also DNA interaction, showing that they are involved in positive and negative regulation. Together, these data demonstrate that not only the C terminus but also the DBD of LeuO is involved in oligomer formation; therefore, each LeuO domain appears to act synergistically to maintain its regulatory functions in Salmonella enterica serovar Typhi.
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Silva-Rocha R, de Lorenzo V. The pWW0 plasmid imposes a stochastic expression regime to the chromosomalorthopathway for benzoate metabolism inPseudomonas putida. FEMS Microbiol Lett 2014; 356:176-83. [DOI: 10.1111/1574-6968.12400] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Affiliation(s)
- Rafael Silva-Rocha
- Systems Biology Program; Centro Nacional de Biotecnología CSIC; Cantoblanco-Madrid Spain
| | - Victor de Lorenzo
- Systems Biology Program; Centro Nacional de Biotecnología CSIC; Cantoblanco-Madrid Spain
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Xie NZ, Wang QY, Zhu QX, Qin Y, Tao F, Huang RB, Xu P. OPTIMIZATION OF MEDIUM COMPOSITION FORcis,cis-MUCONIC ACID PRODUCTION BY APseudomonassp. MUTANT USING STATISTICAL METHODS. Prep Biochem Biotechnol 2013; 44:342-54. [DOI: 10.1080/10826068.2013.829497] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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20
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Shi Y, Chai L, Tang C, Yang Z, Zhang H, Chen R, Chen Y, Zheng Y. Characterization and genomic analysis of kraft lignin biodegradation by the beta-proteobacterium Cupriavidus basilensis B-8. BIOTECHNOLOGY FOR BIOFUELS 2013; 6:1. [PMID: 24225035 PMCID: PMC3560178 DOI: 10.1186/1754-6834-6-1] [Citation(s) in RCA: 231] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Accepted: 12/21/2012] [Indexed: 05/03/2023]
Abstract
BACKGROUND Lignin materials are abundant and among the most important potential sources for biofuel production. Development of an efficient lignin degradation process has considerable potential for the production of a variety of chemicals, including bioethanol. However, lignin degradation using current methods is inefficient. Given their immense environmental adaptability and biochemical versatility, bacterial could be used as a valuable tool for the rapid degradation of lignin. Kraft lignin (KL) is a polymer by-product of the pulp and paper industry resulting from alkaline sulfide treatment of lignocellulose, and it has been widely used for lignin-related studies. RESULTS Beta-proteobacterium Cupriavidus basilensis B-8 isolated from erosive bamboo slips displayed substantial KL degradation capability. With initial concentrations of 0.5-6 g L-1, at least 31.3% KL could be degraded in 7 days. The maximum degradation rate was 44.4% at the initial concentration of 2 g L-1. The optimum pH and temperature for KL degradation were 7.0 and 30°C, respectively. Manganese peroxidase (MnP) and laccase (Lac) demonstrated their greatest level of activity, 1685.3 U L-1 and 815.6 U L-1, at the third and fourth days, respectively. Many small molecule intermediates were formed during the process of KL degradation, as determined using GC-MS analysis. In order to perform metabolic reconstruction of lignin degradation in this bacterium, a draft genome sequence for C. basilensis B-8 was generated. Genomic analysis focused on the catabolic potential of this bacterium against several lignin-derived compounds. These analyses together with sequence comparisons predicted the existence of three major metabolic pathways: β-ketoadipate, phenol degradation, and gentisate pathways. CONCLUSION These results confirmed the capability of C. basilensis B-8 to promote KL degradation. Whole genomic sequencing and systematic analysis of the C. basilensis B-8 genome identified degradation steps and intermediates from this bacterial-mediated KL degradation method. Our findings provide a theoretical basis for research into the mechanisms of lignin degradation as well as a practical basis for biofuel production using lignin materials.
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Affiliation(s)
- Yan Shi
- School of Metallurgical Science and Engineering, Central South University, Changsha, 410017, PR China
| | - Liyuan Chai
- School of Metallurgical Science and Engineering, Central South University, Changsha, 410017, PR China
- Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution, Changsha, 410017, PR China
| | - Chongjian Tang
- School of Metallurgical Science and Engineering, Central South University, Changsha, 410017, PR China
- Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution, Changsha, 410017, PR China
| | - Zhihui Yang
- School of Metallurgical Science and Engineering, Central South University, Changsha, 410017, PR China
- Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution, Changsha, 410017, PR China
| | - Huan Zhang
- School of Metallurgical Science and Engineering, Central South University, Changsha, 410017, PR China
| | - Runhua Chen
- School of Metallurgical Science and Engineering, Central South University, Changsha, 410017, PR China
| | - Yuehui Chen
- School of Metallurgical Science and Engineering, Central South University, Changsha, 410017, PR China
| | - Yu Zheng
- School of Metallurgical Science and Engineering, Central South University, Changsha, 410017, PR China
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Gong W, Xiong G, Maser E. Oligomerization and negative autoregulation of the LysR-type transcriptional regulator HsdR from Comamonas testosteroni. J Steroid Biochem Mol Biol 2012; 132:203-11. [PMID: 22684002 DOI: 10.1016/j.jsbmb.2012.05.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Revised: 05/08/2012] [Accepted: 05/29/2012] [Indexed: 11/25/2022]
Abstract
"3α-Hydroxysteroid dehydrogenase/carbonyl reductase regulator" (HsdR) from Comamonas testosteroni (C. testosteroni) was identified as a member of the LysR-type transcriptional regulator (LTTR) family. We have shown previously that HsdR activates the expression of the hsdA gene, encoding 3α-hydroxysteroid dehydrogenase/carbonyl reductase (3α-HSD/CR), which is an important enzyme involved in the degradation of steroid compounds. Phylogenetic analysis indicated that HsdR is related to the contact-regulated gene A (CrgA) from Neisseria meningitidis, which exists as a homooctamer. Therefore, to further elucidate the regulatory mechanism of HsdR, we investigated the oligomeric state and autoregulation of this transcriptional factor in the present study. To identify the active domains of HsdR, three truncated forms, HsdRΔN (N-terminus deleted), HsdRΔC (C-terminus deleted), and HsdRΔNC (both N- and C-terminus deleted), were constructed and purified. 3α-HSD/CR expression was measured by ELISA to detect the function of HsdR. Functional and biochemical analyses of wild type HsdR and its truncated forms indicated that HsdR may exist as an oligomer where the central domain is crucial for its oligomerization. Gel filtration chromatography revealed that there are two dominant oligomer forms which may be octamers and hexamers. According to electrophoretic mobility shift assays, HsdR specifically binds to its own promoter, where it negatively regulates its own expression. Therefore, the expression of non-functional HsdR variants (an hsdR-gfp fusion mutant and a hsdR gene disrupted mutant) increased compared to the wild type strain, because autorepression of HsdR was prevented. As a consequence, 3α-HSD/CR expression in these hsdR mutant strains was impaired. Combined, in our study we provide evidence that the transcription factor HsdR is a component of the steroid degradation machinery in C. testosteroni, which is active as an oligomer and negatively regulates its own expression.
