1
|
Pacheco PJ, Cabrera JJ, Jiménez-Leiva A, Torres MJ, Gates AJ, Bedmar EJ, Richardson DJ, Mesa S, Tortosa G, Delgado MJ. The copper-responsive regulator CsoR is indirectly involved in Bradyrhizobium diazoefficiens denitrification. FEMS Microbiol Lett 2023; 370:fnad084. [PMID: 37573143 PMCID: PMC10457146 DOI: 10.1093/femsle/fnad084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 08/04/2023] [Accepted: 08/11/2023] [Indexed: 08/14/2023] Open
Abstract
The soybean endosymbiont Bradyrhizobium diazoefficiens harbours the complete denitrification pathway that is catalysed by a periplasmic nitrate reductase (Nap), a copper (Cu)-containing nitrite reductase (NirK), a c-type nitric oxide reductase (cNor), and a nitrous oxide reductase (Nos), encoded by the napEDABC, nirK, norCBQD, and nosRZDFYLX genes, respectively. Induction of denitrification genes requires low oxygen and nitric oxide, both signals integrated into a complex regulatory network comprised by two interconnected cascades, FixLJ-FixK2-NnrR and RegSR-NifA. Copper is a cofactor of NirK and Nos, but it has also a role in denitrification gene expression and protein synthesis. In fact, Cu limitation triggers a substantial down-regulation of nirK, norCBQD, and nosRZDFYLX gene expression under denitrifying conditions. Bradyrhizobium diazoefficiens genome possesses a gene predicted to encode a Cu-responsive repressor of the CsoR family, which is located adjacent to copA, a gene encoding a putative Cu+-ATPase transporter. To investigate the role of CsoR in the control of denitrification gene expression in response to Cu, a csoR deletion mutant was constructed in this work. Mutation of csoR did not affect the capacity of B. diazoefficiens to grow under denitrifying conditions. However, by using qRT-PCR analyses, we showed that nirK and norCBQD expression was much lower in the csoR mutant compared to wild-type levels under Cu-limiting denitrifying conditions. On the contrary, copA expression was significantly increased in the csoR mutant. The results obtained suggest that CsoR acts as a repressor of copA. Under Cu limitation, CsoR has also an indirect role in the expression of nirK and norCBQD genes.
Collapse
Affiliation(s)
- Pedro J Pacheco
- Department of Soil and Plant Microbiology, Estación Experimental del Zaidín, CSIC, C/Profesor Albareda 1, E-18008 Granada, Spain
| | - Juan J Cabrera
- Department of Soil and Plant Microbiology, Estación Experimental del Zaidín, CSIC, C/Profesor Albareda 1, E-18008 Granada, Spain
| | - Andrea Jiménez-Leiva
- Department of Soil and Plant Microbiology, Estación Experimental del Zaidín, CSIC, C/Profesor Albareda 1, E-18008 Granada, Spain
| | - María J Torres
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Colney Lane, Norwich NR4 7TJ, United Kingdom
- Department of Biochemistry and Molecular Biology, Campus Universitario de Rabanales, University of Córdoba, Ed. C6, Planta Baja, 14071 Córdoba, Spain
| | - Andrew J Gates
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Colney Lane, Norwich NR4 7TJ, United Kingdom
| | - Eulogio J Bedmar
- Department of Soil and Plant Microbiology, Estación Experimental del Zaidín, CSIC, C/Profesor Albareda 1, E-18008 Granada, Spain
| | - David J Richardson
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Colney Lane, Norwich NR4 7TJ, United Kingdom
| | - Socorro Mesa
- Department of Soil and Plant Microbiology, Estación Experimental del Zaidín, CSIC, C/Profesor Albareda 1, E-18008 Granada, Spain
| | - Germán Tortosa
- Department of Soil and Plant Microbiology, Estación Experimental del Zaidín, CSIC, C/Profesor Albareda 1, E-18008 Granada, Spain
| | - María J Delgado
- Department of Soil and Plant Microbiology, Estación Experimental del Zaidín, CSIC, C/Profesor Albareda 1, E-18008 Granada, Spain
| |
Collapse
|
2
|
Piper SEH, Casadevall C, Reisner E, Clarke TA, Jeuken LJC, Gates AJ, Butt JN. Photocatalytic Removal of the Greenhouse Gas Nitrous Oxide by Liposomal Microreactors. Angew Chem Int Ed Engl 2022; 61:e202210572. [PMID: 35951464 PMCID: PMC9825952 DOI: 10.1002/anie.202210572] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Indexed: 01/11/2023]
Abstract
Nitrous oxide (N2 O) is a potent greenhouse and ozone-reactive gas for which emissions are growing rapidly due to increasingly intensive agriculture. Synthetic catalysts for N2 O decomposition typically contain precious metals and/or operate at elevated temperatures driving a desire for more sustainable alternatives. Here we demonstrate self-assembly of liposomal microreactors enabling catalytic reduction of N2 O to the climate neutral product N2 . Photoexcitation of graphitic N-doped carbon dots delivers electrons to encapsulated N2 O Reductase enzymes via a lipid-soluble biomolecular wire provided by the MtrCAB protein complex. Within the microreactor, electron transfer from MtrCAB to N2 O Reductase is facilitated by the general redox mediator methyl viologen. The liposomal microreactors use only earth-abundant elements to catalyze N2 O removal in ambient, aqueous conditions.
Collapse
Affiliation(s)
- Samuel E. H. Piper
- School of ChemistryUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJUK
| | - Carla Casadevall
- Yusuf Hamied Department of ChemistryUniversity of CambridgeLensfield RoadCambridgeCB2 1EWUK
| | - Erwin Reisner
- Yusuf Hamied Department of ChemistryUniversity of CambridgeLensfield RoadCambridgeCB2 1EWUK
| | - Thomas A. Clarke
- School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJUK
| | - Lars J. C. Jeuken
- Leiden Institute of ChemistryLeiden UniversityPO Box 95022300 RALeidenThe Netherlands
| | - Andrew J. Gates
- School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJUK
| | - Julea N. Butt
- School of ChemistryUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJUK,School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJUK
| |
Collapse
|
3
|
Piper SEH, Casadevall C, Reisner E, Clarke TA, Jeuken LJC, Gates AJ, Butt JN. Photocatalytic Removal of the Greenhouse Gas Nitrous Oxide by Liposomal Microreactors. Angew Chem Weinheim Bergstr Ger 2022; 134:e202210572. [PMID: 38529325 PMCID: PMC10962689 DOI: 10.1002/ange.202210572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Indexed: 11/11/2022]
Abstract
Nitrous oxide (N2O) is a potent greenhouse and ozone-reactive gas for which emissions are growing rapidly due to increasingly intensive agriculture. Synthetic catalysts for N2O decomposition typically contain precious metals and/or operate at elevated temperatures driving a desire for more sustainable alternatives. Here we demonstrate self-assembly of liposomal microreactors enabling catalytic reduction of N2O to the climate neutral product N2. Photoexcitation of graphitic N-doped carbon dots delivers electrons to encapsulated N2O Reductase enzymes via a lipid-soluble biomolecular wire provided by the MtrCAB protein complex. Within the microreactor, electron transfer from MtrCAB to N2O Reductase is facilitated by the general redox mediator methyl viologen. The liposomal microreactors use only earth-abundant elements to catalyze N2O removal in ambient, aqueous conditions.
Collapse
Affiliation(s)
- Samuel E. H. Piper
- School of ChemistryUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJUK
| | - Carla Casadevall
- Yusuf Hamied Department of ChemistryUniversity of CambridgeLensfield RoadCambridgeCB2 1EWUK
| | - Erwin Reisner
- Yusuf Hamied Department of ChemistryUniversity of CambridgeLensfield RoadCambridgeCB2 1EWUK
| | - Thomas A. Clarke
- School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJUK
| | - Lars J. C. Jeuken
- Leiden Institute of ChemistryLeiden UniversityPO Box 95022300 RALeidenThe Netherlands
| | - Andrew J. Gates
- School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJUK
| | - Julea N. Butt
- School of ChemistryUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJUK
- School of Biological SciencesUniversity of East AngliaNorwich Research ParkNorwichNR4 7TJUK
| |
Collapse
|
4
|
Parejo S, Cabrera JJ, Jiménez-Leiva A, Tomás-Gallardo L, Bedmar EJ, Gates AJ, Mesa S. Fine-Tuning Modulation of Oxidation-Mediated Posttranslational Control of Bradyrhizobium diazoefficiens FixK 2 Transcription Factor. Int J Mol Sci 2022; 23:5117. [PMID: 35563511 PMCID: PMC9104804 DOI: 10.3390/ijms23095117] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 04/22/2022] [Accepted: 04/29/2022] [Indexed: 02/04/2023] Open
Abstract
FixK2 is a CRP/FNR-type transcription factor that plays a central role in a sophisticated regulatory network for the anoxic, microoxic and symbiotic lifestyles of the soybean endosymbiont Bradyrhizobium diazoefficiens. Aside from the balanced expression of the fixK2 gene under microoxic conditions (induced by the two-component regulatory system FixLJ and negatively auto-repressed), FixK2 activity is posttranslationally controlled by proteolysis, and by the oxidation of a singular cysteine residue (C183) near its DNA-binding domain. To simulate the permanent oxidation of FixK2, we replaced C183 for aspartic acid. Purified C183D FixK2 protein showed both low DNA binding and in vitro transcriptional activation from the promoter of the fixNOQP operon, required for respiration under symbiosis. However, in a B. diazoefficiens strain coding for C183D FixK2, expression of a fixNOQP'-'lacZ fusion was similar to that in the wild type, when both strains were grown microoxically. The C183D FixK2 encoding strain also showed a wild-type phenotype in symbiosis with soybeans, and increased fixK2 gene expression levels and FixK2 protein abundance in cells. These two latter observations, together with the global transcriptional profile of the microoxically cultured C183D FixK2 encoding strain, suggest the existence of a finely tuned regulatory strategy to counterbalance the oxidation-mediated inactivation of FixK2 in vivo.
