scholarly journals Role of oxyR from Sinorhizobium meliloti in Regulating the Expression of Catalases

2005 ◽  
Vol 37 (6) ◽  
pp. 421-428 ◽  
Author(s):  
Li Luo ◽  
Ming-Sheng Qi ◽  
Shi-Yi Yao ◽  
Hai-Ping Cheng ◽  
Jia-Bi Zhu ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Sinorhizobium Meliloti ◽  
Wild Type Strain ◽  
Reduced Form ◽  
Insertion Mutant ◽  
Transcriptional Level ◽  
Oxygen Species ◽  
E Coli ◽  
Catalase Peroxidase

AbstractThe process of symbiotic nitrogen fixation results in the generation of reactive oxygen species such as the superoxide anion (O2-) and hydrogen peroxide (H2O2). The response of rhizobia to these toxic oxygen species is an important factor in nodulation and nitrogen fixation. In Sinorhizobium meliloti, one oxyR homologue and three catalase genes, katA, katB, and katC were detected by sequence analysis. This oxyR gene is located next to and divergently from katA on the chromosome. To investigate the possible roles of oxyR in regulating the expression of catalases at the transcriptional level in S. meliloti, an insertion mutant of this gene was constructed. The mutant was more sensitive and less adaptive to H2O2 than the wild type strain, and total catalase/peroxidase activity was reduced approximately fourfold with the OxyR mutation relative to controls. The activities of KatA and KatB and the expression of katA::lacZ and katB::lacZ promoter fusions were increased in the mutant strain compared with the parental strain grown in the absence of H2O2, indicating that katA and katB are repressed by OxyR. However, when exposed to H2O2, katA expression was also increased in both S. meliloti and Escherichia coli. When exposed to H2O2, OxyR is converted from a reduced to an oxidized form in E. coli. We concluded that the reduced form of OxyR functions as a repressor of katA and katB expression. Thus, in the presence of H2O2, reduced OxyR is converted to the oxidized form of OxyR that then results in increased katA expression. We further showed that oxyR expression is autoregulated via negative feedback.

scholarly journals Functional Characterization of the Sinorhizobium meliloti Acetate Metabolism Genes aceA, SMc00767, and glcB

2007 ◽  
Vol 189 (16) ◽  
pp. 5875-5884 ◽  
Author(s):  
J. A. Ramírez-Trujillo ◽  
S. Encarnación ◽  
E. Salazar ◽  
A. García de los Santos ◽  
M. F. Dunn ◽  
...  
Keyword(s):  
Type Strain ◽  
Sinorhizobium Meliloti ◽  
Wild Type Strain ◽  
Isocitrate Lyase ◽  
Functional Characterization ◽  
Malate Synthase ◽  
Acetate Metabolism ◽  
Transcriptional Level ◽  
Wild Type

ABSTRACT The genes encoding malate synthase (glcB) and isocitrate lyase (aceA) and a 240-bp open reading frame (SMc00767) located downstream of aceA were isolated and functionally characterized in Sinorhizobium meliloti. Independent and double interposon mutants of each gene were constructed, and the corresponding phenotypes were analyzed. aceA mutants failed to grow on acetate, and mutants deficient in SMc00767 were also affected in acetate utilization. In contrast, mutants deficient in glcB grew on acetate similar to wild-type strain Rm5000. Complementation experiments showed that aceA and SMc00767 gene constructs were able to restore the growth on acetate in the corresponding single mutants. aceA-glcB, aceA-SMc00767, and glcB-SMc00767 double knockouts were also unable to grow on acetate, but this ability was recovered when the wild-type aceA-glcB or aceA-SMc00767 loci were introduced into the double mutants. These data confirm the functional role of aceA and SMc00767 and show that glcB, in the absence of SMc00767, is required for acetate metabolism. Isocitrate lyase and malate synthase activities were measured in strain Rm5000, the mutant derivatives, and complemented strains. aceA and glcB were able to complement the enzymatic activity lacking in the corresponding single mutants. The enzymatic activities also showed that SMc00767 represses the activity of isocitrate lyase in cells grown on acetate. Gene fusions confirmed the repressor role of SMc00767, which regulates aceA expression at the transcriptional level. Comparison of the transcriptional profiles of the SMc00767 mutant and wild-type strain Rm5000 showed that SMc00767 represses the expression of a moderate number of open reading frames, including aceA; thus, we propose that SMc00767 is a novel repressor involved in acetate metabolism in S. meliloti. Genetic and functional analyses indicated that aceA and SMc00767 constitute a functional two-gene operon, which is conserved in other α-proteobacteria. Alfalfa plants infected with the aceA and glcB mutants were not impaired in nodulation or nitrogen fixation, and so the glyoxylate cycle is not required in the Rhizobium-legume symbiosis.

