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Peuser V, Metz S, Klug G. Response of the photosynthetic bacterium Rhodobacter sphaeroides to iron limitation and the role of a Fur orthologue in this response. ENVIRONMENTAL MICROBIOLOGY REPORTS 2011; 3:397-404. [PMID: 23761286 DOI: 10.1111/j.1758-2229.2011.00245.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We studied the response of the photosynthetic alpha-proteobacterium Rhodobacter sphaeroides to iron limitation in order to get first insights into the underlying mechanisms and the link between iron metabolism and oxidative stress. Our data reveal the production of elevated levels of reactive oxygen species upon iron limitation, nevertheless the response to iron limitation shows clear differences to the oxidative stress response of R. sphaeroides. While most genes of the oxidative stress response were not induced by iron limitation, we observed an upregulation of the alternative sigma factor RpoE, which has a main role in the regulation of the defence to singlet oxygen. Deletion of the Fur orthologue RSP_2494, which was designated Mur as a result of a proposed regulatory role in manganese metabolism, revealed that this protein is involved in regulation of the iron metabolism in R. sphaeroides. One predicted target of Fur/Mur is the sit operon encoding a Mn(2+) /Fe(2+) transport system. The basal level of sitA was higher in a fur/mur deletion strain compared with the wild type, which is in agreement with a repressor function of the Fur/Mur protein. In addition, we could also demonstrate a function of the Fur/Mur protein in manganese homeostasis.
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Affiliation(s)
- Verena Peuser
- Institut für Mikrobiologie und Molekularbiologie, University of Giessen, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany
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Kim EJ, Kim JS, Lee IH, Rhee HJ, Lee JK. Superoxide generation by chlorophyllide a reductase of Rhodobacter sphaeroides. J Biol Chem 2007; 283:3718-30. [PMID: 18079120 DOI: 10.1074/jbc.m707774200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Chlorophyllide a reductase of Rhodobacter sphaeroides, which were reconstituted with the purified subunits of BchX, BchY, and BchZ, reduced ring B of chlorophyllide a using NADH under anaerobic conditions. Interestingly, suppressor mutations rescuing the inability of R. sphaeroides Fe-SOD mutant to grow in succinate-based minimal medium were predominantly mapped to BchZ subunit of chlorophyllide a reductase. The enzyme is labile in the presence of O(2). However, it generates superoxide at low O(2). The enzymes reconstituted with BchX, BchY, and the mutein subunit of BchZ from suppressor mutants showed less activity not only for chlorophyllide a reduction but also for superoxide generation compared with the enzyme reconstituted with the wild-type subunits. BchX, which contains FMN, and BchY are iron-sulfur proteins, whereas BchZ is a hemoprotein containing b-type heme. Neither chlorophyllide a reduction nor superoxide generation was observed with the enzyme reconstituted with the wild-type subunits of BchX and BchY, and the apo-subunit of BchZ that had been refolded without heme, in which FMN of BchX was fully reduced. Thus, superoxide is generated not from FMN of BchX but from heme of BchZ. Consistently, the heme of BchZ muteins was half-reduced in its redox state compared with that of wild-type BchZ.
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Affiliation(s)
- Eui-Jin Kim
- Department of Life Science and Interdisciplinary Program of Integrated Biotechnology, Sogang University, Seoul 121-742, Korea
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Willett J, Smart JL, Bauer CE. RegA control of bacteriochlorophyll and carotenoid synthesis in Rhodobacter capsulatus. J Bacteriol 2007; 189:7765-73. [PMID: 17616588 PMCID: PMC2168725 DOI: 10.1128/jb.00853-07] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2007] [Accepted: 06/29/2007] [Indexed: 11/20/2022] Open
Abstract
We provide in vivo genetic and in vitro biochemical evidence that RegA directly regulates bacteriochlorophyll and carotenoid biosynthesis in Rhodobacter capsulatus. beta-Galactosidase expression assays with a RegA-disrupted strain containing reporter plasmids for Mg-protoporphyrin IX monomethyl ester oxidative cyclase (bchE), Mg-protoporphyrin IX chelatase (bchD), and phytoene dehydrogenase (crtI) demonstrate RegA is responsible for fourfold anaerobic induction of bchE, threefold induction of bchD, and twofold induction of crtI. Promoter mapping studies, coupled with DNase I protection assays, map the region of RegA binding to three sites in the bchE promoter region. Similar studies at the crtA and crtI promoters indicate that RegA binds to a single region equidistant from these divergent promoters. These results demonstrate that RegA is directly responsible for anaerobic induction of bacteriochlorophyll biosynthesis genes bchE, bchD, bchJ, bchI, bchG, and bchP and carotenoid biosynthesis genes crtI, crtB, and crtA.