Collapse
Affiliation(s)
- Sergio Parejo
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, CSIC, 18008 Granada, Spain; (S.P.); (J.J.C.); (A.J.-L.); (E.J.B.)
| | - Juan J. Cabrera
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, CSIC, 18008 Granada, Spain; (S.P.); (J.J.C.); (A.J.-L.); (E.J.B.)
| | - Andrea Jiménez-Leiva
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, CSIC, 18008 Granada, Spain; (S.P.); (J.J.C.); (A.J.-L.); (E.J.B.)
| | - Laura Tomás-Gallardo
- Proteomics and Biochemistry Unit, Andalusian Centre for Developmental Biology, CSIC-Pablo de Olavide University, 41013 Seville, Spain;
| | - Eulogio J. Bedmar
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, CSIC, 18008 Granada, Spain; (S.P.); (J.J.C.); (A.J.-L.); (E.J.B.)
| | - Andrew J. Gates
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK;
| | - Socorro Mesa
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, CSIC, 18008 Granada, Spain; (S.P.); (J.J.C.); (A.J.-L.); (E.J.B.)
| |
Collapse
|
5
|
Salas A, Cabrera JJ, Jiménez-Leiva A, Mesa S, Bedmar EJ, Richardson DJ, Gates AJ, Delgado MJ. Bacterial nitric oxide metabolism: Recent insights in rhizobia. Adv Microb Physiol 2021; 78:259-315. [PMID: 34147187 DOI: 10.1016/bs.ampbs.2021.05.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Nitric oxide (NO) is a reactive gaseous molecule that has several functions in biological systems depending on its concentration. At low concentrations, NO acts as a signaling molecule, while at high concentrations, it becomes very toxic due to its ability to react with multiple cellular targets. Soil bacteria, commonly known as rhizobia, have the capacity to establish a N2-fixing symbiosis with legumes inducing the formation of nodules in their roots. Several reports have shown NO production in the nodules where this gas acts either as a signaling molecule which regulates gene expression, or as a potent inhibitor of nitrogenase and other plant and bacteria enzymes. A better understanding of the sinks and sources of NO in rhizobia is essential to protect symbiotic nitrogen fixation from nitrosative stress. In nodules, both the plant and the microsymbiont contribute to the production of NO. From the bacterial perspective, the main source of NO reported in rhizobia is the denitrification pathway that varies significantly depending on the species. In addition to denitrification, nitrate assimilation is emerging as a new source of NO in rhizobia. To control NO accumulation in the nodules, in addition to plant haemoglobins, bacteroids also contribute to NO detoxification through the expression of a NorBC-type nitric oxide reductase as well as rhizobial haemoglobins. In the present review, updated knowledge about the NO metabolism in legume-associated endosymbiotic bacteria is summarized.
Collapse
Affiliation(s)
- Ana Salas
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Juan J Cabrera
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain; School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, United Kingdom
| | - Andrea Jiménez-Leiva
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Socorro Mesa
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Eulogio J Bedmar
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - David J Richardson
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, United Kingdom
| | - Andrew J Gates
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, United Kingdom
| | - María J Delgado
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain.
| |
Collapse
|
6
|
Bennett SP, Torres MJ, Soriano-Laguna MJ, Richardson DJ, Gates AJ, Le Brun NE. nosX is essential for whole-cell N 2O reduction in Paracoccus denitrificans but not for assembly of copper centres of nitrous oxide reductase. Microbiology (Reading) 2020; 166:909-917. [PMID: 32886603 PMCID: PMC7660919 DOI: 10.1099/mic.0.000955] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Nitrous oxide (N2O) is a potent greenhouse gas that is produced naturally as an intermediate during the process of denitrification carried out by some soil bacteria. It is consumed by nitrous oxide reductase (N2OR), the terminal enzyme of the denitrification pathway, which catalyses a reduction reaction to generate dinitrogen. N2OR contains two important copper cofactors (CuA and CuZ centres) that are essential for activity, and in copper-limited environments, N2OR fails to function, contributing to rising levels of atmospheric N2O and a major environmental challenge. Here we report studies of nosX, one of eight genes in the nos cluster of the soil dwelling α-proteobaterium Paraccocus denitrificans. A P. denitrificans ΔnosX deletion mutant failed to reduce N2O under both copper-sufficient and copper-limited conditions, demonstrating that NosX plays an essential role in N2OR activity. N2OR isolated from nosX-deficient cells was found to be unaffected in terms of the assembly of its copper cofactors, and to be active in in vitro assays, indicating that NosX is not required for the maturation of the enzyme; in particular, it plays no part in the assembly of either of the CuA and CuZ centres. Furthermore, quantitative Reverse Transcription PCR (qRT-PCR) studies showed that NosX does not significantly affect the expression of the N2OR-encoding nosZ gene. NosX is a homologue of the FAD-binding protein ApbE from Pseudomonas stutzeri, which functions in the flavinylation of another N2OR accessory protein, NosR. Thus, it is likely that NosX is a system-specific maturation factor of NosR, and so is indirectly involved in maintaining the reaction cycle of N2OR and cellular N2O reduction.
Collapse
Affiliation(s)
- Sophie P Bennett
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Maria J Torres
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Manuel J Soriano-Laguna
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - David J Richardson
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Andrew J Gates
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Nick E Le Brun
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| |
Collapse
|
7
|
Salas A, Tortosa G, Hidalgo-García A, Delgado A, Bedmar EJ, Richardson DJ, Gates AJ, Delgado MJ. The Hemoglobin Bjgb From Bradyrhizobium diazoefficiens Controls NO Homeostasis in Soybean Nodules to Protect Symbiotic Nitrogen Fixation. Front Microbiol 2020; 10:2915. [PMID: 31998252 PMCID: PMC6965051 DOI: 10.3389/fmicb.2019.02915] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Accepted: 12/03/2019] [Indexed: 11/13/2022] Open
Abstract
Legume-rhizobia symbiotic associations have beneficial effects on food security and nutrition, health and climate change. Hypoxia induced by flooding produces nitric oxide (NO) in nodules from soybean plants cultivated in nitrate-containing soils. As NO is a strong inhibitor of nitrogenase expression and activity, this negatively impacts symbiotic nitrogen fixation in soybean and limits crop production. In Bradyrhizobium diazoefficiens, denitrification is the main process involved in NO formation by soybean flooded nodules. In addition to denitrification, nitrate assimilation is another source of NO in free-living B. diazoefficiens cells and a single domain hemoglobin (Bjgb) has been shown to have a role in NO detoxification during nitrate-dependent growth. However, the involvement of Bjgb in protecting nitrogenase against NO in soybean nodules remains unclear. In this work, we have investigated the effect of inoculation of soybean plants with a bjgb mutant on biological nitrogen fixation. By analyzing the proportion of N in shoots derived from N2-fixation using the 15N isotope dilution technique, we found that plants inoculated with the bjgb mutant strain had higher tolerance to flooding than those inoculated with the parental strain. Similarly, reduction of nitrogenase activity and nifH expression by flooding was less pronounced in bjgb than in WT nodules. These beneficial effects are probably due to the reduction of NO accumulation in bjgb flooded nodules compared to the wild-type nodules. This decrease is caused by an induction of expression and activity of the denitrifying NO reductase enzyme in bjgb bacteroids. As bjgb deficiency promotes NO-tolerance, the negative effect of NO on nitrogenase is partially prevented and thus demonstrates that inoculation of soybean plants with the B. diazoefficiens bjgb mutant confers protection of symbiotic nitrogen fixation during flooding.
Collapse
Affiliation(s)
- Ana Salas
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Germán Tortosa
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Alba Hidalgo-García
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Antonio Delgado
- Laboratory of Stable Isotopes Biogeochemistry, Instituto Andaluz de Ciencias de la Tierra, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Eulogio J Bedmar
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - David J Richardson
- School of Biological Sciences, University of East Anglia, Norwich, United Kingdom
| | - Andrew J Gates
- School of Biological Sciences, University of East Anglia, Norwich, United Kingdom
| | - María J Delgado
- Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| |
Collapse
|
8
|
Gaimster H, Alston M, Richardson DJ, Gates AJ, Rowley G. Transcriptional and environmental control of bacterial denitrification and N2O emissions. FEMS Microbiol Lett 2019; 365:4768087. [PMID: 29272423 DOI: 10.1093/femsle/fnx277] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 12/18/2017] [Indexed: 12/18/2022] Open
Abstract
In oxygen-limited environments, denitrifying bacteria can switch from oxygen-dependent respiration to nitrate (NO3-) respiration in which the NO3- is sequentially reduced via nitrite (NO2-), nitric oxide (NO) and nitrous oxide (N2O) to dinitrogen (N2). However, atmospheric N2O continues to rise, a significant proportion of which is microbial in origin. This implies that the enzyme responsible for N2O reduction, nitrous oxide reductase (NosZ), does not always carry out the final step of denitrification either efficiently or in synchrony with the rest of the pathway. Despite a solid understanding of the biochemistry underpinning denitrification, there is a relatively poor understanding of how environmental signals and respective transcriptional regulators control expression of the denitrification apparatus. This minireview describes the current picture for transcriptional regulation of denitrification in the model bacterium, Paracoccus denitrificans, highlighting differences in other denitrifying bacteria where appropriate, as well as gaps in our understanding. Alongside this, the emerging role of small regulatory RNAs in regulation of denitrification is discussed. We conclude by speculating how this information, aside from providing a better understanding of the denitrification process, can be translated into development of novel greenhouse gas mitigation strategies.
