scholarly journals Gonococcal Nitric Oxide Reductase Is Encoded by a Single Gene, norB, Which Is Required for Anaerobic Growth and Is Induced by Nitric Oxide

2000 ◽  
Vol 68 (9) ◽  
pp. 5241-5246 ◽  
Author(s):  
Tracey C. Householder ◽  
Elizabeth M. Fozo ◽  
Jean A. Cardinale ◽  
Virginia L. Clark
Keyword(s):  
Nitric Oxide ◽  
Ralstonia Eutropha ◽  
Single Gene ◽  
Nitrite Reduction ◽  
Anaerobic Growth ◽  
Nitric Oxide Donor ◽  
Nitric Oxide Reductase ◽  
Wild Type ◽  
Gene Encoding ◽  
Anaerobic Environment

ABSTRACT The gene encoding a nitric oxide reductase has been identified inNeisseria gonorrhoeae. The norB gene product shares significant identity with the nitric oxide reductases inRalstonia eutropha and Synechocystis sp. and, like those organisms, the gonococcus lacks a norC homolog. The gonococcal norB gene was found to be required for anaerobic growth, but the absence of norB did not dramatically decrease anaerobic survival. In a wild-type background, induction of norB expression was seen anaerobically in the presence of nitrite but not anaerobically without nitrite or aerobically. norB expression is not regulated by FNR or NarP, but a functional aniA gene (which encodes an anaerobically induced outer membrane nitrite reductase) is necessary for expression. When aniA is constitutively expressed,norB expression can be induced both anaerobically and aerobically, but only in the presence of nitrite, suggesting that nitric oxide, which is likely to be produced by AniA as a product of nitrite reduction, is the inducing agent. This was confirmed with the use of the nitric oxide donor, spermine-nitric oxide complex, in ananiA null background both anaerobically and aerobically. NorB is important for gonococcal adaptation to an anaerobic environment, a physiologically relevant state during gonococcal infection. The presence of this enzyme, which is induced by nitric oxide, may also have implications in immune evasion and immunomodulation in the human host.

scholarly journals A DNA Region Recognized by the Nitric Oxide-Responsive Transcriptional Activator NorR Is Conserved in β- and γ-Proteobacteria

2004 ◽  
Vol 186 (23) ◽  
pp. 7980-7987 ◽  
Author(s):  
Andrea Büsch ◽  
Anne Pohlmann ◽  
Bärbel Friedrich ◽  
Rainer Cramm
Keyword(s):  
Nitric Oxide ◽  
Transcriptional Activation ◽  
Target Genes ◽  
Ralstonia Eutropha ◽  
Upstream Region ◽  
Nitric Oxide Reductase ◽  
Wild Type ◽  
Genome Database ◽  
Nitric Oxide Metabolism ◽  
Signaling Domain

ABSTRACT The σ54-dependent regulator NorR activates transcription of target genes in response to nitric oxide (NO) or NO-generating agents. In Ralstonia eutropha H16, NorR activates transcription of the dicistronic norAB operon that encodes NorA, a protein of unknown function, and NorB, a nitric oxide reductase. A constitutively activating NorR derivative (NorR′), in which the N-terminal signaling domain was replaced by MalE, specifically bound to the norAB upstream region as revealed by gel retardation analysis. Within a 73-bp DNA segment protected by MalE-NorR′ in a DNase I footprint assay, three conserved inverted repeats, GGT-(N7)-ACC (where N is any base), that we consider to be NorR-binding boxes were identified. Mutations altering the spacing or the base sequence of these repeats resulted in an 80 to 90% decrease of transcriptional activation by wild-type NorR. Genome database analyses demonstrate that the GT-(N7)-AC core of the inverted repeat is found in several proteobacteria upstream of gene loci encoding proteins of nitric oxide metabolism, including nitric oxide reductase (NorB), flavorubredoxin (NorV), NO dioxygenase (Hmp), and hybrid cluster protein (Hcp).

scholarly journals Characterization of the norB Gene, Encoding Nitric Oxide Reductase, in the Nondenitrifying Cyanobacterium Synechocystis sp. Strain PCC6803

