scholarly journals Expression of Uptake Hydrogenase and Molybdenum Nitrogenase in Rhodobacter capsulatus Is Coregulated by the RegB-RegA Two-Component Regulatory System

2000 ◽  
Vol 182 (10) ◽  
pp. 2831-2837 ◽  
Author(s):  
Sylvie Elsen ◽  
Wanda Dischert ◽  
Annette Colbeau ◽  
Carl E. Bauer
Keyword(s):  
Photosynthetic Bacteria ◽  
Rhodobacter Capsulatus ◽  
Regulatory System ◽  
Photosynthetic Bacterium ◽  
Uptake Hydrogenase ◽  
Carbon And Nitrogen ◽  
Cellular Energy ◽  
Purple Photosynthetic Bacteria ◽  
Two Component

ABSTRACT Purple photosynthetic bacteria are capable of generating cellular energy from several sources, including photosynthesis, respiration, and H2 oxidation. Under nutrient-limiting conditions, cellular energy can be used to assimilate carbon and nitrogen. This study provides the first evidence of a molecular link for the coregulation of nitrogenase and hydrogenase biosynthesis in an anoxygenic photosynthetic bacterium. We demonstrated that molybdenum nitrogenase biosynthesis is under the control of the RegB-RegA two-component regulatory system in Rhodobacter capsulatus. Footprint analyses and in vivo transcription studies showed that RegA indirectly activates nitrogenase synthesis by binding to and activating the expression of nifA2, which encodes one of the two functional copies of the nif-specific transcriptional activator, NifA. Expression of nifA2 but notnifA1 is reduced in the reg mutants up to eightfold under derepressing conditions and is also reduced under repressing conditions. Thus, although NtrC is absolutely required fornifA2 expression, RegA acts as a coactivator ofnifA2. We also demonstrated that in regmutants, [NiFe]hydrogenase synthesis and activity are increased up to sixfold. RegA binds to the promoter of the hydrogenase gene operon and therefore directly represses its expression. Thus, the RegB-RegA system controls such diverse processes as energy-generating photosynthesis and H2 oxidation, as well as the energy-demanding processes of N2 fixation and CO2 assimilation.

Regulation of nitrogenase in the photosynthetic bacteriumRhodobacter sphaeroidescontainingdraTGandnifHDKgenes fromRhodobacter capsulatus

2001 ◽  
Vol 47 (3) ◽  
pp. 206-212 ◽  
Author(s):  
Alexander F Yakunin ◽  
Alexander S Fedorov ◽  
Tatyana V Laurinavichene ◽  
Vadim M Glaser ◽  
Nikolay S Egorov ◽  
...  
Keyword(s):  
Photosynthetic Bacteria ◽  
Rhodospirillum Rubrum ◽  
Rhodobacter Capsulatus ◽  
Nitrogenase Activity ◽  
Photosynthetic Bacterium ◽  
Adp Ribosylation ◽  
Fe Protein ◽  
Dinitrogenase Reductase ◽  
Different Strains

The photosynthetic bacteria Rhodobacter capsulatus and Rhodospirillum rubrum regulate their nitrogenase activity by the reversible ADP-ribosylation of nitrogenase Fe-protein in response to ammonium addition or darkness. This regulation is mediated by two enzymes, dinitrogenase reductase ADP-ribosyl transferase (DRAT) and dinitrogenase reductase activating glycohydrolase (DRAG). Recently, we demonstrated that another photosynthetic bacterium, Rhodobacter sphaeroides, appears to have no draTG genes, and no evidence of Fe-protein ADP-ribosylation was found in this bacterium under a variety of growth and incubation conditions. Here we show that four different strains of Rba. sphaeroides are incapable of modifying Fe-protein, whereas four out of five Rba. capsulatus strains possess this ability. Introduction of Rba. capsulatus draTG and nifHDK (structural genes for nitrogenase proteins) into Rba. sphaeroides had no effect on in vivo nitrogenase activity and on nitrogenase switch-off by ammonium. However, transfer of draTG from Rba. capsulatus was sufficient to confer on Rba. sphaeroides the ability to reversibly modify the nitrogenase Fe-protein in response to either ammonium addition or darkness. These data suggest that Rba. sphaeroides, which lacks DRAT and DRAG, possesses all the elements necessary for the transduction of signals generated by ammonium or darkness to these proteins.Key words: nitrogenase regulation, nitrogenase modification, photosynthetic bacteria.