Collapse
Affiliation(s)
- Hannah Gaimster
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Mark Alston
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - David J Richardson
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Andrew J Gates
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Gary Rowley
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| |
Collapse
|
9
|
Abdelhamid MA, Fábián L, MacDonald CJ, Cheesman MR, Gates AJ, Waller ZA. Redox-dependent control of i-Motif DNA structure using copper cations. Nucleic Acids Res 2019; 46:5886-5893. [PMID: 29800233 PMCID: PMC6159522 DOI: 10.1093/nar/gky390] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Accepted: 05/03/2018] [Indexed: 12/21/2022] Open
Abstract
Previous computational studies have shown that Cu+ can act as a substitute for H+ to support formation of cytosine (C) dimers with similar conformation to the hemi-protonated base pair found in i-motif DNA. Through a range of biophysical methods, we provide experimental evidence to support the hypothesis that Cu+ can mediate C–C base pairing in i-motif DNA and preserve i-motif structure. These effects can be reversed using a metal chelator, or exposure to ambient oxygen in the air that drives oxidation of Cu+ to Cu2+, a comparatively weak ligand. Herein, we present a dynamic and redox-sensitive system for conformational control of an i-motif forming DNA sequence in response to copper cations.
Collapse
Affiliation(s)
- Mahmoud As Abdelhamid
- School of Pharmacy, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.,Centre for Molecular and Structural Biochemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - László Fábián
- School of Pharmacy, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Colin J MacDonald
- School of Pharmacy, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.,School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Myles R Cheesman
- Centre for Molecular and Structural Biochemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.,School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Andrew J Gates
- Centre for Molecular and Structural Biochemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.,School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Zoë Ae Waller
- School of Pharmacy, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.,Centre for Molecular and Structural Biochemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| |
Collapse
|
10
|
Kremer K, van Teeseling MCF, Schada von Borzyskowski L, Bernhardsgrütter I, van Spanning RJM, Gates AJ, Remus-Emsermann MNP, Thanbichler M, Erb TJ. Dynamic Metabolic Rewiring Enables Efficient Acetyl Coenzyme A Assimilation in Paracoccus denitrificans. mBio 2019; 10:e00805-19. [PMID: 31289174 PMCID: PMC6747724 DOI: 10.1128/mbio.00805-19] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Accepted: 06/07/2019] [Indexed: 12/21/2022] Open
Abstract
During growth, microorganisms have to balance metabolic flux between energy and biosynthesis. One of the key intermediates in central carbon metabolism is acetyl coenzyme A (acetyl-CoA), which can be either oxidized in the citric acid cycle or assimilated into biomass through dedicated pathways. Two acetyl-CoA assimilation strategies in bacteria have been described so far, the ethylmalonyl-CoA pathway (EMCP) and the glyoxylate cycle (GC). Here, we show that Paracoccus denitrificans uses both strategies for acetyl-CoA assimilation during different growth stages, revealing an unexpected metabolic complexity in the organism's central carbon metabolism. The EMCP is constitutively expressed on various substrates and leads to high biomass yields on substrates requiring acetyl-CoA assimilation, such as acetate, while the GC is specifically induced on these substrates, enabling high growth rates. Even though each acetyl-CoA assimilation strategy alone confers a distinct growth advantage, P. denitrificans recruits both to adapt to changing environmental conditions, such as a switch from succinate to acetate. Time-resolved single-cell experiments show that during this switch, expression of the EMCP and GC is highly coordinated, indicating fine-tuned genetic programming. The dynamic metabolic rewiring of acetyl-CoA assimilation is an evolutionary innovation by P. denitrificans that allows this organism to respond in a highly flexible manner to changes in the nature and availability of the carbon source to meet the physiological needs of the cell, representing a new phenomenon in central carbon metabolism.IMPORTANCE Central carbon metabolism provides organisms with energy and cellular building blocks during growth and is considered the invariable "operating system" of the cell. Here, we describe a new phenomenon in bacterial central carbon metabolism. In contrast to many other bacteria that employ only one pathway for the conversion of the central metabolite acetyl-CoA, Paracoccus denitrificans possesses two different acetyl-CoA assimilation pathways. These two pathways are dynamically recruited during different stages of growth, which allows P. denitrificans to achieve both high biomass yield and high growth rates under changing environmental conditions. Overall, this dynamic rewiring of central carbon metabolism in P. denitrificans represents a new strategy compared to those of other organisms employing only one acetyl-CoA assimilation pathway.
Collapse
Affiliation(s)
- Katharina Kremer
- Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | | | | | | | - Rob J M van Spanning
- Department of Molecular Cell Biology, Vrije Universiteit, HV, Amsterdam, The Netherlands
| | - Andrew J Gates
- School of Biological Sciences, University of East Anglia, Norwich, United Kingdom
| | - Mitja N P Remus-Emsermann
- School of Biological Sciences, University of Canterbury, Christchurch, New Zealand
- Biomolecular Interaction Centre, University of Canterbury, Christchurch, New Zealand
| | - Martin Thanbichler
- Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
- Faculty of Biology, Philipps-Universität, Marburg, Germany
- LOEWE Center for Synthetic Microbiology, Marburg, Germany
| | - Tobias J Erb
- Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
- Faculty of Biology, Philipps-Universität, Marburg, Germany
- LOEWE Center for Synthetic Microbiology, Marburg, Germany
| |
Collapse
|
11
|
Bennett SP, Soriano-Laguna MJ, Bradley JM, Svistunenko DA, Richardson DJ, Gates AJ, Le Brun NE. NosL is a dedicated copper chaperone for assembly of the Cu Z center of nitrous oxide reductase. Chem Sci 2019; 10:4985-4993. [PMID: 31183047 PMCID: PMC6530538 DOI: 10.1039/c9sc01053j] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Accepted: 04/01/2019] [Indexed: 11/21/2022] Open
Abstract
Nitrous oxide reductase (N2OR) is the terminal enzyme of the denitrification pathway of soil bacteria that reduces the greenhouse gas nitrous oxide (N2O) to dinitrogen. In addition to a binuclear CuA site that functions in electron transfer, the active site of N2OR features a unique tetranuclear copper cluster bridged by inorganic sulfide, termed CuZ. In copper-limited environments, N2OR fails to function, resulting in truncation of denitrification and rising levels of N2O released by cells to the atmosphere, presenting a major environmental challenge. Here we report studies of nosL from Paracoccus denitrificans, which is part of the nos gene cluster, and encodes a putative copper binding protein. A Paracoccus denitrificans ΔnosL mutant strain had no denitrification phenotype under copper-sufficient conditions but failed to reduce N2O under copper-limited conditions. N2OR isolated from ΔnosL cells was found to be deficient in copper and to exhibit attenuated activity. UV-visible absorbance spectroscopy revealed that bands due to the CuA center were unaffected, while those corresponding to the CuZ center were significantly reduced in intensity. In vitro studies of a soluble form of NosL without its predicted membrane anchor showed that it binds one Cu(i) ion per protein with attomolar affinity, but does not bind Cu(ii). Together, the data demonstrate that NosL is a copper-binding protein specifically required for assembly of the CuZ center of N2OR, and thus represents the first characterised assembly factor for the CuZ active site of this key environmental enzyme, which is globally responsible for the destruction of a potent greenhouse gas.