2002 ◽  
Vol 68 (2) ◽  
pp. 668-672 ◽  
Author(s):  
Andrea B�sch ◽  
B�rbel Friedrich ◽  
Rainer Cramm
Keyword(s):  
Nitric Oxide ◽  
Reductase Activity ◽  
Nitric Oxide Reductase ◽  
Wild Type ◽  
Gene Encoding ◽  
Single Subunit ◽  
Transcriptional Fusions ◽  
Synechocystis Sp ◽  
Negative Mutant

ABSTRACT A norB gene encoding a putative nitric oxide reductase is present in the genome of the nondenitrifying cyanobacterium Synechocystis sp. strain PCC6803. The gene product belongs to the quinol-oxidizing single-subunit class of nitric oxide reductases, discovered recently in the denitrifier Ralstonia eutropha. Heterologous complementation of a nitric oxide reductase-negative mutant of R. eutropha with norB from Synechocystis restored nitric oxide reductase activity. With reduced menadione as the electron donor, an enzymatic activity of 101 nmol of NO per min per mg of protein was obtained with membrane fractions of Synechocystis wild-type cells. Virtually no nitric oxide reductase activity was present in a norB-negative mutant of Synechocystis. Growing cells of this mutant are more sensitive toward NO than wild-type cells, indicating that the presence of a nitric oxide reductase is beneficial for Synechocystis when the cells are exposed to NO. Transcriptional fusions with the chloramphenicol acetyltransferase reporter gene were constructed to monitor norB expression in Synechocystis. Transcription of norB was not enhanced by the addition of the NO-generating agent sodium nitroprusside.

scholarly journals Antioxidant Functions of Nitric Oxide Synthase in a Methicillin SensitiveStaphylococcus aureus

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Manisha Vaish ◽  
Vineet K. Singh
Keyword(s):  
Oxidative Stress ◽  
Nitric Oxide ◽  
Nitric Oxide Synthase ◽  
Normal Growth ◽  
Growth Conditions ◽  
Nitric Oxide Donor ◽  
Wild Type ◽  
Gene Encoding ◽  
Stress Studies ◽  
Oxide Synthase

Nitric oxide and its derivative peroxynitrites are generated by host defense system to control bacterial infection. However certain Gram positive bacteria includingStaphylococcus aureuspossess a gene encoding nitric oxide synthase (SaNOS) in their chromosome. In this study it was determined that under normal growth conditions, expression ofSaNOSwas highest during early exponential phase of the bacterial growth. In oxidative stress studies, deletion ofSaNOSled to increased susceptibility of the mutant cells compared to wild-typeS. aureus. While inhibition ofSaNOSactivity by the addition of L-NAME increased sensitivity of the wild-typeS. aureusto oxidative stress, the addition of a nitric oxide donor, sodium nitroprusside, restored oxidative stress tolerance of theSaNOSmutant. TheSaNOSmutant also showed reduced survival after phagocytosis by PMN cells with respect to wild-typeS. aureus.

cis- and trans-acting elements involved in regulation of norB (norZ), the gene encoding nitric oxide reductase in Neisseria gonorrhoeae

Microbiology ◽  
2008 ◽  
Vol 154 (1) ◽  
pp. 226-239 ◽  
Author(s):  
Vincent Isabella ◽  
Lori F. Wright ◽  
Kenneth Barth ◽  
Janice M. Spence ◽  
Susan Grogan ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Neisseria Gonorrhoeae ◽  
Nitric Oxide Reductase ◽  
Gene Encoding ◽  
Cis And Trans

scholarly journals A DNase from a Fungal Phytopathogen Is a Virulence Factor Likely Deployed as Counter Defense against Host-Secreted Extracellular DNA

mBio ◽  
2019 ◽  
Vol 10 (2) ◽  
Author(s):  
Hee-Jin Park ◽  
Weiwei Wang ◽  
Gilberto Curlango-Rivera ◽  
Zhongguo Xiong ◽  
Zeran Lin ◽  
...  
Keyword(s):  
Single Gene ◽  
Neutrophil Extracellular Traps ◽  
Extracellular Dna ◽  
Fungal Culture ◽  
Wild Type ◽  
Plant Host ◽  
Gene Encoding ◽  
Content Type ◽  
Extracellular Traps ◽  
Fungal Plant Pathogen