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Affiliation(s)
- Wenjie Gong
- Institute of Toxicology and Pharmacology for Natural Scientists, University Medical School, Schleswig-Holstein, Campus Kiel, Brunswiker Strasse 10, D-24105 Kiel, Germany
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22
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Silva-Rocha R, de Lorenzo V. A GFP-lacZ bicistronic reporter system for promoter analysis in environmental gram-negative bacteria. PLoS One 2012; 7:e34675. [PMID: 22493710 PMCID: PMC3321037 DOI: 10.1371/journal.pone.0034675] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2012] [Accepted: 03/06/2012] [Indexed: 01/08/2023] Open
Abstract
Here, we describe a bicistronic reporter system for the analysis of promoter activity in a variety of Gram-negative bacteria at both the population and single-cell levels. This synthetic genetic tool utilizes an artificial operon comprising the gfp and lacZ genes that are assembled in a suicide vector, which is integrated at specific sites within the chromosome of the target bacterium, thereby creating a monocopy reporter system. This tool was instrumental for the complete in vivo characterization of two promoters, Pb and Pc, that drive the expression of the benzoate and catechol degradation pathways, respectively, of the soil bacterium Pseudomonas putida KT2440. The parameterization of these promoters in a population (using β-galactosidase assays) and in single cells (using flow cytometry) was necessary to examine the basic numerical features of these systems, such as the basal and maximal levels and the induction kinetics in response to an inducer (benzoate). Remarkably, GFP afforded a view of the process at a much higher resolution compared with standard lacZ tests; changes in fluorescence faithfully reflected variations in the transcriptional regimes of individual bacteria. The broad host range of the vector/reporter platform is an asset for the characterization of promoters in different bacteria, thereby expanding the diversity of genomic chasses amenable to Synthetic Biology methods.
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Affiliation(s)
- Rafael Silva-Rocha
- Systems Biology Program, Centro Nacional de Biotecnología, CSIC, Cantoblanco, Madrid, Spain
| | - Victor de Lorenzo
- Systems Biology Program, Centro Nacional de Biotecnología, CSIC, Cantoblanco, Madrid, Spain
- * E-mail:
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23
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van Duuren J, Wijte D, Leprince A, Karge B, Puchałka J, Wery J, dos Santos VM, Eggink G, Mars A. Generation of a catR deficient mutant of P. putida KT2440 that produces cis, cis-muconate from benzoate at high rate and yield. J Biotechnol 2011; 156:163-72. [DOI: 10.1016/j.jbiotec.2011.08.030] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Revised: 08/15/2011] [Accepted: 08/16/2011] [Indexed: 01/21/2023]
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Pérez-Pantoja D, Donoso R, Agulló L, Córdova M, Seeger M, Pieper DH, González B. Genomic analysis of the potential for aromatic compounds biodegradation in Burkholderiales. Environ Microbiol 2011; 14:1091-117. [PMID: 22026719 DOI: 10.1111/j.1462-2920.2011.02613.x] [Citation(s) in RCA: 196] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The relevance of the β-proteobacterial Burkholderiales order in the degradation of a vast array of aromatic compounds, including several priority pollutants, has been largely assumed. In this review, the presence and organization of genes encoding oxygenases involved in aromatics biodegradation in 80 Burkholderiales genomes is analysed. This genomic analysis underscores the impressive catabolic potential of this bacterial lineage, comprising nearly all of the central ring-cleavage pathways reported so far in bacteria and most of the peripheral pathways involved in channelling of a broad diversity of aromatic compounds. The more widespread pathways in Burkholderiales include protocatechuate ortho ring-cleavage, catechol ortho ring-cleavage, homogentisate ring-cleavage and phenylacetyl-CoA ring-cleavage pathways found in at least 60% of genomes analysed. In general, a genus-specific pattern of positional ordering of biodegradative genes is observed in the catabolic clusters of these pathways indicating recent events in its evolutionary history. In addition, a significant bias towards secondary chromosomes, now termed chromids, is observed in the distribution of catabolic genes across multipartite genomes, which is consistent with a genus-specific character. Strains isolated from environmental sources such as soil, rhizosphere, sediment or sludge show a higher content of catabolic genes in their genomes compared with strains isolated from human, animal or plant hosts, but no significant difference is found among Alcaligenaceae, Burkholderiaceae and Comamonadaceae families, indicating that habitat is more of a determinant than phylogenetic origin in shaping aromatic catabolic versatility.
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Affiliation(s)
- Danilo Pérez-Pantoja
- Center for Advanced Studies in Ecology and Biodiversity, Millennium Nucleus in Plant Functional Genomics, Facultad de Ciencias Biológicas, P. Universidad Católica de Chile, Santiago, Chile
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MacLean AM, Haerty W, Golding GB, Finan TM. The LysR-type PcaQ protein regulates expression of a protocatechuate-inducible ABC-type transport system in Sinorhizobium meliloti. Microbiology (Reading) 2011; 157:2522-2533. [DOI: 10.1099/mic.0.050542-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The LysR protein PcaQ regulates the expression of genes encoding products relevant to the degradation of the aromatic acid protocatechuate (3,4-dihydroxybenzoate), and we have previously defined a PcaQ DNA-binding site located upstream of the target pcaDCHGB operon in Sinorhizobium meliloti. In this work, we show that PcaQ also regulates the expression of the S. meliloti smb20568-smb20787-smb20786-smb20785-smb20784 gene cluster, which is predicted to encode an ABC transport system. ABC transport systems have not been shown before to transport protocatechuate, and we have designated this gene cluster pcaMNVWX. The transcriptional start site of pcaM was mapped, and the predicted PcaQ DNA-binding site was located at −73 to −58 relative to this site. Results from electrophoretic mobility shift assays with purified PcaQ and from expression assays indicated that PcaQ activates expression of the transport system in the presence of protocatechuate. To investigate this transport system further, we generated a pcaM deletion mutant (predicted to encode the substrate-binding protein) and introduced a polar insertion mutation into pcaN, a gene that is predicted to encode a permease. These mutants grew poorly on protocatechuate, presumably because they fail to transport protocatechuate. Genome analyses revealed PcaQ-like DNA-binding sites encoded upstream of ABC transport systems in other members of the α-proteobacteria, and thus it appears likely that these systems are involved in the uptake of protocatechuate.