Collapse
Affiliation(s)
- Sophie P Bennett
- Centre for Molecular and Structural Biochemistry , School of Chemistry , University of East Anglia , Norwich Research Park , Norwich , NR4 7TJ , UK .
| | - Manuel J Soriano-Laguna
- Centre for Molecular and Structural Biochemistry , School of Biological Sciences , University of East Anglia , Norwich Research Park , Norwich , NR4 7TJ , UK .
| | - Justin M Bradley
- Centre for Molecular and Structural Biochemistry , School of Chemistry , University of East Anglia , Norwich Research Park , Norwich , NR4 7TJ , UK .
| | - Dimitri A Svistunenko
- School of Biological Sciences , University of Essex , Wivenhoe Park , Colchester CO4 3SQ , UK
| | - David J Richardson
- Centre for Molecular and Structural Biochemistry , School of Biological Sciences , University of East Anglia , Norwich Research Park , Norwich , NR4 7TJ , UK .
| | - Andrew J Gates
- Centre for Molecular and Structural Biochemistry , School of Biological Sciences , University of East Anglia , Norwich Research Park , Norwich , NR4 7TJ , UK .
| | - Nick E Le Brun
- Centre for Molecular and Structural Biochemistry , School of Chemistry , University of East Anglia , Norwich Research Park , Norwich , NR4 7TJ , UK .
| |
Collapse
|
12
|
Pinchbeck BJ, Soriano-Laguna MJ, Sullivan MJ, Luque-Almagro VM, Rowley G, Ferguson SJ, Roldán MD, Richardson DJ, Gates AJ. A dual functional redox enzyme maturation protein for respiratory and assimilatory nitrate reductases in bacteria. Mol Microbiol 2019; 111:1592-1603. [PMID: 30875449 PMCID: PMC6618116 DOI: 10.1111/mmi.14239] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/10/2019] [Indexed: 12/16/2022]
Abstract
Nitrate is available to microbes in many environments due to sustained use of inorganic fertilizers on agricultural soils and many bacterial and archaeal lineages have the capacity to express respiratory (Nar) and assimilatory (Nas) nitrate reductases to utilize this abundant respiratory substrate and nutrient for growth. Here, we show that in the denitrifying bacterium Paracoccus denitrificans, NarJ serves as a chaperone for both the anaerobic respiratory nitrate reductase (NarG) and the assimilatory nitrate reductase (NasC), the latter of which is active during both aerobic and anaerobic nitrate assimilation. Bioinformatic analysis suggests that the potential for this previously unrecognized role for NarJ in functional maturation of other cytoplasmic molybdenum‐dependent nitrate reductases may be phylogenetically widespread as many bacteria contain both Nar and Nas systems.
Collapse
Affiliation(s)
- Benjamin J Pinchbeck
- Centre for Molecular and Structural Biochemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.,School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Manuel J Soriano-Laguna
- Centre for Molecular and Structural Biochemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.,School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Matthew J Sullivan
- School of Medical Science, Gold Coast campus, Griffith University, Southport, QLD 4222, Australia
| | - Victor M Luque-Almagro
- Departamento de Bioquímica y Biología Molecular, Edificio Severo Ochoa, 1 planta, Campus de Rabanales, Universidad de Córdoba, Córdoba 14071, Spain
| | - Gary Rowley
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Stuart J Ferguson
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - M Dolores Roldán
- Departamento de Bioquímica y Biología Molecular, Edificio Severo Ochoa, 1 planta, Campus de Rabanales, Universidad de Córdoba, Córdoba 14071, Spain
| | - David J Richardson
- Centre for Molecular and Structural Biochemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.,School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Andrew J Gates
- Centre for Molecular and Structural Biochemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.,School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| |
Collapse
|
13
|
Abstract
Numerous studies have been published stressing the importance of finding ligands that can bind specifically to DNA secondary structures. Several have identified ligands that are presented as having specific binding to the G-quadruplex; however, these were not originally tested on the complementary i-motif structure. The i-motif was overlooked and presumed to be irrelevant due to the belief that the hemiprotonated (cytosine+-cytosine) base pair at the core of the structure required acidic pH. The pathophysiological relevance of i-motifs has since been documented, as well as the discovery of several genomic sequences, which can form i-motif at neutral pH. Using different biophysical methodologies, we provide experimental evidence to show that widely used G-quadruplex ligands interact with i-motif structures at neutral pH, generally leading to their destabilization. Crucially, this has implications both for the search for quadruplex binding compounds as well as for the effects of compounds reported to have G-quadruplex specificity without examining their effects on i-motif.
Collapse
Affiliation(s)
- Mahmoud A S Abdelhamid
- School of Pharmacy , University of East Anglia , Norwich Research Park , Norwich NR4 7TJ , United Kingdom.,Centre for Molecular and Structural Biochemistry , University of East Anglia , Norwich Research Park , Norwich NR4 7TJ , United Kingdom
| | - Andrew J Gates
- Centre for Molecular and Structural Biochemistry , University of East Anglia , Norwich Research Park , Norwich NR4 7TJ , United Kingdom.,School of Biological Sciences , University of East Anglia , Norwich Research Park , Norwich NR4 7TJ , United Kingdom
| | - Zoë A E Waller
- School of Pharmacy , University of East Anglia , Norwich Research Park , Norwich NR4 7TJ , United Kingdom.,Centre for Molecular and Structural Biochemistry , University of East Anglia , Norwich Research Park , Norwich NR4 7TJ , United Kingdom
| |
Collapse
|
14
|
Olaya-Abril A, Luque-Almagro VM, Manso I, Gates AJ, Moreno-Vivián C, Richardson DJ, Roldán MD. Poly(3-hydroxybutyrate) hyperproduction by a global nitrogen regulator NtrB mutant strain of Paracoccus denitrificans PD1222. FEMS Microbiol Lett 2018; 365:4705890. [PMID: 29228177 PMCID: PMC5812496 DOI: 10.1093/femsle/fnx251] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Accepted: 11/29/2017] [Indexed: 12/27/2022] Open
Abstract
Paracoccus denitrificans PD1222 accumulates short-length polyhydroxyalkanoates, poly(3-hydroxybutyrate), under nitrogen-deficient conditions. Polyhydroxybutyrate metabolism requires the 3-ketoacyl-CoA thiolase PhaA, the acetoacetyl-CoA dehydrogenase/reductase PhaB and the synthase PhaC for polymerization. Additionally, P. denitrificans PD1222 grows aerobically with nitrate as sole nitrogen source. Nitrate assimilation is controlled negatively by ammonium through the two-component NtrBC system. NtrB is a sensor kinase that autophosphorylates a histidine residue under low-nitrogen concentrations and, in turn, transfers a phosphoryl group to an aspartate residue of the response regulator NtrC protein, which acts as a transcriptional activator of the P. denitrificans PD1222 nasABGHC genes. The P. denitrificans PD1222 NtrB mutant was unable to use nitrate efficiently as nitrogen source when compared to the wild-type strain, and it also overproduced poly(3-hydroxybutyrate). Acetyl-CoA concentration in the P. denitrificans PD1222 NtrB mutant strain was higher than in the wild-type strain. The expression of the phaC gene was also increased in the NtrB mutant when compared to the wild-type strain. These results suggest that accumulation of poly(3-hydroxybutyrate) in the NtrB mutant strain of PD1222 responds to the high levels of acetyl-CoA that accumulate in the cytoplasm as consequence of its inability to efficiently use nitrate as nitrogen source.
Collapse
Affiliation(s)
- Alfonso Olaya-Abril
- Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, Edificio Severo Ochoa, 1a planta, Campus de Rabanales, Córdoba, 14071, Spain
| | - Víctor M Luque-Almagro
- Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, Edificio Severo Ochoa, 1a planta, Campus de Rabanales, Córdoba, 14071, Spain
| | - Isabel Manso
- Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, Edificio Severo Ochoa, 1a planta, Campus de Rabanales, Córdoba, 14071, Spain
| | - Andrew J Gates
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Conrado Moreno-Vivián
- Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, Edificio Severo Ochoa, 1a planta, Campus de Rabanales, Córdoba, 14071, Spain
| | - David J Richardson
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - María Dolores Roldán
- Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, Edificio Severo Ochoa, 1a planta, Campus de Rabanales, Córdoba, 14071, Spain
| |
Collapse
|
15
|
Giannopoulos G, Sullivan MJ, Hartop KR, Rowley G, Gates AJ, Watmough NJ, Richardson DJ. Tuning the modular Paracoccus denitrificans respirome to adapt from aerobic respiration to anaerobic denitrification. Environ Microbiol 2017; 19:4953-4964. [PMID: 29076595 DOI: 10.1111/1462-2920.13974] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2017] [Revised: 10/10/2017] [Accepted: 10/16/2017] [Indexed: 12/31/2022]
Abstract
Bacterial denitrification is a respiratory process that is a major source and sink of the potent greenhouse gas nitrous oxide. Many denitrifying bacteria can adjust to life in both oxic and anoxic environments through differential expression of their respiromes in response to environmental signals such as oxygen, nitrate and nitric oxide. We used steady-state oxic and anoxic chemostat cultures to demonstrate that the switch from aerobic to anaerobic metabolism is brought about by changes in the levels of expression of relatively few genes, but this is sufficient to adjust the configuration of the respirome to allow the organism to efficiently respire nitrate without the significant release of intermediates, such as nitrous oxide. The regulation of the denitrification respirome in strains deficient in the transcription factors FnrP, Nnr and NarR was explored and revealed that these have both inducer and repressor activities, possibly due to competitive binding at similar DNA binding sites. This may contribute to the fine tuning of expression of the denitrification respirome and so adds to the understanding of the regulation of nitrous oxide emission by denitrifying bacteria in response to different environmental signals.