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Mascher T, Helmann JD, Unden G. Stimulus perception in bacterial signal-transducing histidine kinases. Microbiol Mol Biol Rev 2007; 70:910-38. [PMID: 17158704 PMCID: PMC1698512 DOI: 10.1128/mmbr.00020-06] [Citation(s) in RCA: 505] [Impact Index Per Article: 29.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Two-component signal-transducing systems are ubiquitously distributed communication interfaces in bacteria. They consist of a histidine kinase that senses a specific environmental stimulus and a cognate response regulator that mediates the cellular response, mostly through differential expression of target genes. Histidine kinases are typically transmembrane proteins harboring at least two domains: an input (or sensor) domain and a cytoplasmic transmitter (or kinase) domain. They can be identified and classified by virtue of their conserved cytoplasmic kinase domains. In contrast, the sensor domains are highly variable, reflecting the plethora of different signals and modes of sensing. In order to gain insight into the mechanisms of stimulus perception by bacterial histidine kinases, we here survey sensor domain architecture and topology within the bacterial membrane, functional aspects related to this topology, and sequence and phylogenetic conservation. Based on these criteria, three groups of histidine kinases can be differentiated. (i) Periplasmic-sensing histidine kinases detect their stimuli (often small solutes) through an extracellular input domain. (ii) Histidine kinases with sensing mechanisms linked to the transmembrane regions detect stimuli (usually membrane-associated stimuli, such as ionic strength, osmolarity, turgor, or functional state of the cell envelope) via their membrane-spanning segments and sometimes via additional short extracellular loops. (iii) Cytoplasmic-sensing histidine kinases (either membrane anchored or soluble) detect cellular or diffusible signals reporting the metabolic or developmental state of the cell. This review provides an overview of mechanisms of stimulus perception for members of all three groups of bacterial signal-transducing histidine kinases.
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Affiliation(s)
- Thorsten Mascher
- Department of General Microbiology, Georg-August-University, Grisebachstr. 8, D-37077 Göttingen, Germany.
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Happ HN, Braatsch S, Broschek V, Osterloh L, Klug G. Light-dependent regulation of photosynthesis genes in Rhodobacter sphaeroides 2.4.1 is coordinately controlled by photosynthetic electron transport via the PrrBA two-component system and the photoreceptor AppA. Mol Microbiol 2006; 58:903-14. [PMID: 16238636 DOI: 10.1111/j.1365-2958.2005.04882.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Formation of the photosynthetic apparatus in Rhodobacter is regulated by oxygen tension and light intensity. Here we show that in anaerobically grown Rhodobacter cells a light-dependent increase in expression of the puc and puf operons encoding structural proteins of the photosynthetic complexes requires an active photosynthetic electron transport. The redox-sensitive CrtJ/PpsR repressor of photosynthesis genes, which was suggested to mediate electron transport-dependent signals, is not involved in this light-dependent signal chain. Our data reveal that the signal initiated in the photosynthetic reaction centre is transmitted via components of the electron transport chain and the PrrB/PrrA two-component system in Rhodobacter sphaeroides. Under blue light illumination in the absence of oxygen this signal leads to activation of photosynthesis genes and interferes with a blue-light repression mediated by the AppA photoreceptor and the PpsR transcriptional repressor in R. sphaeroides. Thus, light either sensed by a photoreceptor or initiating photosynthetic electron transport has opposite effects on the transcription of photosynthesis genes. Both signalling pathways involve redox-dependent steps that finally determine the effect of light on gene expression.