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Affiliation(s)
- Allyson M. MacLean
- Center for Environmental Genomics, Department of Biology, McMaster University, Hamilton L8S 4K1, Canada
| | - Wilfried Haerty
- Center for Environmental Genomics, Department of Biology, McMaster University, Hamilton L8S 4K1, Canada
| | - G. Brian Golding
- Center for Environmental Genomics, Department of Biology, McMaster University, Hamilton L8S 4K1, Canada
| | - Turlough M. Finan
- Center for Environmental Genomics, Department of Biology, McMaster University, Hamilton L8S 4K1, Canada
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Pande SG, Pagliai FA, Gardner CL, Wrench A, Narvel R, Gonzalez CF, Lorca GL. Lactobacillus brevis responds to flavonoids through KaeR, a LysR-type of transcriptional regulator. Mol Microbiol 2011; 81:1623-39. [PMID: 21819457 DOI: 10.1111/j.1365-2958.2011.07796.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The ability of transcription factors to respond to flavonoids as signal molecules was investigated in Lactobacillus brevis. Through in vitro screening of a small library of flavonoids, LVIS1989 (KaeR), a LysR-type transcriptional regulator (LTTR), was identified as responsive to kaempferol. The modulation of KaeR activity by flavonoids was characterized in vivo and in vitro. DNase I footprint assays identified the binding of KaeR at two distinctive sites, one in the intergenic region between LVIS1988 and kaeR (-39 to +2) and another within LVIS1988 (-314 to -353, from kaeR translational start point). EMSA assays revealed that both binding sites are required for KaeR binding in vitro. Furthermore, KaeR-DNA interactions were stabilized by the addition of kaempferol (20 µM). In vivo qRT-PCR experiments performed in L. brevis confirmed that the divergently transcribed genes LVIS1988, LVIS1987 and LVIS1986 and kaeR are upregulated in the presence of kaempferol, indicating the role of KaeR as a transcriptional activator. Transcriptional lacZ fusions using Bacillus subtilis as a surrogate host showed that expression of kaeR and LVIS1988 were induced by the presence of the flavonoid. These results indicate that KaeR belongs to a small and poorly understood group of LTTRs that are positively autoregulated in the presence of a ligand.
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Affiliation(s)
- Santosh G Pande
- Department of Microbiology and Cell Science, Genetics Institute, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32610-3610, USA
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Most mutant OccR proteins that are defective in positive control hold operator DNA in a locked high-angle bend. J Bacteriol 2011; 193:5442-9. [PMID: 21804007 DOI: 10.1128/jb.05352-11] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
OccR is a LysR-type transcriptional regulator of Agrobacterium tumefaciens that positively regulates the octopine catabolism operon of the Ti plasmid. Positive control of the occ genes occurs in response to octopine, a nutrient released from crown gall tumors. OccR also functions as an autorepressor in the presence or absence of octopine. OccR binds to a site between occQ and occR in the presence or absence of octopine, although octopine triggers a conformational change that shortens the DNA footprint and relaxes a DNA bend. In order to determine the roles of this conformational change in transcriptional activation, we isolated 11 OccR mutants that were defective in activation of the occQ promoter but were still capable of autorepression. The mutations in these mutants spanned most of the length of the protein. Two additional positive-control mutants were isolated using site-directed mutagenesis. Twelve mutant proteins displayed a high-angle DNA bend in the presence or absence of octopine. One mutant, the L26A mutant, showed ligand-responsive DNA binding similar to that of wild-type OccR and therefore must be impaired in a subsequent step in activation.
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Regulatory system of the protocatechuate 4,5-cleavage pathway genes essential for lignin downstream catabolism. J Bacteriol 2010; 192:3394-405. [PMID: 20435721 DOI: 10.1128/jb.00215-10] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sphingobium sp. strain SYK-6 converts various lignin-derived biaryls with guaiacyl (4-hydroxy-3-methoxyphenyl) and syringyl (4-hydroxy-3,5-dimethoxyphenyl) moieties to vanillate and syringate. These compounds are further catabolized through the protocatechuate (PCA) 4,5-cleavage (PCA45) pathway. In this article, the regulatory system of the PCA45 pathway is described. A LysR-type transcriptional regulator (LTTR), LigR, activated the transcription of the ligK-orf1-ligI-lsdA and ligJABC operons in the presence of PCA or gallate (GA), which is an intermediate metabolite of vanillate or syringate, respectively, and repressed transcription of its own gene. LigR bound to the positions -77 to -51 and -80 to -48 of the ligK and ligJ promoters, respectively, and induced DNA bending. In the presence of PCA or GA, DNA bending on both promoters was enhanced. The LigR-binding regions of the ligK and ligJ promoters in the presence of inducer molecules were extended and shortened, respectively. The LTTR consensus sequences (Box-K and Box-J) in the ligK and ligJ promoters were essential for the binding of LigR and transcriptional activation of both operons. In addition, the regions between the LigR binding boxes and the -35 regions were required for the enhancement of DNA bending, although the binding of LigR to the -35 region of the ligJ promoter was not observed in DNase I footprinting experiments. This study shows the binding features of LigR on the ligK and ligJ promoters and explains how the PCA45 pathway genes are expressed during degradation of lignin-derived biaryls by this bacterium.
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Li D, Yan Y, Ping S, Chen M, Zhang W, Li L, Lin W, Geng L, Liu W, Lu W, Lin M. Genome-wide investigation and functional characterization of the beta-ketoadipate pathway in the nitrogen-fixing and root-associated bacterium Pseudomonas stutzeri A1501. BMC Microbiol 2010; 10:36. [PMID: 20137101 PMCID: PMC2907835 DOI: 10.1186/1471-2180-10-36] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2009] [Accepted: 02/08/2010] [Indexed: 11/20/2022] Open
Abstract
Background Soil microorganisms are mainly responsible for the complete mineralization of aromatic compounds that usually originate from plant products or environmental pollutants. In many cases, structurally diverse aromatic compounds can be converted to a small number of structurally simpler intermediates, which are metabolized to tricarboxylic acid intermediates via the β-ketoadipate pathway. This strategy provides great metabolic flexibility and contributes to increased adaptation of bacteria to their environment. However, little is known about the evolution and regulation of the β-ketoadipate pathway in root-associated diazotrophs. Results In this report, we performed a genome-wide analysis of the benzoate and 4-hydroxybenzoate catabolic pathways of Pseudomonas stutzeri A1501, with a focus on the functional characterization of the β-ketoadipate pathway. The P. stutzeri A1501 genome contains sets of catabolic genes involved in the peripheral pathways for catabolism of benzoate (ben) and 4-hydroxybenzoate (pob), and in the catechol (cat) and protocatechuate (pca) branches of the β-ketoadipate pathway. A particular feature of the catabolic gene organization in A1501 is the absence of the catR and pcaK genes encoding a LysR family regulator and 4-hydroxybenzoate permease, respectively. Furthermore, the BenR protein functions as a transcriptional activator of the ben operon, while transcription from the catBC promoter can be activated in response to benzoate. Benzoate degradation is subject to carbon catabolite repression induced by glucose and acetate in A1501. The HPLC analysis of intracellular metabolites indicated that low concentrations of 4-hydroxybenzoate significantly enhance the ability of A1501 to degrade benzoate. Conclusions The expression of genes encoding proteins involved in the β-ketoadipate pathway is tightly modulated by both pathway-specific and catabolite repression controls in A1501. This strain provides an ideal model system for further study of the evolution and regulation of aromatic catabolic pathways.