Collapse
Affiliation(s)
- Georgios Giannopoulos
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
| | - Matthew J Sullivan
- School of Medical Science, Griffith University, Gold Coast campus, Southport, Australia
| | - Katherine R Hartop
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
| | - Gary Rowley
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
| | - Andrew J Gates
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
| | - Nicholas J Watmough
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
| | - David J Richardson
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
| |
Collapse
|
16
|
Phelps A, Gates AJ, Eastaugh L, Hillier M, Ulaeto DO. Comparative Efficacy of Intramuscular and Scarification Routes of Administration of Live Smallpox Vaccine in a Murine Challenge Model. Vaccine 2017; 35:3889-3896. [PMID: 28606813 PMCID: PMC9628712 DOI: 10.1016/j.vaccine.2017.05.058] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 05/17/2017] [Accepted: 05/20/2017] [Indexed: 12/17/2022]
Abstract
In recent years concern has mounted regarding the possibility of a re-emergence of smallpox through biowarfare or bioterrorism. There is also concern over the incidence of human monkeypox in endemic areas and the potential for monkeypox to be accidentally transported to non-endemic areas. In the event of re-emergence of smallpox or emergence of monkeypox, the accepted route of administration for live replicating smallpox vaccine is dermal scarification, which generates a virus-shedding lesion that persists for several days at the vaccination site. The lesion is a potential source of contact transmission of vaccine to individuals who may be contra-indicated for receipt of the live vaccine. In this study, we compare dermal scarification with intramuscular vaccination for replicating smallpox vaccine in a mouse lethal challenge model. Comparisons are made over multiple vaccine and challenge doses and data recorded for lethality, disease severity, and antibody responses. Qualitative and quantitative differences between the two routes are observed, and for the intramuscular route the febrile response is not suppressed after subsequent virulent vaccinia virus challenge. However both routes generate an immune response and protect from severe disease and death. Although dermal scarification is the preferred route of vaccination for the general population, intramuscular vaccination may be an option for people who are not contraindicated for the live vaccine, but who are close contacts of people who are contraindicated for the live vaccine, in an emergency situation.
Collapse
Affiliation(s)
- A Phelps
- CBR Division, Dstl Porton Down, Salisbury SP4 0JQ, UK
| | - A J Gates
- CBR Division, Dstl Porton Down, Salisbury SP4 0JQ, UK
| | - L Eastaugh
- CBR Division, Dstl Porton Down, Salisbury SP4 0JQ, UK
| | - M Hillier
- CBR Division, Dstl Porton Down, Salisbury SP4 0JQ, UK
| | - D O Ulaeto
- CBR Division, Dstl Porton Down, Salisbury SP4 0JQ, UK; The Pirbright Institute, Ash Road, Woking GU24 0NF, UK.
| |
Collapse
|
17
|
Hartop KR, Sullivan MJ, Giannopoulos G, Gates AJ, Bond PL, Yuan Z, Clarke TA, Rowley G, Richardson DJ. The metabolic impact of extracellular nitrite on aerobic metabolism of Paracoccus denitrificans. Water Res 2017; 113:207-214. [PMID: 28214776 PMCID: PMC5339346 DOI: 10.1016/j.watres.2017.02.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 01/31/2017] [Accepted: 02/06/2017] [Indexed: 05/22/2023]
Abstract
Nitrite, in equilibrium with free nitrous acid (FNA), can inhibit both aerobic and anaerobic growth of microbial communities through bactericidal activities that have considerable potential for control of microbial growth in a range of water systems. There has been much focus on the effect of nitrite/FNA on anaerobic metabolism and so, to enhance understanding of the metabolic impact of nitrite/FNA on aerobic metabolism, a study was undertaken with a model denitrifying bacterium Paracoccus denitrificans PD1222. Extracellular nitrite inhibits aerobic growth of P. denitrificans in a pH-dependent manner that is likely to be a result of both nitrite and free nitrous acid (pKa = 3.25) and subsequent reactive nitrogen oxides generated from the intracellular passage of FNA into P. denitrificans. Increased expression of a gene encoding a flavohemoglobin protein (Fhp) (Pden_1689) was observed in response to extracellular nitrite. Construction and analysis of a deletion mutant established Fhp to be involved in endowing nitrite/FNA resistance at high extracellular nitrite concentrations. Global transcriptional analysis confirmed nitrite-dependent expression of fhp and indicated that P. denitrificans expressed a number of stress response systems associated with protein, DNA and lipid repair. It is therefore suggested that nitrite causes a pH-dependent stress response that is due to the production of associated reactive nitrogen species, such as nitric oxide from the internalisation of FNA.
Collapse
Affiliation(s)
- K R Hartop
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - M J Sullivan
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - G Giannopoulos
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - A J Gates
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - P L Bond
- Advanced Water Management Centre (AWMC), University of Queensland, St Lucia, Brisbane, QLD, 4072, Australia
| | - Z Yuan
- Advanced Water Management Centre (AWMC), University of Queensland, St Lucia, Brisbane, QLD, 4072, Australia
| | - T A Clarke
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - G Rowley
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - D J Richardson
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK.
| |
Collapse
|
18
|
Gaimster H, Chalklen L, Alston M, Munnoch JT, Richardson DJ, Gates AJ, Rowley G. Genome-Wide Discovery of Putative sRNAs in Paracoccus denitrificans Expressed under Nitrous Oxide Emitting Conditions. Front Microbiol 2016; 7:1806. [PMID: 27895629 PMCID: PMC5107571 DOI: 10.3389/fmicb.2016.01806] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Accepted: 10/27/2016] [Indexed: 12/18/2022] Open
Abstract
Nitrous oxide (N2O) is a stable, ozone depleting greenhouse gas. Emissions of N2O into the atmosphere continue to rise, primarily due to the use of nitrogen-containing fertilizers by soil denitrifying microbes. It is clear more effective mitigation strategies are required to reduce emissions. One way to help develop future mitigation strategies is to address the currently poor understanding of transcriptional regulation of the enzymes used to produce and consume N2O. With this ultimate aim in mind we performed RNA-seq on a model soil denitrifier, Paracoccus denitrificans, cultured anaerobically under high N2O and low N2O emitting conditions, and aerobically under zero N2O emitting conditions to identify small RNAs (sRNAs) with potential regulatory functions transcribed under these conditions. sRNAs are short (∼40–500 nucleotides) non-coding RNAs that regulate a wide range of activities in many bacteria. Hundred and sixty seven sRNAs were identified throughout the P. denitrificans genome which are either present in intergenic regions or located antisense to ORFs. Furthermore, many of these sRNAs are differentially expressed under high N2O and low N2O emitting conditions respectively, suggesting they may play a role in production or reduction of N2O. Expression of 16 of these sRNAs have been confirmed by RT-PCR. Ninety percent of the sRNAs are predicted to form secondary structures. Predicted targets include transporters and a number of transcriptional regulators. A number of sRNAs were conserved in other members of the α-proteobacteria. Better understanding of the sRNA factors which contribute to expression of the machinery required to reduce N2O will, in turn, help to inform strategies for mitigation of N2O emissions.
Collapse
Affiliation(s)
- Hannah Gaimster
- School of Biological Sciences, University of East Anglia Norwich, UK
| | - Lisa Chalklen
- School of Biological Sciences, University of East Anglia Norwich, UK
| | - Mark Alston
- Earlham Institute (formerly The Genome Analysis Centre) Norwich, UK
| | - John T Munnoch
- School of Biological Sciences, University of East Anglia Norwich, UK
| | | | - Andrew J Gates
- School of Biological Sciences, University of East Anglia Norwich, UK
| | - Gary Rowley
- School of Biological Sciences, University of East Anglia Norwich, UK
| |
Collapse
|
19
|
Waller ZAE, Pinchbeck BJ, Buguth BS, Meadows TG, Richardson DJ, Gates AJ. Control of bacterial nitrate assimilation by stabilization of G-quadruplex DNA. Chem Commun (Camb) 2016; 52:13511-13514. [PMID: 27805200 PMCID: PMC5123632 DOI: 10.1039/c6cc06057a] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Here we present a chemical-biology study in the model soil bacterium Paracoccus denitrificans, where we show ligand-specific control of nitrate assimilation. Stabilization of a G-quadruplex in the promoter region of the nas genes, encoding the assimilatory nitrate/nitrite reductase system, is achieved using known quadruplex ligands and results in attenuation of gene transcription.
Collapse
Affiliation(s)
- Zoë A E Waller
- School of Pharmacy, University of East Anglia, Norwich Research Park, NR4 7TJ, UK.
| | | | | | | | | | | |
Collapse
|
20
|
Goddard AD, Bali S, Mavridou DAI, Luque-Almagro VM, Gates AJ, Dolores Roldán M, Newstead S, Richardson DJ, Ferguson SJ. The Paracoccus denitrificans NarK-like nitrate and nitrite transporters-probing nitrate uptake and nitrate/nitrite exchange mechanisms. Mol Microbiol 2016; 103:117-133. [PMID: 27696579 PMCID: PMC5217062 DOI: 10.1111/mmi.13546] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/29/2016] [Indexed: 12/17/2022]
Abstract
Nitrate and nitrite transport across biological membranes is often facilitated by protein transporters that are members of the major facilitator superfamily. Paracoccus denitrificans contains an unusual arrangement whereby two of these transporters, NarK1 and NarK2, are fused into a single protein, NarK, which delivers nitrate to the respiratory nitrate reductase and transfers the product, nitrite, to the periplasm. Our complementation studies, using a mutant lacking the nitrate/proton symporter NasA from the assimilatory nitrate reductase pathway, support that NarK1 functions as a nitrate/proton symporter while NarK2 is a nitrate/nitrite antiporter. Through the same experimental system, we find that Escherichia coli NarK and NarU can complement deletions in both narK and nasA in P. denitrificans, suggesting that, while these proteins are most likely nitrate/nitrite antiporters, they can also act in the net uptake of nitrate. Finally, we argue that primary sequence analysis and structural modelling do not readily explain why NasA, NarK1 and NarK2, as well as other transporters from this protein family, have such different functions, ranging from net nitrate uptake to nitrate/nitrite exchange.
