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Pucelik S, Becker M, Heyber S, Wöhlbrand L, Rabus R, Jahn D, Härtig E. The blue light-dependent LOV-protein LdaP of Dinoroseobacter shibae acts as antirepressor of the PpsR repressor, regulating photosynthetic gene cluster expression. Front Microbiol 2024; 15:1351297. [PMID: 38404597 PMCID: PMC10890935 DOI: 10.3389/fmicb.2024.1351297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Accepted: 01/17/2024] [Indexed: 02/27/2024] Open
Abstract
In the marine α-proteobacterium Dinoroseobacter shibae more than 40 genes of the aerobic anoxygenic photosynthesis are regulated in a light-dependent manner. A genome-wide screen of 5,605 clones from a D. shibae transposon library for loss of pigmentation and changes in bacteriochlorophyll absorbance identified 179 mutant clones. The gene encoding the LOV-domain containing protein Dshi_1135 was identified by its colorless phenotype. The mutant phenotype was complemented by the expression of a Dshi_1135-strep fusion protein in trans. The recombinantly produced and chromatographically purified Dshi_1135 protein was able to undergo a blue light-induced photocycle mediated by bound FMN. Transcriptome analyses revealed an essential role for Dshi_1135 in the light-dependent expression of the photosynthetic gene cluster. Interactomic studies identified the repressor protein PpsR as an interaction partner of Dshi_1135. The physical contact between PpsR and the Dshi_1135 protein was verified in vivo using the bacterial adenylate cyclase-based two-hybrid system. In addition, the antirepressor function of the Dshi_1135 protein was demonstrated in vivo testing of a bchF-lacZ reporter gene fusion in a heterologous Escherichia coli-based host system. We therefore propose to rename the Dshi_1135 protein to LdaP (light-dependent antirepressor of PpsR). Using the bacterial two-hybrid system, it was also shown that cobalamin (B12) is essential for the interaction of the antirepressor PpaA with PpsR. A regulatory model for the photosynthetic gene cluster in D. shibae was derived, including the repressor PpsR, the light-dependent antirepressor LdaP and the B12-dependent antirepressor PpaA.
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Affiliation(s)
- Saskia Pucelik
- Institute of Microbiology, Technische Universität Braunschweig, Braunschweig, Germany
| | - Miriam Becker
- Institute of Microbiology, Technische Universität Braunschweig, Braunschweig, Germany
| | - Steffi Heyber
- Institute of Microbiology, Technische Universität Braunschweig, Braunschweig, Germany
| | - Lars Wöhlbrand
- Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky University of Oldenburg, Oldenburg, Germany
| | - Ralf Rabus
- Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl von Ossietzky University of Oldenburg, Oldenburg, Germany
| | - Dieter Jahn
- Braunschweig Integrated Centre of Systems Biology (BRICS), Technische Universität Braunschweig, Braunschweig, Germany
| | - Elisabeth Härtig
- Institute of Microbiology, Technische Universität Braunschweig, Braunschweig, Germany
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Almeida JR, León ES, Corona EL, Fradinho JC, Oehmen A, Reis MAM. Ammonia impact on the selection of a phototrophic - chemotrophic consortium for polyhydroxyalkanoates production under light-feast / dark-aerated-famine conditions. WATER RESEARCH 2023; 244:120450. [PMID: 37574626 DOI: 10.1016/j.watres.2023.120450] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Revised: 08/01/2023] [Accepted: 08/03/2023] [Indexed: 08/15/2023]
Abstract
Phototrophic polyhydroxyalkanoate (PHA) production is an emerging technology for recovering carbon and nutrients from diverse wastewater streams. However, reliable selection methods for the enrichment of PHA accumulating purple phototrophic bacteria (PPB) in phototrophic mixed cultures (PMC) are needed. This research evaluates the impact of ammonia on the selection of a PHA accumulating phototrophic-chemotrophic consortium, towards the enrichment of PHA accumulating PPB. The culture was operated under light-feast/dark-aerated-famine and winter simulated-outdoor conditions (13.2 ± 0.9 °C, transient light, 143.5 W/m2), using real fermented domestic wastewater with molasses as feedstock. Three ammonia supply strategies were assessed: 1) ammonia available only in the light phase, 2) ammonia always present and 3) ammonia available only during the dark-aerated-famine phase. Results showed that the PMC selected under 1) ammonia only in the light and 3) dark-famine ammonia conditions, presented the lowest PHA accumulation capacity during the light period (11.1 % g PHA/g VSS and 10.4 % g PHA/g VSS, respectively). In case 1), the absence of ammonia during the dark-aerated-famine phase did not promote the selection of PHA storing PPB, whereas in case 3) the absence of ammonia during the light period favoured cyanobacteria growth as well as purple sulphur bacteria with increased non-PHA inclusions, resulting in an overall decrease of phototrophic PHA accumulation capacity. The best PHA accumulation performance was obtained with selection under permanent presence of ammonia (case 2), which attained a PHA content of 21.6 % g PHA/g VSS (10.2 Cmmol PHA/L), at a production rate of 0.57 g PHA/L·day, during the light period in the selection reactor. Results in case 2 also showed that feedstock composition impacts the PMC performance, with feedstocks richer in more reduced volatile fatty acids (butyric and valeric acids) decreasing phototrophic performance and leading to acids entering the dark-aerated phase. Nevertheless, the presence of organic carbon in the aerated phase was not detrimental to the system. In fact, it led to the establishment of a phototrophic-chemotrophic consortium that could photosynthetically accumulate a PHA content of 13.2 % g PHA/g VSS (6.7 Cmmol PHA/L) at a production rate of 0.20 g PHA/L·day in the light phase, and was able to further increase that storage up to 18.5 % g PHA/g VSS (11.0 Cmmol PHA/L) at a production rate of 1.35 g PHA/L·day in the dark-aerated period. Furthermore, the light-feast/dark-aerated-famine operation was able to maintain the performance of the selection reactor under winter conditions, unlike non-aerated PMC systems operated under summer conditions, suggesting that night-time aeration coupled with the constant presence of ammonia can contribute to overcoming the seasonal constraints of outdoor operation of PMCs for PHA production.
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Affiliation(s)
- J R Almeida
- Associate Laboratory i4HB - Institute for Health and Bioeconomy, NOVA School of Science and Technology, NOVA University Lisbon, 2829-516 Caparica, Portugal; UCIBIO - Applied Molecular Biosciences Unit, Department of Chemistry, NOVA School of Science and Technology, NOVA University Lisbon, 2829-516 Caparica, Portugal
| | - E Serrano León
- FCC Servicios Ciudadanos, Av. del Camino de Santiago, 40, edificio 3, 4ª planta, 28050 Madrid, Spain
| | - E Lara Corona
- FCC Servicios Ciudadanos, Av. del Camino de Santiago, 40, edificio 3, 4ª planta, 28050 Madrid, Spain
| | - J C Fradinho
- Associate Laboratory i4HB - Institute for Health and Bioeconomy, NOVA School of Science and Technology, NOVA University Lisbon, 2829-516 Caparica, Portugal; UCIBIO - Applied Molecular Biosciences Unit, Department of Chemistry, NOVA School of Science and Technology, NOVA University Lisbon, 2829-516 Caparica, Portugal.
| | - A Oehmen
- UCIBIO - Applied Molecular Biosciences Unit, Department of Chemistry, NOVA School of Science and Technology, NOVA University Lisbon, 2829-516 Caparica, Portugal
| | - M A M Reis
- Associate Laboratory i4HB - Institute for Health and Bioeconomy, NOVA School of Science and Technology, NOVA University Lisbon, 2829-516 Caparica, Portugal; UCIBIO - Applied Molecular Biosciences Unit, Department of Chemistry, NOVA School of Science and Technology, NOVA University Lisbon, 2829-516 Caparica, Portugal
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Xu X, Gao Z, Wu X, Chen X. Light and oxygen facilitating the directly treatment food wastewater and poly-β-hydroxybutyrate, 5-aminolevulinic acid, pigment productions by Rubrivivax gelatinosus. WATER SCIENCE AND TECHNOLOGY : A JOURNAL OF THE INTERNATIONAL ASSOCIATION ON WATER POLLUTION RESEARCH 2023; 87:1367-1375. [PMID: 37001154 DOI: 10.2166/wst.2023.070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Rubrivivax gelatinosus has the advantage of using wastewater to realize biomass recovery. However, they still cannot be applied large scale because they cannot directly treat the wastewater containing macromolecular organics. Thus, this article investigated the effects of light-oxygen conditions on R. gelatinosus by directly recycling wastewater containing macromolecular organics to produce biomass, poly-β-hydroxybutyrate (PHB), 5-aminolevulinic acid (5-ALA), and pigment. Results showed that R. gelatinosus directly treated the macromolecule organic (soybean protein and starch) wastewaters and achieved biomass recovery under light-anaerobic and light-micro-oxygen in six conditions. Chemical oxygen demand, protein, and starch removals for two wastewaters all reached above 70%. Renewable bio-resources such as biomass, PHB, 5-ALA, and pigment production were 10 times the initial content. Theoretical analysis indicated that light activated the synthesis of protease and amylase. However, oxygen concentration decided the number of enzymes. When oxygen was at micro-oxygen or anaerobic, the aforementioned expression and synthesis were conducted. In summary, this study expanded the viewpoint ignored by traditional theory. It was realized that R. gelatinosus directly treated wastewater and accumulated nutrients (biomass, PHB, pigment, and 5-ALA) for recycling, which reduced the secondary pollution of excess sludge into the environment.
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Affiliation(s)
- Xiaohan Xu
- College of Natural Resources and Environment, South China Agricultural University, Guangzhou 510642, China E-mail:
| | - Ziqing Gao
- College of Marine Sciences, South China Agricultural University, Guangzhou 510642, China
| | - Xian Wu
- College of Animal Science and Animal Medicine, Tianjin Agricultural University, Tianjin 300384, China
| | - Xi Chen
- College of Natural Resources and Environment, South China Agricultural University, Guangzhou 510642, China E-mail: ; College of Marine Sciences, South China Agricultural University, Guangzhou 510642, China
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Suyama T, Kanno N, Matsukura S, Chihara K, Noda N, Hanada S. Transcriptome and Deletion Mutant Analyses Revealed that an RpoH Family Sigma Factor Is Essential for Photosystem Production in Roseateles depolymerans under Carbon Starvation. Microbes Environ 2023; 38. [PMID: 36878600 PMCID: PMC10037100 DOI: 10.1264/jsme2.me22072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/08/2023] Open
Abstract
Roseateles depolymerans is an obligately aerobic bacterium that produces a photosynthetic apparatus only under the scarcity of carbon substrates. We herein examined changes in the transcriptomes of R. depolymerans cells to clarify the expression of photosynthesis genes and their upstream regulatory factors under carbon starvation. Transcriptomes 0, 1, and 6 h after the depletion of a carbon substrate indicated that transcripts showing the greatest variations (a 500-fold increase [6 h/0 h]) were light-harvesting proteins (PufA and PufB). Moreover, loci with more than 50-fold increases (6 h/0 h) were fully related to the photosynthetic gene cluster. Among 13 sigma factor genes, the transcripts of a sigma 70 family sigma factor related to RpoH (SP70) increased along photosynthesis genes under starvation; therefore, a knockout experiment of SP70 was performed. ΔSP70 mutants were found to lack photosynthetic pigments (carotenoids and bacteriochlo-rophyll a) regardless of carbon starvation. We also examined the effects of heat stress on ΔSP70 mutants, and found that SP70 was also related to heat stress tolerance, similar to other RpoH sigma factors (while heat stress did not trigger photosystem production). The deficient accumulation of photosynthetic pigments and the heat stress tolerance of ΔSP70 mutants were both complemented by the introduction of an intact SP70 gene. Furthermore, the transcription of photosynthetic gene operons (puf, puh, and bch) was markedly reduced in the ΔSP70 mutant. The RpoH homologue SP70 was concluded to be a sigma factor that is essential for the transcription of photosynthetic gene operons in R. depolymerans.