scholarly journals The RcsCB His-Asp Phosphorelay System Is Essential To Overcome Chlorpromazine-Induced Stress in Escherichia coli

2002 ◽  
Vol 184 (10) ◽  
pp. 2850-2853 ◽  
Author(s):  
Annie Conter ◽  
Rachel Sturny ◽  
Claude Gutierrez ◽  
Kaymeuang Cam
Keyword(s):  
Escherichia Coli ◽  
Type Strain ◽  
Wild Type Strain ◽  
Cell Envelope ◽  
Wild Type ◽  
E Coli ◽  
Induced Stress ◽  
Mutant Strains ◽  
Molecular Nature

ABSTRACT The RcsCB His-Asp phosphorelay system regulates the expression of several genes of Escherichia coli, but the molecular nature of the inducing signal is still unknown. We show here that treatment of an exponentially growing culture of E. coli with the cationic amphipathic compound chlorpromazine (CPZ) stimulates expression of a set of genes positively regulated by the RcsCB system. This induction is abolished in rcsB or rcsC mutant strains. In addition, treatment with CPZ inhibits growth. The wild-type strain is able to recover from this inhibition and resume growth after a period of adaptation. In contrast, strains deficient in the RcsCB His-Asp phosphorelay system are hypersensitive to CPZ. These results suggest that cells must express specific RcsCB-regulated genes in order to cope with the CPZ-induced stress. This is the first report of the essential role of the RcsCB system in a stress situation. These results also strengthen the notion that alterations of the cell envelope induce a signal recognized by the RcsC sensor.

scholarly journals Role of Burkholderia pseudomallei Sigma N2 in Amino Acids Utilization and in Regulation of Catalase E Expression at the Transcriptional Level

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Duong Thi Hong Diep ◽  
Nguyen Thi Thanh Phuong ◽  
Mya Myintzu Hlaing ◽  
Potjanee Srimanote ◽  
Sumalee Tungpradabkul
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Burkholderia Pseudomallei ◽  
Transcriptional Level ◽  
Chromosome 2 ◽  
E Coli ◽  
Alternative Sigma Factors ◽  
Amino Acid Utilization ◽  
Genes Expression

Burkholderia pseudomallei is the causative agent of melioidosis. The complete genome sequences of this pathogen have been revealed, which explain some pathogenic mechanisms. In various hostile conditions, for example, during nitrogen and amino acid starvation, bacteria can utilize alternative sigma factors such as RpoS and RpoN to modulate genes expression for their adaptation and survival. In this study, we demonstrate that mutagenesis of rpoN2, which lies on chromosome 2 of B. pseudomallei and encodes a homologue of the sigma factor RpoN, did not alter nitrogen and amino acid utilization of the bacterium. However, introduction of B. pseudomallei rpoN2 into E. coli strain deficient for rpoN restored the ability to utilize amino acids. Moreover, comparative partial proteomic analysis of the B. pseudomallei wild type and its rpoN2 isogenic mutant was performed to elucidate its amino acids utilization property which was comparable to its function found in the complementation assay. By contrast, the rpoN2 mutant exhibited decreased katE expression at the transcriptional and translational levels. Our finding indicates that B. pseudomallei RpoN2 is involved in a specific function in the regulation of catalase E expression.

scholarly journals Evaluation of the Role of the Bvg Intermediate Phase in Bordetella pertussis during Experimental Respiratory Infection