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Affiliation(s)
- Hendrik N Happ
- Institut für Mikrobiologie und Molekularbiologie, Universität Giessen, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany
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Elsen S, Jaubert M, Pignol D, Giraud E. PpsR: a multifaceted regulator of photosynthesis gene expression in purple bacteria. Mol Microbiol 2005; 57:17-26. [PMID: 15948946 DOI: 10.1111/j.1365-2958.2005.04655.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Purple bacteria control the level of expression and the composition of their photosystem according to light and redox conditions. This control involves several regulatory systems that have been now well characterized. Among them, the PpsR regulator plays a central role, because it directly or indirectly controls the synthesis of all of the different components of the photosystem. In this review, we report our knowledge of the PpsR protein, highlighting the diversity of its mode of action and focusing on the proteins identified in four model purple bacteria (Rhodobacter capsulatus, Rhodobacter sphaeroides, Rubrivivax gelatinosus, Bradyrhizobium ORS278). This regulator exhibits unique regulatory features in each bacterium: it can activate and/or repress the expression of photosynthesis genes, its activity can be modulated or not by the redox conditions, it can interact with other specific regulators and therefore be involved differently in light and/or redox regulatory circuits.
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Affiliation(s)
- Sylvie Elsen
- Laboratoire de Biochimie et Biophysique des Systèmes Intégrés (UMR 5092 CNRS-CEA-UJF), CEA-Grenoble, 38054 Grenoble Cedex 9, France
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Aklujkar M, Prince RC, Beatty JT. The puhE gene of Rhodobacter capsulatus is needed for optimal transition from aerobic to photosynthetic growth and encodes a putative negative modulator of bacteriochlorophyll production. Arch Biochem Biophys 2005; 437:186-98. [PMID: 15850558 DOI: 10.1016/j.abb.2005.03.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2005] [Revised: 03/10/2005] [Accepted: 03/11/2005] [Indexed: 10/25/2022]
Abstract
A conserved orf of previously unknown function (herein designated as puhE) is located 3' of the reaction centre H (puhA) gene in purple photosynthetic bacteria, in the order puhABCE in Rhodobacter capsulatus. Disruptions of R. capsulatus puhE resulted in a long lag in the growth of photosynthetic cultures inoculated with cells grown under high aeration, and increased the level of the peripheral antenna, light-harvesting complex 2 (LH2). The amount of the photosynthetic reaction centre (RC) and its core antenna, light-harvesting complex 1 (LH1), was reduced; however, there was no decrease in expression of a lacZ reporter fused to the puf (RC and LH1) promoter, in RC assembly in the absence of LH1, or in LH1 assembly in the absence of the RC. In strains that lack LH2, disruption of puhE increased the in vivo absorption at 780 nm, which we attribute to excess bacteriochlorophyll a (BChl) pigment production. This effect was seen in the presence and absence of PufQ, a protein that stimulates BChl biosynthesis. Expression of puhE from a plasmid reduced A(780) production in puhE mutants. We suggest that PuhE modulates BChl biosynthesis independently of PufQ, and that the presence of excess BChl in PuhE(-)LH2(+) strains results in excess LH2 assembly and also interferes with the adaptation of cells during the transition from aerobic respiratory to anaerobic photosynthetic growth.
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Affiliation(s)
- Muktak Aklujkar
- Department of Microbiology and Immunology, University of British Columbia, 300-6174 University Blvd., Vancouver, BC, Canada V6T 1Z3
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Elsen S, Swem LR, Swem DL, Bauer CE. RegB/RegA, a highly conserved redox-responding global two-component regulatory system. Microbiol Mol Biol Rev 2004; 68:263-79. [PMID: 15187184 PMCID: PMC419920 DOI: 10.1128/mmbr.68.2.263-279.2004] [Citation(s) in RCA: 154] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Reg regulon from Rhodobacter capsulatus and Rhodobacter sphaeroides encodes proteins involved in numerous energy-generating and energy-utilizing processes such as photosynthesis, carbon fixation, nitrogen fixation, hydrogen utilization, aerobic and anaerobic respiration, denitrification, electron transport, and aerotaxis. The redox signal that is detected by the membrane-bound sensor kinase, RegB, appears to originate from the aerobic respiratory chain, given that mutations in cytochrome c oxidase result in constitutive RegB autophosphorylation. Regulation of RegB autophosphorylation also involves a redox-active cysteine that is present in the cytosolic region of RegB. Both phosphorylated and unphosphorylated forms of the cognate response regulator RegA are capable of activating or repressing a variety of genes in the regulon. Highly conserved homologues of RegB and RegA have been found in a wide number of photosynthetic and nonphotosynthetic bacteria, with evidence suggesting that RegB/RegA plays a fundamental role in the transcription of redox-regulated genes in many bacterial species.