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Affiliation(s)
- Tetsushi Suyama
- Bio-Analytical Research Group, Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST)
| | - Nanako Kanno
- Photosynthetic Microbial Consortia Laboratory, Department of Biological Sciences, Graduate School of Science, Tokyo Metropolitan University
| | - Satoko Matsukura
- Bio-Analytical Research Group, Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST)
| | - Kotaro Chihara
- Bio-Analytical Research Group, Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST)
- Department of Life Science and Medical Bioscience, Waseda University
| | - Naohiro Noda
- Bio-Analytical Research Group, Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST)
- Department of Life Science and Medical Bioscience, Waseda University
| | - Satoshi Hanada
- Photosynthetic Microbial Consortia Laboratory, Department of Biological Sciences, Graduate School of Science, Tokyo Metropolitan University
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Purple bacteria screening for photoautohydrogenotrophic food production: Are new H 2-fed isolates faster and nutritionally better than photoheterotrophically obtained reference species? N Biotechnol 2022; 72:38-47. [PMID: 36049649 DOI: 10.1016/j.nbt.2022.08.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 08/26/2022] [Accepted: 08/28/2022] [Indexed: 12/14/2022]
Abstract
Photoautohydrogenotrophic enrichments of wastewater treatment microbiomes were performed to obtain hypothetically high-potential specialist species for biotechnological applications. From these enrichment cultures, ten photoautohydrogenotrophic species were isolated: six Rhodopseudomonas species, three Rubrivivax members and Rhodobacter blasticus. The performance of these isolates was compared to three commonly studied, and originally photoheterotrophically enriched species (Rhodopseudomonas palustris, Rhodobacter capsulatus and Rhodobacter sphaeroides), designated as reference species. Repeated subcultivations were applied to improve the initial poor performance of the isolates (acclimation effect), which resulted in increases in both maximum growth rate and protein productivity. However, the maximum growth rate of the reference species remained 3-7 times higher compared to the isolates (0.42-0.84 d-1 at 28 °C), while protein productivities remained 1.5-1.7 times higher. This indicated that H2-based enrichment did not result in photoautohydrogenotrophic specialists, suggesting that the reference species are more suitable for intensified biomass and protein production. On the other hand, the isolates were able to provide equally high protein quality profiles as the references species, providing full dietary essential amino acid matches for human food. Lastly, the effect of metabolic carbon/electron switching (back and forth between auto- to heterotrophic conditions) initially boosted µmax when returning to photoautohydrogenotrophic conditions. However, the switch negatively impacted lag phase, protein productivities and pigment contents. In the case of protein productivity, the acquired acclimation was partially lost with decreases of up to 44 % and 40 % respectively for isolates and reference species. Finally, the three reference species, and specifically Rh. capsulatus, remained the most suitable candidate(s) for further biotechnological development.
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Dragnea V, Gonzalez-Gutierrez G, Bauer CE. Structural Analyses of CrtJ and Its B 12-Binding Co-Regulators SAerR and LAerR from the Purple Photosynthetic Bacterium Rhodobacter capsulatus. Microorganisms 2022; 10:912. [PMID: 35630357 PMCID: PMC9144470 DOI: 10.3390/microorganisms10050912] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 04/25/2022] [Accepted: 04/26/2022] [Indexed: 02/01/2023] Open
Abstract
Among purple photosynthetic bacteria, the transcription factor CrtJ is a major regulator of photosystem gene expression. Depending on growing conditions, CrtJ can function as an aerobic repressor or an anaerobic activator of photosystem genes. Recently, CrtJ's activity was shown to be modulated by two size variants of a B12 binding co-regulator called SAerR and LAerR in Rhodobacter capsulatus. The short form, SAerR, promotes CrtJ repression, while the longer variant, LAerR, converts CrtJ into an activator. In this study, we solved the crystal structure of R. capsulatus SAerR at a 2.25 Å resolution. Hydroxycobalamin bound to SAerR is sandwiched between a 4-helix bundle cap, and a Rossman fold. This structure is similar to a AerR-like domain present in CarH from Thermus termophilus, which is a combined photoreceptor/transcription regulator. We also utilized AlphaFold software to predict structures for the LAerR, CrtJ, SAerR-CrtJ and LAerR-CrtJ co-complexes. These structures provide insights into the role of B12 and an LAerR N-terminal extension in regulating the activity of CrtJ.
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Affiliation(s)
| | | | - Carl E. Bauer
- Molecular and Cellular Biochemistry Department, Indiana University, Bloomington, IN 47405, USA; (V.D.); (G.G.-G.)
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Alloul A, Cerruti M, Adamczyk D, Weissbrodt DG, Vlaeminck SE. Operational Strategies to Selectively Produce Purple Bacteria for Microbial Protein in Raceway Reactors. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:8278-8286. [PMID: 34085818 DOI: 10.1021/acs.est.0c08204] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Purple non-sulfur bacteria (PNSB) show potential for microbial protein production on wastewater as animal feed. They offer good selectivity (i.e., low microbial diversity and high abundance of one species) when grown anaerobically in the light. However, the cost of closed anaerobic photobioreactors is prohibitive for protein production. Although open raceway reactors are cheaper, their feasibility to selectively grow PNSB is thus far unexplored. This study developed operational strategies to boost PNSB abundance in the biomass of a raceway reactor fed with volatile fatty acids. For a flask reactor run at a 2 day sludge retention time (SRT), matching the chemical oxygen demand (COD) loading rate to the removal rate in the light period prevented substrate availability during the dark period and increased the PNSB abundance from 50-67 to 88-94%. A raceway reactor run at a 2 day SRT showed an increased PNSB abundance from 14 to 56% when oxygen supply was reduced (no stirring at night). The best performance was achieved at the highest surface-to-volume ratio (10 m2 m-3 increased light availability) showing productivities up to 0.2 g protein L-1 day-1 and a PNSB abundance of 78%. This study pioneered in PNSB-based microbial protein production in raceway reactors, yielding high selectivity while avoiding the combined availability of oxygen, COD, and darkness.
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Affiliation(s)
- Abbas Alloul
- Research Group of Sustainable Energy, Air and Water Technology, Department of Bioscience Engineering, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerpen, Belgium
| | - Marta Cerruti
- Department of Biotechnology, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, the Netherlands
| | - Damian Adamczyk
- Research Group of Sustainable Energy, Air and Water Technology, Department of Bioscience Engineering, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerpen, Belgium
| | - David G Weissbrodt
- Department of Biotechnology, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, the Netherlands
| | - Siegfried E Vlaeminck
- Research Group of Sustainable Energy, Air and Water Technology, Department of Bioscience Engineering, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerpen, Belgium
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Capson-Tojo G, Lin S, Batstone DJ, Hülsen T. Purple phototrophic bacteria are outcompeted by aerobic heterotrophs in the presence of oxygen. WATER RESEARCH 2021; 194:116941. [PMID: 33640750 DOI: 10.1016/j.watres.2021.116941] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 02/14/2021] [Accepted: 02/15/2021] [Indexed: 06/12/2023]
Abstract
There is an ongoing debate around the effect of microaerobic/aerobic conditions on the wastewater treatment performance and stability of enriched purple phototrophic bacteria (PPB) cultures. It is well known that oxygen-induced oxidative conditions inhibit the synthesis of light harvesting complexes, required for photoheterotrophy. However, in applied research, several publications have reported efficient wastewater treatment at high dissolved oxygen (DO) levels. This study evaluated the impact of different DO concentrations (0-0.25 mg·L-1, 0-0.5 mg·L-1 and 0-4.5 mg·L-1) on the COD, nitrogen and phosphorus removal performances, the biomass yields, and the final microbial communities of PPB-enriched cultures, treating real wastewaters (domestic and poultry processing wastewater). The results show that the presence of oxygen suppressed photoheterotrophic growth, which led to a complete pigment and colour loss in a matter of 20-30 h after starting the batch. Under aerobic conditions, chemoheterotrophy was the dominant catabolic pathway, with wastewater treatment performances similar to those achieved in common aerobic reactors, rather than those corresponding to phototrophic systems (i.e. considerable total COD decrease (45-57% aerobically vs. ± 10% anaerobically). This includes faster consumption of COD and nutrients, lower nutrient removal efficiencies (50-58% vs. 72-99% for NH4+-N), lower COD:N:P substrate ratios (100:4.5-5.0:0.4-0.8 vs. 100:6.7-12:0.9-1.2), and lower apparent biomass yields (0.15-0.31 vs. 0.8-1.2 g CODbiomass·g CODremoved-1)). The suppression of photoheterotrophy inevitably resulted in a reduction of the relative PPB abundances in all the aerated tests (below 20% at the end of the tests), as PPB lost their main competitive advantage against competing aerobic heterotrophic microbes. This was explained by the lower aerobic PPB growth rates (2.4 d-1 at 35 °C) when compared to common growth rates for aerobic heterotrophs (6.0 d-1 at 20 °C). Therefore, PPB effectively outcompete other microbes under illuminated-anaerobic conditions, but not under aerobic or even micro-aerobic conditions, as shown by continuously aerated tests controlled at undetectable DO levels. While their aerobic heterotrophic capabilities provide some resilience, at non-sterile conditions PPB cannot dominate when growing chemoheterotrophically, and will be outcompeted.
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Affiliation(s)
- Gabriel Capson-Tojo
- Advanced Water Management Centre, The University of Queensland, Brisbane, QLD 4072, Australia; CRETUS Institute, Department of Chemical Engineering, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Galicia, Spain
| | - Shengli Lin
- Advanced Water Management Centre, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Damien J Batstone
- Advanced Water Management Centre, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Tim Hülsen
- Advanced Water Management Centre, The University of Queensland, Brisbane, QLD 4072, Australia.
