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Giri DD, Dwivedi H, Khalaf D Alsukaibi A, Pal DB, Otaibi AA, Areeshi MY, Haque S, Gupta VK. Sustainable production of algae-bacteria granular consortia based biological hydrogen: New insights. BIORESOURCE TECHNOLOGY 2022; 352:127036. [PMID: 35331885 DOI: 10.1016/j.biortech.2022.127036] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2022] [Revised: 03/15/2022] [Accepted: 03/17/2022] [Indexed: 06/14/2023]
Abstract
Microbes recycling nutrient and detoxifying ecosystems are capable to fulfil the future energy need by producing biohydrogen by due to the coupling of autotrophic and heterotrophic microbes. In granules microbes mutualy exchanging nutrients and electrons for hydrogen production. The consortial biohydrogen production depend upon constituent microbes, their interdependence, competition for resources, and other operating parameters while remediating a waste material in nature or bioreactor. The present review deals with development of granular algae-bacteria consortia, hydrogen yield in coculture, important enzymes and possible engineering for improved hydrogen production.
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Affiliation(s)
- Deen Dayal Giri
- Department of Botany, Maharaj Singh College, Saharanpur-247001,Uttar Pradesh, India
| | - Himanshu Dwivedi
- Department of Botany, Maharaj Singh College, Saharanpur-247001,Uttar Pradesh, India
| | | | - Dan Bahadur Pal
- Department of Chemical Engineering, Birla Institute of Technology, Mesra, Ranchi-835215, Jharkhand, India
| | - Ahmed Al Otaibi
- Department of Chemistry, College of Sciences, University of Ha'il, Ha'il 2440, Saudi Arabia
| | - Mohammed Y Areeshi
- Research and Scientific Studies Unit, College of Nursing, Jazan University, Jazan 45142, Saudi Arabia; Medical Laboratory Technology Department, College of Applied Medical Sciences, Jazan University, Jazan 45142, Saudi Arabia
| | - Shafiul Haque
- Research and Scientific Studies Unit, College of Nursing, Jazan University, Jazan 45142, Saudi Arabia; Bursa Uludağ University Faculty of Medicine,Görükle Campus, 16059, Nilüfer, Bursa, Turkey
| | - Vijai Kumar Gupta
- Center for Safe and Improved Food, SRUC, Kings Buildings, West Mains Road, Edinburgh, EH9 3JG, UK; Biorefining and Advanced Materials Research Center, SRUC, Kings Buildings, West Mains Road, Edinburgh, EH9 3JG, UK.
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Kojima K, Matsumoto U, Keta S, Nakahigashi K, Ikeda K, Takatani N, Omata T, Aichi M. High-Light-Induced Stress Activates Lipid Deacylation at the Sn-2 Position in the Cyanobacterium Synechocystis Sp. PCC 6803. PLANT & CELL PHYSIOLOGY 2022; 63:82-91. [PMID: 34623441 PMCID: PMC8789269 DOI: 10.1093/pcp/pcab147] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Revised: 10/06/2021] [Accepted: 10/08/2021] [Indexed: 06/01/2023]
Abstract
Cyanobacterial mutants defective in acyl-acyl carrier protein synthetase (Aas) produce free fatty acids (FFAs) because the FFAs generated by deacylation of membrane lipids cannot be recycled. An engineered Aas-deficient mutant of Synechocystis sp. PCC 6803 grew normally under low-light (LL) conditions (50 µmol photons m-2 s-1) but was unable to sustain growth under high-light (HL) conditions (400 µmol photons m-2 s-1), revealing a crucial role of Aas in survival under the HL conditions. Several-times larger amounts of FFAs were produced by HL-exposed cultures than LL-grown cultures. Palmitic acid accounted for ∼85% of total FFAs in HL-exposed cultures, while C18 fatty acids (FAs) constituted ∼80% of the FFAs in LL-grown cultures. Since C16 FAs are esterified to the sn-2 position of lipids in the Synechocystis species, it was deduced that HL irradiation activated deacylation of lipids at the sn-2 position. Heterologous expression of FarB, the FFA exporter protein of Neisseria lactamica, prevented intracellular FFA accumulation and rescued the growth defect of the mutant under HL, indicating that intracellular FFA was the cause of growth inhibition. FarB expression also decreased the 'per-cell' yield of FFA under HL by 90% and decreased the proportion of palmitic acid to ∼15% of total FFA. These results indicated that the HL-induced lipid deacylation is triggered not by strong light per se but by HL-induced damage to the cells. It was deduced that there is a positive feedback loop between HL-induced damage and lipid deacylation, which is lethal unless FFA accumulation is prevented by Aas.
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Affiliation(s)
| | - Ui Matsumoto
- Department of Biological Chemistry, Chubu University, 1200 Matsumoto-cho, Kasugai, 487-8501 Japan
- Japan Science and Technology Agency, CREST, 4-1-8 Honmachi, Kwaguchi, Saitama 332-0012, Japan
| | - Sumie Keta
- Department of Biological Chemistry, Chubu University, 1200 Matsumoto-cho, Kasugai, 487-8501 Japan
- Japan Science and Technology Agency, CREST, 4-1-8 Honmachi, Kwaguchi, Saitama 332-0012, Japan
| | | | | | - Nobuyuki Takatani
- Japan Science and Technology Agency, CREST, 4-1-8 Honmachi, Kwaguchi, Saitama 332-0012, Japan
- Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601 Japan
| | - Tatsuo Omata
- Japan Science and Technology Agency, CREST, 4-1-8 Honmachi, Kwaguchi, Saitama 332-0012, Japan
- Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601 Japan
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Chu LL, Bae H. Bacterial endophytes from ginseng and their biotechnological application. J Ginseng Res 2022; 46:1-10. [PMID: 35035239 PMCID: PMC8753428 DOI: 10.1016/j.jgr.2021.04.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 03/30/2021] [Accepted: 04/09/2021] [Indexed: 12/19/2022] Open
Abstract
Ginseng has been well-known as a medicinal plant for thousands of years. Bacterial endophytes ubiquitously colonize the inside tissues of ginseng without any disease symptoms. The identification of bacterial endophytes is conducted through either the internal transcribed spacer region combined with ribosomal sequences or metagenomics. Bacterial endophyte communities differ in their diversity and composition profile, depending on the geographical location, cultivation condition, and tissue, age, and species of ginseng. Bacterial endophytes have a significant effect on the growth of ginseng through indole-3-acetic acid (IAA) and siderophore production, phosphate solubilization, and nitrogen fixation. Moreover, bacterial endophytes can protect ginseng by acting as biocontrol agents. Interestingly, bacterial endophytes isolated from Panax species have the potential to produce ginsenosides and bioactive metabolites, which can be used in the production of food and medicine. The ability of bacterial endophytes to transform major ginsenosides into minor ginsenosides using β-glucosidase is gaining increasing attention as a promising biotechnology. Recently, metabolic engineering has accelerated the possibilities for potential applications of bacterial endophytes in producing beneficial secondary metabolites.
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Affiliation(s)
- Luan Luong Chu
- Faculty of Biotechnology, Chemistry and Environmental Engineering, Phenikaa University, Hanoi, Viet Nam
- Bioresource Research Center, Phenikaa University, Hanoi, Viet Nam
| | - Hanhong Bae
- Department of Biotechnology, Yeungnam University, Gyeongsan, Republic of Korea
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Maeda SI, Aoba R, Nishino Y, Omata T. A Novel Bacterial Nitrate Transporter Composed of Small Transmembrane Proteins. PLANT & CELL PHYSIOLOGY 2019; 60:2180-2192. [PMID: 31198965 DOI: 10.1093/pcp/pcz112] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2018] [Accepted: 05/27/2019] [Indexed: 06/09/2023]
Abstract
A putative silent gene of the freshwater cyanobacterium Synechococcus elongatus strain PCC 7942, encoding a small protein with two transmembrane helices, was named nrtS, since its overexpression from an inducible promoter conferred nitrate uptake activity on the nitrate transport-less NA4 mutant of S. elongatus. Homologs of nrtS, encoding proteins of 67-118 amino acid residues, are present in a limited number of eubacteria including mostly cyanobacteria and proteobacteria, but some others, e.g. the actinobacteria of the Mycobacterium tuberculosis complex, also have the gene. When expressed in NA4, the nrtS homolog of the γ-proteobacterium Marinomonas mediterranea took up nitrate with higher affinity for the substrate as compared with the S. elongatus NrtS (Km of 0.49 mM vs. 2.5 mM). Among the 61 bacterial species carrying the nrtS homolog, the marine cyanobacterium Synechococcus sp. strain PCC 7002 is unique in having two nrtS genes (nrtS1 and nrtS2) located in tandem on the chromosome. Coexpression of the two genes in NA4 resulted in nitrate uptake with a Km (NO3-) of 0.15 mM, while expression of either of the two resulted in low-affinity nitrate uptake activity with Km values of >3 mM, indicating that NrtS1 and NrtS2 form a heteromeric transporter complex. The heteromeric transporter was shown to transport nitrite as well. A Synechococcus sp. strain PCC 7002 mutant defective in the nitrate transporter (NrtP) showed a residual activity of nitrate uptake, which was ascribed to the NrtS proteins. Blue-native PAGE and immunoblotting analysis suggested a hexameric structure for the NrtS proteins.