ABSTRACT Histone-linked extracellular DNA (exDNA) is a component of neutrophil extracellular traps (NETs). NETs have been shown to play a role in immune response to bacteria, fungi, viruses, and protozoan parasites. Mutation of genes encoding group A Streptococcus extracellular DNases (exDNases) results in reduced virulence in animals, a finding that implies that exDNases are deployed as counter defense against host DNA-containing NETs. Is the exDNA/exDNase mechanism also relevant to plants and their pathogens? It has been demonstrated previously that exDNA is a component of a matrix secreted from plant root caps and that plants also carry out an extracellular trapping process. Treatment with DNase I destroys root tip resistance to infection by fungi, the most abundant plant pathogens. We show that the absence of a single gene encoding a candidate exDNase results in significantly reduced virulence of a fungal plant pathogen to its host on leaves, the known infection site, and on roots. Mg2+-dependent exDNase activity was demonstrated in fungal culture filtrates and induced when host leaf material was present. It is speculated that the enzyme functions to degrade plant-secreted DNA, a component of a complex matrix akin to neutrophil extracellular traps of animals. IMPORTANCE We document that the absence of a single gene encoding a DNase in a fungal plant pathogen results in significantly reduced virulence to a plant host. We compared a wild-type strain of the maize pathogen Cochliobolus heterostrophus and an isogenic mutant lacking a candidate secreted DNase-encoding gene and demonstrated that the mutant is reduced in virulence on leaves and on roots. There are no previous reports of deletion of such a gene from either an animal or plant fungal pathogen accompanied by comparative assays of mutants and wild type for alterations in virulence. We observed DNase activity, in fungal culture filtrates, that is Mg2+ dependent and induced when plant host leaf material is present. Our findings demonstrate not only that fungi use extracellular DNases (exDNases) for virulence, but also that the relevant molecules are deployed in above-ground leaves as well as below-ground plant tissues. Overall, these data provide support for a common defense/counter defense virulence mechanism used by animals, plants, and their fungal and bacterial pathogens and suggest that components of the mechanism might be novel targets for the control of plant disease.

scholarly journals Diverse effects of nitric oxide reductase NorV on Aeromonas hydrophila virulence-associated traits under aerobic and anaerobic conditions

2019 ◽  
Vol 50 (1) ◽  
Author(s):  
Jin Liu ◽  
Yuhao Dong ◽  
Nannan Wang ◽  
Shuiyan Ma ◽  
Chengping Lu ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Aeromonas Hydrophila ◽  
Dependent Manner ◽  
Nitric Oxide Reductase ◽  
Wild Type ◽  
Anaerobic Conditions ◽  
Aerobic Conditions ◽  
Significant Difference ◽  
Aerobic And Anaerobic ◽  
Aerobic And Anaerobic Conditions

Abstract NorV has been known to be an anaerobic nitric oxide reductase associated with nitric oxide (NO) detoxification. Recently, we showed that the norV gene of Aeromonas hydrophila was highly upregulated after co-culturing with Tetrahymena thermophila. Here, we demonstrated that the transcription and expression levels of norV were upregulated in a dose-dependent manner after exposure to NO under aerobic and anaerobic conditions. To investigate the roles of norV in resisting predatory protists and virulence of A. hydrophila, we constructed the norV gene-deletion mutant (ΔnorV). Compared to the wild type, the ΔnorV mutant showed no significant difference in growth at various NO concentrations under aerobic conditions but significantly stronger NO-mediated growth inhibition under anaerobic conditions. The deletion of norV exhibited markedly decreased cytotoxicity, hemolytic and protease activities under aerobic and anaerobic conditions. Also, the hemolysin co-regulated protein (Hcp) in the ΔnorV mutant showed increased secretion under aerobic conditions but decreased secretion under anaerobic conditions as compared to the wild-type. Moreover, the inactivation of norV led to reduced resistance to predation by T. thermophila, decreased survival within macrophages and highly attenuated virulence in zebrafish. Our data indicate a diverse role for norV in the expression of A. hydrophila virulence-associated traits that is not completely dependent on its function as a nitric oxide reductase. This study provides insights into an unexplored area of NorV, which will contribute to our understanding of bacterial pathogenesis and the development of new control strategies for A. hydrophila infection.