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Izaki K, Haruta S. Aerobic Production of Bacteriochlorophylls in the Filamentous Anoxygenic Photosynthetic Bacterium, Chloroflexus aurantiacus in the Light. Microbes Environ 2020; 35. [PMID: 32418929 PMCID: PMC7308566 DOI: 10.1264/jsme2.me20015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Filamentous anoxygenic photosynthetic bacteria grow by photosynthesis and aerobic respiration. The present study investigated the effects of light and O2 on bacteriochlorophyll contents and the transcription levels of photosynthesis-related genes in Chloroflexus aurantiacus J-10-fl T. Under aerobic conditions, C. aurantiacus produced marked amounts of bacteriochlorophylls in the presence of light, although their production was strongly suppressed in the dark. The transcription levels of genes related to the synthesis of bacteriochlorophylls, photosystems, and chlorosomes: bchM, bchU, pufL, pufBA, and csmM, were markedly increased by illumination. These results suggest that C. aurantiacus continuously synthesizes ATP by photophosphorylation even in the presence of O2.
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Affiliation(s)
- Kazaha Izaki
- Department of Biological Sciences, Tokyo Metropolitan University
| | - Shin Haruta
- Department of Biological Sciences, Tokyo Metropolitan University
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Wu T, Liu J, Li M, Zhang G, Liu L, Li X, Men X, Xian M, Zhang H. Improvement of sabinene tolerance of Escherichia coli using adaptive laboratory evolution and omics technologies. BIOTECHNOLOGY FOR BIOFUELS 2020; 13:79. [PMID: 32346395 PMCID: PMC7181518 DOI: 10.1186/s13068-020-01715-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Accepted: 04/13/2020] [Indexed: 05/28/2023]
Abstract
BACKGROUND Biosynthesis of sabinene, a bicyclic monoterpene, has been accomplished in engineered microorganisms by introducing heterologous pathways and using renewable sugar as a carbon source. However, the efficiency and titers of this method are limited by the low host tolerance to sabinene (in both eukaryotes and prokaryotes). RESULTS In this study, Escherichia coli BL21(DE3) was selected as the strain for adaptive laboratory evolution. The strain was evolved by serial passaging in the medium supplemented with gradually increasing concentration of sabinene, and the evolved strain XYF(DE3), which exhibited significant tolerance to sabinene, was obtained. Then, XYF(DE3) was used as the host for sabinene production and an 8.43-fold higher sabinene production was achieved compared with the parental BL21(DE3), reaching 191.76 mg/L. Whole genomes resequencing suggested the XYF(DE3) strain is a hypermutator. A comparative analysis of transcriptomes of XYF(DE3) and BL21(DE3) was carried out to reveal the mechanism underlying the improvement of sabinene tolerance, and 734 up-regulated genes and 857 down-regulated genes were identified. We further tested the roles of the identified genes in sabinene tolerance via reverse engineering. The results demonstrated that overexpressions of ybcK gene of the DLP12 family, the inner membrane protein gene ygiZ, and the methylmalonyl-CoA mutase gene scpA could increase sabinene tolerance of BL21(DE3) by 127.7%, 71.1%, and 75.4%, respectively. Furthermore, scanning electron microscopy was applied to monitor cell morphology. Under sabinene stress, the parental BL21(DE3) showed increased cell length, whereas XYF(DE3) showed normal cell morphology. In addition, overexpression of ybcK, ygiZ or scpA could partially rescue cell morphology under sabinene stress and overexpression of ygiZ or scpA could increase sabinene production in BL21(DE3). CONCLUSIONS This study not only obtained a sabinene-tolerant strain for microbial production of sabinene but also revealed potential regulatory mechanisms that are important for sabinene tolerance. In addition, for the first time, ybcK, ygiZ, and scpA were identified to be important for terpene tolerance in E. coli BL21(DE3).
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Affiliation(s)
- Tong Wu
- CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Laoshan District, Qingdao, 266101 China
- University of Chinese Academy of Sciences, Beijing, 100049 China
| | - Jinfeng Liu
- CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Laoshan District, Qingdao, 266101 China
- School of Life Science and Engineering, Lanzhou University of Technology, Lanzhou, 730050 China
| | - Meijie Li
- CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Laoshan District, Qingdao, 266101 China
- University of Chinese Academy of Sciences, Beijing, 100049 China
| | - Ge Zhang
- CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Laoshan District, Qingdao, 266101 China
| | - Lijuan Liu
- CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Laoshan District, Qingdao, 266101 China
| | - Xing Li
- CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Laoshan District, Qingdao, 266101 China
| | - Xiao Men
- CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Laoshan District, Qingdao, 266101 China
| | - Mo Xian
- CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Laoshan District, Qingdao, 266101 China
| | - Haibo Zhang
- CAS Key Laboratory of Biobased Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Laoshan District, Qingdao, 266101 China
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Shimizu T, Shen J, Fang M, Zhang Y, Hori K, Trinidad JC, Bauer CE, Giedroc DP, Masuda S. Sulfide-responsive transcriptional repressor SqrR functions as a master regulator of sulfide-dependent photosynthesis. Proc Natl Acad Sci U S A 2017; 114:2355-2360. [PMID: 28196888 PMCID: PMC5338557 DOI: 10.1073/pnas.1614133114] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Sulfide was used as an electron donor early in the evolution of photosynthesis, with many extant photosynthetic bacteria still capable of using sulfur compounds such as hydrogen sulfide (H2S) as a photosynthetic electron donor. Although enzymes involved in H2S oxidation have been characterized, mechanisms of regulation of sulfide-dependent photosynthesis have not been elucidated. In this study, we have identified a sulfide-responsive transcriptional repressor, SqrR, that functions as a master regulator of sulfide-dependent gene expression in the purple photosynthetic bacterium Rhodobacter capsulatus SqrR has three cysteine residues, two of which, C41 and C107, are conserved in SqrR homologs from other bacteria. Analysis with liquid chromatography coupled with an electrospray-interface tandem-mass spectrometer reveals that SqrR forms an intramolecular tetrasulfide bond between C41 and C107 when incubated with the sulfur donor glutathione persulfide. SqrR is oxidized in sulfide-stressed cells, and tetrasulfide-cross-linked SqrR binds more weakly to a target promoter relative to unmodified SqrR. C41S and C107S R. capsulatus SqrRs lack the ability to respond to sulfide, and constitutively repress target gene expression in cells. These results establish that SqrR is a sensor of H2S-derived reactive sulfur species that maintain sulfide homeostasis in this photosynthetic bacterium and reveal the mechanism of sulfide-dependent transcriptional derepression of genes involved in sulfide metabolism.
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Affiliation(s)
- Takayuki Shimizu
- Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Kanagawa 226-8501, Japan
| | - Jiangchuan Shen
- Department of Chemistry, Indiana University, Bloomington, IN 47405-7102
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN 47405
| | - Mingxu Fang
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN 47405
| | - Yixiang Zhang
- Department of Chemistry, Indiana University, Bloomington, IN 47405-7102
- Laboratory for Biological Mass Spectrometry, Indiana University, Bloomington, IN 47405-7102
| | - Koichi Hori
- School of Life Science and Technology, Tokyo Institute of Technology, Kanagawa 226-8501, Japan
| | - Jonathan C Trinidad
- Department of Chemistry, Indiana University, Bloomington, IN 47405-7102
- Laboratory for Biological Mass Spectrometry, Indiana University, Bloomington, IN 47405-7102
| | - Carl E Bauer
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN 47405
| | - David P Giedroc
- Department of Chemistry, Indiana University, Bloomington, IN 47405-7102
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN 47405
| | - Shinji Masuda
- Center for Biological Resources and Informatics, Tokyo Institute of Technology, Kanagawa 226-8501, Japan;
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo 152-8551, Japan
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12
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Muzziotti D, Adessi A, Faraloni C, Torzillo G, De Philippis R. Acclimation strategy of Rhodopseudomonas palustris to high light irradiance. Microbiol Res 2017; 197:49-55. [PMID: 28219525 DOI: 10.1016/j.micres.2017.01.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Revised: 01/02/2017] [Accepted: 01/23/2017] [Indexed: 12/30/2022]
Abstract
The ability of Rhodopseudomonas palustris cells to rapidly acclimate to high light irradiance is an essential issue when cells are grown under sunlight. The aim of this study was to investigate the photo-acclimation process in Rhodopseudomonas palustris 42OL under different culturing conditions: (i) anaerobic (AnG), (ii) aerobic (AG), and (iii) under H2-producing (HP) conditions both at low (LL) and high light (HL) irradiances. The results obtained clearly showed that the photosynthetic unit was significantly affected by the light irradiance at which Rp. palustris 42OL was grown. The synthesis of carotenoids was affected by both illumination and culturing conditions. At LL, lycopene was the main carotenoid synthetized under all conditions tested, while at HL under HP conditions, it resulted the predominant carotenoid. Oppositely, under AnG and AG at HL, rhodovibrin was the major carotenoid detected. The increase in light intensity produced a deeper variation in light-harvesting complexes (LHC) ratio. These findings are important for understanding the ecological distribution of PNSB in natural environments, mostly characterized by high light intensities, and for its growth outdoors.
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Affiliation(s)
- Dayana Muzziotti
- Department of Agrifood Production and Environmental Sciences, University of Florence, via Maragliano 77, 50144, Florence, Italy.
| | - Alessandra Adessi
- Department of Agrifood Production and Environmental Sciences, University of Florence, via Maragliano 77, 50144, Florence, Italy; Institute of Chemistry of Organometallic Compounds (ICCOM), CNR, Via Madonna del Piano, 10-50019 Sesto Fiorentino, Florence, Italy.
| | - Cecilia Faraloni
- Institute of Ecosystem Study (ISE), CNR, Via Madonna del Piano, 10-50019 Sesto Fiorentino, Florence, Italy.
| | - Giuseppe Torzillo
- Institute of Ecosystem Study (ISE), CNR, Via Madonna del Piano, 10-50019 Sesto Fiorentino, Florence, Italy.
| | - Roberto De Philippis
- Department of Agrifood Production and Environmental Sciences, University of Florence, via Maragliano 77, 50144, Florence, Italy; Institute of Chemistry of Organometallic Compounds (ICCOM), CNR, Via Madonna del Piano, 10-50019 Sesto Fiorentino, Florence, Italy.