scholarly journals The VirS/VirR Two-Component System Regulates the Anaerobic Cytotoxicity, Intestinal Pathogenicity, and Enterotoxemic Lethality of Clostridium perfringens Type C Isolate CN3685

mBio ◽  
2011 ◽  
Vol 2 (1) ◽  
Author(s):  
Menglin Ma ◽  
Jorge Vidal ◽  
Juliann Saputo ◽  
Bruce A. McClane ◽  
Francisco Uzal
Keyword(s):  
Clostridium Perfringens ◽  
Regulatory System ◽  
Gas Gangrene ◽  
Necrotic Enteritis ◽  
Vegetative Cells ◽  
Content Type ◽  
Two Component ◽  
Type C ◽  
Beta Toxin

ABSTRACT Clostridium perfringens vegetative cells cause both histotoxic infections (e.g., gas gangrene) and diseases originating in the intestines (e.g., hemorrhagic necrotizing enteritis or lethal enterotoxemia). Despite their medical and veterinary importance, the molecular pathogenicity of C. perfringens vegetative cells causing diseases of intestinal origin remains poorly understood. However, C. perfringens beta toxin (CPB) was recently shown to be important when vegetative cells of C. perfringens type C strain CN3685 induce hemorrhagic necrotizing enteritis and lethal enterotoxemia. Additionally, the VirS/VirR two-component regulatory system was found to control CPB production by CN3685 vegetative cells during aerobic infection of cultured enterocyte-like Caco-2 cells. Using an isogenic virR null mutant, the current study now reports that the VirS/VirR system also regulates CN3685 cytotoxicity during infection of Caco-2 cells under anaerobic conditions, as found in the intestines. More importantly, the virR mutant lost the ability to cause hemorrhagic necrotic enteritis in rabbit small intestinal loops. Western blot analyses demonstrated that the VirS/VirR system mediates necrotizing enteritis, at least in part, by controlling in vivo CPB production. In addition, vegetative cells of the isogenic virR null mutant were, relative to wild-type vegetative cells, strongly attenuated in their lethality in a mouse enterotoxemia model. Collectively, these results identify the first regulator of in vivo pathogenicity for C. perfringens vegetative cells causing disease originating in the complex intestinal environment. Since VirS/VirR also mediates histotoxic infections, this two-component regulatory system now assumes a global role in regulating a spectrum of infections caused by C. perfringens vegetative cells. IMPORTANCE Clostridium perfringens is an important human and veterinary pathogen. C. perfringens vegetative cells cause both histotoxic infections, e.g., traumatic gas gangrene, and infections originating when this bacterium grows in the intestines. The VirS/VirR two-component regulatory system has been shown to control the pathogenicity of C. perfringens type A strains in a mouse gas gangrene model, but there is no understanding of pathogenicity regulation when C. perfringens vegetative cells cause disease originating in the complex intestinal environment. The current study establishes that VirS/VirR controls vegetative cell pathogenicity when C. perfringens type C isolates cause hemorrhagic necrotic enteritis and lethal enterotoxemia (i.e., toxin absorption from the intestines into the circulation, allowing targeting of internal organs). This effect involves VirS/VirR-mediated regulation of beta toxin production in vivo. Therefore, VirS/VirR is the first identified global in vivo regulator controlling the ability of C. perfringens vegetative cells to cause gas gangrene and, at least some, intestinal infections.