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Affiliation(s)
- Danhua Li
- College of Biological Sciences, China Agricultural University, Beijing 100094, China
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Zhou X, Lou Z, Fu S, Yang A, Shen H, Li Z, Feng Y, Bartlam M, Wang H, Rao Z. Crystal structure of ArgP from Mycobacterium tuberculosis confirms two distinct conformations of full-length LysR transcriptional regulators and reveals its function in DNA binding and transcriptional regulation. J Mol Biol 2009; 396:1012-24. [PMID: 20036253 DOI: 10.1016/j.jmb.2009.12.033] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2009] [Revised: 12/16/2009] [Accepted: 12/17/2009] [Indexed: 10/20/2022]
Abstract
Mycobacterium tuberculosis presents a challenging medical problem partly due to its persistent nonreplicative state. The inhibitor of chromosomal replication (iciA) protein encoded by M. tuberculosis has been suggested to inhibit chromosome replication initiation in vitro. However, iciA has also been identified as arginine permease (ArgP), a regulatory transcription factor for arginine outward transport. In order to understand the function of ArgP, we have determined its crystal structure by X-ray crystallography to a resolution of 2.7 A. ArgP is a member of the LysR-type transcriptional regulators (LTTRs) and forms a homodimer with each subunit containing two domains: a DNA binding domain (DBD) and a regulatory domain (RD). Two conformationally distinct subunits were identified: closed subunit and open subunit. This phenomenon was first observed in LTTR CbnR, but not in LTTR CrgA, and might be common in LTTRs. We identified two forms of dimers: DBD-type dimers and RD-type dimers. The former is confirmed in solution, and the latter is considered to form oligomers during function. We provide the first structural insights into the interaction of the extreme C-terminal residues with the DBD, which is confirmed by mutagenesis and analytical ultracentrifugation to be important for stability of the functional dimer. The structure serves as a model to suggest how three critical aspects, namely, DNA binding, homo-oligomerization, and interaction with RNAP, are mediated during regulation processing. A model is proposed for the LysR family of dimeric regulators.
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Affiliation(s)
- Xiaohong Zhou
- National Laboratory of Macromolecules, Institute of Biophysics, Chinese Academy of Science, Beijing 100101, China
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Porrúa O, García-González V, Santero E, Shingler V, Govantes F. Activation and repression of a sigmaN-dependent promoter naturally lacking upstream activation sequences. Mol Microbiol 2009; 73:419-33. [PMID: 19570137 DOI: 10.1111/j.1365-2958.2009.06779.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The Pseudomonas sp. strain ADP protein AtzR is a LysR-type transcriptional regulator required for activation of the atzDEF operon in response to nitrogen limitation and cyanuric acid. Transcription of atzR is directed by the sigma(N)-dependent promoter PatzR, activated by NtrC and repressed by AtzR. Here we use in vivo and in vitro approaches to address the mechanisms of PatzR activation and repression. Activation by NtrC did not require any promoter sequences other than the sigma(N) recognition motif both in vivo and in vitro, suggesting that NtrC activates PatzR in an upstream activation sequences-independent fashion. Regarding AtzR-dependent autorepression, our in vitro transcription experiments show that the concentration of AtzR required for repression of the PatzR promoter in vitro correlates with AtzR affinity for its binding site. In addition, AtzR prevents transcription from PatzR when added to a preformed E-sigma(N)-PatzR closed complex, but isomerization to an open complex prevents repression. Gel mobility shift and DNase I footprint assays indicate that DNA-bound AtzR and E-sigma(N) are mutually exclusive. Taken together, these results strongly support the notion that AtzR represses transcription from PatzR by competing with E-sigma(N) for their overlapping binding sites. There are no previous reports of a similar mechanism for repression of sigma(N)-dependent transcription.
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Affiliation(s)
- Odil Porrúa
- Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide/CSIC, Carretera de Utrera, Km. 1. 41013 Sevilla, Spain
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Uchiyama T, Watanabe K. The SIGEX scheme: high throughput screening of environmental metagenomes for the isolation of novel catabolic genes. Biotechnol Genet Eng Rev 2008; 24:107-16. [PMID: 18059628 DOI: 10.1080/02648725.2007.10648094] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Taku Uchiyama
- Department of Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan
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The target for the Pseudomonas putida Crc global regulator in the benzoate degradation pathway is the BenR transcriptional regulator. J Bacteriol 2007; 190:1539-45. [PMID: 18156252 DOI: 10.1128/jb.01604-07] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Crc protein is a global regulator involved in catabolite repression control of several pathways for the assimilation of carbon sources in pseudomonads when other preferred substrates are present. In Pseudomonas putida cells growing exponentially in a complete medium containing benzoate, Crc strongly inhibits the expression of the benzoate degradation genes. These genes are organized into several transcriptional units. We show that Crc directly inhibits the expression of the peripheral genes that transform benzoate into catechol (the ben genes) but that its effect on genes corresponding to further steps of the pathway (the cat and pca genes of the central catechol and beta-ketoadipate pathways) is indirect, since these genes are not induced because the degradation intermediates, which act as inducers, are not produced. Crc inhibits the translation of target genes by binding to mRNA. The expression of the ben, cat, and pca genes requires the BenR, CatR, and PcaR transcriptional activators, respectively. Crc significantly reduced benABCD mRNA levels but did not affect those of benR. Crc bound to the 5' end of benR mRNA but not to equivalent regions of catR and pcaR mRNAs. A translational fusion of the benR and lacZ genes was sensitive to Crc, but a transcriptional fusion was not. We propose that Crc acts by reducing the translation of benR mRNA, decreasing BenR levels below those required for the full expression of the benABCD genes. This strategy provides great metabolic flexibility, allowing the hierarchical assimilation of different structurally related compounds that share a common central pathway by selectively regulating the entry of each substrate into the central pathway.