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13
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Peng T, Berghoff BA, Oh JI, Weber L, Schirmer J, Schwarz J, Glaeser J, Klug G. Regulation of a polyamine transporter by the conserved 3' UTR-derived sRNA SorX confers resistance to singlet oxygen and organic hydroperoxides in Rhodobacter sphaeroides. RNA Biol 2016; 13:988-999. [PMID: 27420112 DOI: 10.1080/15476286.2016.1212152] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Singlet oxygen is generated by bacteriochlorophylls when light and oxygen are simultaneously present in Rhodobacter sphaeroides. Singlet oxygen triggers a specific response that is partly regulated by the alternative sigma factor RpoHI/HII. The sRNA RSs2461 has previously been identified as an RpoHI/HII-dependent sRNA and is derived from the 3' UTR of the mRNA for an OmpR-type transcriptional regulator. Similar to the RpoHI/HII-dependent CcsR and SorY sRNAs, RSs2461 affects the resistance of R. sphaeroides against singlet oxygen and was therefore renamed here SorX. Furthermore, SorX has a strong impact on resistance against organic hydroperoxides that usually occur as secondary damages downstream of singlet oxygen. The 75-nt SorX 3' fragment, which is generated by RNase E cleavage and highly conserved among related species, represents the functional entity. A target search identified potA mRNA, which encodes a subunit of a polyamine transporter, as a direct SorX target and stress resistance via SorX could be linked to potA. The PotABCD transporter is an uptake system for spermidine in E. coli. While spermidine is generally described as beneficial during oxidative stress, we observed significantly increased sensitivity of R. sphaeroides to organic hydroperoxides in the presence of spermidine. We therefore propose that the diminished import of spermidine, due to down-regulation of potA by SorX, counteracts oxidative stress. Together with results from other studies this underlines the importance of regulated transport to bacterial stress defense.
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Affiliation(s)
- Tao Peng
- a Institut für Mikrobiologie und Molekularbiologie, IFZ, Universität Giessen , Giessen , Germany
| | - Bork A Berghoff
- a Institut für Mikrobiologie und Molekularbiologie, IFZ, Universität Giessen , Giessen , Germany
| | - Jeong-Il Oh
- b Department of Microbiology , Pusan National University , Busan , Korea
| | - Lennart Weber
- a Institut für Mikrobiologie und Molekularbiologie, IFZ, Universität Giessen , Giessen , Germany
| | - Jasmin Schirmer
- a Institut für Mikrobiologie und Molekularbiologie, IFZ, Universität Giessen , Giessen , Germany
| | - Johannes Schwarz
- a Institut für Mikrobiologie und Molekularbiologie, IFZ, Universität Giessen , Giessen , Germany
| | - Jens Glaeser
- a Institut für Mikrobiologie und Molekularbiologie, IFZ, Universität Giessen , Giessen , Germany
| | - Gabriele Klug
- a Institut für Mikrobiologie und Molekularbiologie, IFZ, Universität Giessen , Giessen , Germany
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14
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Abstract
A substantial proportion of the dazzling diversity of colors displayed by living organisms throughout the tree of life is determined by the presence of carotenoids, which most often provide distinctive yellow, orange and red hues. These metabolites play fundamental roles in nature that extend far beyond their importance as pigments. In photosynthetic lineages, carotenoids are essential to sustain life, since they have been exploited to maximize light harvesting and protect the photosynthetic machinery from photooxidative stress. Consequently, photosynthetic organisms have evolved several mechanisms that adjust the carotenoid metabolism to efficiently cope with constantly fluctuating light environments. This chapter will focus on the current knowledge concerning the regulation of the carotenoid biosynthetic pathway in leaves, which are the primary photosynthetic organs of most land plants.
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15
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Proteome Profiling of the Rhodobacter capsulatus Molybdenum Response Reveals a Role of IscN in Nitrogen Fixation by Fe-Nitrogenase. J Bacteriol 2015; 198:633-43. [PMID: 26644433 DOI: 10.1128/jb.00750-15] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 11/12/2015] [Indexed: 01/11/2023] Open
Abstract
UNLABELLED Rhodobacter capsulatus is capable of synthesizing two nitrogenases, a molybdenum-dependent nitrogenase and an alternative Mo-free iron-only nitrogenase, enabling this diazotroph to grow with molecular dinitrogen (N2) as the sole nitrogen source. Here, the Mo responses of the wild type and of a mutant lacking ModABC, the high-affinity molybdate transporter, were examined by proteome profiling, Western analysis, epitope tagging, and lacZ reporter fusions. Many Mo-controlled proteins identified in this study have documented or presumed roles in nitrogen fixation, demonstrating the relevance of Mo control in this highly ATP-demanding process. The levels of Mo-nitrogenase, NifHDK, and the Mo storage protein, Mop, increased with increasing Mo concentrations. In contrast, Fe-nitrogenase, AnfHDGK, and ModABC, the Mo transporter, were expressed only under Mo-limiting conditions. IscN was identified as a novel Mo-repressed protein. Mo control of Mop, AnfHDGK, and ModABC corresponded to transcriptional regulation of their genes by the Mo-responsive regulators MopA and MopB. Mo control of NifHDK and IscN appeared to be more complex, involving different posttranscriptional mechanisms. In line with the simultaneous control of IscN and Fe-nitrogenase by Mo, IscN was found to be important for Fe-nitrogenase-dependent diazotrophic growth. The possible role of IscN as an A-type carrier providing Fe-nitrogenase with Fe-S clusters is discussed. IMPORTANCE Biological nitrogen fixation is a central process in the global nitrogen cycle by which the abundant but chemically inert dinitrogen (N2) is reduced to ammonia (NH3), a bioavailable form of nitrogen. Nitrogen reduction is catalyzed by nitrogenases found in diazotrophic bacteria and archaea but not in eukaryotes. All diazotrophs synthesize molybdenum-dependent nitrogenases. In addition, some diazotrophs, including Rhodobacter capsulatus, possess catalytically less efficient alternative Mo-free nitrogenases, whose expression is repressed by Mo. Despite the importance of Mo in biological nitrogen fixation, this is the first study analyzing the proteome-wide Mo response in a diazotroph. IscN was recognized as a novel member of the molybdoproteome in R. capsulatus. It was dispensable for Mo-nitrogenase activity but supported diazotrophic growth under Mo-limiting conditions.
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16
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Kis M, Sipka G, Asztalos E, Rázga Z, Maróti P. Purple non-sulfur photosynthetic bacteria monitor environmental stresses. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2015; 151:110-7. [PMID: 26232748 DOI: 10.1016/j.jphotobiol.2015.07.017] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Revised: 07/21/2015] [Accepted: 07/23/2015] [Indexed: 11/19/2022]
Abstract
Heavy metal ion pollution and oxygen deficiency are major environmental risks for microorganisms in aqueous habitat. The potential of purple non-sulfur photosynthetic bacteria for biomonitoring and bioremediation was assessed by investigating the photosynthetic capacity in heavy metal contaminated environments. Cultures of bacterial strains Rhodobacter sphaeroides, Rhodospirillum rubrum and Rubrivivax gelatinosus were treated with heavy metal ions in micromolar (Hg(2+)), submillimolar (Cr(6+)) and millimolar (Pb(2+)) concentration ranges. Functional assays (flash-induced absorption changes and bacteriochlorophyll fluorescence induction) and electron micrographs were taken to specify the harmful effects of pollution and to correlate to morphological changes of the membrane. The bacterial strains and functional tests showed differentiated responses to environmental stresses, revealing that diverse mechanisms of tolerance and/or resistance are involved. The microorganisms were vulnerable to the prompt effect of Pb(2+), showed weak tolerance to Hg(2+) and proved to be tolerant to Cr(6+). The reaction center controlled electron transfer in Rvx. gelatinosus demonstrated the highest degree of resistance against heavy metal exposure.
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Affiliation(s)
- Mariann Kis
- Department of Medical Physics, University of Szeged, Hungary
| | - Gábor Sipka
- Department of Medical Physics, University of Szeged, Hungary
| | - Emese Asztalos
- Department of Medical Physics, University of Szeged, Hungary
| | - Zsolt Rázga
- Department of Pathology, University of Szeged, Hungary
| | - Péter Maróti
- Department of Medical Physics, University of Szeged, Hungary.
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17
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Members of the PpaA/AerR Antirepressor Family Bind Cobalamin. J Bacteriol 2015; 197:2694-703. [PMID: 26055116 DOI: 10.1128/jb.00374-15] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 06/03/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED PpaA from Rhodobacter sphaeroides is a member of a family of proteins that are thought to function as antirepressors of PpsR, a widely disseminated repressor of photosystem genes in purple photosynthetic bacteria. PpaA family members exhibit sequence similarity to a previously defined SCHIC (sensor containing heme instead of cobalamin) domain; however, the tetrapyrrole-binding specificity of PpaA family members has been unclear, as R. sphaeroides PpaA has been reported to bind heme while the Rhodobacter capsulatus homolog has been reported to bind cobalamin. In this study, we reinvestigated tetrapyrrole binding of PpaA from R. sphaeroides and show that it is not a heme-binding protein but is instead a cobalamin-binding protein. We also use bacterial two-hybrid analysis to show that PpaA is able to interact with PpsR and activate the expression of photosynthesis genes in vivo. Mutations in PpaA that cause loss of cobalamin binding also disrupt PpaA antirepressor activity in vivo. We also tested a number of PpaA homologs from other purple bacterial species and found that cobalamin binding is a conserved feature among members of this family of proteins. IMPORTANCE Cobalamin (vitamin B12) has only recently been recognized as a cofactor that affects gene expression by interacting in a light-dependent manner with transcription factors. A group of related antirepressors known as the AppA/PpaA/AerR family are known to control the expression of photosynthesis genes in part by interacting with either heme or cobalamin. The specificity of which tetrapyrroles that members of this family interact with has, however, remained cloudy. In this study, we address the tetrapyrrole-binding specificity of the PpaA/AerR subgroup and establish that it preferentially binds cobalamin over heme.
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18
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Shimizu T, Cheng Z, Matsuura K, Masuda S, Bauer CE. Evidence that Altered Cis Element Spacing Affects PpsR Mediated Redox Control of Photosynthesis Gene Expression in Rubrivivax gelatinosus. PLoS One 2015; 10:e0128446. [PMID: 26030916 PMCID: PMC4452267 DOI: 10.1371/journal.pone.0128446] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Accepted: 04/27/2015] [Indexed: 11/18/2022] Open
Abstract
PpsR is a major regulator of photosynthesis gene expression among all characterized purple photosynthetic bacteria. This transcription regulator has been extensively characterized in Rhodobacter (Rba.) capsulatus and Rba. sphaeroides which are members of the α-proteobacteria lineage. In this study, we have investigated the biochemical properties and mutational effects of a ppsR deletion strain in the β-proteobacterium Rubrivivax (Rvi.) gelatinosus in order to reveal phylogenetically conserved mechanisms and species-specific characteristics. A deletion of the ppsR gene resulted in de-repression of photosystem synthesis showing that PpsR functions as a repressor of photosynthesis genes in this species. We also constructed a Rvi. gelatinosus PpsR mutant in which a conserved cysteine at position 436 was changed to an alanine to examine whether or not this residue is important for sensing redox, as reported in Rhodobacter species. Surprisingly, the Cys436 Ala mutant retained the ability to repress photosynthesis gene expression under aerobic conditions, suggesting that PpsR from Rvi. gelatinosus has different redox-responding characteristics. Furthermore, biochemical analyses demonstrated that Rvi. gelatinosus PpsR only shows redox-dependent binding to promoters with 9-bp spacing, but not 8-bp spacing, between two PpsR-recognition sequences. These results indicate that redox-dependent binding of PpsR requires appropriate cis configuration of PpsR target sequences in Rvi. gelatinosus. These results also indicate that PpsR homologs from different species regulate photosynthesis genes with altered biochemical properties.