The RegB/RegA two-component regulatory system controls synthesis of photosynthesis and respiratory electron transfer components in Rhodobacter capsulatus

2001 ◽  
Vol 309 (1) ◽  
pp. 121-138 ◽  
Author(s):  
Lee R Swem ◽  
Sylvie Elsen ◽  
Terry H Bird ◽  
Danielle L Swem ◽  
Hans-Georg Koch ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Rhodobacter Capsulatus ◽  
Regulatory System ◽  
Two Component

Organization of the Genes Encoding Uptake Hydrogenase in the Photosynthetic Bacterium Rhodobacter Capsulatus

1991 ◽  
pp. 503-508
Author(s):  
A. Colbeau ◽  
P. Richaud ◽  
J. P. Magnin ◽  
J. Caballero ◽  
B. Cauvin ◽  
...  
Keyword(s):  
Rhodobacter Capsulatus ◽  
Photosynthetic Bacterium ◽  
Uptake Hydrogenase ◽  
Genes Encoding

scholarly journals Regulation and Characterization of Two Nitroreductase Genes, nprA and nprB, of Rhodobacter capsulatus

2005 ◽  
Vol 71 (12) ◽  
pp. 7643-7649 ◽  
Author(s):  
Eva Pérez-Reinado ◽  
Rafael Blasco ◽  
Francisco Castillo ◽  
Conrado Moreno-Vivián ◽  
M. Dolores Roldán
Keyword(s):  
Gene Expression ◽  
Salicylic Acid ◽  
Rhodobacter Capsulatus ◽  
Sequence Data ◽  
Regulatory System ◽  
Wide Range ◽  
Nitrofuran Derivatives ◽  
Response To Stress

ABSTRACT Among photosynthetic bacteria, strains B10 and E1F1 of Rhodobacter capsulatus photoreduce 2,4-dinitrophenol (DNP), which is stoichiometrically converted into 2-amino-4-nitrophenol by a nitroreductase activity. The reduction of DNP is inhibited in vivo by ammonium, which probably acts at the level of the DNP transport system and/or physiological electron transport to the nitroreductase, since this enzyme is not inhibited by ammonium in vitro. Using the complete genome sequence data for strain SB1003 of R. capsulatus, two putative genes coding for possible nitroreductases were isolated from R. capsulatus B10 and disrupted. The phenotypes of these mutant strains revealed that both genes are involved in the reduction of DNP and code for two major nitroreductases, NprA and NprB. Both enzymes use NAD(P)H as the main physiological electron donor. The nitroreductase NprA is under ammonium control, whereas the nitroreductase NprB is not. In addition, the expression of the nprB gene seems to be constitutive, whereas nprA gene expression is inducible by a wide range of nitroaromatic and heterocyclic compounds, including several dinitroaromatics, nitrofuran derivatives, CB1954, 2-aminofluorene, benzo[a]pyrene, salicylic acid, and paraquat. The identification of two putative mar/sox boxes in the possible promoter region of the nprA gene and the induction of nprA gene expression by salicylic acid and 2,4-dinitrophenol suggest a role in the control of the nprA gene for the two-component MarRA regulatory system, which in Escherichia coli controls the response to some antibiotics and environmental contaminants. In addition, upregulation of the nprA gene by paraquat indicates that this gene is probably a member of the SoxRS regulon, which is involved in the response to stress conditions in other bacteria.

scholarly journals The Two-Component System 09 of Streptococcus pneumoniae Is Important for Metabolic Fitness and Resistance during Dissemination in the Host

2021 ◽  
Vol 9 (7) ◽  
pp. 1365
Author(s):  
Stephanie Hirschmann ◽  
Alejandro Gómez-Mejia ◽  
Thomas P. Kohler ◽  
Franziska Voß ◽  
Manfred Rohde ◽  
...  
Keyword(s):  
Streptococcus Pneumoniae ◽  
Regulatory System ◽  
Immunoblot Analysis ◽  
Defined Medium ◽  
Host Cells ◽  
Two Component ◽  
Regulatory Effects ◽  
The Impact