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Affiliation(s)
- Shin-Ichi Maeda
- Laboratory of Photosynthesis Research, Department of Applied Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 Japan
| | - Risa Aoba
- Laboratory of Photosynthesis Research, Department of Applied Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 Japan
| | - Yuma Nishino
- Laboratory of Photosynthesis Research, Department of Applied Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 Japan
| | - Tatsuo Omata
- Laboratory of Photosynthesis Research, Department of Applied Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 Japan
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Esteves-Ferreira AA, Inaba M, Fort A, Araújo WL, Sulpice R. Nitrogen metabolism in cyanobacteria: metabolic and molecular control, growth consequences and biotechnological applications. Crit Rev Microbiol 2018. [DOI: 10.1080/1040841x.2018.1446902] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Affiliation(s)
- Alberto A. Esteves-Ferreira
- National University of Ireland – Galway, Plant Systems Biology Lab, School of Natural Sciences, Plant and AgriBiosciences Research Centre, Galway, Ireland
- CAPES Foundation, Ministry of Education of Brazil, Brasilia, Brazil
| | - Masami Inaba
- National University of Ireland – Galway, Plant Systems Biology Lab, School of Natural Sciences, Plant and AgriBiosciences Research Centre, Galway, Ireland
| | - Antoine Fort
- National University of Ireland – Galway, Plant Systems Biology Lab, School of Natural Sciences, Plant and AgriBiosciences Research Centre, Galway, Ireland
| | - Wagner L. Araújo
- Max-Planck Partner Group at the Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, Brazil
| | - Ronan Sulpice
- National University of Ireland – Galway, Plant Systems Biology Lab, School of Natural Sciences, Plant and AgriBiosciences Research Centre, Galway, Ireland
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Esteves-Ferreira AA, Cavalcanti JHF, Vaz MGMV, Alvarenga LV, Nunes-Nesi A, Araújo WL. Cyanobacterial nitrogenases: phylogenetic diversity, regulation and functional predictions. Genet Mol Biol 2017; 40:261-275. [PMID: 28323299 PMCID: PMC5452144 DOI: 10.1590/1678-4685-gmb-2016-0050] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 12/21/2016] [Indexed: 12/21/2022] Open
Abstract
Cyanobacteria is a remarkable group of prokaryotic photosynthetic microorganisms, with several genera capable of fixing atmospheric nitrogen (N2) and presenting a wide range of morphologies. Although the nitrogenase complex is not present in all cyanobacterial taxa, it is spread across several cyanobacterial strains. The nitrogenase complex has also a high theoretical potential for biofuel production, since H2 is a by-product produced during N2 fixation. In this review we discuss the significance of a relatively wide variety of cell morphologies and metabolic strategies that allow spatial and temporal separation of N2 fixation from photosynthesis in cyanobacteria. Phylogenetic reconstructions based on 16S rRNA and nifD gene sequences shed light on the evolutionary history of the two genes. Our results demonstrated that (i) sequences of genes involved in nitrogen fixation (nifD) from several morphologically distinct strains of cyanobacteria are grouped in similarity with their morphology classification and phylogeny, and (ii) nifD genes from heterocytous strains share a common ancestor. By using this data we also discuss the evolutionary importance of processes such as horizontal gene transfer and genetic duplication for nitrogenase evolution and diversification. Finally, we discuss the importance of H2 synthesis in cyanobacteria, as well as strategies and challenges to improve cyanobacterial H2 production.
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Affiliation(s)
- Alberto A Esteves-Ferreira
- Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, Brazil.,Max-Planck-partner group at the Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, Brazil
| | - João Henrique Frota Cavalcanti
- Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, Brazil.,Max-Planck-partner group at the Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, Brazil
| | - Marcelo Gomes Marçal Vieira Vaz
- Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, Brazil.,Max-Planck-partner group at the Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, Brazil
| | - Luna V Alvarenga
- Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, Brazil.,Max-Planck-partner group at the Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, Brazil
| | - Adriano Nunes-Nesi
- Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, Brazil.,Max-Planck-partner group at the Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, Brazil
| | - Wagner L Araújo
- Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, Brazil.,Max-Planck-partner group at the Departamento de Biologia Vegetal, Universidade Federal de Viçosa, Viçosa, MG, Brazil
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One day of nitrogen starvation reveals the effect of sigE and rre37 overexpression on the expression of genes related to carbon and nitrogen metabolism in Synechocystis sp. PCC 6803. J Biosci Bioeng 2015; 120:128-34. [DOI: 10.1016/j.jbiosc.2014.12.020] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Revised: 12/19/2014] [Accepted: 12/20/2014] [Indexed: 01/08/2023]
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Induction of the Nitrate Assimilation nirA Operon and Protein-Protein Interactions in the Maturation of Nitrate and Nitrite Reductases in the Cyanobacterium Anabaena sp. Strain PCC 7120. J Bacteriol 2015; 197:2442-52. [PMID: 25962912 DOI: 10.1128/jb.00198-15] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 05/05/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Nitrate is widely used as a nitrogen source by cyanobacteria, in which the nitrate assimilation structural genes frequently constitute the so-called nirA operon. This operon contains the genes encoding nitrite reductase (nirA), a nitrate/nitrite transporter (frequently an ABC-type transporter; nrtABCD), and nitrate reductase (narB). In the model filamentous cyanobacterium Anabaena sp. strain PCC 7120, which can fix N2 in specialized cells termed heterocysts, the nirA operon is expressed at high levels only in media containing nitrate or nitrite and lacking ammonium, a preferred nitrogen source. Here we examined the genes downstream of the nirA operon in Anabaena and found that a small open reading frame of unknown function, alr0613, can be cotranscribed with the operon. The next gene in the genome, alr0614 (narM), showed an expression pattern similar to that of the nirA operon, implying correlated expression of narM and the operon. A mutant of narM with an insertion mutation failed to produce nitrate reductase activity, consistent with the idea that NarM is required for the maturation of NarB. Both narM and narB mutants were impaired in the nitrate-dependent induction of the nirA operon, suggesting that nitrite is an inducer of the operon in Anabaena. It has previously been shown that the nitrite reductase protein NirA requires NirB, a protein likely involved in protein-protein interactions, to attain maximum activity. Bacterial two-hybrid analysis confirmed possible NirA-NirB and NarB-NarM interactions, suggesting that the development of both nitrite reductase and nitrate reductase activities in cyanobacteria involves physical interaction of the corresponding enzymes with their cognate partners, NirB and NarM, respectively. IMPORTANCE Nitrate is an important source of nitrogen for many microorganisms that is utilized through the nitrate assimilation system, which includes nitrate/nitrite membrane transporters and the nitrate and nitrite reductases. Many cyanobacteria assimilate nitrate, but regulation of the nitrate assimilation system varies in different cyanobacterial groups. In the N2-fixing, heterocyst-forming cyanobacteria, the nirA operon, which includes the structural genes for the nitrate assimilation system, is expressed in the presence of nitrate or nitrite if ammonium is not available to the cells. Here we studied the genes required for production of an active nitrate reductase, providing information on the nitrate-dependent induction of the operon, and found evidence for possible protein-protein interactions in the maturation of nitrate reductase and nitrite reductase.
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Maeda SI, Murakami A, Ito H, Tanaka A, Omata T. Functional Characterization of the FNT Family Nitrite Transporter of Marine Picocyanobacteria. Life (Basel) 2015; 5:432-46. [PMID: 25809962 PMCID: PMC4390861 DOI: 10.3390/life5010432] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 01/29/2015] [Indexed: 11/16/2022] Open
Abstract
Many of the cyanobacterial species found in marine and saline environments have a gene encoding a putative nitrite transporter of the formate/nitrite transporter (FNT) family. The presumed function of the gene (designated nitM) was confirmed by functional expression of the gene from the coastal marine species Synechococcus sp. strain PCC7002 in the nitrite-transport-less mutant (NA4) of the freshwater cyanobacterium Synechococcus elongatus strain PCC7942. The NitM-mediated nitrite uptake showed an apparent Km (NO2-) of about 8 μM and was not inhibited by nitrate, cyanate or formate. Of the nitM orthologs from the three oceanic cyanobacterial species, which are classified as α-cyanobacteria on the basis of the occurrence of Type 1a RuBisCO, the one from Synechococcus sp. strain CC9605 conferred nitrite uptake activity on NA4, but those from Synechococcus sp. strain CC9311 and Prochlorococcus marinus strain MIT9313 did not. A strongly conserved hydrophilic amino acid sequence was found at the C-termini of the deduced NitM sequences from α-cyanobacteria, with a notable exception of the Synechococcus sp. strain CC9605 NitM protein, which entirely lacked the C-terminal amino acids. The C-terminal sequence was not conserved in the NitM proteins from β-cyanobacteria carrying the Type 1b RuBisCO, including the one from Synechococcus sp. strain PCC7002. Expression of the truncated nitM genes from Synechococcus sp. strain CC9311 and Prochlorococcus marinus strain MIT9313, encoding the proteins lacking the conserved C-terminal region, conferred nitrite uptake activity on the NA4 mutant, indicating that the C-terminal region of α-cyanobacterial NitM proteins inhibits the activity of the transporter.