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Affiliation(s)
- Takayuki Shimizu
- Department of Biological Sciences, Tokyo Institute of Technology, Kanagawa 226–8501, Japan
| | - Zhuo Cheng
- Department of Molecular and Cellar Biochemistry, Indiana University, Bloomington, Indiana 47405, United States of America
| | - Katsumi Matsuura
- Graduate School of Science and Engineering, Tokyo Metropolitan University, Tokyo 192–0397, Japan
| | - Shinji Masuda
- Center for Biological Resources and Informatics, Tokyo Institute of Technology, Kanagawa 226–8501, Japan
- Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo 152–8551, Japan
| | - Carl E. Bauer
- Department of Molecular and Cellar Biochemistry, Indiana University, Bloomington, Indiana 47405, United States of America
- * E-mail:
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19
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Molano-Arevalo JC, Hernandez DR, Gonzalez WG, Miksovska J, Ridgeway ME, Park MA, Fernandez-Lima F. Flavin adenine dinucleotide structural motifs: from solution to gas phase. Anal Chem 2014; 86:10223-30. [PMID: 25222439 PMCID: PMC4204916 DOI: 10.1021/ac5023666] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
![]()
Flavin
adenine dinucleotide (FAD) is involved in important metabolic
reactions where the biological function is intrinsically related to
changes in conformation. In the present work, FAD conformational changes
were studied in solution and in gas phase by measuring the fluorescence
decay time and ion-neutral collision cross sections (CCS, in a trapped
ion mobility spectrometer, TIMS) as a function of the solvent conditions
(i.e., organic content) and gas-phase collisional partner (i.e., N2 doped with organic molecules). Changes in the fluorescence
decay suggest that FAD can exist in four conformations in solution,
where the abundance of the extended conformations increases with the
organic content. TIMS-MS experiments showed that FAD can exist in
the gas phase as deprotonated (M = C27H31N9O15P2) and protonated forms (M = C27H33N9O15P2) and
that multiple conformations (up to 12) can be observed as a function
of the starting solution for the [M + H]+ and [M + Na]+molecular ions. In addition, changes in the relative abundances
of the gas-phase structures were observed from a “stack”
to a “close” conformation when organic molecules were
introduced in the TIMS cell as collision partners. Candidate structures
optimized at the DFT/B3LYP/6-31G(d,p) were proposed for each IMS band,
and results showed that the most abundant IMS band corresponds to
the most stable candidate structure. Solution and gas-phase experiments
suggest that the driving force that stabilizes the different conformations
is based on the interaction of the adenine and isoalloxazine rings
that can be tailored by the “solvation” effect created
with the organic molecules.
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Affiliation(s)
- Juan Camilo Molano-Arevalo
- Department of Chemistry and Biochemistry, Florida International University , Miami, Florida 33199, United States
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Guan Y, Zhao HB, Yu LX, Chen SC, Wang YZ. Multi-stimuli sensitive supramolecular hydrogel formed by host–guest interaction between PNIPAM-Azo and cyclodextrin dimers. RSC Adv 2014. [DOI: 10.1039/c3ra45461d] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
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Integrative "omics"-approach discovers dynamic and regulatory features of bacterial stress responses. PLoS Genet 2013; 9:e1003576. [PMID: 23818867 PMCID: PMC3688512 DOI: 10.1371/journal.pgen.1003576] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2013] [Accepted: 05/03/2013] [Indexed: 01/08/2023] Open
Abstract
Bacteria constantly face stress conditions and therefore mount specific responses to ensure adaptation and survival. Stress responses were believed to be predominantly regulated at the transcriptional level. In the phototrophic bacterium Rhodobacter sphaeroides the response to singlet oxygen is initiated by alternative sigma factors. Further adaptive mechanisms include post-transcriptional and post-translational events, which have to be considered to gain a deeper understanding of how sophisticated regulation networks operate. To address this issue, we integrated three layers of regulation: (1) total mRNA levels at different time-points revealed dynamics of the transcriptome, (2) mRNAs in polysome fractions reported on translational regulation (translatome), and (3) SILAC-based mass spectrometry was used to quantify protein abundances (proteome). The singlet oxygen stress response exhibited highly dynamic features regarding short-term effects and late adaptation, which could in part be assigned to the sigma factors RpoE and RpoH2 generating distinct expression kinetics of corresponding regulons. The occurrence of polar expression patterns of genes within stress-inducible operons pointed to an alternative of dynamic fine-tuning upon stress. In addition to transcriptional activation, we observed significant induction of genes at the post-transcriptional level (translatome), which identified new putative regulators and assigned genes of quorum sensing to the singlet oxygen stress response. Intriguingly, the SILAC approach explored the stress-dependent decline of photosynthetic proteins, but also identified 19 new open reading frames, which were partly validated by RNA-seq. We propose that comparative approaches as presented here will help to create multi-layered expression maps on the system level ("expressome"). Finally, intense mass spectrometry combined with RNA-seq might be the future tool of choice to re-annotate genomes in various organisms and will help to understand how they adapt to alternating conditions.
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22
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Spring S, Riedel T. Mixotrophic growth of bacteriochlorophyll a-containing members of the OM60/NOR5 clade of marine gammaproteobacteria is carbon-starvation independent and correlates with the type of carbon source and oxygen availability. BMC Microbiol 2013; 13:117. [PMID: 23705861 PMCID: PMC3666943 DOI: 10.1186/1471-2180-13-117] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Accepted: 05/16/2013] [Indexed: 11/19/2022] Open
Abstract
Background Populations of aerobic anoxygenic photoheterotrophic bacteria in marine environments are dominated by members of the Roseobacter lineage within the Alphaproteobacteria and the OM60/NOR5 clade of gammaproteobacteria. A wealth of information exists about the regulation of pigment production and mixotrophic growth in various members of the Roseobacter clade, but a detailed knowledge about aerobic bacteriochlorophyll a-containing gammaproteobacteria is still limited to one strain of the species Congregibacter litoralis. Results The production of photosynthetic pigments and light-dependent mixotrophic growth was analysed in Luminiphilus syltensis DSM 22749T, Chromatocurvus halotolerans DSM 23344T and Pseudohaliea rubra DSM 19751T, representing three taxonomically diverse strains of bacteriochlorophyll a-containing gammaproteobacteria affiliated to the OM60/NOR5 clade. In these strains the expression of a photosynthetic apparatus depended mainly on the type of carbon source and availability of oxygen. The effect of illumination on pigment expression varied significantly between strains. In contrast to Chromatocurvus halotolerans, pigment production in Luminiphilus syltensis and Pseudohaliea rubra was repressed by light of moderate intensities, probably indicating a higher sensitivity to light-induced oxidative stress. The efficiency of using light for mixotrophic growth did not correlate with the cellular level of photosynthetic pigments, but depended mainly on the type of metabolized substrate with malate being the optimal carbon source in most cases. Conclusions Oligotrophic growth conditions or carbon limitation were not required for light-dependent mixotrophic growth in members of the OM60/NOR5 clade. The ability of using light as energy source and the fine tuning of photosynthesis gene expression depended mainly on the type of carbon source and oxygen availability, which indicates that the regulation of pigment production is controlled by the cellular redox state. While light has the main impact on the regulation of photosynthetic pigments in photoheterotrophic representatives of the Roseobacter lineage this was not the case in strains of the OM60/NOR5 clade.
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Affiliation(s)
- Stefan Spring
- Leibniz Institute DSMZ - German Collection of Microorganisms and Cell Cultures, Inhoffenstr, 7B, Braunschweig 38124, Germany.
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Characterization of an ntrX mutant of Neisseria gonorrhoeae reveals a response regulator that controls expression of respiratory enzymes in oxidase-positive proteobacteria. J Bacteriol 2013; 195:2632-41. [PMID: 23564168 DOI: 10.1128/jb.02062-12] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
NtrYX is a sensor-histidine kinase/response regulator two-component system that has had limited characterization in a small number of Alphaproteobacteria. Phylogenetic analysis of the response regulator NtrX showed that this two-component system is extensively distributed across the bacterial domain, and it is present in a variety of Betaproteobacteria, including the human pathogen Neisseria gonorrhoeae. Microarray analysis revealed that the expression of several components of the respiratory chain was reduced in an N. gonorrhoeae ntrX mutant compared to that in the isogenic wild-type (WT) strain 1291. These included the cytochrome c oxidase subunit (ccoP), nitrite reductase (aniA), and nitric oxide reductase (norB). Enzyme activity assays showed decreased cytochrome oxidase and nitrite reductase activities in the ntrX mutant, consistent with microarray data. N. gonorrhoeae ntrX mutants had reduced capacity to survive inside primary cervical cells compared to the wild type, and although they retained the ability to form a biofilm, they exhibited reduced survival within the biofilm compared to wild-type cells, as indicated by LIVE/DEAD staining. Analyses of an ntrX mutant in a representative alphaproteobacterium, Rhodobacter capsulatus, showed that cytochrome oxidase activity was also reduced compared to that in the wild-type strain SB1003. Taken together, these data provide evidence that the NtrYX two-component system may be a key regulator in the expression of respiratory enzymes and, in particular, cytochrome c oxidase, across a wide range of proteobacteria, including a variety of bacterial pathogens.
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24
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Steunou AS, Liotenberg S, Soler MN, Briandet R, Barbe V, Astier C, Ouchane S. EmbRS a new two-component system that inhibits biofilm formation and saves Rubrivivax gelatinosus from sinking. Microbiologyopen 2013; 2:431-46. [PMID: 23520142 PMCID: PMC3684757 DOI: 10.1002/mbo3.82] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Revised: 02/11/2013] [Accepted: 02/15/2013] [Indexed: 11/06/2022] Open
Abstract
Photosynthetic bacteria can switch from planktonic lifestyle to phototrophic biofilm in mats in response to environmental changes. The mechanisms of phototrophic biofilm formation are, however, not characterized. Herein, we report a two-component system EmbRS that controls the biofilm formation in a photosynthetic member of the Burkholderiales order, the purple bacterium Rubrivivax gelatinosus. EmbRS inactivation results in cells that form conspicuous bacterial veils and fast-sinking aggregates in liquid. Biofilm analyses indicated that EmbRS represses the production of an extracellular matrix and biofilm formation. Mapping of transposon mutants that partially or completely restore the wild-type (WT) phenotype allowed the identification of two gene clusters involved in polysaccharide synthesis, one fully conserved only in Thauera sp., a floc-forming wastewater bacterium. A second two-component system BmfRS and a putative diguanylate cyclase BdcA were also identified in this screen suggesting their involvement in biofilm formation in this bacterium. The role of polysaccharides in sinking of microorganisms and organic matter, as well as the importance and the evolution of such regulatory system in phototrophic microorganisms are discussed.