scholarly journals Identification, Functional Studies, and Genomic Comparisons of New Members of the NnrR Regulon in Rhodobacter sphaeroides

2009 ◽  
Vol 192 (4) ◽  
pp. 903-911 ◽  
Author(s):  
Angela Hartsock ◽  
James P. Shapleigh
Keyword(s):  
Nitric Oxide ◽  
Rhodobacter Sphaeroides ◽  
Nitrite Reductase ◽  
Reductase Activity ◽  
Nitrite Reduction ◽  
No Production ◽  
Nitric Oxide Reductase ◽  
New Members ◽  
Functional Studies ◽  
The Status

ABSTRACT Analysis of the Rhodobacter sphaeroides 2.4.3 genome revealed four previously unidentified sequences similar to the binding site of the transcriptional regulator NnrR. Expression studies demonstrated that three of these sequences are within the promoters of genes, designated paz, norEF, and cdgA, in the NnrR regulon, while the status of the fourth sequence, within the tat operon promoter, remains uncertain. nnrV, under control of a previously identified NnrR site, was also identified. paz encodes a pseudoazurin that is a donor of electrons to nitrite reductase. paz inactivation did not decrease nitrite reductase activity, but loss of pseudoazurin and cytochrome c2 together reduced nitrite reduction. Inactivation of norEF reduced nitrite and nitric oxide reductase activity and increased the sensitivity to nitrite in a taxis assay. This suggests that loss of norEF increases NO production as a result of decreased nitric oxide reductase activity. 2.4.3 is the only strain of R. sphaeroides with norEF, even though all four of the strains whose genomes have been sequenced have the norCBQD operon and nnrR. norEF was shown to provide resistance to nitrite when it was mobilized into R. sphaeroides strain 2.4.1 containing nirK. Inactivation of the other identified genes did not reveal any detectable denitrification-related phenotype. The distribution of members of the NnrR regulon in R. sphaeroides revealed patterns of coselection of structural genes with the ancillary genes identified here. The strong coselection of these genes indicates their functional importance under real-world conditions, even though inactivation of the majority of them does not impact denitrification under laboratory conditions.

scholarly journals Effects of Nitrogen Dioxide and Anoxia on Global Gene and Protein Expression in Long-Term Continuous Cultures of Nitrosomonas eutropha C91

2012 ◽  
Vol 78 (14) ◽  
pp. 4788-4794 ◽  
Author(s):  
Boran Kartal ◽  
Hans J. C. T. Wessels ◽  
Erwin van der Biezen ◽  
Kees-Jan Francoijs ◽  
Mike S. M. Jetten ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Protein Expression ◽  
Wastewater Treatment Plants ◽  
Batch Cultivation ◽  
Culture Conditions ◽  
Anaerobic Growth ◽  
Nitric Oxide Reductase ◽  
Content Type ◽  
Anoxic Conditions ◽  
Gene And Protein Expression

ABSTRACTNitrosomonas eutrophais an ammonia-oxidizing betaproteobacterium found in environments with high ammonium levels, such as wastewater treatment plants. The effects of NO2on gene and protein expression under oxic and anoxic conditions were determined by maintainingN. eutrophastrain C91 in a chemostat fed with ammonium under oxic, oxic-plus-NO2, and anoxic-plus-NO2culture conditions. Cells remained viable but ceased growing under anoxia; hence, the chemostat was switched from continuous to batch cultivation to retain biomass. After several weeks under each condition, biomass was harvested for total mRNA and protein isolation. Exposure ofN. eutrophaC91 to NO2under either oxic or anoxic conditions led to a decrease in proteins involved in N and C assimilation and storage and an increase in proteins involved in energy conservation, including ammonia monooxygenase (AmoCAB). Exposure to anoxia plus NO2resulted in increased representation of proteins and transcripts reflective of an energy-deprived state. Several proteins implicated in N-oxide metabolism were expressed and remained unchanged throughout the experiment, except for NorCB nitric oxide reductase, which was not detected in the proteome. Rather, NorY nitric oxide reductase was expressed under oxic-plus-NO2and anoxic-plus-NO2conditions. The results indicate that exposure to NO2results in an energy-deprived state ofN. eutrophaC91 and that anaerobic growth could not be supported with NO2as an oxidant.