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Affiliation(s)
- Shin-Ichi Maeda
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
- CREST, Japan Science and Technology Agency, Chiyoda-ku, Tokyo 102-0076 Japan.
| | - Akio Murakami
- CREST, Japan Science and Technology Agency, Chiyoda-ku, Tokyo 102-0076 Japan.
- Research Center for Inland Seas, Kobe University, Awaji, Hyogo 656-2401, Japan.
| | - Hisashi Ito
- CREST, Japan Science and Technology Agency, Chiyoda-ku, Tokyo 102-0076 Japan.
- Institute of Low Temperature Science, Hokkaido University, Kita-ku, Sapporo 060-0819, Japan.
| | - Ayumi Tanaka
- CREST, Japan Science and Technology Agency, Chiyoda-ku, Tokyo 102-0076 Japan.
- Institute of Low Temperature Science, Hokkaido University, Kita-ku, Sapporo 060-0819, Japan.
| | - Tatsuo Omata
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
- CREST, Japan Science and Technology Agency, Chiyoda-ku, Tokyo 102-0076 Japan.
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Maeda SI, Konishi M, Yanagisawa S, Omata T. Nitrite transport activity of a novel HPP family protein conserved in cyanobacteria and chloroplasts. PLANT & CELL PHYSIOLOGY 2014; 55:1311-24. [PMID: 24904028 DOI: 10.1093/pcp/pcu075] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Some cyanobacterial genomes encode an integral membrane protein of the HPP family, which exhibited nitrite transport activity when expressed in the nitrite transport-less NA4 mutant of the cyanobacterium Synechococcus elongatus strain PCC 7942. AT5G62720 and AT3G47980 were found to encode Arabidopsis homologs of the cyanobacterial protein. The product of AT5G62720 was localized to the chloroplast envelope membrane and was shown to confer nitrite uptake activity on the NA4 mutant when expressed with an N-terminally truncated transit peptide or as a fusion with the N-terminal region of the cyanobacterial HPP family protein. Kinetic analyses showed that the Arabidopsis protein has much higher affinity for nitrite (K(m) = 13 µM) than the cyanobacterial protein (K(m) = 150 µM). Illuminated chloroplasts isolated from the mutant lines of AT5G62720 showed much lower activity of nitrite uptake than the chloroplasts isolated from the wild-type Col-0 plants, while the chloroplasts of the mutants of AT1G68570 (AtNPF3.1), the gene previously reported to encode a plastid nitrite transporter AtNitr1, showed wild-type levels of nitrite uptake activity. AT3G47980 was expressed in roots but not in shoots. It has a putative transit peptide similar to that of AT5G62720 and its fusion with the N-terminal region of the cyanobacterial HPP protein showed low but significant activity of nitrite transport in the cyanobacterial cell. Transcription of AT5G62720 (AtNITR2;1) and AT3G47980 (AtNITR2;2) was stimulated by nitrate under the control of the NIN-like proteins, suggesting that the HPP proteins represent nitrate-inducible components of the nitrite transport system of plastids.
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Affiliation(s)
- Shin-ichi Maeda
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 JapanJapan Science and Technology, Agency, CREST
| | - Mineko Konishi
- Biotechnology Research Center, The University of Tokyo, Tokyo, 113-8657 Japan
| | - Shuichi Yanagisawa
- Biotechnology Research Center, The University of Tokyo, Tokyo, 113-8657 Japan
| | - Tatsuo Omata
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 JapanJapan Science and Technology, Agency, CREST
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Chang Y, Takatani N, Aichi M, Maeda SI, Omata T. Evaluation of the Effects of PII Deficiency and the Toxicity of PipX on Growth Characteristics of the PII-Less Mutant of the Cyanobacterium Synechococcus elongatus. ACTA ACUST UNITED AC 2013; 54:1504-14. [DOI: 10.1093/pcp/pct092] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Global transcription profiles of the nitrogen stress response resulting in heterocyst or hormogonium development in Nostoc punctiforme. J Bacteriol 2011; 193:6874-86. [PMID: 22001509 DOI: 10.1128/jb.05999-11] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The filamentous cyanobacterium Nostoc punctiforme differentiates from vegetative cells into three distinct cell types, heterocysts, hormogonia, and akinetes, in response to different stimuli. Cultures growing with ammonium can be induced to form hormogonia or heterocysts upon removal of the combined nitrogen. A DNA microarray consisting of 94% of the open reading frames predicted from the 9.059-Mb N. punctiforme genome was used to generate a global transcription data set consisting of seven time points over a 24-h period of nitrogen deprivation, which results in heterocyst formation. This data set was compared to a similarly generated data set of nitrogen-starved N. punctiforme resulting in hormogonium formation that had previously been published (E. L. Campbell, H. Christman, and J. C. Meeks, J. Bacteriol. 190:7382-7391, 2008). The transition from vegetative cells to either heterocysts or hormogonia resulted in rapid and sustained expression of genes required for utilization of alternate nitrogen sources. Overall, 1,036 and 1,762 genes were found to be differentially transcribed during the heterocyst and hormogonium time courses, respectively, as analyzed with the Bayesian user-friendly software for analyzing time series microarray experiments (BATS). Successive transcription of heterocyst regulatory, structural, and functional genes occurred over the 24 h required to form a functional heterocyst. During hormogonium differentiation, some heterocyst structural and functional genes were upregulated, while the heterocyst master regulator hetR was downregulated. There are commonalities in differential expression between cells bound for differentiation into heterocysts or hormogonia, yet the two paths are distinguished by their developmentally specific transcription profiles.
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Hfq is required for optimal nitrate assimilation in the Cyanobacterium Anabaena sp. strain PCC 7120. J Bacteriol 2011; 193:3546-55. [PMID: 21602329 DOI: 10.1128/jb.00254-11] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Hfq is an RNA binding protein involved in posttranscriptional regulation of gene expression in bacteria. It acts by binding to regulatory small RNAs (sRNAs), which confer specificity for the regulation. Recently, orthologues of the Hfq protein were annotated in cyanobacterial genomes, although its capacity to regulate gene expression by interacting with sRNAs has not been yet demonstrated. Anabaena sp. strain PCC 7120 is a filamentous cyanobacterium that, in the absence of combined nitrogen, is able to fix atmospheric nitrogen by differentiating specialized cells called heterocysts. We have generated an hfq knockout mutant of Anabaena sp. PCC 7120. Deletion of this gene results in differentiation of heterocysts in the presence of nitrate, suggesting a defect in nitrate assimilation. We show that hfq mutant cells are affected in transport and use of nitrate and nitrite. An analysis of the expression of several genes in the nir operon, encoding different elements of the nitrate assimilation pathway, demonstrates a downregulation of their transcription in mutant cells. We also observed that genes ntcB and cnaT, involved in the regulation of the nir operon, show a lower expression in cells lacking Hfq. Finally, when hfq was reintroduced in the mutant, heterocyst differentiation was no longer observed in the presence of nitrate. Therefore, our results indicate that the RNA chaperone Hfq is involved in the regulation of the nir operon, although the mechanism for this regulation is still unknown.
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Ohashi Y, Shi W, Takatani N, Aichi M, Maeda SI, Watanabe S, Yoshikawa H, Omata T. Regulation of nitrate assimilation in cyanobacteria. JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:1411-1424. [PMID: 21282331 DOI: 10.1093/jxb/erq427] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Nitrate assimilation by cyanobacteria is inhibited by the presence of ammonium in the growth medium. Both nitrate uptake and transcription of the nitrate assimilatory genes are regulated. The major intracellular signal for the regulation is, however, not ammonium or glutamine, but 2-oxoglutarate (2-OG), whose concentration changes according to the change in cellular C/N balance. When nitrogen is limiting growth, accumulation of 2-OG activates the transcription factor NtcA to induce transcription of the nitrate assimilation genes. Ammonium inhibits transcription by quickly depleting the 2-OG pool through its metabolism via the glutamine synthetase/glutamate synthase cycle. The P(II) protein inhibits the ABC-type nitrate transporter, and also nitrate reductase in some strains, by an unknown mechanism(s) when the cellular 2-OG level is low. Upon nitrogen limitation, 2-OG binds to P(II) to prevent the protein from inhibiting nitrate assimilation. A pathway-specific transcriptional regulator NtcB activates the nitrate assimilation genes in response to nitrite, either added to the medium or generated intracellularly by nitrate reduction. It plays an important role in selective activation of the nitrate assimilation pathway during growth under a limited supply of nitrate. P(II) was recently shown to regulate the activity of NtcA negatively by binding to PipX, a small coactivator protein of NtcA. On the basis of accumulating genome information from a variety of cyanobacteria and the molecular genetic data obtained from the representative strains, common features and group- or species-specific characteristics of the response of cyanobacteria to nitrogen is summarized and discussed in terms of ecophysiological significance.