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Affiliation(s)
- Anne Soisig Steunou
- CNRS, CGM, UPR 3404, Université Paris Sud, 1 Ave. de la Terrasse, Gif-sur-Yvette, F-91198, France
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Carius L, Hädicke O, Grammel H. Stepwise reduction of the culture redox potential allows the analysis of microaerobic metabolism and photosynthetic membrane synthesis inRhodospirillum rubrum. Biotechnol Bioeng 2012; 110:573-85. [DOI: 10.1002/bit.24734] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Revised: 08/29/2012] [Accepted: 09/21/2012] [Indexed: 11/09/2022]
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Abstract
This study investigates the role iron oxidation plays in the purple non-sulfur bacterium Rhodobacter capsulatus SB1003. This organism is unable to grow photoautotrophically on unchelated ferrous iron [Fe(II)] despite its ability to oxidize chelated Fe(II). This apparent paradox was partly resolved by the discovery that SB1003 can grow photoheterotrophically on the photochemical breakdown products of certain ferric iron-ligand complexes, yet whether it could concomitantly benefit from the oxidation of Fe(II) to fix CO(2) was unknown. Here, we examine carbon fixation by stable isotope labeling of the inorganic carbon pool in cultures growing phototrophically on acetate with and without Fe(II). We show that R. capsulatus SB1003, an organism formally thought incapable of phototrophic growth on Fe(II), can actually harness the reducing power of this substrate and grow photomixotrophically, deriving carbon both from organic sources and from fixation of inorganic carbon. This suggests the possibility of a wider occurrence of photoferrotrophy than previously assumed.
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Affiliation(s)
| | - Dianne K. Newman
- Division of Geological and Planetary Sciences, Pasadena, CA 91125
- Division of Biological Sciences, California Institute of Technology, Pasadena, CA 91125
- Howard Hughes Medical Institute, Pasadena, CA 91125
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Pandey R, Flockerzi D, Hauser MJB, Straube R. An extended model for the repression of photosynthesis genes by the AppA/PpsR system inRhodobacter sphaeroides. FEBS J 2012; 279:3449-61. [DOI: 10.1111/j.1742-4658.2012.08520.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Puthiyaveetil S, Ibrahim IM, Allen JF. Oxidation-reduction signalling components in regulatory pathways of state transitions and photosystem stoichiometry adjustment in chloroplasts. PLANT, CELL & ENVIRONMENT 2012; 35:347-59. [PMID: 21554328 DOI: 10.1111/j.1365-3040.2011.02349.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
State transitions and photosystem stoichiometry adjustment are two oxidation-reduction (redox)-regulated acclimatory responses in photosynthesis. State transitions are short-term adaptations that, in chloroplasts, involve reversible post-translational modification by phosphorylation of light-harvesting complex II (LHC II). Photosystem stoichiometry adjustments are long-term responses involving transcriptional regulation of reaction centre genes. Both responses are initiated by changes in light quality and are regulated by the redox state of plastoquinone (PQ). The LHC II kinase involved in the state 2 transition is a serine/threonine kinase known as STT7 in Chlamydomonas, and as STN7 in Arabidopsis. The phospho-LHC II phosphatase that produces the state 1 transition is a PP2C-type protein phosphatase currently termed both TAP38 and PPH1. In plants and algae, photosystem stoichiometry adjustment is governed by a modified two-component sensor kinase of cyanobacterial origin - chloroplast sensor kinase (CSK). CSK is a sensor of the PQ redox state. Chloroplast sigma factor 1 (SIG1) and plastid transcription kinase (PTK) are the functional partners of CSK in chloroplast gene regulation. We suggest a signalling pathway for photosystem stoichiometry adjustment. The signalling pathways of state transitions and photosystem stoichiometry adjustments are proposed to be distinct, with the two pathways sensing PQ redox state independently of each other.
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Affiliation(s)
- Sujith Puthiyaveetil
- Queen Mary, University of London, School of Biological and Chemical Sciences, London, UK
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29
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A T7 RNA polymerase-based toolkit for the concerted expression of clustered genes. J Biotechnol 2012; 159:162-71. [PMID: 22285639 DOI: 10.1016/j.jbiotec.2012.01.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Revised: 12/16/2011] [Accepted: 01/10/2012] [Indexed: 11/21/2022]
Abstract
Bacterial genes whose enzymes are either assembled into complex multi-domain proteins or form biosynthetic pathways are frequently organized within large chromosomal clusters. The functional expression of clustered genes, however, remains challenging since it generally requires an expression system that facilitates the coordinated transcription of numerous genes irrespective of their natural promoters and terminators. Here, we report on the development of a novel expression system that is particularly suitable for the homologous expression of multiple genes organized in a contiguous cluster. The new expression toolkit consists of an Ω interposon cassette carrying a T7 RNA polymerase specific promoter which is designed for promoter tagging of clustered genes and a small set of broad-host-range plasmids providing the respective polymerase in different bacteria. The uptake hydrogenase gene locus of the photosynthetic non-sulfur purple bacterium Rhodobacter capsulatus which consists of 16 genes was used as an example to demonstrate functional expression only by T7 RNA polymerase but not by bacterial RNA polymerase. Our findings clearly indicate that due to its unique properties T7 RNA polymerase can be applied for overexpression of large and complex bacterial gene regions.
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Allen JF, Santabarbara S, Allen CA, Puthiyaveetil S. Discrete redox signaling pathways regulate photosynthetic light-harvesting and chloroplast gene transcription. PLoS One 2011; 6:e26372. [PMID: 22039472 PMCID: PMC3198397 DOI: 10.1371/journal.pone.0026372] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Accepted: 09/26/2011] [Indexed: 11/24/2022] Open
Abstract
In photosynthesis in chloroplasts, two related regulatory processes balance the actions of photosystems I and II. These processes are short-term, post-translational redistribution of light-harvesting capacity, and long-term adjustment of photosystem stoichiometry initiated by control of chloroplast DNA transcription. Both responses are initiated by changes in the redox state of the electron carrier, plastoquinone, which connects the two photosystems. Chloroplast Sensor Kinase (CSK) is a regulator of transcription of chloroplast genes for reaction centres of the two photosystems, and a sensor of plastoquinone redox state. We asked whether CSK is also involved in regulation of absorbed light energy distribution by phosphorylation of light-harvesting complex II (LHC II). Chloroplast thylakoid membranes isolated from a CSK T-DNA insertion mutant and from wild-type Arabidopsis thaliana exhibit similar light- and redox-induced (32)P-labelling of LHC II and changes in 77 K chlorophyll fluorescence emission spectra, while room-temperature chlorophyll fluorescence emission transients from Arabidopsis leaves are perturbed by inactivation of CSK. The results indicate indirect, pleiotropic effects of reaction centre gene transcription on regulation of photosynthetic light-harvesting in vivo. A single, direct redox signal is transmitted separately to discrete transcriptional and post-translational branches of an integrated cytoplasmic regulatory system.
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Affiliation(s)
- John F Allen
- School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom.
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31
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Pandey R, Flockerzi D, Hauser MJB, Straube R. Modeling the light- and redox-dependent interaction of PpsR/AppA in Rhodobacter sphaeroides. Biophys J 2011; 100:2347-55. [PMID: 21575568 DOI: 10.1016/j.bpj.2011.04.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2010] [Revised: 03/16/2011] [Accepted: 04/06/2011] [Indexed: 10/18/2022] Open
Abstract
Facultative photosynthetic bacteria switch their energy generation mechanism from respiration to photosynthesis depending on oxygen tension and light. Part of this transition is mediated by the aerobic transcriptional repressor PpsR. In Rhodobacter sphaeroides, the repressive action of PpsR is antagonized by the redox- and blue-light-sensitive flavoprotein AppA which results in a unique phenotype: the repression of photosynthesis genes at intermediate oxygen levels and high light intensity, which is believed to reduce the risk of photooxidative stress. To analyze the underlying mechanism we developed a simple mathematical model based on the AppA-dependent reduction of a disulfide bond in PpsR and the light-sensitive complex formation between the reduced forms of AppA and PpsR. A steady-state analysis shows that high light repression can indeed occur at intermediate oxygen levels if PpsR is reduced on a faster timescale than AppA and if the electron transfer from AppA to PpsR is effectively irreversible. The model further predicts that if AppA copy numbers exceed those of PpsR by at least a factor of two, the transition from aerobic to anaerobic growth mode can occur via a bistable regime. We provide necessary conditions for the emergence of bistability and discuss possible experimental verifications.
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Affiliation(s)
- Rakesh Pandey
- Systems Biology Group, Max Planck Institute for Dynamics of Complex Technical Systems, Magdeburg, Germany
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32
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Abstract
Phytochromes are environmental sensors, historically thought of as red/far-red photoreceptors in plants. Their photoperception occurs through a covalently linked tetrapyrrole chromophore, which undergoes a light-dependent conformational change propagated through the protein to a variable output domain. The phytochrome composition is modular, typically consisting of a PAS-GAF-PHY architecture for the N-terminal photosensory core. A collection of three-dimensional structures has uncovered key features, including an unusual figure-of-eight knot, an extension reaching from the PHY domain to the chromophore-binding GAF domain, and a centrally located, long α-helix hypothesized to be crucial for intramolecular signaling. Continuing identification of phytochromes in microbial systems has expanded the assigned sensory abilities of this family out of the red and into the yellow, green, blue, and violet portions of the spectrum. Furthermore, phytochromes acting not as photoreceptors but as redox sensors have been recognized. In addition, architectures other than PAS-GAF-PHY are known, thus revealing phytochromes to be a varied group of sensory receptors evolved to utilize their modular design to perceive a signal and respond accordingly. This review focuses on the structures of bacterial phytochromes and implications for signal transmission. We also discuss the small but growing set of bacterial phytochromes for which a physiological function has been ascertained.