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Affiliation(s)
- Sylvie Elsen
- Laboratoire de Biochimie et de Biophysique des Systèmes Intégrés (UMR 5092 CNRS-CEA-UJF), Grenoble, France
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Oh JI, Ko IJ, Kaplan S. Digging deeper: uncovering genetic loci which modulate photosynthesis gene expression in Rhodobacter sphaeroides 2.4.1. MICROBIOLOGY (READING, ENGLAND) 2003; 149:949-960. [PMID: 12686637 DOI: 10.1099/mic.0.26010-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A new genetic locus was identified in Rhodobacter sphaeroides which is required for optimal synthesis of the light-harvesting spectral complexes as well as for optimal growth under anaerobic conditions with dimethyl sulfoxide (DMSO) as a terminal electron acceptor. The primary structure of the deduced osp gene product shows significant homology to the receiver domain of known response regulators common to bacterial two-component systems. However, site-directed mutagenesis revealed that the Osp protein appears not to be involved in a phospho-relay signal transduction pathway. Paradoxically, the effect of the Osp protein upon spectral complex levels is exerted at the transcriptional level of photosynthesis gene expression. The absence of the Osp protein does not appear to have a general effect on house-keeping metabolism. In cells lacking Osp, the levels of DMSO reductase appear to be normal. The quaternary structure of the Osp protein was determined to be a homodimer and it was directly demonstrated that Osp does not bind to the promoter region of photosynthesis genes as judged by mobility-shift experiments and primary structure analysis.
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Affiliation(s)
- Jeong-Ii Oh
- Department of Microbiology and Molecular Genetics, The University of Texas Health Science Center, Medical School, 6431 Fannin, Houston, TX 77030, USA
| | - In-Jeong Ko
- Department of Microbiology and Molecular Genetics, The University of Texas Health Science Center, Medical School, 6431 Fannin, Houston, TX 77030, USA
| | - Samuel Kaplan
- Department of Microbiology and Molecular Genetics, The University of Texas Health Science Center, Medical School, 6431 Fannin, Houston, TX 77030, USA
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Gomelsky L, Sram J, Moskvin OV, Horne IM, Dodd HN, Pemberton JM, McEwan AG, Kaplan S, Gomelsky M. Identification and in vivo characterization of PpaA, a regulator of photosystem formation in Rhodobacter sphaeroides. MICROBIOLOGY (READING, ENGLAND) 2003; 149:377-388. [PMID: 12624200 DOI: 10.1099/mic.0.25972-0] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A regulatory protein, PpaA, involved in photosystem formation in the anoxygenic phototrophic proteobacterium Rhodobacter sphaeroides has been identified and characterized in vivo. Based on the phenotypes of cells expressing the ppaA gene in extra copy and on the phenotype of the ppaA null mutant, it was concluded that PpaA activates photopigment production and puc operon expression under aerobic conditions. This is in contrast to the function of the PpaA homologue from Rhodobacter capsulatus, AerR, which acts as a repressor under aerobic conditions [Dong, C., Elsen, S., Swem, L. R. & Bauer, C. E. (2002). J Bacteriol 184, 2805-2814]. The expression of the ppaA gene increases several-fold in response to a decrease in oxygen tension, suggesting that the PpaA protein is active under conditions of low or no oxygen. However, no discernible phenotype of a ppaA null mutant was observed under anaerobic conditions tested thus far. The photosystem gene repressor PpsR mediates repression of ppaA gene expression under aerobic conditions. Sequence analysis of PpaA homologues from several anoxygenic phototrophic bacteria revealed a putative corrinoid-binding domain. It is suggested that PpaA binds a corrinoid cofactor and the availability or structure of this cofactor affects PpaA activity.
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Affiliation(s)
- Larissa Gomelsky
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071-3944, USA
| | - Jakub Sram
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071-3944, USA
| | - Oleg V Moskvin
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071-3944, USA
| | - Irene M Horne
- Department of Microbiology and Parasitology, University of Queensland, Brisbane 4072, Australia
| | - Helen N Dodd
- Department of Microbiology and Parasitology, University of Queensland, Brisbane 4072, Australia
| | - John M Pemberton
- Department of Microbiology and Parasitology, University of Queensland, Brisbane 4072, Australia
| | - Alastair G McEwan
- Department of Microbiology and Parasitology, University of Queensland, Brisbane 4072, Australia
| | - Samuel Kaplan
- Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston, TX 77030, USA
| | - Mark Gomelsky
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071-3944, USA
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