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Affiliation(s)
- Yoshitake Ohashi
- Graduate School of Bioagricultural Sciences, Nagoya University, Furo, Chikusa, Nagoya 464-8601, Japan
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Kuritz T. Cyanobacteria as agents for the control of pollution by pesticides and chlorinated organic compounds. J Appl Microbiol 2010; 85 Suppl 1:186S-192S. [DOI: 10.1111/j.1365-2672.1998.tb05298.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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16
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Negative regulation of expression of the nitrate assimilation nirA operon in the heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120. J Bacteriol 2010; 192:2769-78. [PMID: 20348260 DOI: 10.1128/jb.01668-09] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In the filamentous, heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120, expression of the nitrate assimilation nirA operon takes place in the absence of ammonium and the presence of nitrate or nitrite. Several positive-action proteins that are required for expression of the nirA operon have been identified. Whereas NtcA and NtcB exert their action by direct binding to the nirA operon promoter, CnaT acts by an as yet unknown mechanism. In the genome of this cyanobacterium, open reading frame (ORF) all0605 (the nirB gene) is found between the nirA (encoding nitrite reductase) and ntcB genes. A nirB mutant was able to grow at the expense of nitrate as a nitrogen source and showed abnormally high levels of nirA operon mRNA both in the presence and in the absence of nitrate. This mutant showed increased nitrate reductase activity but decreased nitrite reductase activity, an imbalance that resulted in excretion of nitrite, which accumulated in the extracellular medium, when the nirB mutant was grown in the presence of nitrate. A nirA in-frame deletion mutant also showed a phenotype of increased expression of the nirA operon in the absence of ammonium, independent of the presence of nitrate in the medium. Both NirB and NirA are therefore needed to keep low levels of expression of the nirA operon in the absence of an inducer. Because NirB is also needed to attain high levels of nitrite reductase activity, NirA appears to be a negative element in the nitrate regulation of expression of the nirA operon in Anabaena sp. strain PCC 7120.
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Wyman M, Bird C. Lack of control of nitrite assimilation by ammonium in an oceanic picocyanobacterium, Synechococcus sp. strain WH 8103. Appl Environ Microbiol 2007; 73:3028-33. [PMID: 17337543 PMCID: PMC1892888 DOI: 10.1128/aem.02606-06] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In cyanobacteria, the transcriptional activator NtcA is involved in global nitrogen control and, in the absence of ammonium, regulates the expression of genes involved in the assimilation of alternative nitrogen sources. The oceanic picocyanobacterium Synechococcus sp. strain WH 8103 harbors a copy of ntcA, but in the present study, we show that unlike other marine cyanobacteria that have been investigated, this strain is capable of coassimilating nitrite when grown in the presence of ammonium. Transcript levels for the genes encoding the nitrate/nitrite-bispecific permease NrtP and nitrate reductase (NarB) were substantially down-regulated by ammonium, whereas the abundances of nitrite reductase (NirA) transcripts were similar in nitrite- and ammonium-grown cells. The growth of Synechococcus sp. strain WH 8103 in medium containing both ammonium and nitrite resulted in only minor changes in the expression profile in comparison to that of nitrite-grown cells with the exception that the gene encoding the high-affinity ammonium transporter Amt1 was down-regulated to the levels seen in ammonium-grown cells. Whereas the expression of nrtP, narB, and amt1 appears to be NtcA dependent in this marine cyanobacterium, the transcription and expression of nirA appear not to be. The ability to coassimilate nitrite and reduced-nitrogen sources like ammonium may be an adaptive trait that enables oceanic strains like Synechococcus sp. strain WH 8103 to exploit the low nitrite concentrations found in oceanic surface waters that are not available to their principal and more numerous competitor, Prochlorococcus.
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Affiliation(s)
- Michael Wyman
- School of Biological and Environmental Sciences, University of Stirling, Stirling FK9 4LA, United Kingdom.
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Osanai T, Imamura S, Asayama M, Shirai M, Suzuki I, Murata N, Tanaka K. Nitrogen Induction of Sugar Catabolic Gene Expression in Synechocystis sp. PCC 6803. DNA Res 2006; 13:185-95. [PMID: 17046957 DOI: 10.1093/dnares/dsl010] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Nitrogen starvation requires cells to change their transcriptome in order to cope with this essential nutrient limitation. Here, using microarray analysis, we investigated changes in transcript profiles following nitrogen depletion in the unicellular cyanobacterium Synechocystis sp. PCC 6803. Results revealed that genes for sugar catabolic pathways including glycolysis, oxidative pentose phosphate (OPP) pathway, and glycogen catabolism were induced by nitrogen depletion, and activities of glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD), two key enzymes of the OPP pathway, were demonstrated to increase under this condition. We recently showed that a group 2 sigma factor SigE, which is under the control of the global nitrogen regulator NtcA, positively regulated these sugar catabolic pathways. However, increases of transcript levels of these sugar catabolic genes under nitrogen starvation were still observed even in a sigE-deficient mutant, indicating the involvement of other regulatory element(s) in addition to SigE. Since these nitrogen activations were abolished in an ntcA mutant, and since these genes were not directly included in the NtcA regulon, we suggested that sugar catabolic genes were induced by nitrogen depletion under complex and redundant regulations including SigE and other unknown factor(s) under the control of NtcA.
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Affiliation(s)
- Takashi Osanai
- Institute of Molecular and Cellular Biosciences, The University of Tokyo 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
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Kloft N, Forchhammer K. Signal transduction protein PII phosphatase PphA is required for light-dependent control of nitrate utilization in synechocystis sp. strain PCC 6803. J Bacteriol 2005; 187:6683-90. [PMID: 16166530 PMCID: PMC1251587 DOI: 10.1128/jb.187.19.6683-6690.2005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Signal transduction protein P(II) is dephosphorylated in Synechocystis sp. strain PCC 6803 by protein phosphatase PphA. To determine the impact of PphA-mediated P(II) dephosphorylation on physiology, the phenotype of a PphA-deficient mutant was analyzed. Mutants lacking either PphA or P(II) were impaired in efficient utilization of nitrate as the nitrogen source. Under conditions of limiting photosystem I (PSI)-reduced ferredoxin, excess reduction of nitrate along with impaired reduction of nitrite occurred in P(II) signaling mutants, resulting in excretion of nitrite to the medium. This effect could be reversed by increasing the level of PSI-reduced ferredoxin. We present evidence that nonphosphorylated P(II) controls the utilization of nitrate in response to low light intensity by tuning down nitrate uptake to meet the actual reduction capacity. This control mechanism can be bypassed by exposing cells to excess levels of nitrate. Uncontrolled nitrate uptake leads to light-dependent nitrite excretion even in wild-type cells, confirming that nitrate uptake controls nitrate utilization in response to limiting photon flux densities.
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Affiliation(s)
- Nicole Kloft
- Institut für Mikrobiologie und Molekularbiologie, Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany
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Flores E, Frías JE, Rubio LM, Herrero A. Photosynthetic nitrate assimilation in cyanobacteria. PHOTOSYNTHESIS RESEARCH 2005; 83:117-33. [PMID: 16143847 DOI: 10.1007/s11120-004-5830-9] [Citation(s) in RCA: 141] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2004] [Accepted: 11/02/2004] [Indexed: 05/03/2023]
Abstract
Nitrate uptake and reduction to nitrite and ammonium are driven in cyanobacteria by photosynthetically generated assimilatory power, i.e., ATP and reduced ferredoxin. High-affinity nitrate and nitrite uptake takes place in different cyanobacteria through either an ABC-type transporter or a permease from the major facilitator superfamily (MFS). Nitrate reductase and nitrite reductase are ferredoxin-dependent metalloenzymes that carry as prosthetic groups a [4Fe-4S] center and Mo-bis-molybdopterin guanine dinucleotide (nitrate reductase) and [4Fe-4S] and siroheme centers (nitrite reductase). Nitrate assimilation genes are commonly found forming an operon with the structure: nir (nitrite reductase)-permease gene(s)-narB (nitrate reductase). When the cells perceive a high C to N ratio, this operon is transcribed from a complex promoter that includes binding sites for NtcA, a global nitrogen-control regulator that belongs to the CAP family of bacterial transcription factors, and NtcB, a pathway-specific regulator that belongs to the LysR family of bacterial transcription factors. Transcription is also affected by other factors such as CnaT, a putative glycosyl transferase, and the signal transduction protein P(II). The latter is also a key factor for regulation of the activity of the ABC-type nitrate/nitrite transporter, which is inhibited when the cells are incubated in the presence of ammonium or in the absence of CO(2). Notwithstanding significant advance in understanding the regulation of nitrate assimilation in cyanobacteria, further post-transcriptional regulatory mechanisms are likely to be discovered.