2005 ◽  
Vol 73 (2) ◽  
pp. 748-760 ◽  
Author(s):  
Nuria Vergara-Irigaray ◽  
Alberto Chávarri-Martínez ◽  
Juan Rodríguez-Cuesta ◽  
Jeff F. Miller ◽  
Peggy A. Cotter ◽  
...  
Keyword(s):  
Respiratory Tract ◽  
Bordetella Pertussis ◽  
Wild Type Strain ◽  
Intermediate Phase ◽  
Transcriptional Level ◽  
Wild Type ◽  
Environmental Signals ◽  
Time Point

ABSTRACT The BvgAS system of Bordetella pertussis was traditionally considered to mediate a transition between two phenotypic phases (Bvg+ and Bvg−) in response to environmental signals. We characterized a third state, the intermediate (Bvgi) phase, which can be induced by introducing a 1-bp substitution into bvgS (the bvgS-I1 mutation) or by growing B. pertussis under conditions intermediate between those leading to the Bvg+ and Bvg− phases. Like B. bronchiseptica, B. pertussis displays in its Bvgi phase a characteristic colony morphology and hemolytic activity and expresses a Bvgi-phase-specific polypeptide called BipA, whose synthesis is regulated by bvgAS at the transcriptional level. Based on our results, we hypothesize that the Bvgi phase of B. pertussis may be involved in facilitating transmission between hosts. Thus, a B. pertussis mutant carrying the bvgS-I1 mutation (GMT1i) persisted at wild-type levels only in the upper murine respiratory tract. Interestingly, a bipA deletion derivative of GMT1i displayed a reduced ability to colonize the nasal cavity of mice compared with GMT1i. However, in experimental mixed infections GMT1i expressing the Bvgi phase could establish an initial colonization in the nose and trachea of mice as efficiently as GMT1, but the wild-type strain outcompeted GMT1i at a later time point at all sites of the respiratory tract, suggesting that the Bvgi phase does not serve as a phenotypic phase specialized in colonization. Finally, even though B. pertussis expresses in vitro the Bvgi phase at the human nasal temperature, anti-BipA antibodies were undetectable in a large collection of sera from pertussis patients.

scholarly journals An Orphan LuxR Homolog of Sinorhizobium meliloti Affects Stress Adaptation and Competition for Nodulation

2008 ◽  
Vol 75 (4) ◽  
pp. 946-955 ◽  
Author(s):  
Arati V. Patankar ◽  
Juan E. Gonz�lez
Keyword(s):  
Sinorhizobium Meliloti ◽  
Wild Type Strain ◽  
Symbiotic Association ◽  
Response Regulators ◽  
Sensing System ◽  
Luxr Homolog ◽  
Active Methyl ◽  
Quorum Sensing System ◽  
Type Response

ABSTRACT The Sin/ExpR quorum-sensing system of Sinorhizobium meliloti plays an important role in the symbiotic association with its host plant, Medicago sativa. The LuxR-type response regulators of the Sin system include the synthase (SinI)-associated SinR and the orphan regulator ExpR. Interestingly, the S. meliloti Rm1021 genome codes for four additional putative orphan LuxR homologs whose regulatory roles remain to be identified. These response regulators contain the characteristic domains of the LuxR family of proteins, which include an N-terminal autoinducer/response regulatory domain and a C-terminal helix-turn-helix domain. This study elucidates the regulatory role of one of the orphan LuxR-type response regulators, NesR. Through expression and phenotypic analyses, nesR was determined to affect the active methyl cycle of S. meliloti. Moreover, nesR was shown to influence nutritional and stress response activities in S. meliloti. Finally, the nesR mutant was deficient in competing with the wild-type strain for plant nodulation. Taken together, these results suggest that NesR potentially contributes to the adaptability of S. meliloti when it encounters challenges such as high osmolarity, nutrient starvation, and/or competition for nodulation, thus increasing its chances for survival in the stressful rhizosphere.

scholarly journals Expanding the regulatory network that controls nitrogen fixation in Sinorhizobium meliloti: elucidating the role of the two-component system hFixL-FxkR