Collapse
Affiliation(s)
- Alan D Goddard
- School of Life Sciences, University of Lincoln, Lincoln, LN6 7TS, UK.,School of Life and Health Sciences, Aston University, Birmingham, B4 7ET, UK.,Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Shilpa Bali
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - Despoina A I Mavridou
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK.,MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Imperial College London, Kensington, London, SW7 2DD, UK
| | - Victor M Luque-Almagro
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ, UK.,Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, Edificio Severo Ochoa, 1a planta, Campus de Rabanales, Córdoba, 14071, Spain
| | - Andrew J Gates
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ, UK
| | - M Dolores Roldán
- Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, Edificio Severo Ochoa, 1a planta, Campus de Rabanales, Córdoba, 14071, Spain
| | - Simon Newstead
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - David J Richardson
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ, UK
| | - Stuart J Ferguson
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| |
Collapse
|
21
|
Edwards MJ, Baiden NA, Johs A, Tomanicek SJ, Liang L, Shi L, Fredrickson JK, Zachara JM, Gates AJ, Butt JN, Richardson DJ, Clarke TA. The X-ray crystal structure of Shewanella oneidensis OmcA reveals new insight at the microbe-mineral interface. FEBS Lett 2014; 588:1886-90. [PMID: 24747425 DOI: 10.1016/j.febslet.2014.04.013] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 04/03/2014] [Accepted: 04/04/2014] [Indexed: 11/28/2022]
Abstract
The X-ray crystal structure of Shewanella oneidensis OmcA, an extracellular decaheme cytochrome involved in mineral reduction, was solved to a resolution of 2.7 Å. The four OmcA molecules in the asymmetric unit are arranged so the minimum distance between heme 5 on adjacent OmcA monomers is 9 Å, indicative of a transient OmcA dimer capable of intermolecular electron transfer. A previously identified hematite binding motif was identified near heme 10, forming a hydroxylated surface that would bring a heme 10 electron egress site to ∼10 Å of a mineral surface.
Collapse
Affiliation(s)
- Marcus J Edwards
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom
| | - Nanakow A Baiden
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom
| | - Alexander Johs
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Stephen J Tomanicek
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Liyuan Liang
- Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Liang Shi
- Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | | | - John M Zachara
- Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Andrew J Gates
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom
| | - Julea N Butt
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom
| | - David J Richardson
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom.
| | - Thomas A Clarke
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom.
| |
Collapse
|
22
|
Luque-Almagro VM, Lyall VJ, Ferguson SJ, Roldán MD, Richardson DJ, Gates AJ. Nitrogen oxyanion-dependent dissociation of a two-component complex that regulates bacterial nitrate assimilation. J Biol Chem 2013; 288:29692-702. [PMID: 24005668 PMCID: PMC3795266 DOI: 10.1074/jbc.m113.459032] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nitrogen is an essential nutrient for growth and is readily available to microbes in many environments in the form of ammonium and nitrate. Both ions are of environmental significance due to sustained use of inorganic fertilizers on agricultural soils. Diverse species of bacteria that have an assimilatory nitrate/nitrite reductase system (NAS) can use nitrate or nitrite as the sole nitrogen source for growth when ammonium is limited. In Paracoccus denitrificans, the pathway-specific two-component regulator for NAS expression is encoded by the nasT and nasS genes. Here, we show that the putative RNA-binding protein NasT is a positive regulator essential for expression of the nas gene cluster (i.e. nasABGHC). By contrast, a nitrogen oxyanion-binding sensor (NasS) is required for nitrate/nitrite-responsive control of nas gene expression. The NasS and NasT proteins co-purify as a stable heterotetrameric regulatory complex, NasS-NasT. This protein-protein interaction is sensitive to nitrate and nitrite, which cause dissociation of the NasS-NasT complex into monomeric NasS and an oligomeric form of NasT. NasT has been shown to bind the leader RNA for nasA. Thus, upon liberation from the complex, the positive regulator NasT is free to up-regulate nas gene expression.
Collapse
|
23
|
Woolfenden HC, Gates AJ, Bocking C, Blyth MG, Richardson DJ, Moulton V. Modeling the effect of copper availability on bacterial denitrification. Microbiologyopen 2013; 2:756-65. [PMID: 23913488 PMCID: PMC3831637 DOI: 10.1002/mbo3.111] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Revised: 06/07/2013] [Accepted: 06/10/2013] [Indexed: 11/10/2022] Open
Abstract
When denitrifying bacteria such as Paracoccus denitrificans respire anaerobically they convert nitrate to dinitrogen gas via a pathway which includes the potent greenhouse gas, nitrous oxide (N2O). The copper-dependent enzyme Nitrous Oxide reductase (Nos) catalyzes the reduction of N2O to dinitrogen. In low-copper conditions, recent experiments in chemostats have demonstrated that Nos efficiency decreases resulting in significant N2O emissions. For the first time, a chemostat-based mathematical model is developed that describes the anaerobic denitrification pathway based on Michaelis–Menten kinetics and published kinetic parameters. The model predicts steady-state enzyme levels from experimental data. For low copper concentrations, the predicted Nos level is significantly reduced, whereas the levels for the non copper-dependent reductases in the pathway remain relatively unaffected. The model provides time courses for the pathway metabolites that accurately reflect previously published experimental data. In the absence of experimental data purely predictive analyses can also be readily performed by calculating the relative Nos level directly from the copper concentration. Here, the model quantitatively estimates the increasing level of emitted N2O as the copper level decreases.
Collapse
Affiliation(s)
- Hugh C Woolfenden
- School of Computing Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, U.K
| | | | | | | | | | | |
Collapse
|
24
|
Richardson DJ, Butt JN, Fredrickson JK, Zachara JM, Shi L, Edwards MJ, White G, Baiden N, Gates AJ, Marritt SJ, Clarke TA. The 'porin-cytochrome' model for microbe-to-mineral electron transfer. Mol Microbiol 2012; 85:201-12. [PMID: 22646977 DOI: 10.1111/j.1365-2958.2012.08088.x] [Citation(s) in RCA: 149] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Many species of bacteria can couple anaerobic growth to the respiratory reduction of insoluble minerals containing Fe(III) or Mn(III/IV). It has been suggested that in Shewanella species electrons cross the outer membrane to extracellular substrates via 'porin-cytochrome' electron transport modules. The molecular structure of an outer-membrane extracellular-facing deca-haem terminus for such a module has recently been resolved. It is debated how, once outside the cells, electrons are transferred from outer-membrane cytochromes to insoluble electron sinks. This may occur directly or by assemblies of cytochromes, perhaps functioning as 'nanowires', or via electron shuttles. Here we review recent work in this field and explore whether it allows for unification of the electron transport mechanisms supporting extracellular mineral respiration in Shewanella that may extend into other genera of Gram-negative bacteria.
Collapse
Affiliation(s)
- David J Richardson
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich NR47TJ, UK.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
25
|
Felgate H, Giannopoulos G, Sullivan MJ, Gates AJ, Clarke TA, Baggs E, Rowley G, Richardson DJ. The impact of copper, nitrate and carbon status on the emission of nitrous oxide by two species of bacteria with biochemically distinct denitrification pathways. Environ Microbiol 2012; 14:1788-800. [DOI: 10.1111/j.1462-2920.2012.02789.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
26
|
Gates AJ, Kemp GL, To CY, Mann J, Marritt SJ, Mayes AG, Richardson DJ, Butt JN. The relationship between redox enzyme activity and electrochemical potential—cellular and mechanistic implications from protein film electrochemistry. Phys Chem Chem Phys 2011; 13:7720-31. [DOI: 10.1039/c0cp02887h] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
27
|
Sánchez C, Gates AJ, Meakin GE, Uchiumi T, Girard L, Richardson DJ, Bedmar EJ, Delgado MJ. Production of nitric oxide and nitrosylleghemoglobin complexes in soybean nodules in response to flooding. Mol Plant Microbe Interact 2010; 23:702-11. [PMID: 20367476 DOI: 10.1094/mpmi-23-5-0702] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Nitric oxide (NO) has gained interest as a major signaling molecule during plant development and in response to environmental cues. Formation of NO during symbiotic interactions has been reported, but the role and sources of NO in nodules remain unclear. In this work, the involvement of denitrification, performed by the symbiont Bradyrhizobium japonicum, in NO formation in soybean nodules in response to flooding conditions has been investigated by inoculating plants with napA-, nirK-, or norC-deficient mutants. Levels of nitrosylleghemoglobin (LbNO) in flooded nirK and norC nodules were significantly higher than those observed in wild-type nodules. In addition, nirK and norC nodules accumulated more nitrite and NO, respectively, than wild-type nodules. By contrast, levels of LbNO, nitrite, and NO in flooded napA nodules were lower than in wild-type nodules. These results suggest that LbNO formation in soybean nodules in response to flooding conditions is caused by nitrite and NO generated from periplasmic nitrate reductase (Nap) and also containing nitrite reductase (NirK) denitrification enzymes. Flooding caused a decrease of nifH expression and nitrogenase activity in wild-type and norC nodules but not in napA or nirK nodules. Incubation of wild-type and norC nodules with a NO scavenger counteracted the effect of flooding. Under free-living conditions, beta-galactosidase activity from a nifD'-'lacZ fusion decreased in a norC mutant, which also accumulated NO in the medium. These results suggest that NO formed by Cu-containing nitrite reductase in soybean nodules in response to flooding has a negative effect on expression of nitrogenase. We propose that Lb has a major role in detoxifying NO and nitrite produced by bacteroidal denitrification in response to flooding conditions.