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Affiliation(s)
- Enrique Flores
- Instituto de Bioquímica Vegetal y Fotosíntesis, C.S.I.C.-Universidad de Sevilla, Avda. Américo Vespucio 49, Seville 41092, Spain.
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Aichi M, Maeda SI, Ichikawa K, Omata T. Nitrite-responsive activation of the nitrate assimilation operon in Cyanobacteria plays an essential role in up-regulation of nitrate assimilation activities under nitrate-limited growth conditions. J Bacteriol 2004; 186:3224-9. [PMID: 15126485 PMCID: PMC400610 DOI: 10.1128/jb.186.10.3224-3229.2004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
NtcB of the cyanobacterium Synechococcus elongatus strain PCC 7942 is a LysR family protein that enhances expression of the nitrate assimilation operon (nirA operon) in response to the presence of nitrite, an intermediate of assimilatory nitrate reduction. Inactivation of ntcB in this cyanobacterium specifically abolishes the nitrite responsiveness of nirA operon expression, but under nitrate-replete conditions (wherein negative feedback by intracellularly generated ammonium prevails over the positive effect of nitrite) activity levels of the nitrate assimilation enzymes are marginally higher in the wild-type cells than in the mutant cells, raising the issue of whether the nitrite-promoted regulation has physiological importance. On the other hand, the strains carrying ntcB expressed much higher nitrate assimilation enzyme activities under nitrate-limited growth conditions than under nitrate-replete conditions whereas the ntcB-deficient strains showed levels of the enzyme activities lower than those seen under the nitrate-replete conditions. Although the ntcB mutant maintained a constant cell population in a nitrate-limited chemostat when grown as a single culture, it was diluted at a rate expected for nondividing cells when mixed with the wild-type cells and subjected to nitrate limitation in the chemostat culture system. These results demonstrated that the nitrite-promoted activation of the nitrate assimilation operon is essential for up-regulation of the nitrate assimilation activities under the conditions of nitrate limitation and for competitive utilization of nitrate.
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Affiliation(s)
- Makiko Aichi
- Department of Biological Chemistry, Chubu University, Kasugai 487-8501, Japan
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Maeda SI, Omata T. A novel gene (narM) required for expression of nitrate reductase activity in the cyanobacterium Synechococcus elongatus strain PCC7942. J Bacteriol 2004; 186:2107-14. [PMID: 15028696 PMCID: PMC374400 DOI: 10.1128/jb.186.7.2107-2114.2004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A new class of mutants deficient in nitrate assimilation was obtained from the cyanobacterium Synechococcus elongatus strain PCC7942 by means of random insertional mutagenesis. A 0.5-kb genomic region had been replaced by a kanamycin resistance gene cassette in the mutant, resulting in inactivation of two genes, one of which was homologous to the recently characterized cnaT gene of Anabaena sp. strain PCC7120 (J. E. Frías, A. Herrero, and E. Flores, J. Bacteriol. 185:5037-5044, 2003). While insertional mutation of the cnaT homolog did not affect expression of the nitrate assimilation operon or the activity of the nitrate assimilation enzymes in S. elongatus, inactivation of the other gene, designated narM, resulted in specific loss of the cellular nitrate reductase activity. The deduced NarM protein is a hydrophilic protein consisting of 161 amino acids. narM was expressed constitutively at a low level. The narM gene has its homolog only in the cyanobacterial strains that are capable of nitrate assimilation. In most of the cyanobacterial strains, narM is located downstream of narB, the structural gene of the cyanobacterial nitrate reductase, suggesting the functional link between the two genes. NarM is clearly not the structural component of the cyanobacterial nitrate reductase. The narM insertional mutant normally expressed narB, indicating that narM is not the transcriptional regulator of the structural gene of nitrate reductase. These results suggested that narM is required for either synthesis of the prosthetic group of nitrate reductase or assembly of the prosthetic groups to the NarB polypeptide to form functional nitrate reductase in cyanobacteria.
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Affiliation(s)
- Shin-ichi Maeda
- Laboratory of Molecular Plant Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
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Frías JE, Herrero A, Flores E. Open reading frame all0601 from Anabaena sp. strain PCC 7120 represents a novel gene, cnaT, required for expression of the nitrate assimilation nir operon. J Bacteriol 2003; 185:5037-44. [PMID: 12923076 PMCID: PMC180997 DOI: 10.1128/jb.185.17.5037-5044.2003] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Expression of the nitrate assimilation nir operon in the filamentous, heterocyst-forming cyanobacterium Anabaena sp. strain PCC 7120 requires the action of both the global nitrogen control transcription factor NtcA and the pathway-specific transcriptional regulator NtcB. In the genome of this cyanobacterium, the ntcB gene is found in a cluster of genes located in the complementary strand, upstream from the nir operon. Just downstream of ntcB, there is an open reading frame, all0601 (previously designated orf356 and now designated the cnaT gene), that putatively encodes a protein similar to proteins with glycosyl transferase activity and that is also present clustered together with ntcB homologues or nitrate assimilation structural genes in other cyanobacterial genomes. An insertional mutant of cnaT was generated and found to be unable to assimilate nitrate, although it could use ammonium or dinitrogen as a source of nitrogen for growth. In the mutant, under derepression conditions, nir operon mRNA (as determined by RNA-DNA hybridization and primer extension analysis) and enzymes of the nitrate reduction system (i.e., nitrate reductase and nitrite reductase) were expressed at low or undetectable levels. Inactivation of cnaT did not impair expression of ntcB, and expression of cnaT itself was constitutive and regulated by neither NtcA nor NtcB. Regulation of expression of the nir operon in Anabaena sp. strain PCC 7120 by CnaT and the previously described regulatory elements, NtcA and NtcB, is discussed.
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Affiliation(s)
- José E Frías
- Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, Centro de Investigaciones Científicas Isla de la Cartuja, E-41092 Seville, Spain
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Aichi M, Takatani N, Omata T. Role of NtcB in activation of nitrate assimilation genes in the cyanobacterium Synechocystis sp. strain PCC 6803. J Bacteriol 2001; 183:5840-7. [PMID: 11566981 PMCID: PMC99660 DOI: 10.1128/jb.183.20.5840-5847.2001] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Synechocystis sp. strain PCC 6803, the genes encoding the proteins involved in nitrate assimilation are organized into two transcription units, nrtABCD-narB and nirA, the expression of which was repressed by ammonium and induced by inhibition of ammonium assimilation, suggesting involvement of NtcA in the transcriptional regulation. Under inducing conditions, expression of the two transcription units was enhanced by nitrite, suggesting regulation by NtcB, the nitrite-responsive transcriptional enhancer we previously identified in Synechococcus sp. strain PCC 7942. The slr0395 gene, which encodes a protein 47% identical to Synechococcus NtcB, was identified as the Synechocystis ntcB gene, on the basis of the inability of an slr0395 mutant to rapidly accumulate the transcripts of the nitrate assimilation genes upon induction and to respond to nitrite. While Synechococcus NtcB strictly requires nitrite for its action, Synechocystis NtcB enhanced transcription significantly even in the absence of nitrite. Whereas the Synechococcus ntcB mutant expresses the nitrate assimilation genes to a significant level in an NtcA-dependent manner, the Synechocystis ntcB mutant showed only low-level expression of the nitrate assimilation genes, indicating that NtcA by itself cannot efficiently promote expression of these genes in Synechocystis. Activities of the nitrate assimilation enzymes in the Synechocystis ntcB mutant were consequently low, being 40 to 50% of the wild-type level, and the cells grew on nitrate at a rate approximately threefold lower than that of the wild-type strain. These results showed that the contribution of NtcB to the expression of nitrate assimilation capability varies considerably among different strains of cyanobacteria.
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Affiliation(s)
- M Aichi
- Laboratory of Molecular Plant Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601 Japan
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25
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Luque I, Zabulon G, Contreras A, Houmard J. Convergence of two global transcriptional regulators on nitrogen induction of the stress-acclimation gene nblA in the cyanobacterium Synechococcus sp. PCC 7942. Mol Microbiol 2001; 41:937-47. [PMID: 11532155 DOI: 10.1046/j.1365-2958.2001.02566.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Cyanobacteria respond to environmental stress conditions by degrading their phycobilisomes, the light harvesting complexes for photosynthesis. The expression of nblA, a key gene in this process, is controlled by the response regulator NblR in Synechococcus sp. PCC 7942. Here we show that, under nitrogen stress, nblA is also regulated by NtcA, the global regulator for nitrogen control. NtcA activation of nblA was found to be nitrogen-specific and did not take place under sulphur stress. Transcripts from the two major transcription start points (tsp) for the nblA gene were induced in response to nitrogen and sulphur starvation. The most active one (tspII) required both NblR and NtcA to induce full nblA expression under nitrogen starvation. NblR and NtcA bound in vitro to a DNA fragment from the nblA promoter region, suggesting that, under nitrogen stress, both NblR and NtcA activate the main regulated promoter (PnblA-2) by direct DNA-binding. The structure of PnblA-2 differs from that of the canonical NtcA-activated promoter and it is therefore proposed to represent a novel type of NtcA-dependent promoter. We analysed expression patterns from ntcA and selected NtcA targets in NtcA(-), NblR(-) and wild-type strains, and discuss data suggesting further interrelations between phycobilisome degradation and nitrogen assimilation regulatory pathways.