Microbiology ◽  
2016 ◽  
Vol 162 (6) ◽  
pp. 979-988 ◽  
Author(s):  
Alma Reyes-González ◽  
Chouhra Talbi ◽  
Susana Rodríguez ◽  
Patricia Rivera ◽  
David Zamorano-Sánchez ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Regulatory Network ◽  
Sinorhizobium Meliloti ◽  
Two Component System ◽  
Component System ◽  
Two Component

scholarly journals Regulation of d-Aspartate Oxidase Gene Expression by Pyruvate Metabolism in the Yeast Cryptococcus humicola

2021 ◽  
Vol 9 (12) ◽  
pp. 2444
Author(s):  
Daiki Imanishi ◽  
Sota Zaitsu ◽  
Shouji Takahashi
Keyword(s):  
Gene Expression ◽  
Growth Retardation ◽  
Wild Type Strain ◽  
Transcriptional Level ◽  
Oxidative Deamination ◽  
Pyruvate Metabolism ◽  
Oxidase Gene ◽  
Cryptococcus Humicola ◽  
In The Wild

d-Aspartate oxidase (DDO) is a peroxisomal flavoenzyme that catalyzes the oxidative deamination of acidic d-amino acids. In the yeast Cryptococcus humicola strain UJ1, the enzyme ChDDO is essential for d-Asp utilization and is expressed only in the presence of d-Asp. Pyruvate carboxylase (Pyc) catalyzes the conversion of pyruvate to oxaloacetate and is involved in the import and activation of certain peroxisomal flavoenzymes in yeasts. In this study, we analyzed the role of Pyc in the expression of ChDDO gene in C. humicola strain UJ1. PYC gene disruption (∆Chpyc1) in strain UJ1 resulted in growth retardation on glucose and NH4Cl medium. The growth was restored by supplying oxaloacetate from l-Asp or α-ketoglutarate by a transaminase. On the other hand, the supply of oxaloacetate from d-Asp by ChDDO was not able to prevent growth retardation because of a significant decrease in ChDDO gene expression at the transcriptional level. The addition of pyruvate significantly decreased ChDDO gene transcription in the ∆Chpyc1 strain but increased the same in the wild-type strain, even though the intracellular pyruvate content was similar in both strains. These results suggest that ChDDO gene expression might be regulated by pyruvate metabolism, as well as by the presence of d-Asp.

Redox-mediated interactions of VHb (Vitreoscilla haemoglobin) with OxyR: novel regulation of VHb biosynthesis under oxidative stress

2010 ◽  
Vol 426 (3) ◽  
pp. 271-280 ◽  
Author(s):  
Arvind Anand ◽  
Brian T. Duk ◽  
Sandeep Singh ◽  
Meltem Y. Akbas ◽  
Dale A. Webster ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Transcriptional Control ◽  
High Sensitivity ◽  
Reduced Form ◽  
Gene Encoding ◽  
Antioxidant Genes ◽  
E Coli ◽  
Hypoxic Conditions ◽  
Catalase Peroxidase

The bacterial haemoglobin from Vitreoscilla, VHb, displays several unusual properties that are unique among the globin family. When the gene encoding VHb, vgb, is expressed from its natural promoter in either Vitreoscilla or Escherichia coli, the level of VHb increases more than 50-fold under hypoxic conditions and decreases significantly during oxidative stress, suggesting similar functioning of the vgb promoter in both organisms. In the present study we show that expression of VHb in E. coli induced the antioxidant genes katG (catalase–peroxidase G) and sodA (superoxide dismutase A) and conferred significant protection from oxidative stress. In contrast, when vgb was expressed in an oxyR mutant of E. coli, VHb levels increased and the strain showed high sensitivity to oxidative stress without induction of antioxidant genes; this indicates the involvement of the oxidative stress regulator OxyR in mediating the protective effect of VHb under oxidative stress. A putative OxyR-binding site was identified within the vgb promoter and a gel-shift assay confirmed its interaction with oxidized OxyR, an interaction which was disrupted by the reduced form of the transcriptional activator Fnr (fumurate and nitrate reductase). This suggested that the redox state of OxyR and Fnr modulates their interaction with the vgb promoter. VHb associated with reduced OxyR in two-hybrid screen experiments and in vitro, converting it into an oxidized state in the presence of NADH, a condition where VHb is known to generate H2O2. These observations unveil a novel mechanism by which VHb may transmit signals to OxyR to autoregulate its own biosynthesis, simultaneously activating oxidative stress functions. The activation of OxyR via VHb, reported in the present paper for the first time, suggests the involvement of VHb in transcriptional control of many other genes as well.