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Martínez-Pérez O, López-Sánchez A, Reyes-Ramírez F, Floriano B, Santero E. Integrated response to inducers by communication between a catabolic pathway and its regulatory system. J Bacteriol 2007; 189:3768-75. [PMID: 17351041 PMCID: PMC1913338 DOI: 10.1128/jb.00057-07] [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: 11/20/2022] Open
Abstract
Efficient gene regulation of metabolic pathways implies that the profile of molecules inducing the pathway matches that of the molecules that are metabolized. Gratuitous induction, a well-known phenomenon in catabolic pathways, is the consequence of differences in the substrate and inducer profiles. This phenomenon is particularly evident in pathways for biodegradation of organic contaminants that can be induced by a variety of molecules similar to the real substrates. Analysis of the regulation of tetralin biodegradation genes in mutant strains with mutations that affect each component of the initial dioxygenase enzymatic complex indicated that the response of the regulatory system to potential inducers is altered differently depending on the mutated component. Based on the expression phenotypes of a number of single or double mutants, we propose a model that represents an unprecedented way of communication between a catabolic pathway and its regulatory system to prevent efficient induction by a molecule that is not a real substrate. This communication allows a better fit of the substrate and inducer profiles, thus minimizing gratuitous induction, without a requirement for optimal coevolution to match the specificity of catabolic enzymes and their regulatory systems. Modulation of the regulatory system in this way not only provides a more appropriate response to potential inducers recognized by the regulatory system but also may properly adjust the levels of gene expression to the substrate availability.
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Affiliation(s)
- Olga Martínez-Pérez
- Departamento de Biología Molecular e Ingeniería Bioquímica and Centro Andaluz de Biología del Desarrollo, Universidad Pablo de Olavide-CSIC, Ctra. Utrera, Km. 1, 41013 Sevilla, Spain
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Cámara B, Bielecki P, Kaminski F, dos Santos VM, Plumeier I, Nikodem P, Pieper DH. A gene cluster involved in degradation of substituted salicylates via ortho cleavage in Pseudomonas sp. strain MT1 encodes enzymes specifically adapted for transformation of 4-methylcatechol and 3-methylmuconate. J Bacteriol 2006; 189:1664-74. [PMID: 17172348 PMCID: PMC1855727 DOI: 10.1128/jb.01192-06] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas sp. strain MT1 has recently been reported to degrade 4- and 5-chlorosalicylate by a pathway assumed to consist of a patchwork of reactions comprising enzymes of the 3-oxoadipate pathway. Genes encoding the initial steps in the degradation of salicylate and substituted derivatives were now localized and sequenced. One of the gene clusters characterized (sal) showed a novel gene arrangement, with salA, encoding a salicylate 1-hydroxylase, being clustered with salCD genes, encoding muconate cycloisomerase and catechol 1,2-dioxygenase, respectively, and was expressed during growth on salicylate and chlorosalicylate. A second gene cluster (cat), exhibiting the typical catRBCA arrangement of genes of the catechol branch of the 3-oxoadipate pathway in Pseudomonas strains, was expressed during growth on salicylate. Despite their high sequence similarities with isoenzymes encoded by the cat gene cluster, the catechol 1,2-dioxygenase and muconate cycloisomerase encoded by the sal cluster showed unusual kinetic properties. Enzymes were adapted for turnover of 4-chlorocatechol and 3-chloromuconate; however, 4-methylcatechol and 3-methylmuconate were identified as the preferred substrates. Investigation of the substrate spectrum identified 4- and 5-methylsalicylate as growth substrates, which were effectively converted by enzymes of the sal cluster into 4-methylmuconolactone, followed by isomerization to 3-methylmuconolactone. The function of the sal gene cluster is therefore to channel both chlorosubstituted and methylsubstituted salicylates into a catechol ortho cleavage pathway, followed by dismantling of the formed substituted muconolactones through specific pathways.
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Affiliation(s)
- Beatriz Cámara
- Division of Microbiology, HZI-Helmholtz Zentrum für Infektionsforschung, Inhoffenstrasse 7, D-38124 Braunschweig, Germany
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Peck MC, Fisher RF, Long SR. Diverse flavonoids stimulate NodD1 binding to nod gene promoters in Sinorhizobium meliloti. J Bacteriol 2006; 188:5417-27. [PMID: 16855231 PMCID: PMC1540014 DOI: 10.1128/jb.00376-06] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
NodD1 is a member of the NodD family of LysR-type transcriptional regulators that mediates the expression of nodulation (nod) genes in the soil bacterium Sinorhizobium meliloti. Each species of rhizobia establishes a symbiosis with a limited set of leguminous plants. This host specificity results in part from a NodD-dependent upregulation of nod genes in response to a cocktail of flavonoids in the host plant's root exudates. To demonstrate that NodD is a key determinant of host specificity, we expressed nodD genes from different species of rhizobia in a strain of S. meliloti lacking endogenous NodD activity. We observed that nod gene expression was initiated in response to distinct sets of flavonoid inducers depending on the source of NodD. To better understand the effects of flavonoids on NodD, we assayed the DNA binding activity of S. meliloti NodD1 treated with the flavonoid inducer luteolin. In the presence of luteolin, NodD1 exhibited increased binding to nod gene promoters compared to binding in the absence of luteolin. Surprisingly, although they do not stimulate nod gene expression in S. meliloti, the flavonoids naringenin, eriodictyol, and daidzein also stimulated an increase in the DNA binding affinity of NodD1 to nod gene promoters. In vivo competition assays demonstrate that noninducing flavonoids act as competitive inhibitors of luteolin, suggesting that both inducing and noninducing flavonoids are able to directly bind to NodD1 and mediate conformational changes at nod gene promoters but that only luteolin is capable of promoting the downstream changes necessary for nod gene induction.
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Affiliation(s)
- Melicent C Peck
- Department of Biological Sciences, Gilbert Lab, 371 Serra Mall, Stanford University, Stanford, CA 94305, USA
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Vallaeys T, Persello-Cartieaux F, Rouard N, Lors C, Laguerre G, Soulas G. PCR-RFLP analysis of 16S rRNA, tfdA and tfdB genes reveals a diversity of 2,4-D degraders in soil aggregates. FEMS Microbiol Ecol 2006. [DOI: 10.1111/j.1574-6941.1997.tb00444.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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Dangel AW, Gibson JL, Janssen AP, Tabita FR. Residues that influence in vivo and in vitro CbbR function in Rhodobacter sphaeroides and identification of a specific region critical for co-inducer recognition. Mol Microbiol 2005; 57:1397-414. [PMID: 16102008 DOI: 10.1111/j.1365-2958.2005.04783.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
CbbR is a LysR-type transcriptional regulator (LTTR) that is required to activate transcription of the cbb operons, responsible for CO2 fixation, in Rhodobacter sphaeroides. LTTR proteins often require a co-inducer to regulate transcription. Previous studies suggested that ribulose 1,5-bisphosphate (RuBP) is a positive effector for CbbR function in this organism. In the current study, RuBP was found to increase the electrophoretic mobility of the CbbR/cbb(I) promoter complex. To define and analyse the co-inducer recognition region of CbbR, constitutively active mutant CbbR proteins were isolated. Under growth conditions that normally maintain transcriptionally inactive cbb operons, the mutant CbbR proteins activated transcription. Fourteen of the constitutively active mutants resulted from a single amino acid substitution. One mutant was derived from amino acid substitutions at two separate residues that appeared to act synergistically. Different mutant proteins showed both sensitivity and insensitivity to RuBP and residues that conferred constitutive transcriptional activity could be highlighted on a three-dimensional model, with several residues unique to CbbR shown to be at locations critical to LTTR function. Many of the constitutive residues clustered in or near two specific loops in the LTTR tertiary structure, corresponding to a proposed site of co-inducer binding.