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Affiliation(s)
- I Luque
- Unité Mixte de Recherche 8543, Centre National de la Recherche Scientifique, Photorégulation et Dynamique des Membranes Végétales, Ecole Normale Supérieure, 46 rue d'Ulm, 75230 Paris cedex 05, France.
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26
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Miller SR, Castenholz RW. Ecological physiology of Synechococcus sp. strain SH-94-5, a naturally occurring cyanobacterium deficient in nitrate assimilation. Appl Environ Microbiol 2001; 67:3002-9. [PMID: 11425713 PMCID: PMC92972 DOI: 10.1128/aem.67.7.3002-3009.2001] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2001] [Accepted: 04/11/2001] [Indexed: 11/20/2022] Open
Abstract
Synechococcus sp. strain SH-94-5 is a nitrate assimilation-deficient cyanobacterium which was isolated from an ammonium-replete hot spring in central Oregon. While this clone could grow on ammonium and some forms of organic nitrogen as sole nitrogen sources, it could not grow on either nitrate or nitrite, even under conditions favoring passive diffusion. It was determined that this clone does not express functional nitrate reductase or nitrite reductase and that the lack of activity of either enzyme is not due to inactivation of the cyanobacterial nitrogen control protein NtcA. A few other naturally occurring cyanobacterial strains are also nitrate assimilation deficient, and phylogenetic analyses indicated that the ability to utilize nitrate has been independently lost at least four times during the evolutionary history of the cyanobacteria. This phenotype is associated with the presence of environmental ammonium, a negative regulator of nitrate assimilation gene expression, which may indicate that natural selection to maintain functional copies of nitrate assimilation genes has been relaxed in these habitats. These results suggest how the evolutionary fates of conditionally expressed genes might differ between environments and thereby effect ecological divergence and biogeographical structure in the microbial world.
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Affiliation(s)
- S R Miller
- Department of Biology, University of Oregon, Eugene, Oregon 97403, USA.
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27
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Affiliation(s)
- A Herrero
- Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, E-41092 Seville, Spain
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Frías JE, Flores E, Herrero A. Activation of the Anabaena nir operon promoter requires both NtcA (CAP family) and NtcB (LysR family) transcription factors. Mol Microbiol 2000; 38:613-25. [PMID: 11069684 DOI: 10.1046/j.1365-2958.2000.02156.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A region of the genome of the heterocyst-forming cyanobacterium Anabaena sp. PCC 7120 containing the ntcB gene was identified. This region is located upstream from the nir operon involved in nitrate assimilation in this cyanobacterium. An Anabaena ntcB mutant was able to use ammonium and dinitrogen as sources of nitrogen for growth but was unable to assimilate nitrate. Enzymes of the nitrate reduction system were not synthesized in the ntcB mutant under derepression conditions. The transcription start-point of the Anabaena nir operon, which has been shown to be subjected to ammonium-stimulated repression and whose expression requires the global nitrogen regulator NtcA, was only weakly used in the ntcB mutant. The expression of the ntcB gene in strain PCC 7120 was also subjected to repression by ammonium and was found to take place from an NtcA-activated promoter located 31 bp upstream from the start of the ntcB gene. NtcB binds to the nir promoter region in vitro and protects a region localized just upstream from the NtcA-binding site in footprinting assays. These results showed that NtcB, a LysR-family protein, is required in addition to NtcA, a CAP-family protein, for the expression of genes encoding proteins specifically involved in nitrate assimilation in Anabaena sp. PCC 7120.
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Affiliation(s)
- J E Frías
- Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, Centro de Investigaciones Científicas Isla de la Cartuja, Avda. Américo Vespucio s/n, E-41092, Sevilla, Spain
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Jiang F, Wisén S, Widersten M, Bergman B, Mannervik B. Examination of the transcription factor NtcA-binding motif by in vitro selection of DNA sequences from a random library. J Mol Biol 2000; 301:783-93. [PMID: 10966785 DOI: 10.1006/jmbi.2000.4000] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A recursive in vitro selection among random DNA sequences was used for analysis of the cyanobacterial transcription factor NtcA-binding motifs. An eight-base palindromic sequence, TGTA-(N(8))-TACA, was found to be the optimal NtcA-binding sequence. The more divergent the binding sequences, compared to this consensus sequence, the lower the NtcA affinity. The second and third bases in each four-nucleotide half of the consensus sequence were crucial for NtcA binding, and they were in general highly conserved. The most frequently occurring sequence in the middle weakly conserved region was similar to that of the NtcA-binding motif of the Anabaena sp. strain PCC 7120 glnA gene, previously known to have high affinity for NtcA. This indicates that the middle sequences were selected for high NtcA affinity. Analysis of natural NtcA-binding motifs showed that these could be classified into two groups based on differences in recognition consensus sequences. It is suggested that NtcA naturally recognizes different DNA-binding motifs, or has differential affinities to these sequences under different physiological conditions.
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Affiliation(s)
- F Jiang
- Department of Biochemistry, Uppsala University, Biomedical Center, Uppsala, S-751 23, Sweden
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Lee HM, Flores E, Forchhammer K, Herrero A, Tandeau De Marsac N. Phosphorylation of the signal transducer PII protein and an additional effector are required for the PII-mediated regulation of nitrate and nitrite uptake in the Cyanobacterium synechococcus sp. PCC 7942. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:591-600. [PMID: 10632730 DOI: 10.1046/j.1432-1327.2000.01043.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the cyanobacterium Synechococcus sp. strain PCC 7942, the phosphorylation states of the signal transducer PII protein (GlnB) can change rapidly depending on the nitrogen and carbon supply. A PII-null mutant (MP2) shows no ammonium-dependent inhibition of the nitrate and nitrite uptake, in contrast to the wild-type. New mutants with different types of PII, which may mimic either the phosphorylated (GlnBS49E or GlnBS49D) or unphosphorylated (GlnBS49A) form of the protein, were constructed using site-directed in vitro mutagenesis. Mutant MP2-A (GlnBS49A) grew poorly using nitrate as a nitrogen source and was unable to take up nitrate supplied at 100 microM, even in the absence of externally added ammonium. Mutants MP2-D and MP2-E (GlnBS49D and GlnBS49E, respectively), however, showed nitrate-dependent growth and regulation of nitrate uptake by ammonium, as in the wild-type. Characterization of the mutants also included an analysis of nitrite uptake and of the levels of the nir (nitrate/nitrite assimilation) operon transcripts, the presence of NrtA (nitrate/nitrite transport binding protein), and nitrate and nitrite reductase activities. In vitro, no significant difference was observed in the cooperative binding of ATP and 2-oxoglutarate between the wild-type and the unphosphorylated or phosphorylated-like forms of the mutant PII proteins. The results obtained indicate that both unphosphorylated and phosphorylated-like forms of PII are able to inhibit nitrate uptake in the presence of ammonium, but the unphosphorylated form also has a negative effect in the absence of this nitrogen source. Therefore, an additional effector, possibly 2-oxoglutarate, is required for the PII protein to relieve inhibition of nitrate uptake in the absence of ammonium.
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Affiliation(s)
- H M Lee
- Département de Biochimie et Génétique Moléculaire, Unité de Physiologie Microbienne, Paris, France
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Lee HM, Vázquez-Bermúdez MF, de Marsac NT. The global nitrogen regulator NtcA regulates transcription of the signal transducer PII (GlnB) and influences its phosphorylation level in response to nitrogen and carbon supplies in the Cyanobacterium synechococcus sp. strain PCC 7942. J Bacteriol 1999; 181:2697-702. [PMID: 10217756 PMCID: PMC93707 DOI: 10.1128/jb.181.9.2697-2702.1999] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The PII protein is encoded by a unique glnB gene in Synechococcus sp. strain PCC 7942. Its expression has been analyzed in the wild type and in NtcA-null mutant cells grown under different conditions of nitrogen and carbon supply. RNA-DNA hybridization experiments revealed the presence of one transcript species 680 nucleotides long, whatever the nutrient conditions tested. A second transcript species, 620 nucleotides long, absent in the NtcA null mutant, was observed in wild-type cells that were nitrogen starved for 2 h under both high and low CO2 and in the presence of nitrate under a high CO2 concentration. Primer extension analysis indicated that the two transcript species are generated from two tandem promoters, a sigma70 Escherichia coli-type promoter and an NtcA-dependent promoter, located 120 and 53 nucleotides, respectively, from the glnB initiation codon. The NtcA-dependent promoter is up-regulated under the conditions mentioned above, while the sigma70 E. coli-type promoter displays constitutive levels of transcripts in the NtcA null mutant and slightly different levels in the wild-type cells, depending on the nitrogen and carbon supplies. In general, a good correlation between the amounts of the two transcript species and that of the PII protein was observed, as revealed by immunodetection with specific antibodies. The phosphorylation level of PII in the wild type is inversely correlated with nitrogen availability and directly correlated with higher CO2 concentration. This regulation is correspondingly less stringent in the NtcA null mutant cells. In contrast, the dephosphorylation of PII is NtcA independent.