Phospholipid synthesis in Borrelia burgdorferi: BB0249 and BB0721 encode functional phosphatidylcholine synthase and phosphatidylglycerolphosphate synthase proteins

Microbiology ◽  
2004 ◽  
Vol 150 (2) ◽  
pp. 391-397 ◽  
Author(s):  
Xing-Guo Wang ◽  
Joanna P. Scagliotti ◽  
Linden T. Hu
Keyword(s):  
Borrelia Burgdorferi ◽  
Sinorhizobium Meliloti ◽  
Biosynthetic Pathways ◽  
Phospholipid Synthesis ◽  
Membrane Phospholipids ◽  
Bacterial Membranes ◽  
E Coli ◽  
Methylation Pathway ◽  
And Function

Phospholipids are an important component of bacterial membranes. Borrelia burgdorferi differs from many other bacteria in that it contains only two major membrane phospholipids: phosphatidylglycerol (PG) and phosphatidylcholine (PC). B. burgdorferi appears to lack enzymes required for synthesis of PC through the well-described methylation pathway. However, B. burgdorferi does contain a gene (BB0249) with significant identity to a recently described phosphatidylcholine synthase gene (pcs) of Sinorhizobium meliloti. B. burgdorferi also contains a gene (BB0721) with significant identity to the gene (pgs) encoding phosphatidylglycerolphosphate synthase, an enzyme in the synthetic pathway of PG. Activity of BB0249 was confirmed by cloning the gene into Escherichia coli, which does not produce PC. Transformation with a plasmid carrying BB0249 resulted in production of PC by E. coli, but only in the presence of exogenously supplied choline, as would be predicted for a Pcs. Because loss of Pgs activity is lethal to E. coli, activity of BB0721 was confirmed by the ability of BB0721 to complement an E. coli Pgs− mutant. A plasmid containing BB0721 was transformed into a Pgs− mutant of E. coli containing a copy of the native gene on a temperature-regulated plasmid. The temperature-regulated plasmid was exchanged for a plasmid containing BB0721 and it was shown that BB0721 was able to replace the lost Pgs function and restore bacterial growth. This study has established the existence and function of two critical enzymes in the synthesis of PC and PG in B. burgdorferi. Understanding of the biosynthetic pathways of PC and PG in B. burgdorferi is the first step in delineating the role of these phospholipids in the pathogenesis of Lyme disease.

scholarly journals Studies on the mechanism of mutagenicity and genotoxicity induced by dihydralazine.

1995 ◽  
Vol 42 (3) ◽  
pp. 291-295 ◽  
Author(s):  
B Chłopkiewicz ◽  
A Ejchart ◽  
J Marczewska
Keyword(s):  
Superoxide Anion ◽  
Reduction Method ◽  
Active Oxygen Species ◽  
Active Oxygen ◽  
Oxygen Species ◽  
Oxygen Scavengers ◽  
E Coli ◽  
Sos Chromotest ◽  
Tetrazolium Reduction

Dihydralazine was found to be mutagenic towards S. typhimurium TA1537, TA97, TA1538 and TA98 and genotoxic towards E. coli PQ37. Using the nitro blue tetrazolium reduction method we have found that dihydralazine can generate active oxygen species. The possible role of active oxygen species in mutagenicity (Ames test) and genotoxicity (SOS Chromotest) of dihydralazine was studied by testing the influence of the different active oxygen species scavengers on these two processes. Of the active oxygen scavengers tested, only superoxide dismutase suppressed partially the mutagenic and genotoxic activity of dihydralazine. This result seems to indicate that superoxide anion play a role in these two biological events.

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