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Affiliation(s)
- Michele E Auldridge
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI 53706, USA
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33
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Elías-Arnanz M, Padmanabhan S, Murillo FJ. Light-dependent gene regulation in nonphototrophic bacteria. Curr Opin Microbiol 2011; 14:128-35. [DOI: 10.1016/j.mib.2010.12.009] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2010] [Revised: 12/15/2010] [Accepted: 12/15/2010] [Indexed: 11/24/2022]
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34
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Losi A, Gärtner W. Old Chromophores, New Photoactivation Paradigms, Trendy Applications: Flavins in Blue Light-Sensing Photoreceptors†. Photochem Photobiol 2011; 87:491-510. [DOI: 10.1111/j.1751-1097.2011.00913.x] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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35
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A glutathione redox effect on photosynthetic membrane expression in Rhodospirillum rubrum. J Bacteriol 2011; 193:1893-900. [PMID: 21317329 DOI: 10.1128/jb.01353-10] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The formation of intracytoplasmic photosynthetic membranes by facultative anoxygenic photosynthetic bacteria has become a prime example for exploring redox control of gene expression in response to oxygen and light. Although a number of redox-responsive sensor proteins and transcription factors have been characterized in several species during the last several years in some detail, the overall understanding of the metabolic events that determine the cellular redox environment and initiate redox signaling is still poor. In the present study we demonstrate that in Rhodospirillum rubrum, the amount of photosynthetic membranes can be drastically elevated by external supplementation of the growth medium with the low-molecular-weight thiol glutathione. Neither the widely used reductant dithiothreitol nor oxidized glutathione caused the same response, suggesting that the effect was specific for reduced glutathione. By determination of the extracellular and intracellular glutathione levels, we correlate the GSH/GSSG redox potential to the expression level of photosynthetic membranes. Possible regulatory interactions with periplasmic, membrane, and cytosolic proteins are discussed. Furthermore, we found that R. rubrum cultures excrete substantial amounts of glutathione to the environment.
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36
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Hassani BK, Steunou AS, Liotenberg S, Reiss-Husson F, Astier C, Ouchane S. Adaptation to oxygen: role of terminal oxidases in photosynthesis initiation in the purple photosynthetic bacterium, Rubrivivax gelatinosus. J Biol Chem 2010; 285:19891-9. [PMID: 20335164 DOI: 10.1074/jbc.m109.086066] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The appearance of oxygen in the Earth's atmosphere via oxygenic photosynthesis required strict anaerobes and obligate phototrophs to cope with the presence of this toxic molecule. Here we show that in the anoxygenic phototroph Rubrivivax gelatinosus, the terminal oxidases (cbb(3), bd, and caa(3)) expand the range of ambient oxygen tensions under which the organism can initiate photosynthesis. Unlike the wild type, the cbb(3)(-)/bd(-) double mutant can start photosynthesis only in deoxygenated medium or when oxygen is removed, either by sparging cultures with nitrogen or by co-inoculation with strict aerobes bacteria. In oxygenated environments, this mutant survives nonphotosynthetically until the O(2) tension is reduced. The cbb(3) and bd oxidases are therefore required not only for respiration but also for reduction of the environmental O(2) pressure prior to anaerobic photosynthesis. Suppressor mutations that restore respiration simultaneously restore photosynthesis in nondeoxygenated medium. Furthermore, induction of photosystem in the cbb(3)(-) mutant led to a highly unstable strain. These results demonstrate that photosynthetic metabolism in environments exposed to oxygen is critically dependent on the O(2)-detoxifying action of terminal oxidases.
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Affiliation(s)
- Bahia Khalfaoui Hassani
- CNRS, Centre de Génétique Moléculaire, F-91198 Gif-sur-Yvette, the Université Paris-Sud, F-91405 Orsay, France
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37
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Zeiger L, Grammel H. Model-based high cell density cultivation of Rhodospirillum rubrum under respiratory dark conditions. Biotechnol Bioeng 2010; 105:729-39. [PMID: 19882736 DOI: 10.1002/bit.22589] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The potential of facultative photosynthetic bacteria as producers of photosynthetic pigments, vitamins, coenzymes and other valuable products has been recognized for decades. However, mass cultivation under photosynthetic conditions is generally inefficient due to the inevitable limitation of light supply when cell densities become very high. The previous development of a new cultivation process for maximal expression of photosynthetic genes under semi-aerobic dark conditions in common bioreactors offers a new perspective for utilizing the facultative photosynthetic bacterium Rhodospirillum rubrum for large-scale applications. Based on this cultivation system, the present study aimed in determining the maximal achievable cell density of R. rubrum in a bioreactor, thereby providing a major milestone on the way to industrial bioprocesses. As a starting point, we focus on aerobic growth due to higher growth rates and more facile process control under this condition, with the option to extend the process by an anaerobic production phase. Process design and optimization were supported by an unstructured computational process model, based on mixed-substrate kinetics. Key parameters for growth and process control were determined in shake-flask experiments or estimated by simulation studies. For fed-batch cultivation, a computer-controlled exponential feed algorithm in combination with a pH-stat element was implemented. As a result, a maximal cell density of 59 g cell dry weight (CDW) L(-1) was obtained, representing so far not attainable cell densities for photosynthetic bacteria. The applied exponential fed-batch methodology therefore enters a range which is commonly employed for industrial applications with microbial cells. The biochemical analysis of high cell density cultures revealed metabolic imbalances, such as the accumulation and excretion of tetrapyrrole intermediates of the bacteriochlorophyll biosynthetic pathway.
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Affiliation(s)
- Lisa Zeiger
- Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstr. 1, 39106 Magdeburg, Germany.
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38
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Katzke N, Arvani S, Bergmann R, Circolone F, Markert A, Svensson V, Jaeger KE, Heck A, Drepper T. A novel T7 RNA polymerase dependent expression system for high-level protein production in the phototrophic bacterium Rhodobacter capsulatus. Protein Expr Purif 2009; 69:137-46. [PMID: 19706327 DOI: 10.1016/j.pep.2009.08.008] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2009] [Revised: 08/19/2009] [Accepted: 08/20/2009] [Indexed: 10/20/2022]
Abstract
The functional expression of heterologous genes using standard bacterial expression hosts such as Escherichia coli is often limited, e.g. by incorrect folding, assembly or targeting of recombinant proteins. Consequently, alternative bacterial expression systems have to be developed to provide novel strategies for protein synthesis exceeding the repertoire of the standard expression host E. coli. Here, we report on the construction of a novel expression system that combines the high processivity of T7 RNA polymerase with the unique physiological properties of the facultative photosynthetic bacterium Rhodobacter capsulatus. This system basically consists of a recombinant R. capsulatus T7 expression strain (R. capsulatus B10S-T7) harboring the respective polymerase gene under control of a fructose inducible promoter. In addition, a set of different broad-host-range vectors (pRho) was constructed allowing T7 RNA polymerase dependent and independent target gene expression in R. capsulatus and other Gram-negative bacteria. The expression efficiency of the novel system was studied in R. capsulatus and E. coli using the yellow fluorescent protein (YFP) as model protein. Expression levels were comparable in both expression hosts and yielded up to 80mg/l YFP in phototrophically grown R. capsulatus cultures. This result clearly indicates that the novel R. capsulatus-based expression system is well suited for the high-level expression of soluble proteins.
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Affiliation(s)
- Nadine Katzke
- Institute of Molecular Enzyme Technology, Heinrich-Heine-University Duesseldorf, Forschungszentrum Juelich, Stetternicher Forst, D-52426 Juelich, Germany
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Regulation of gene expression by PrrA in Rhodobacter sphaeroides 2.4.1: role of polyamines and DNA topology. J Bacteriol 2009; 191:4341-52. [PMID: 19411327 DOI: 10.1128/jb.00243-09] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
In the present study, we show in vitro binding of PrrA, a global regulator in Rhodobacter sphaeroides 2.4.1, to the PrrA site 2, within the RSP3361 locus. Specific binding, as shown by competition experiments, requires the phosphorylation of PrrA. The binding affinity of PrrA for site 2 was found to increase 4- to 10-fold when spermidine was added to the binding reaction. The presence of extracellular concentrations of spermidine in growing cultures of R. sphaeroides gave rise to a twofold increase in the expression of the photosynthesis genes pucB and pufB, as well as the RSP3361 gene, under aerobic growth conditions, as shown by the use of lacZ transcriptional fusions, and led to the production of light-harvesting spectral complexes. In addition, we show that negative supercoiling positively regulates the expression of the RSP3361 gene, as well as pucB. We show the importance of supercoiling through an evaluation of the regulation of gene expression in situ by supercoiling, in the case of the former gene, as well as using the DNA gyrase inhibitor novobiocin. We propose that polyamines and DNA supercoiling act synergistically to regulate expression of the RSP3361 gene, partly by affecting the affinity of PrrA binding to the PrrA site 2 within the RSP3361 gene.
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40
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Swingley WD, Blankenship RE, Raymond J. Evolutionary Relationships Among Purple Photosynthetic Bacteria and the Origin of Proteobacterial Photosynthetic Systems. ACTA ACUST UNITED AC 2009. [DOI: 10.1007/978-1-4020-8815-5_2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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41
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Gomelsky L, Moskvin OV, Stenzel RA, Jones DF, Donohue TJ, Gomelsky M. Hierarchical regulation of photosynthesis gene expression by the oxygen-responsive PrrBA and AppA-PpsR systems of Rhodobacter sphaeroides. J Bacteriol 2008; 190:8106-14. [PMID: 18931128 PMCID: PMC2593241 DOI: 10.1128/jb.01094-08] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2008] [Accepted: 10/03/2008] [Indexed: 11/20/2022] Open
Abstract
In the facultatively phototrophic proteobacterium Rhodobacter sphaeroides, formation of the photosynthetic apparatus is oxygen dependent. When oxygen tension decreases, the response regulator PrrA of the global two-component PrrBA system is believed to directly activate transcription of the puf, puh, and puc operons, encoding structural proteins of the photosynthetic complexes, and to indirectly upregulate the photopigment biosynthesis genes bch and crt. Decreased oxygen also results in inactivation of the photosynthesis-specific repressor PpsR, bringing about derepression of the puc, bch, and crt operons. We uncovered a hierarchical relationship between these two regulatory systems, earlier thought to function independently. We also more accurately assessed the spectrum of gene targets of the PrrBA system. First, expression of the appA gene, encoding the PpsR antirepressor, is PrrA dependent, which establishes one level of hierarchical dominance of the PrrBA system over AppA-PpsR. Second, restoration of the appA transcript to the wild-type level is insufficient for rescuing phototrophic growth impairment of the prrA mutant, whereas inactivation of ppsR is sufficient. This suggests that in addition to controlling appA transcription, PrrA affects the activity of the AppA-PpsR system via an as yet unidentified mechanism(s). Third, PrrA directly activates several bch and crt genes, traditionally considered to be the PpsR targets. Therefore, in R. sphaeroides, the global PrrBA system regulates photosynthesis gene expression (i) by rigorous control over the photosynthesis-specific AppA-PpsR regulatory system and (ii) by extensive direct transcription activation of genes encoding structural proteins of photosynthetic complexes as well as genes encoding photopigment biosynthesis enzymes.