The two-component regulatory system 09 of Streptococcus pneumoniae has been shown to modulate resistance against oxidative stress as well as capsule expression. These data and the implication of TCS09 in cell wall integrity have been shown for serotype 2 strain D39. Other data have suggested strain-specific regulatory effects of TCS09. Contradictory data are known on the impact of TCS09 on virulence, but all have been explored using only the rr09-mutant. In this study, we have therefore deleted one or both components of the TCS09 (SP_0661 and SP_0662) in serotype 4 S. pneumoniae TIGR4. In vitro growth assays in chemically defined medium (CDM) using sucrose or lactose as a carbon source indicated a delayed growth of nonencapsulated tcs09-mutants, while encapsulated wild-type TIGR4 and tcs09-mutants have reduced growth in CDM with glucose. Using a set of antigen-specific antibodies, immunoblot analysis showed that only the pilus 1 backbone protein RrgB is significantly reduced in TIGR4ΔcpsΔhk09. Electron microscopy, adherence and phagocytosis assays showed no impact of TCS09 on the TIGR4 cell morphology and interaction with host cells. In contrast, in vivo infections and in particular competitive co-infection experiments demonstrated that TCS09 enhances robustness during dissemination in the host by maintaining bacterial fitness.

Short-Term Regulation of Nitrogenase Activity by NH4+ in Rhodobacter capsulatus: Multiple In Vivo Nitrogenase Responses to NH4+ Addition

1998 ◽  
Vol 180 (23) ◽  
pp. 6392-6395 ◽  
Author(s):  
Alexander F. Yakunin ◽  
Patrick C. Hallenbeck
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Rhodobacter Capsulatus ◽  
Nitrogenase Activity ◽  
Photosynthetic Bacterium ◽  
Wild Type ◽  
Magnitude Response ◽  
Short Term ◽  
Reversible Inhibition

ABSTRACT The photosynthetic bacterium Rhodobacter capsulatus has been shown to carry out nitrogenase “switch-off,” a rapid, reversible inhibition of in vivo activity. Here, we demonstrate that highly nitrogen-limited cultures of both the wild-type strain and adraT draG mutant are capable of nitrogenase switch-off while moderately nitrogen-limited cultures show instead a “magnitude” response, with a decrease in in vivo nitrogenase activity that is proportional to the amount of added NH4 +.

scholarly journals Interaction between the H2Sensor HupUV and the Histidine Kinase HupT Controls HupSL HydrogenaseSynthesis in Rhodobactercapsulatus

2003 ◽  
Vol 185 (24) ◽  
pp. 7111-7119 ◽  
Author(s):  
Sylvie Elsen ◽  
Ophélie Duché ◽  
Annette Colbeau
Keyword(s):  
Histidine Kinase ◽  
Rhodobacter Capsulatus ◽  
Expression System ◽  
Photosynthetic Bacterium ◽  
Homologous Expression ◽  
Uptake Activity ◽  
Mutant Phenotypes ◽  
In Vitro Interaction

ABSTRACT The photosynthetic bacterium Rhodobacter capsulatus contains two [NiFe]hydrogenases: an energy-generating hydrogenase, HupSL, and a regulatory hydrogenase, HupUV. The synthesis of HupSL is specifically activated by H2 through a signal transduction cascade comprising three proteins: the H2-sensing HupUV protein, the histidine kinase HupT, and the transcriptional regulator HupR. Whereas a phosphotransfer between HupT and HupR was previously demonstrated, interaction between HupUV and HupT was only hypothesized based on in vivo analyses of mutant phenotypes. To visualize the in vitro interaction between HupUV and HupT proteins, a six-His (His6)-HupU fusion protein and the HupV protein were coproduced by using a homologous expression system. The two proteins copurified as a His6-HupUHupV complex present in dimeric and tetrameric forms, both of which had H2 uptake activity. We demonstrated that HupT and HupUV interact and form stable complexes that could be separated on a native gel. Interaction was also monitored with surface plasmon resonance technology and was shown to be insensitive to salt concentration and pH changes, suggesting that the interactions involve hydrophobic residues. As expected, H2 affects the interaction between HupUV and HupT, leading to a weakening of the interaction, which is independent of the phosphate status of HupT. Several forms of HupT were tested for their ability to interact with HupUV and to complement hupT mutants. Strong interaction with HupUV was obtained with the isolated PAS domain of HupT and with inactive HupT mutated in the phosphorylable histidine residue, but only the wild-type HupT protein was able to restore normal H2 regulation.