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Affiliation(s)
- Andrew W Dangel
- Department of Microbiology and Plant Molecular Biology/Biotechnology Program, The Ohio State University, 484 West 12th Avenue, Columbus, OH 43210-1292, USA
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Kim SI, Ha KS, Leem SH. Differential organization and transcription of the cat2 gene cluster in aniline-assimilating Acinetobacter lwoffii K24. J Biosci Bioeng 2005; 88:250-7. [PMID: 16232607 DOI: 10.1016/s1389-1723(00)80005-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/1999] [Accepted: 05/28/1999] [Indexed: 11/19/2022]
Abstract
CatABC genes encode proteins that are responsible for the first three steps of one branch of the beta-ketoadipate pathway involved in the degradation of various aromatic compound by bacteria. Aniline-assimilating Acinetobacter lwoffii K24 is known to have the two-catABC gene clusters (cat1 and cat2) on the chromosome (Kim et al., J. Bacteriol., 179: 5226-5231, 1997). The order of the cat2 gene cluster is catB2A2C2, which has not been found in other bacteria. In this report, we analyzed the transcriptional pattern of the cat2 gene cluster and completely sequenced a 5.8 kbp fragment containing the compactly clustered catB2A2C2 genes and four ORFs. Similar to the ORF(R1) of the cat1 gene cluster, an ORF highly homologous with the catR gene was found 102 by upstream of the catB2 gene and was designated as ORF(R2). Three ORFs, one putative reductase component (ORF(X2)) and two putative LysR family regulatory proteins (ORF(Y2), ORF(Z2)) were located next to the catC2 gene in the opposite direction of the cat2 gene cluster. Two ORFs, ORF(X2) and ORF(Y2), were significantly homologous with tdnB and tdnR of the aniline oxygenase complex of Pseudomonas putida UCC22. RT-PCR analysis and Northern blotting revealed that the catB2 gene is independently transcribed and that the catA2C2 genes are cotranscribed. A primer extension assay revealed that transcription of the catA2C2 gene starts in the C-terminal region of the catB2 gene. These results suggest that the cat2 gene cluster may be under a different gene adaptation from other cat gene clusters.
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Affiliation(s)
- S I Kim
- Biomolecule Research Group, Korea Basic Science Institute, Taejon 305-333, Korea
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Uchiyama T, Abe T, Ikemura T, Watanabe K. Substrate-induced gene-expression screening of environmental metagenome libraries for isolation of catabolic genes. Nat Biotechnol 2005; 23:88-93. [PMID: 15608629 DOI: 10.1038/nbt1048] [Citation(s) in RCA: 199] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2004] [Accepted: 10/18/2004] [Indexed: 11/09/2022]
Abstract
Recent awareness that most microorganisms in the environment are resistant to cultivation has prompted scientists to directly clone useful genes from environmental metagenomes. Two screening methods are currently available for the metagenome approach, namely, nucleotide sequence-based screening and enzyme activity-based screening. Here we have introduced and optimized a third option for the isolation of novel catabolic operons, that is, substrate-induced gene expression screening (SIGEX). This method is based on the knowledge that catabolic-gene expression is generally induced by relevant substrates and, in many cases, controlled by regulatory elements situated proximate to catabolic genes. For SIGEX to be high throughput, we constructed an operon-trap gfp-expression vector available for shotgun cloning that allows for the selection of positive clones in liquid cultures by fluorescence-activated cell sorting. The utility of SIGEX was demonstrated by the cloning of aromatic hydrocarbon-induced genes from a groundwater metagenome library and subsequent genome-informatics analysis.
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Affiliation(s)
- Taku Uchiyama
- Laboratory of Applied Microbiology, Marine Biotechnology Institute, 3-75-1 Heita, Kamaishi, Iwate 026-0001, Japan
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Tropel D, van der Meer JR. Bacterial transcriptional regulators for degradation pathways of aromatic compounds. Microbiol Mol Biol Rev 2004; 68:474-500, table of contents. [PMID: 15353566 PMCID: PMC515250 DOI: 10.1128/mmbr.68.3.474-500.2004] [Citation(s) in RCA: 288] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human activities have resulted in the release and introduction into the environment of a plethora of aromatic chemicals. The interest in discovering how bacteria are dealing with hazardous environmental pollutants has driven a large research community and has resulted in important biochemical, genetic, and physiological knowledge about the degradation capacities of microorganisms and their application in bioremediation, green chemistry, or production of pharmacy synthons. In addition, regulation of catabolic pathway expression has attracted the interest of numerous different groups, and several catabolic pathway regulators have been exemplary for understanding transcription control mechanisms. More recently, information about regulatory systems has been used to construct whole-cell living bioreporters that are used to measure the quality of the aqueous, soil, and air environment. The topic of biodegradation is relatively coherent, and this review presents a coherent overview of the regulatory systems involved in the transcriptional control of catabolic pathways. This review summarizes the different regulatory systems involved in biodegradation pathways of aromatic compounds linking them to other known protein families. Specific attention has been paid to describing the genetic organization of the regulatory genes, promoters, and target operon(s) and to discussing present knowledge about signaling molecules, DNA binding properties, and operator characteristics, and evidence from regulatory mutants. For each regulator family, this information is combined with recently obtained protein structural information to arrive at a possible mechanism of transcription activation. This demonstrates the diversity of control mechanisms existing in catabolic pathways.