scholarly journals Role of Manganese-Containing Superoxide Dismutase in Oxidative Stress and Virulence of Streptococcus pneumoniae

2000 ◽  
Vol 68 (5) ◽  
pp. 2819-2826 ◽  
Author(s):  
Hasan Yesilkaya ◽  
Aras Kadioglu ◽  
Neill Gingles ◽  
Janet E. Alexander ◽  
Tim J. Mitchell ◽  
...  
Keyword(s):  
Superoxide Dismutase ◽  
Streptococcus Pneumoniae ◽  
Anaerobic Growth ◽  
Wild Type ◽  
Gene Encoding ◽  
Lower Growth ◽  
Redox Active ◽  
Lower Growth Rate

ABSTRACT Streptococcus pneumoniae was shown to contain two types of superoxide dismutase, MnSOD and FeSOD. Levels of MnSOD increased during growth in an aerobic environment. The sodA gene, encoding MnSOD, of virulent S. pneumoniae type 2 strain D39 was inactivated to give mutant D39HY1. Aerobically, D39HY1 had a lower growth rate than the wild type and exhibited susceptibility to the redox-active compound paraquat, but anaerobic growth of D39HY1 was identical to that of the wild type. Virulence studies showed that the median survival time of mice infected intranasally with D39HY1 was significantly longer than that of mice infected with the wild-type pneumococcus. In contrast to the wild type, D39HY1 did not multiply in lungs during the first 24 h but thereafter grew at the same rate as the wild type. Appearance in the bloodstream was also delayed, but growth in the blood was unimpaired by the sodA mutation. The pattern of inflammation in lungs infected with D39HY1 differed from that in wild-type-infected mice. After infection with D39HY1, neutrophils were densely packed around bronchioles, in contrast to the wild-type infection, where neutrophils were more diffusely localized.

scholarly journals Nitric Oxide Induced stx2 Expression Is Inhibited by the Nitric Oxide Reductase, NorV, in a Clade 8 Escherichia coli O157:H7 Outbreak Strain

2022 ◽  
Vol 10 (1) ◽  
pp. 106
Author(s):  
Rim Al Safadi ◽  
Michelle L. Korir ◽  
Shannon D. Manning
Keyword(s):  
Nitric Oxide ◽  
Escherichia Coli ◽  
Shiga Toxin ◽  
Toxin Production ◽  
Anaerobic Growth ◽  
Escherichia Coli O157 ◽  
Similar Increase ◽  
Nitric Oxide Reductase ◽  
Outbreak Strain ◽  
Uremic Syndrome

Escherichia coli O157:H7 pathogenesis is due to Shiga toxin (Stx) production, though variation in virulence has been observed. Clade 8 strains, for instance, were shown to overproduce Stx and were more common among hemolytic uremic syndrome cases. One candidate gene, norV, which encodes a nitric oxide (NO) reductase found in a clade 8 O157:H7 outbreak strain (TW14359), was thought to impact virulence. Hence, we screened for norV in 303 O157 isolates representing multiple clades, examined stx2 expression following NO exposure in TW14359 for comparison to an isogenic mutant (ΔnorV), and evaluated survival in THP-1 derived macrophages. norV was intact in strains representing clades 6–9, whereas a 204 bp deletion was found in clades 2 and 3. During anaerobic growth, NO induced stx2 expression in TW14359. A similar increase in stx2 expression was observed for the ΔnorV mutant in anaerobiosis, though it was not impaired in its ability to survive within macrophages relative to TW14359. Altogether, these data suggest that NO enhances virulence by inducing Stx2 production in TW14359, and that toxin production is inhibited by NorV encoded by a gene found in most clade 8 strains. The mechanism linked to these responses, however, remains unclear and likely varies across genotypes.

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