scholarly journals Genome Sequence of the Unusual Purple Photosynthetic Bacterium Phaeovibrio sulfidiphilus, Only Distantly Related to Rhodospirillaceae, Reveals Unique Genes for Respiratory Nitrate Reduction and Glycerol Metabolism

2020 ◽  
Vol 9 (49) ◽  
Author(s):  
S. Dubey ◽  
T. E. Meyer ◽  
J. A. Kyndt
Keyword(s):  
Nitrate Reduction ◽  
Photosynthetic Bacteria ◽  
Photosynthetic Bacterium ◽  
Gene Clusters ◽  
Glycerol Metabolism ◽  
Freshwater Species ◽  
Content Type ◽  
Purple Photosynthetic Bacteria ◽  
Purple Photosynthetic Bacterium ◽  
Unique Genes

ABSTRACT Phaeovibrio sulfidiphilus was reported to be a divergent member of the purple photosynthetic bacteria with limited ability to metabolize organic compounds. Whole-genome-based analysis shows that it is indeed only distantly related to freshwater species of Rhodospirillaceae. Unexpectedly, the genome contains unique gene clusters for potential respiratory nitrate reduction and anaerobic glycerol metabolism.

scholarly journals Phosphorylation at the D53 but Not the T65 Residue of CovR Determines the Repression ofrggandspeBTranscription inemm1- andemm49-Type Group A Streptococci

2018 ◽  
Vol 201 (4) ◽  
Author(s):  
Chuan Chiang-Ni ◽  
Chih-Yuan Kao ◽  
Chih-Yun Hsu ◽  
Cheng-Hsun Chiu
Keyword(s):  
Intergenic Region ◽  
Dominant Role ◽  
Transcriptional Repressor ◽  
Regulatory System ◽  
Independent Manner ◽  
Content Type ◽  
Two Component ◽  
Group A ◽  
Direct Binding

ABSTRACTCovR/CovS is a two-component regulatory system in group AStreptococcusand primarily acts as a transcriptional repressor. The D53 residue of CovR (CovRD53) is phosphorylated by the sensor kinase CovS, and the phosphorylated CovRD53protein binds to the intergenic region ofrgg-speBto inhibitspeBtranscription. Nonetheless, the transcription ofrggandspeBis suppressed incovSmutants. The T65 residue of CovR is phosphorylated in a CovS-independent manner, and phosphorylation at the D53 and T65 residues of CovR is mutually exclusive. Therefore, how phosphorylation at the D53 and T65 residues of CovR contributes to the regulation ofrggandspeBexpression was elucidated. The transcription ofrggandspeBwas suppressed in the strain that cannot phosphorylate the D53 residue of CovR (CovRD53Amutant) but restored to levels similar to those of the wild-type strain in the CovRT65Amutant. Nonetheless, inactivation of the T65 residue phosphorylation in the CovRD53Amutant cannot derepress therggandspeBtranscription, indicating that phosphorylation at the T65 residue of CovR is not required for repressingrggandspeBtranscription. Furthermore,transcomplementation of the CovRD53Aprotein in the strain that expresses the phosphorylated CovRD53resulted in the repression ofrggandspeBtranscription. Unlike the direct binding of the phosphorylated CovRD53protein and its inhibition ofspeBtranscription demonstrated previously, the present study showed that inactivation of phosphorylation at the D53 residue of CovR contributes dominantly in suppressingrggandspeBtranscription.IMPORTANCECovR/CovS is a two-component regulatory system in group AStreptococcus(GAS). The D53 residue of CovR is phosphorylated by CovS, and the phosphorylated CovRD53binds to thergg-speBintergenic region and acts as the transcriptional repressor. Nonetheless, the transcription ofrggand Rgg-controlledspeBis upregulated in thecovRmutant but inhibited in thecovSmutant. The present study showed that nonphosphorylated CovRD53protein inhibitsrggandspeBtranscription in the presence of the phosphorylated CovRD53in vivo, indicating that nonphosphorylated CovRD53has a dominant role in suppressingrggtranscription. These results reveal the roles of nonphosphorylated CovRD53in regulatingrggtranscription, which could contribute significantly to invasive phenotypes ofcovSmutants.

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