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Affiliation(s)
- David Tropel
- Swiss Federal Institute for Environmental Science and Technology (EAWAG), Dübendorf, Switzerland
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Shaw LJ, Burns RG. Enhanced mineralization of [U-(14)C]2,4-dichlorophenoxyacetic acid in soil from the rhizosphere of Trifolium pratense. Appl Environ Microbiol 2004; 70:4766-74. [PMID: 15294813 PMCID: PMC492430 DOI: 10.1128/aem.70.8.4766-4774.2004] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Enhanced biodegradation in the rhizosphere has been reported for many organic xenobiotic compounds, although the mechanisms are not fully understood. The purpose of this study was to discover whether rhizosphere-enhanced biodegradation is due to selective enrichment of degraders through growth on compounds produced by rhizodeposition. We monitored the mineralization of [U-(14)C]2,4-dichlorophenoxyacetic acid (2,4-D) in rhizosphere soil with no history of herbicide application collected over a period of 0 to 116 days after sowing of Lolium perenne and Trifolium pratense. The relationships between the mineralization kinetics, the number of 2,4-D degraders, and the diversity of genes encoding 2,4-D/alpha-ketoglutarate dioxygenase (tfdA) were investigated. The rhizosphere effect on [(14)C]2,4-D mineralization (50 microg g(-1)) was shown to be plant species and plant age specific. In comparison with nonplanted soil, there were significant (P < 0.05) reductions in the lag phase and enhancements of the maximum mineralization rate for 25- and 60-day T. pratense soil but not for 116-day T. pratense rhizosphere soil or for L. perenne rhizosphere soil of any age. Numbers of 2,4-D degraders in planted and nonplanted soil were low (most probable number, <100 g(-1)) and were not related to plant species or age. Single-strand conformational polymorphism analysis showed that plant species had no impact on the diversity of alpha-Proteobacteria tfdA-like genes, although an impact of 2,4-D application was recorded. Our results indicate that enhanced mineralization in T. pratense rhizosphere soil is not due to enrichment of 2,4-D-degrading microorganisms by rhizodeposits. We suggest an alternative mechanism in which one or more components of the rhizodeposits induce the 2,4-D pathway.
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Affiliation(s)
- Liz J Shaw
- Research School of Biosciences, University of Kent, Canterbury, Kent, UK
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Ogawa N, Miyashita K, Chakrabarty AM. Microbial genes and enzymes in the degradation of chlorinated compounds. CHEM REC 2003; 3:158-71. [PMID: 12900936 DOI: 10.1002/tcr.10059] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Microorganisms are well known for degrading numerous natural compounds. The synthesis of a multitude of chlorinated compounds by the chemical industry and their release into the natural environment have created major pollution problems. Part of the cause of such pollution is the inability of natural microorganisms to efficiently degrade synthetic chlorinated compounds. Microorganisms are, however, highly adaptable to changes in the environment and have consequently evolved the genes that specify the degradation of chlorinated compounds to varying degrees. Highly selective laboratory techniques have also enabled the isolation of microbial strains capable of utilizing normally recalcitrant highly chlorinated compounds as their sole source of carbon and energy. The evolution and role of microbial genes and enzymes, as well as their mode of regulation and genetic interrelationships, have therefore been the subjects of intense study. This review emphasizes the genetic organization and the regulation of gene expression, as well as evolutionary considerations, regarding the microbial degradation of chlorobenzoates, chlorocatechols, and chlorophenoxyacetic acids.
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Affiliation(s)
- Naoto Ogawa
- National Institute for Agro-Environmental Sciences, 3-1-3 Kan-nondai, Tsukuba, Ibaraki 305-8604, Japan.
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van Keulen G, Ridder ANJA, Dijkhuizen L, Meijer WG. Analysis of DNA binding and transcriptional activation by the LysR-type transcriptional regulator CbbR of Xanthobacter flavus. J Bacteriol 2003; 185:1245-52. [PMID: 12562794 PMCID: PMC142840 DOI: 10.1128/jb.185.4.1245-1252.2003] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The LysR-type transcriptional regulator CbbR controls the expression of the cbb and gap-pgk operons in Xanthobacter flavus, which encode the majority of the enzymes of the Calvin cycle required for autotrophic CO2 fixation. The cbb operon promoter of this chemoautotrophic bacterium contains three potential CbbR binding sites, two of which partially overlap. Site-directed mutagenesis and subsequent analysis of DNA binding by CbbR and cbb promoter activity were used to show that the potential CbbR binding sequences are functional. Inverted repeat IR1 is a high-affinity CbbR binding site. The main function of this repeat is to recruit CbbR to the cbb operon promoter. In addition, it is required for negative autoregulation of cbbR expression. IR3 represents the main low-affinity binding site of CbbR. Binding to IR3 occurs in a cooperative manner, since mutations preventing the binding of CbbR to IR1 also prevent binding to the low-affinity site. Although mutations in IR3 have a negative effect on the binding of CbbR to this site, they result in an increased promoter activity. This is most likely due to steric hindrance of RNA polymerase by CbbR since IR3 partially overlaps with the -35 region of the cbb operon promoter. Mutations in IR2 do not affect the DNA binding of CbbR in vitro but have a severe negative effect on the activity of the cbb operon promoter. This IR2 binding site is therefore critical for transcriptional activation by CbbR.
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Affiliation(s)
- Geertje van Keulen
- Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9750 AA Haren, The Netherlands
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Shaw LJ, Burns RG. Biodegradation of Organic Pollutants in the Rhizosphere. ADVANCES IN APPLIED MICROBIOLOGY 2003; 53:1-60. [PMID: 14696315 DOI: 10.1016/s0065-2164(03)53001-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Liz J Shaw
- Research School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, United Kingdom
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Suzuki K, Ichimura A, Ogawa N, Hasebe A, Miyashita K. Differential expression of two catechol 1,2-dioxygenases in Burkholderia sp. strain TH2. J Bacteriol 2002; 184:5714-22. [PMID: 12270830 PMCID: PMC139607 DOI: 10.1128/jb.184.20.5714-5722.2002] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Burkholderia sp. strain TH2, a 2-chlorobenzoate (2CB)-degrading bacterium, metabolizes benzoate (BA) and 2CB via catechol. Two different gene clusters for the catechol ortho-cleavage pathway (cat1 and cat2) were cloned from TH2 and analyzed. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analysis showed that while both catechol dioxygenases (CatA1 and CatA2) were produced in BA-grown cells, CatA1 was undetectable when strain TH2 was grown on 2CB or cis,cis-muconate (CCM), an intermediate of catechol degradation. However, production of CatA1 during growth on 2CB or CCM was observed when cat2 genes were disrupted. The difference in the production of CatA1 and CatA2 was apparently due to a difference in inducer recognition by the regulators of the gene clusters. The inducer of CatA1 was found to be BA, not 2CB, by using a 2-halobenzoate dioxygenase gene (cbd) disruptant, which is incapable of transforming (chloro)benzoate. It was also found that CCM or its metabolite acts as an inducer for CatA2. When cat2 genes were disrupted, the growth rate in 2CB culture was reduced while that in BA culture was not. These results suggest that although cat2 genes are not indispensable for growth of TH2 on 2CB, they are advantageous.
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Affiliation(s)
- Katsuhisa Suzuki
- National Institute for Agro-Environmental Sciences, 3-1-3 Kan-nondai, Tsukuba, Ibaraki 305-8604, Japan.