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Affiliation(s)
- H M Lee
- Département de Biochimie et Génétique Moléculaire, Unité de Physiologie Microbienne, Institut Pasteur, 75724 Paris Cedex 15, France
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Dolganov N, Grossman AR. A polypeptide with similarity to phycocyanin alpha-subunit phycocyanobilin lyase involved in degradation of phycobilisomes. J Bacteriol 1999; 181:610-7. [PMID: 9882677 PMCID: PMC93417 DOI: 10.1128/jb.181.2.610-617.1999] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To optimize the utilization of photosynthate and avoid damage that can result from the absorption of excess excitation energy, photosynthetic organisms must rapidly modify the synthesis and activities of components of the photosynthetic apparatus in response to environmental cues. During nutrient-limited growth, cyanobacteria degrade their light-harvesting complex, the phycobilisome, and dramatically reduce the rate of photosynthetic electron transport. In this report, we describe the isolation and characterization of a cyanobacterial mutant that does not degrade its phycobilisomes during either sulfur or nitrogen limitation and exhibits an increased ratio of phycocyanin to chlorophyll during nutrient-replete growth. The mutant phenotype was complemented by a gene encoding a polypeptide with similarities to polypeptides that catalyze covalent bond formation between linear tetrapyrrole chromophores and subunits of apophycobiliproteins. The complementing gene, designated nblB, is expressed at approximately the same level in cells grown in nutrient-replete medium and medium devoid of either sulfur or nitrogen. These results suggest that the NblB polypeptide may be a constitutive part of the machinery that coordinates phycobilisome degradation with environmental conditions.
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Affiliation(s)
- N Dolganov
- Department of Plant Biology, The Carnegie Institution of Washington, Stanford, California 94305, USA
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33
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Montesinos ML, Muro-Pastor AM, Herrero A, Flores E. Ammonium/methylammonium permeases of a Cyanobacterium. Identification and analysis of three nitrogen-regulated amt genes in synechocystis sp. PCC 6803. J Biol Chem 1998; 273:31463-70. [PMID: 9813059 DOI: 10.1074/jbc.273.47.31463] [Citation(s) in RCA: 99] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ammonium is an important nitrogen source for many microorganisms and plants. Ammonium transporters whose activity can be probed with [14C]methylammonium have been described in several organisms including some cyanobacteria, and amt genes encoding ammonium/methylammonium permeases have been recently identified in yeast, Arabidopsis thaliana, and some bacteria. The unicellular cyanobacterium Synechocystis sp. PCC 6803 exhibited a [14C]methylammonium uptake activity that was inhibited by externally added ammonium. Three putative amt genes that are found in the recently published complete sequence of the chromosome of strain PCC 6803 were inactivated by insertion of antibiotic resistance-encoding gene-cassettes. The corresponding mutant strains were impaired in uptake of [14C]methylammonium. Open reading frame sll0108 (amt1) was responsible for a high affinity uptake activity (Ks for methylammonium, 2.7 microM), whereas open reading frames sll1017 (amt2) and sll0537 (amt3) made minor contributions to uptake at low substrate concentrations. Expression of the three amt genes was higher in nitrogen-starved cells than in cells incubated in the presence of a source of nitrogen (either ammonium or nitrate), but amt1 was expressed at higher levels than the other two amt genes. Transcription of amt1 was found to take place from a promoter bearing the structure of the cyanobacterial promoters activated by the nitrogen control transcription factor, NtcA.
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Affiliation(s)
- M L Montesinos
- Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, E-41092 Sevilla, Spain
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Maeda S, Kawaguchi Y, Ohe TA, Omata T. cis-acting sequences required for NtcB-dependent, nitrite-responsive positive regulation of the nitrate assimilation operon in the cyanobacterium Synechococcus sp. strain PCC 7942. J Bacteriol 1998; 180:4080-8. [PMID: 9696753 PMCID: PMC107401 DOI: 10.1128/jb.180.16.4080-4088.1998] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/1998] [Accepted: 06/04/1998] [Indexed: 11/20/2022] Open
Abstract
There are three binding sites for NtcA (nirI, nirII, and nirIII), the global nitrogen regulator of cyanobacteria, in the DNA region between the two divergently transcribed operons (nirA and nirB operons) involved in nitrate assimilation in Synechococcus sp. strain PCC 7942. Using the luxAB reporter system, we showed that nirI and nirIII, which are located 23 bp upstream from the -10 promoter element of nirA and nirB, respectively, are required for induction by nitrogen depletion of the nirA and nirB operons, respectively. The induction of nirA operon transcription was a prerequisite for the nitrite-responsive positive regulation of the transcription by NtcB, a LysR-type protein. The NtcA-binding site nirII, located in the middle of the nirA-nirB intergenic region, and a potential binding site for a LysR-type protein (TGCAN5TGCA; designated L1), located between nirI and nirII, were required for the nitrite-responsive, NtcB-dependent enhancement of nirA operon transcription. Although the requirement for the L1 site was consistent with the involvement of the LysR family protein NtcB in transcriptional regulation, NtcB did not bind to the nirA regulatory region in vitro in the presence of nitrite and NtcA, suggesting the involvement of some additional factor(s) in the regulation. An L1-like inverted repeat with the consensus sequence TGCN7GCA was conserved in the nirA promoter region of cyanobacteria, being centered at position -23 with respect to the NtcA-binding site corresponding to nirI, which suggested the common occurrence of nitrite-responsive regulation of the nitrate assimilation operon among cyanobacteria.
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Affiliation(s)
- S Maeda
- Department of Applied Biological Sciences, School of Agricultural Sciences, Nagoya University, Nagoya 464-01, Japan
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Lindell D, Padan E, Post AF. Regulation of ntcA expression and nitrite uptake in the marine Synechococcus sp. strain WH 7803. J Bacteriol 1998; 180:1878-86. [PMID: 9537388 PMCID: PMC107103 DOI: 10.1128/jb.180.7.1878-1886.1998] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/1997] [Accepted: 01/20/1998] [Indexed: 02/07/2023] Open
Abstract
NtcA is a transcriptional activator involved in global nitrogen control in cyanobacteria. In the absence of ammonium it regulates the transcription of a series of genes encoding proteins required for the uptake and assimilation of alternative nitrogen sources (I. Luque, E. Flores, and A. Herrero, EMBO J. 13:2862-2869, 1994). ntcA, present in a single copy in the marine Synechococcus sp. strain WH 7803, was cloned and sequenced. The putative amino acid sequence shows a high degree of identity to NtcA from freshwater cyanobacteria in two functional domains. The expression of ntcA was negatively regulated by ammonium from a putative transcription start point located downstream of an NtcA consensus recognition sequence. Addition of either rifampin or ammonium led to a rapid decline in ntcA transcript levels with half-lives of less than 2 min in both cases. Nitrate-grown cells showed high ntcA transcript levels, as well as the capacity for active nitrite uptake. However, ammonium-grown cells showed low levels of the ntcA transcript and did not utilize nitrite. The addition of ammonium to nitrite uptake-active cells resulted in a gradual decline in the rate of uptake over a 24-h period. Active nitrite uptake was not induced in cells transferred to medium lacking a nitrogen source despite evidence of elevated expression of ntcA, indicating that ntcA expression is not sufficient for uptake capacity to develop. Nitrate and nitrite addition led to the development of nitrite uptake, whereas the addition of leucine did not. Furthermore, nitrite addition triggered the de novo protein synthesis required for uptake capacity to develop. These data suggest that nitrite and nitrate act as specific inducers for the synthesis of proteins required for nitrite uptake.