Collapse
|
28
|
Gates AJ, Richardson DJ, Butt JN. Voltammetric characterization of the aerobic energy-dissipating nitrate reductase of Paracoccus pantotrophus: exploring the activity of a redox-balancing enzyme as a function of electrochemical potential. Biochem J 2008; 409:159-68. [PMID: 17900239 DOI: 10.1042/bj20071088] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Paracoccus pantotrophus expresses two nitrate reductases associated with respiratory electron transport, termed NapABC and NarGHI. Both enzymes derive electrons from ubiquinol to reduce nitrate to nitrite. However, while NarGHI harnesses the energy of the quinol/nitrate couple to generate a transmembrane proton gradient, NapABC dissipates the energy associated with these reducing equivalents. In the present paper we explore the nitrate reductase activity of purified NapAB as a function of electrochemical potential, substrate concentration and pH using protein film voltammetry. Nitrate reduction by NapAB is shown to occur at potentials below approx. 0.1 V at pH 7. These are lower potentials than required for NarGH nitrate reduction. The potentials required for Nap nitrate reduction are also likely to require ubiquinol/ubiquinone ratios higher than are needed to activate the H(+)-pumping oxidases expressed during aerobic growth where Nap levels are maximal. Thus the operational potentials of P. pantotrophus NapAB are consistent with a productive role in redox balancing. A Michaelis constant (K(M)) of approx. 45 muM was determined for NapAB nitrate reduction at pH 7. This is in line with studies on intact cells where nitrate reduction by Nap was described by a Monod constant (K(S)) of less than 15 muM. The voltammetric studies also disclosed maximal NapAB activity in a narrow window of potential. This behaviour is resistant to change of pH, nitrate concentration and inhibitor concentration and its possible mechanistic origins are discussed.
Collapse
Affiliation(s)
- Andrew J Gates
- Centre for Metalloprotein Spectroscopy and Biology, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | | | | |
Collapse
|
29
|
Jepson BJN, Mohan S, Clarke TA, Gates AJ, Cole JA, Butler CS, Butt JN, Hemmings AM, Richardson DJ. Spectropotentiometric and structural analysis of the periplasmic nitrate reductase from Escherichia coli. J Biol Chem 2006; 282:6425-37. [PMID: 17130127 DOI: 10.1074/jbc.m607353200] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Escherichia coli NapA (periplasmic nitrate reductase) contains a [4Fe-4S] cluster and a Mo-bis-molybdopterin guanine dinucleotide cofactor. The NapA holoenzyme associates with a di-heme c-type cytochrome redox partner (NapB). These proteins have been purified and studied by spectropotentiometry, and the structure of NapA has been determined. In contrast to the well characterized heterodimeric NapAB systems ofalpha-proteobacteria, such as Rhodobacter sphaeroides and Paracoccus pantotrophus, the gamma-proteobacterial E. coli NapA and NapB proteins purify independently and not as a tight heterodimeric complex. This relatively weak interaction is reflected in dissociation constants of 15 and 32 mum determined for oxidized and reduced NapAB complexes, respectively. The surface electrostatic potential of E. coli NapA in the apparent NapB binding region is markedly less polar and anionic than that of the alpha-proteobacterial NapA, which may underlie the weaker binding of NapB. The molybdenum ion coordination sphere of E. coli NapA includes two molybdopterin guanine dinucleotide dithiolenes, a protein-derived cysteinyl ligand and an oxygen atom. The Mo-O bond length is 2.6 A, which is indicative of a water ligand. The potential range over which the Mo(6+) state is reduced to the Mo(5+) state in either NapA (between +100 and -100 mV) or the NapAB complex (-150 to -350 mV) is much lower than that reported for R. sphaeroides NapA (midpoint potential Mo(6+/5+) > +350 mV), and the form of the Mo(5+) EPR signal is quite distinct. In E. coli NapA or NapAB, the Mo(5+) state could not be further reduced to Mo(4+). We then propose a catalytic cycle for E. coli NapA in which nitrate binds to the Mo(5+) ion and where a stable des-oxo Mo(6+) species may participate.
Collapse
Affiliation(s)
- Brian J N Jepson
- Centre for Metalloprotein Spectroscopy and Biology, University of East Anglia, Norwich NR4 7TJ, United Kingdom
| | | | | | | | | | | | | | | | | |
Collapse
|
30
|
Phelps AL, Gates AJ, Hillier M, Eastaugh L, Ulaeto DO. Comparative efficacy of modified vaccinia Ankara (MVA) as a potential replacement smallpox vaccine. Vaccine 2006; 25:34-42. [PMID: 16950548 DOI: 10.1016/j.vaccine.2006.07.022] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2006] [Accepted: 07/14/2006] [Indexed: 10/24/2022]
Abstract
International concern over the potential consequences of a Bioterrorist or Biowarfare associated release of variola virus have prompted renewed interest in the vaccines for smallpox. The traditional live, replicating vaccine strains are subject to novel safety concerns associated with historical production methods in domesticated ruminants and the additional hazards that vaccinia virus poses for people with immune system abnormalities or a history of eczematous skin conditions. In this study we have examined the longevity and efficacy of immunity induced by a non-replicating smallpox vaccine candidate, modified vaccinia Ankara (MVA) in a murine model using intranasal and aerosol routes of infection. Two-step vaccinations of MVA followed by traditional Lister vaccine are compared with either Lister alone or MVA alone, and the longevity of the protection induced by MVA is assessed. MVA is found to be broadly similar to Lister. Although protection is shown to decay with time, when administered at a standard human dose the longevity of protection induced by MVA is comparable to that induced by Lister.
Collapse
Affiliation(s)
- A L Phelps
- Department of Biomedical Sciences, Dstl Porton Down, Salisbury SP4 0JQ, UK
| | | | | | | | | |
Collapse
|
31
|
Phelps A, Gates AJ, Hillier M, Eastaugh L, Ulaeto DO. Comparative efficacy of replicating smallpox vaccine strains in a murine challenge model. Vaccine 2005; 23:3500-7. [PMID: 15855008 DOI: 10.1016/j.vaccine.2005.02.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2004] [Accepted: 02/01/2005] [Indexed: 11/22/2022]
Abstract
There is currently considerable concern about the vulnerability of human populations to biowarfare or bioterrorist attacks with variola virus (VARV). Traditional smallpox vaccines were manufactured using the lymph of ruminants infected with the vaccinia virus (VACV). However, these production methods do not meet current standards for vaccines, especially since the emergence of transmissable spongiform encephalopathies in domesticated ruminants. This study has examined the protective efficacy of the Lister (Elstree) vaccine strain from various sources in a murine lethal challenge model. Considerable variation in efficacy is observed between the Lister material obtained from the American Type Culture Collection (ATCC) and the same strain obtained from vaccine stockpiles. A new, tissue-culture derived Lister vaccine is assessed against a bench-mark of multiple lots from a historical stockpile of the traditional vaccine. Apparent qualitative differences are observed between historical and new vaccines. Statistically significant differences are observed between different batches of the traditional vaccine, and the efficacy of the tissue-culture produced vaccine falls within this range.
Collapse
Affiliation(s)
- A Phelps
- Department of Biomedical Sciences, Dstl Porton Down, Salisbury SP4 0JQ, UK
| | | | | | | | | |
Collapse
|
32
|
Field SJ, Thornton NP, Anderson LJ, Gates AJ, Reilly A, Jepson BJN, Richardson DJ, George SJ, Cheesman MR, Butt JN. Reductive activation of nitrate reductases. Dalton Trans 2005:3580-6. [PMID: 16234941 DOI: 10.1039/b505530j] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Protein film voltammetry of Paracoccus pantotrophus respiratory nitrate reductase (NarGH) and Synechococcus elongatus assimilatory nitrate reductase (NarB) shows that reductive activation of these enzymes may be required before steady state catalysis is observed. For NarGH complementary spectroscopic studies suggest a structural context for the activation. Catalytic protein film voltammetry at a range of temperatures has allowed quantitation of the activation energies for nitrate reduction. For NarGH with an operating potential of ca. 0.05 V the activation energy of ca. 35 kJ mol-1 is over twice that measured for NarB whose operating potential is ca. -0.35 V.