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Akakura R, Winans SC. Mutations in the occQ operator that decrease OccR-induced DNA bending do not cause constitutive promoter activity. J Biol Chem 2002; 277:15773-80. [PMID: 11877409 DOI: 10.1074/jbc.m200109200] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
OccR is a LysR-type transcriptional regulator of Agrobacterium tumefaciens that positively regulates the octopine catabolism operon of the Ti plasmid. Positive control of the occ genes occurs in response to octopine, a metabolite released from plant tumors. Octopine causes DNA-bound OccR to undergo a conformational change from an inactive to an active state; this change is marked by a decrease in footprint length from 55 to 45 nucleotides as well as a relaxation of a high angle DNA bend. In this study, we first used gel filtration chromatography to show that OccR is dimeric in solution, and we used gel shift assays to show that OccR is tetrameric when bound to DNA. We then created a series of site-directed mutations in the OccR-binding site. Some mutations were designed to lock OccR-DNA complexes into a conformation resembling the inactive conformation, whereas other mutations were designed to lock complexes into the active conformation. These mutations altered the conformation of OccR-DNA complexes and their responses to octopine in ways that we had predicted. As expected, operator mutations that locked complexes into a conformation having a long footprint and a high angle DNA bend blocked activation by octopine in vivo. Surprisingly, however, mutations that lock OccR into a short footprint and low angle DNA bend failed to cause the protein to function constitutively. Furthermore, some of the latter mutations interfered with activation by octopine. We conclude that locking OccR into a conformation having a short footprint is not sufficient to cause constitutive activation, and octopine must cause at least one additional conformational change in the protein.
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Affiliation(s)
- Reiko Akakura
- Department of Microbiology, Cornell University, Ithaca, New York 14853, USA
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Kovacikova G, Skorupski K. Binding site requirements of the virulence gene regulator AphB: differential affinities for the Vibrio cholerae classical and El Tor tcpPH promoters. Mol Microbiol 2002; 44:533-47. [PMID: 11972789 DOI: 10.1046/j.1365-2958.2002.02914.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The differential expression of virulence genes be-tween the two disease-causing biotypes of Vibrio cholerae, classical and El Tor, is primarily due to a single basepair change in the tcpPH promoter, which strongly influences the ability of the LysR regulator AphB to activate transcription in response to environmental conditions. We show here that this single basepair change influences virulence gene expression by dramatically altering the affinity of AphB for its recognition site in the tcpPH promoter. AphB binds greater than 10-fold more efficiently to a wild-type classical tcpPH promoter fragment with an A at -65 relative to a wild-type El Tor fragment that has a G at this position. As this single basepair change is located within the left arm of the LysR recognition motif (5'-TGCAA-N7-TTGCA), which extends from -69 to -53, a systematic mutagenesis of the other positions within this site was carried out to assess their influence on AphB binding in vitro and transcriptional activation in vivo. This analysis revealed that the left and right arms of the interrupted dyad display a high degree of symmetry with respect to their role in AphB binding. The right promoter proximal arm also plays a role in transcriptional activation that is distinct from its role in AphB binding. A second AphB binding site (5'-TGCAA-N7-TGTCA) was identified upstream of the aphB gene itself, which extends from +17 to +33 relative to the start of transcription and functions in autorepression. Although the sequences of the AphB binding sites at the tcpPH and aphB promoters are highly conserved, important differences exist in the way that AphB functions at each of these sites.
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Affiliation(s)
- Gabriela Kovacikova
- Department of Microbiology, Dartmouth Medical School, Hanover, New Hampshire, USA
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Clark TJ, Momany C, Neidle EL. The benPK operon, proposed to play a role in transport, is part of a regulon for benzoate catabolism in Acinetobacter sp. strain ADP1. MICROBIOLOGY (READING, ENGLAND) 2002; 148:1213-1223. [PMID: 11932465 DOI: 10.1099/00221287-148-4-1213] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
BenM and CatM are distinct, but similar, LysR-type transcriptional regulators of the soil bacterium Acinetobacter sp. strain ADP1. Together, the two regulators control the expression of at least 14 genes involved in the degradation of aromatic compounds via the catechol branch of the beta-ketoadipate pathway. In these studies, BenM and CatM were each purified to homogeneity to test the possibility that they regulate the expression of two additional genes, benP and benK, that are adjacent to benM on the chromosome. Each regulator bound to a DNA fragment containing the benP promoter region. Additional transcriptional studies suggested that benP and benK are co-transcribed as an operon, and a site of transcription initiation was identified. Alignment of this initiation site with those of several CatM- and BenM-regulated genes revealed common regulatory motifs. Mutants lacking both CatM and BenM failed to activate benP transcription. The ability of each protein to regulate gene expression was inferred from strains lacking either CatM or BenM that were still capable of increasing benP expression in response to cis,cis-muconate. This compound has previously been shown to induce all enzymes of the catechol branch of the beta-ketoadipate pathway through a complex transcriptional circuit involving CatM and BenM. Thus, the regulated expression of the benPK operon in concert with other genes of the regulon is consistent with the model that BenP, a putative outer-membrane porin, and BenK, an inner-membrane permease, transport aromatic compounds in strain ADP1.
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Affiliation(s)
- Todd J Clark
- Department of Microbiology, University of Georgia, Athens, GA 30602-2605, USA1
| | - Cory Momany
- Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, GA 30602, USA2
| | - Ellen L Neidle
- Department of Microbiology, University of Georgia, Athens, GA 30602-2605, USA1
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Miyauchi K, Lee HS, Fukuda M, Takagi M, Nagata Y. Cloning and characterization of linR, involved in regulation of the downstream pathway for gamma-hexachlorocyclohexane degradation in Sphingomonas paucimobilis UT26. Appl Environ Microbiol 2002; 68:1803-7. [PMID: 11916699 PMCID: PMC123885 DOI: 10.1128/aem.68.4.1803-1807.2002] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Sphingomonas paucimobilis UT26, LinD and LinE activities, which are responsible for the degradation of gamma-hexachlorocyclohexane, are inducibly expressed in the presence of their substrates, 2,5-dichlorohydroquinone (2,5-DCHQ) and chlorohydroquinone (CHQ). The nucleotide sequence of the 1-kb upstream region of the linE gene was determined, and an open reading frame (ORF) was found in divergent orientation from linE. Because the putative protein product of the ORF showed similarity to the LysR-type transcriptional regulator (LTTR) family, we named it linR. The fragment containing the putative LTTR recognition sequence (a palindromic TN(11)A sequence), which exists immediately upstream of linE, was ligated with the reporter gene lacZ and was inserted into the plasmid expressing LinR under the control of the lac promoter. When the resultant plasmid was introduced into Escherichia coli, the LacZ activity rose in the presence of 2,5-DCHQ and CHQ. RNA slot blot analysis for the total RNAs of UT26 and UT102, which has an insertional mutation in linR, revealed that the expression of the linD and linE genes was induced in the presence of 2,5-DCHQ, CHQ, and hydroquinone in UT26 but not in UT102. These results indicated that the linR gene is directly involved in the inducible expression of the linD and linE genes.
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Affiliation(s)
- Keisuke Miyauchi
- Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
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