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Affiliation(s)
- D Lindell
- H. Steinitz Marine Biology Laboratory, Interuniversity Institute for Marine Sciences, Eilat, Israel
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36
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Abstract
Nitrate is a significant nitrogen source for plants and microorganisms. Recent molecular genetic analyses of representative bacterial species have revealed structural and regulatory genes responsible for the nitrate-assimilation phenotype. Together with results from physiological and biochemical studies, this information has unveiled fundamental aspects of bacterial nitrate assimilation and provides the foundation for further investigations. Well-studied genera are: the cyanobacteria, including the unicellular Synechococcus and the filamentous Anabaena; the gamma-proteobacteria Klebsiella and Azotobacter; and a Gram-positive bacterium, Bacillus. Nitrate uptake in most of these groups seems to involve a periplasmic binding protein-dependent system that presumably is energized by ATP hydrolysis (ATP-binding cassette transporters). However, Bacillus may, like fungi and plants, utilize electrogenic uptake through a representative of the major facilitator superfamily of transport proteins. Nitrate reductase contains both molybdenum cofactor and an iron-sulfur cluster. Electron donors for the enzymes from cyanobacteria and Azotobacter are ferredoxin and flavodoxin, respectively, whereas the Klebsiella and Bacillus enzymes apparently accept electrons from a specific NAD(P)H-reducing subunit. These subunits share sequence similarity with the reductase components of bacterial aromatic ring-hydroxylating dehydrogenases such as toluene dioxygenase. Nitrite reductase contains sirohaem and an iron-sulfur cluster. The enzymes from cyanobacteria and plants use ferredoxin as the electron donor, whereas the larger enzymes from other bacteria and fungi contain FAD and NAD(P)H binding sites. Nevertheless, the two forms of nitrite reductase share recognizable sequence and structural similarity. Synthesis of nitrate assimilation enzymes and uptake systems is controlled by nitrogen limitation in all bacteria examined, but the relevant regulatory proteins exhibit considerable structural and mechanistic diversity in different bacterial groups. A second level of control, pathway-specific induction by nitrate and nitrite in Klebsiella, involves transcription antitermination. Several issues await further experimentation, including the mechanism and energetics of nitrate uptake, the pathway(s) for nitrite uptake, the nature of electron flow during nitrate reduction, and the action of transcriptional regulatory circuits. Fundamental knowledge of nitrate assimilation physiology should also enhance the study of nitrate metabolism in soil, water and other natural environments, a challenging topic of considerable interest and importance.
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Affiliation(s)
- J T Lin
- Section of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, New York 14853, USA
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Harano Y, Suzuki I, Maeda S, Kaneko T, Tabata S, Omata T. Identification and nitrogen regulation of the cyanase gene from the cyanobacteria Synechocystis sp. strain PCC 6803 and Synechococcus sp. strain PCC 7942. J Bacteriol 1997; 179:5744-50. [PMID: 9294430 PMCID: PMC179462 DOI: 10.1128/jb.179.18.5744-5750.1997] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
An open reading frame (slr0899) on the genome of Synechocystis sp. strain PCC 6803 encodes a polypeptide of 149 amino acid residues, the sequence of which is 40% identical to that of cyanase from Escherichia coli. Introduction into a cyanase-deficient E. coli strain of a plasmid-borne slr0899 resulted in expression of low but significant activity of cyanase. Targeted interruption of a homolog of slr0899 from Synechococcus sp. strain PCC 7942, encoding a protein 77% identical to that encoded by slr0899, resulted in loss of cellular cyanase activity. These results indicated that slr0899 and its homolog in the strain PCC 7942 represent the cyanobacterial cyanase gene (designated cynS). While cynS of strain PCC 6803 is tightly clustered with the four putative molybdenum cofactor biosynthesis genes located downstream, cynS of strain PCC 7942 was found to be tightly clustered with the two genes located upstream, which encode proteins similar to the subunits of the cyanobacterial nitrate-nitrite transporter. In both strains, cynS was transcribed as a part of a large transcription unit and the transcription was negatively regulated by ammonium. Cyanase activity was low in ammonium-grown cells and was induced 7- to 13-fold by inhibition of ammonium fixation or by transfer of the cells to ammonium-free media. These findings indicated that cyanase is an ammonium-repressible enzyme in cyanobacteria, the expression of which is regulated at the level of transcription. Similar to other ammonium-repressible genes in cyanobacteria, expression of cynS required NtcA, a global nitrogen regulator of cyanobacteria.
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Affiliation(s)
- Y Harano
- Department of Applied Biological Sciences, School of Agricultural Sciences, Nagoya University, Japan
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Aichi M, Omata T. Involvement of NtcB, a LysR family transcription factor, in nitrite activation of the nitrate assimilation operon in the cyanobacterium Synechococcus sp. strain PCC 7942. J Bacteriol 1997; 179:4671-5. [PMID: 9244251 PMCID: PMC179310 DOI: 10.1128/jb.179.15.4671-4675.1997] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Nitrite, either exogenously supplied or endogenously generated by nitrate reduction, activates transcription of the nitrate assimilation operon (nirA-nrtABCD-narB) in Synechococcus sp. strain PCC 7942 cells treated with L-methionine-DL-sulfoximine (an inhibitor of glutamine synthetase), in which there is no negative feedback resulting from fixation of the ammonium generated by nitrite reduction (Kikuchi et al., J. Bacteriol. 178:5822-5825, 1996). Other transcription units related to nitrogen assimilation, i.e., the nirB-ntcB operon, glnA, and ntcA, were not activated by nitrite. Nitrite did not activate nirA operon transcription in a mutant with a deletion of ntcB, an ammonium-repressible gene encoding a LysR-type DNA-binding protein. Introduction of plasmid-borne ntcB into the ntcB deletion mutant restored the response of the cells to nitrite, indicating that NtcB activates the nirA operon in response to nitrite. Supplementation of nitrite or nitrate to nitrogen-starved cultures of the wild-type strain, but not of the ntcB deletion mutant, caused activation of the nirA operon without L-methionine-DL-sulfoximine treatment of the cells. The results suggested that the positive-regulation mechanism of nirA operon transcription plays a role in rapid adaptation of nitrogen-starved cells to changing availability of nitrate and nitrite.
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Affiliation(s)
- M Aichi
- Department of Applied Biological Sciences, School of Agricultural Sciences, Nagoya University, Japan
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Kuritz T, Bocanera LV, Rivera NS. Dechlorination of lindane by the cyanobacterium Anabaena sp. strain PCC7120 depends on the function of the nir operon. J Bacteriol 1997; 179:3368-70. [PMID: 9150239 PMCID: PMC179122 DOI: 10.1128/jb.179.10.3368-3370.1997] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Nitrate is essential for lindane dechlorination by the cyanobacteria Anabaena sp. strain PCC7120 and Nostoc ellipsosporum, as it is for dechlorination of other organic compounds by heterotrophic microorganisms. Based on analyses of mutants and effects of environmental factors, we conclude that lindane dechlorination by Anabaena sp. requires a functional nir operon that encodes the enzymes for nitrate utilization.
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Affiliation(s)
- T Kuritz
- Life Sciences Division, Oak Ridge National Laboratory, Tennessee 37830, USA.
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Suzuki I, Sugiyami T, Omata T. Regulation by cyanate of the genes involved in carbon and nitrogen assimilation in the cyanobacterium Synechococcus sp. strain PCC 7942. J Bacteriol 1996; 178:2688-94. [PMID: 8626339 PMCID: PMC177996 DOI: 10.1128/jb.178.9.2688-2694.1996] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
A mutant (M45) of the cyanobacterium Synechococcus sp. strain PCC 7942, which is defective in active transport of nitrate, was used for the studies of the nitrogen regulation of the genes involved in nitrate and CO2 assimilation. In a medium containing 30 mM nitrate as the nitrogen source, M45 grew under constant stress of nitrogen deficiency and accumulated a five-times-larger amount of the transcript of nirA, the gene for nitrite reductase, compared with nitrate-grown wild-type cells. By contrast, the level of the transcript of rbcL, the gene for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase, was 40% of the wild-type level. Addition of ammonium to the culture of M45 abolished the accumulation of the nirA transcript and stimulated the accumulation of the rbcL transcript, showing that ammonium repressed and activated the transcription of nirA and rbcL, respectively. Glutamine, the initial product of ammonium fixation, also showed negative and positive effects on nirA and rbcL, respectively. One of the metabolites of glutamine, carbamoylphosphate, and its decomposition product, cyanate, were found to repress nirA and also to markedly activate rbcL. Cyanate negatively regulated another ammonium-repressible gene, glnA, but had no effect on the psbAI and rps1 genes. The effects of cyanate were not ascribable to the ammonium and CO, resulting from its decomposition. These findings suggested that cyanate may act as a regulator of the ammonium-responsive genes involved in carbon and nitrogen assimilation in the cyanobacterium.
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Affiliation(s)
- I Suzuki
- Department of Applied Biological Sciences, School of Agricultural Sciences, Nagoya University, Japan
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Abstract
Nitrogen metabolism in prokaryotes involves the coordinated expression of a large number of enzymes concerned with both utilization of extracellular nitrogen sources and intracellular biosynthesis of nitrogen-containing compounds. The control of this expression is determined by the availability of fixed nitrogen to the cell and is effected by complex regulatory networks involving regulation at both the transcriptional and posttranslational levels. While the most detailed studies to date have been carried out with enteric bacteria, there is a considerable body of evidence to show that the nitrogen regulation (ntr) systems described in the enterics extend to many other genera. Furthermore, as the range of bacteria in which the phenomenon of nitrogen control is examined is being extended, new regulatory mechanisms are also being discovered. In this review, we have attempted to summarize recent research in prokaryotic nitrogen control; to show the ubiquity of the ntr system, at least in gram-negative organisms; and to identify those areas and groups of organisms about which there is much still to learn.
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Affiliation(s)
- M J Merrick
- Nitrogen Fixation Laboratory, John Innes Centre, Norwich, United Kingdom
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