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Affiliation(s)
- Larissa Gomelsky
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA
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42
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Masuda S, Berleman J, Hasselbring BM, Bauer CE. Regulation of aerobic photosystem synthesis in the purple bacterium Rhodospirillum centenum by CrtJ and AerR. Photochem Photobiol Sci 2008; 7:1267-72. [PMID: 18846293 PMCID: PMC2774734 DOI: 10.1039/b802365b] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2008] [Accepted: 08/29/2008] [Indexed: 11/21/2022]
Abstract
Genes coding for putative CrtJ and AerR homologs were identified and characterized in the purple photosynthetic bacterium Rhodospirillum centenum (also known as Rhodocista centenaria), an organism that synthesizes photopigments even under highly aerated conditions. Mutational analysis indicated that in Rsp. centenum, gene crtJ codes for a repressor for photosynthesis gene expression as in Rhodobacter capsulatus, which exhibits a high level of oxygen repression of photosystem synthesis. In contrast to Rba. capsulatus, AerR in Rsp. centenum appears to be an aerobic activator; an aerR mutation resulted in significantly reduced levels of photopigment synthesis. Both aerR and crtJ mutants retained essentially normal levels of photosystem synthesis under anaerobic conditions, indicating that their activities are specific for aerobic photosystem synthesis. The readthrough transcript from crtE promoter, which is regulated by AerR and CrtJ, seems to be significant in maintaining the expression levels of the light harvesting I (puf) genes in Rsp. centenum. We suggest that AerR and CrtJ regulate aerobic photosystem synthesis primarily through controlling activity of the transcriptional readthrough.
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Affiliation(s)
- Shinji Masuda
- Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, 226-8501, Japan.
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43
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Giraud E, Verméglio A. Bacteriophytochromes in anoxygenic photosynthetic bacteria. PHOTOSYNTHESIS RESEARCH 2008; 97:141-153. [PMID: 18612842 DOI: 10.1007/s11120-008-9323-0] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2008] [Accepted: 06/16/2008] [Indexed: 05/26/2023]
Abstract
Since the first discovery of a bacteriophytochrome in Rhodospirillum centenum, numerous bacteriophytochromes have been identified and characterized in other anoxygenic photosynthetic bacteria. This review is focused on the biochemical and biophysical properties of bacteriophytochromes with a special emphasis on their roles in the synthesis of the photosynthetic apparatus.
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Affiliation(s)
- Eric Giraud
- Laboratoire des Symbioses Tropicales et Méditerranéennes, IRD, CIRAD, AGRO-M, INRA, UM2, TA A-82/J, Campus de Baillarguet, 34398, Montpellier Cedex 5, France
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Puthiyaveetil S, Kavanagh TA, Cain P, Sullivan JA, Newell CA, Gray JC, Robinson C, van der Giezen M, Rogers MB, Allen JF. The ancestral symbiont sensor kinase CSK links photosynthesis with gene expression in chloroplasts. Proc Natl Acad Sci U S A 2008; 105:10061-6. [PMID: 18632566 PMCID: PMC2474565 DOI: 10.1073/pnas.0803928105] [Citation(s) in RCA: 123] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2008] [Indexed: 11/18/2022] Open
Abstract
We describe a novel, typically prokaryotic, sensor kinase in chloroplasts of green plants. The gene for this chloroplast sensor kinase (CSK) is found in cyanobacteria, prokaryotes from which chloroplasts evolved. The CSK gene has moved, during evolution, from the ancestral chloroplast to the nuclear genomes of eukaryotic algae and green plants. The CSK protein is now synthesised in the cytosol of photosynthetic eukaryotes and imported into their chloroplasts as a protein precursor. In the model higher plant Arabidopsis thaliana, CSK is autophosphorylated and required for control of transcription of chloroplast genes by the redox state of an electron carrier connecting photosystems I and II. CSK therefore provides a redox regulatory mechanism that couples photosynthesis to gene expression. This mechanism is inherited directly from the cyanobacterial ancestor of chloroplasts, is intrinsic to chloroplasts, and is targeted to chloroplast genes.
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Affiliation(s)
- Sujith Puthiyaveetil
- *School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, United Kingdom
| | | | - Peter Cain
- Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - James A. Sullivan
- *School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, United Kingdom
| | - Christine A. Newell
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, United Kingdom; and
| | - John C. Gray
- Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EA, United Kingdom; and
| | - Colin Robinson
- Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom
| | - Mark van der Giezen
- Centre for Eukaryotic Evolutionary Microbiology, School of Biosciences, University of Exeter, Exeter EX4 4QD, United Kingdom
| | - Matthew B. Rogers
- Centre for Eukaryotic Evolutionary Microbiology, School of Biosciences, University of Exeter, Exeter EX4 4QD, United Kingdom
| | - John F. Allen
- *School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, United Kingdom
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Yamazaki Y, Fukusumi H, Kamikubo H, Kataoka M. Role of the N-terminal region in the function of the photosynthetic bacterium transcription regulator PpsR. Photochem Photobiol 2008; 84:839-44. [PMID: 18282179 DOI: 10.1111/j.1751-1097.2008.00306.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PpsR is a transcription repressor for the gene cluster encoding photosystem genes in Rhodobacter sphaeroides. Repression activity is accomplished by DNA binding on the promoter regions of the photosystem gene clusters, and depends on both the redox potential and the presence of antirepressor protein AppA. To understand DNA repression regulation by PpsR, we investigated the function of PpsR domains in self-association for DNA binding. We constructed domain-deletion mutants and verified DNA-binding activity and dimer formation. Gel shift assay for measuring the DNA-binding activity of three sequential N-terminal deletion mutants revealed that N-terminal deletions (of minimum 121 residues) caused loss of binding activity. Size-exclusion gel chromatography revealed that deletion mutant which lacks the N-terminal 121-amino acid deletion mutant to exist as a dimer, although it was less stable than the intact PpsR. The mutants lacking the adjacent regions, Q-linker region and the first Per-Ant-Sim domain, did not form dimers, suggesting the involvement of the N-terminal region in dimer formation. This region is thus considered to be a functional domain in self-association, although not yet identified as a structural domain. Circular dichroism spectrum of the N-terminal region fragment exhibited a alpha/beta structure. We conclude that this region is a structural and functional domain, contributing to PpsR repression through dimer stabilization.
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Affiliation(s)
- Yoichi Yamazaki
- Graduate School of Materials Science, Nara Institute of Science and Technology, Ikoma, Nara, Japan
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Puthiyaveetil S, Allen JF. Transients in chloroplast gene transcription. Biochem Biophys Res Commun 2008; 368:871-4. [PMID: 18275851 DOI: 10.1016/j.bbrc.2008.01.167] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2008] [Accepted: 01/29/2008] [Indexed: 10/22/2022]
Abstract
Transcriptional regulation of chloroplast genes is demonstrated by Quantitative Polymerase Chain Reaction (qPCR). These genes encode apoproteins of the reaction centres of photosystem I and photosystem II. Their transcription is regulated by changes in wavelength of light selectively absorbed by photosystem I and photosystem II, and therefore by the redox state of an electron carrier located between the two photosystems. Chloroplast transcriptional redox regulation is shown to have greater amplitude, and the kinetics of transcriptional changes are more complex, than suggested by previous experiments using only DNA probes in Northern blot experiments. Redox effects on chloroplast transcription appear to be superimposed on an endogenous rhythm of mRNA abundance. The functional significance of these transients in chloroplast gene transcription is discussed.
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Affiliation(s)
- Sujith Puthiyaveetil
- School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK
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Harada J, Mizoguchi T, Yoshida S, Isaji M, Oh-Oka H, Tamiaki H. Composition and localization of bacteriochlorophyll a intermediates in the purple photosynthetic bacterium Rhodopseudomonas sp. Rits. PHOTOSYNTHESIS RESEARCH 2008; 95:213-21. [PMID: 17912605 DOI: 10.1007/s11120-007-9254-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2007] [Accepted: 09/07/2007] [Indexed: 05/17/2023]
Abstract
Rhodopseudomonas sp. Rits is a recently isolated new species of photosynthetic bacteria and found to accumulate a significantly high amount of bacteriochlorophyll (BChl) a intermediates possessing non-, di- and tetra-hydrogenated geranylgeranyl groups at the 17-propionate as well as normal phytylated BChl a (Mizoguchi T et al. (2006) FEBS Lett 580:137-143). A phylogenetic analysis showed that this bacterium was closely related to Rhodopseudomonas palustris. The strain Rits synthesizes light-harvesting complexes 2 and 4 (LH2/4), as peripheral antennas, as well as the reaction center and light-harvesting 1 core complex (RC-LH1 core). The amounts of these complexes were dependent upon the incident light intensities, which was also a typical behavior of Rhodopseudomonas palustris. HPLC analyses of extracted pigments indicated that all four BChls a were associated with the purified photosynthetic pigment-protein, as complexes described above. The results suggested that this bacterium could use these pigments as functional molecules within the LH2/4 and RC-LH1 core. Pigment compositional analyses in several purple photosynthetic bacteria showed that such BChl a intermediates were always detected and were more widely distributed than expected. Long chains in the propionate moiety of BChl a would be one of the important factors for assembly of LH systems in purple photosynthetic bacteria.
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Affiliation(s)
- Jiro Harada
- Department of Bioscience and Biotechnology, Faculty of Science and Engineering, Ritsumeikan University, Kusatsu, Shiga, 525-8577, Japan
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Kojadinovic M, Laugraud A, Vuillet L, Fardoux J, Hannibal L, Adriano JM, Bouyer P, Giraud E, Verméglio A. Dual role for a bacteriophytochrome in the bioenergetic control of Rhodopsdeudomonas palustris: Enhancement of photosystem synthesis and limitation of respiration. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2008; 1777:163-72. [DOI: 10.1016/j.bbabio.2007.09.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2007] [Revised: 08/30/2007] [Accepted: 09/04/2007] [Indexed: 10/22/2022]
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Klamt S, Grammel H, Straube R, Ghosh R, Gilles ED. Modeling the electron transport chain of purple non-sulfur bacteria. Mol Syst Biol 2008; 4:156. [PMID: 18197174 PMCID: PMC2238716 DOI: 10.1038/msb4100191] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2007] [Accepted: 10/18/2007] [Indexed: 11/09/2022] Open
Abstract
Purple non-sulfur bacteria (Rhodospirillaceae) have been extensively employed for studying principles of photosynthetic and respiratory electron transport phosphorylation and for investigating the regulation of gene expression in response to redox signals. Here, we use mathematical modeling to evaluate the steady-state behavior of the electron transport chain (ETC) in these bacteria under different environmental conditions. Elementary-modes analysis of a stoichiometric ETC model reveals nine operational modes. Most of them represent well-known functional states, however, two modes constitute reverse electron flow under respiratory conditions, which has been barely considered so far. We further present and analyze a kinetic model of the ETC in which rate laws of electron transfer steps are based on redox potential differences. Our model reproduces well-known phenomena of respiratory and photosynthetic operation of the ETC and also provides non-intuitive predictions. As one key result, model simulations demonstrate a stronger reduction of ubiquinone when switching from high-light to low-light conditions. This result is parameter insensitive and supports the hypothesis that the redox state of ubiquinone is a suitable signal for controlling photosynthetic gene expression.
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Affiliation(s)
- Steffen Klamt
- Max Planck Institute for Dynamics of Complex Technical Systems, Magdeburg, Germany.
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