Collapse
Affiliation(s)
- Sarah J Field
- Centre for Metalloprotein Spectroscopy and Biology, School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich, UK NR4 7TJ
| | | | | | | | | | | | | | | | | | | |
Collapse
|
33
|
Gates AJ, Hughes RO, Sharp SR, Millington PD, Nilavongse A, Cole JA, Leach ER, Jepson B, Richardson DJ, Butler CS. Properties of the periplasmic nitrate reductases from Paracoccus pantotrophus and Escherichia coli after growth in tungsten-supplemented media. FEMS Microbiol Lett 2003; 220:261-9. [PMID: 12670690 DOI: 10.1016/s0378-1097(03)00122-8] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
Paracoccus pantotrophus grown anaerobically under denitrifying conditions expressed similar levels of the periplasmic nitrate reductase (NAP) when cultured in molybdate- or tungstate-containing media. A native PAGE gel stained for nitrate reductase activity revealed that only NapA from molybdate-grown cells displayed readily detectable nitrate reductase activity. Further kinetic analysis showed that the periplasmic fraction from cells grown on molybdate (3 microM) reduced nitrate at a rate of V(max)=3.41+/-0.16 micromol [NO(3)(-)] min(-1) mg(-1) with an affinity for nitrate of K(m)=0.24+/-0.05 mM and was heat-stable up to 50 degrees C. In contrast, the periplasmic fraction obtained from cells cultured in media supplemented with tungstate (100 microM) reduced nitrate at a much slower rate, with much lower affinity (V(max)=0.05+/-0.002 micromol [NO(3)(-)] min(-1) mg(-1) and K(m)=3.91+/-0.45 mM) and was labile during prolonged incubation at >20 degrees C. Nitrate-dependent growth of Escherichia coli strains expressing only nitrate reductase A was inhibited by sub-mM concentrations of tungstate in the medium. In contrast, a strain expressing only NAP was only partially inhibited by 10 mM tungstate. However, none of the above experimental approaches revealed evidence that tungsten could replace molybdenum at the active site of E. coli NapA. The combined data show that tungsten can function at the active site of some, but not all, molybdoenzymes from mesophilic bacteria.
Collapse
Affiliation(s)
- Andrew J Gates
- School of Cell and Molecular Biosciences, The Medical School, University of Newcastle, Newcastle upon Tyne NE2 4HH, UK
| | | | | | | | | | | | | | | | | | | |
Collapse
|
34
|
Phillpotts RJ, Lescott T, Gates AJ, Jones L. The immune response to vaccinia virus is significantly reduced after scarification with TK- recombinants as compared to wild-type virus. Acta Virol 2000; 44:151-6. [PMID: 11155357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
Although it is unlikely that large-scale vaccination against smallpox will ever be required again, it is conceivable that the need may arise to vaccinate against a human orthopoxvirus infection. A possible example could be the emergence of monkey poxvirus (MPV) as a significant human disease in Africa. Vaccinia virus (VV) recombinants, genetically modified to carry the immunogenic proteins of other pathogenic organisms, have potential use as vaccines against other diseases present in this region. The immune response to parental wild-type (wt) or recombinant VV was examined by binding and functional assays, relevant to protection: total IgG, IgG subclass profile, B5R gene product (gp42)-specific IgG, neutralizing antibodies and class 1-mediated cytotoxic lymphocyte activity. There was a substantial reduction in the immune response to VV after scarification with about 10(8) PFU of recombinant as compared to wt virus. These data suggest that to achieve the levels of immunity associated with protection against human orthopoxvirus infection, and to control a possible future outbreak of orthopoxvirus disease, the use of wt VV would be necessary.
Collapse
Affiliation(s)
- R J Phillpotts
- DERA, Biological Sciences Department, Chemical and Biological Defense Sector, Porton Down, Wiltshire, SP4 0JQ, U.K.
| | | | | | | |
Collapse
|
35
|
Craver RD, Golladay SE, Warrier RP, Gates AJ, Nelson JS. Neurocutaneous melanosis with Dandy-Walker malformation complicated by primary spinal leptomeningeal melanoma. J Child Neurol 1996; 11:410-4. [PMID: 8877612 DOI: 10.1177/088307389601100515] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- R D Craver
- Louisiana State University Medical Center, New Orleans Children's Hospital, USA
| | | | | | | | | |
Collapse
|
36
|
Clarke JR, Gates AJ, Coker RJ, Douglass JA, Williamson JD, Mitchell DM. HIV-1 proviral DNA copy number in peripheral blood leucocytes and bronchoalveolar lavage cells of AIDS patients. Clin Exp Immunol 1994; 96:182-6. [PMID: 8187325 PMCID: PMC1534888 DOI: 10.1111/j.1365-2249.1994.tb06539.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
In this study we have determined by polymerase chain reaction (PCR) the quantity of HIV-1 proviral DNA in cells obtained by bronchoalveolar lavage (BAL) from the lung of HIV-1+ individuals. This has been compared quantitatively with the proviral DNA in peripheral blood leucocytes (PBL) obtained simultaneously from the same patients. The mean HIV DNA copy number per 10(6) cells was 391 for PBL, with a range of 1-9000, and 2971 for BAL cells, with a range of < 1-70,000. The quantity of HIV DNA detected in BAL cells was higher than that detected in the corresponding PBL samples in 44 out of 78 (56%) individuals, whilst more HIV DNA was detected in the PBL compared with BAL cells in 14 out of 78 (18%) patients. In both BAL and PBL higher levels of HIV DNA were detected in the adherent (monocyte/macrophage) enriched cell populations compared with other non-adherent cells (leucocytes). A direct relationship between HIV DNA copy number and ability to recover infectious HIV progeny in vitro by co-cultivation with cord blood leucocytes was found for both PBL and BAL cells. Individuals known to be receiving azidothymidine treatment had a lower mean HIV DNA load in all cell fractions compared with those patients on no antiretroviral therapy.
Collapse
Affiliation(s)
- J R Clarke
- Department of Medical Microbiology, St Mary's Hospital Medical School, London, UK
| | | | | | | | | | | |
Collapse
|
37
|
Abstract
An interdisciplinary review of 16 ventilator-assisted, cervical-cord injured youth, aged 3-19 years, was completed to explore long-term outcomes and develop recommendations for care. Ten youths were younger than 12 years; 6 were adolescents. The mean initial hospital length of stay was 192 days. Discharged youths were followed for 1-73 months after hospitalization. Nursing implications were developed using a systems approach with North American Nursing Diagnosis Association (NANDA) approved diagnoses. Nursing case management was used to coordinate discharge planning and continuity of care. At the time of data collection 13 youths had been successfully reintegrated to home, school and community, the least restrictive environments for all.
Collapse
Affiliation(s)
- M D Miller
- Children's Hospital, New Orleans, Louisiana 70118
| | | | | | | | | |
Collapse
|
38
|
Kirkhart KA, Steele NF, Pomeroy M, Anguzza R, French W, Gates AJ. Louisiana's ventilator assisted care program: case management services to link tertiary with community-based care. Child Health Care 1989; 17:106-11. [PMID: 10290556 DOI: 10.1207/s15326888chc1702_8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
The Ventilator Assisted Care Program has provided case management services to 36 youths and their families throughout Louisiana. It has served to link tertiary care centers with community-based service systems for the comprehensive care management of children and adolescents who use ventilators. The hospital-based, state-licensed service has been funded by Louisiana's Medicaid and Handicapped Children's Services Programs on a fee for service basis. It was originally funded by a grant from the Bureau of Maternal and Child Health. The service planning, coordination, and monitoring activities for individual families have usually begun predischarge and have been continued throughout the home care experience. The child and family have been considered to be the center of the care matrix, actively directing the service systems as well as service development.
Collapse
|
39
|
Abstract
Four patients with Down's syndrome suffered compression of the spinal cord secondary to atlantoaxial dislocation. All four developed inability to walk and quadriparesis, with signs of cervical myelopathy. It is important to recognize this potentially fatal complication of the syndrome. Immediate immobilization of the neck, followed by cervical roentgenograms, should be done in any patient with Down's syndrome who presents with neck pain, torticollis, urinary incontinence, or loss of ambulation. Surgical repair with fusion of the first and second cervical vertebrae can be carried out later.
Collapse
|
40
|
Lemen RJ, Gates AJ, Mathé AA, Waring WW, Hyman AL, Kadowitz PD. Relationships among digital clubbing, disease severity, and serum prostaglandins F2alpha and E concentrations in cystic fibrosis patients. Am Rev Respir Dis 1978; 117:639-46. [PMID: 646216 DOI: 10.1164/arrd.1978.117.4.639] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Nine patients with cystic fibrosis but without digital clubbing (Group A) were matched, prospectively, by sex and approximate age to 9 cystic fibrosis patients with digital clubbing (Group B) and to 9 normal persons (control subjects). Patients in Group B had significantly (P less than 0.05) lower clinical scores and forced vital capacity than did those in Group A, indicating more severe pulmonary disease in the former; however, other spirometer tests of pulmonary function revealed no differences between Groups A and B. The degree of digital clubbing had significant (P less than 0.05) linear relationships to forced vital capacity (r = -0.73) and clinical scores (r = 0.853) for Groups A and B. Plasma concentrations of prostaglandins F2alpha and E were significantly increased (P less than 0.05) in both Group A (X +/- SE, 0.48 +/- 0.03 and 0.87 +/- 0.10 ng per ml, respectively) and Group B (X +/- SE, 0.68 +/- 0.04 and 1.81 +/- 0.16 ng per ml, respectively) compared to the control group (X +/- SE, 0.14 +/- 0.01 and 0.39 +/- 0.02 ng per ml, respectively). Group B had significantly larger concentrations than did Group A; however, plasma concentrations of prostaglandin 15-keto-13, 14-dihydro metabolite were not different in Groups A and B, and were significantly smaller than in the control group. These studies suggest that the degree of digital clubbing in cystic fibrosis is related to the severity of the pulmonary involvement and that the prostaglandin system may play an important role in this disease.
Collapse
|