scholarly journals Revision of N2O-Producing Pathways in the Ammonia-Oxidizing Bacterium Nitrosomonas europaea ATCC 19718

2014 ◽  
Vol 80 (16) ◽  
pp. 4930-4935 ◽  
Author(s):  
Jessica A. Kozlowski ◽  
Jennifer Price ◽  
Lisa Y. Stein
Keyword(s):  
Nitric Oxide ◽  
Nitrite Reductase ◽  
Nitrosomonas Europaea ◽  
Ammonia Oxidizers ◽  
Nitric Oxide Reductase ◽  
Wild Type ◽  
Content Type ◽  
Resting Cell ◽  
Nitrifier Denitrification ◽  
Cell Assays

ABSTRACTNitrite reductase (NirK) and nitric oxide reductase (NorB) have long been thought to play an essential role in nitrous oxide (N2O) production by ammonia-oxidizing bacteria. However, essential gaps remain in our understanding of how and when NirK and NorB are active and functional, putting into question their precise roles in N2O production by ammonia oxidizers. The growth phenotypes of theNitrosomonas europaeaATCC 19718 wild-type and mutant strains deficient in expression of NirK, NorB, and both gene products were compared under atmospheric and reduced O2tensions. Anoxic resting-cell assays and instantaneous nitrite (NO2−) reduction experiments were done to assess the ability of the wild-type and mutantN. europaeastrains to produce N2O through the nitrifier denitrification pathway. Results confirmed the role of NirK for efficient substrate oxidation ofN. europaeaand showed that NorB is involved in N2O production during growth at both atmospheric and reduced O2tensions. Anoxic resting-cell assays and measurements of instantaneous NO2−reduction using hydrazine as an electron donor revealed that an alternate nitrite reductase to NirK is present and active. These experiments also clearly demonstrated that NorB was the sole nitric oxide reductase for nitrifier denitrification. The results of this study expand the enzymology for nitrogen metabolism and N2O production byN. europaeaand will be useful to interpret pathways in other ammonia oxidizers that lack NirK and/or NorB genes.

scholarly journals Nitrite Reductase of Nitrosomonas europaea Is Not Essential for Production of Gaseous Nitrogen Oxides and Confers Tolerance to Nitrite

2002 ◽  
Vol 184 (9) ◽  
pp. 2557-2560 ◽  
Author(s):  
Hubertus J. E. Beaumont ◽  
Norman G. Hommes ◽  
Luis A. Sayavedra-Soto ◽  
Daniel J. Arp ◽  
David M. Arciero ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Nitrous Oxide ◽  
Nitrogen Oxides ◽  
Nitrite Reductase ◽  
Nitrosomonas Europaea ◽  
Wild Type ◽  
Gaseous Nitrogen ◽  
Cell Extracts

ABSTRACT A gene that encodes a periplasmic copper-type nitrite reductase (NirK) was identified in Nitrosomonas europaea. Disruption of this gene resulted in the disappearance of Nir activity in cell extracts. The nitrite tolerance of NirK-deficient cells was lower than that of wild-type cells. Unexpectedly, NirK-deficient cells still produced nitric oxide (NO) and nitrous oxide (N2O), the latter in greater amounts than that of wild-type cells. This demonstrates that NirK is not essential for the production of NO and N2O by N. europaea. Inactivation of the putative fnr gene showed that Fnr is not essential for the expression of nirK.

The Requirement of RpoN (Sigma Factor ς54) in Denitrification by Pseudomonas stutzeri Is Indirect and Restricted to the Reduction of Nitrite and Nitric Oxide

1998 ◽  
Vol 64 (8) ◽  
pp. 3092-3095 ◽  
Author(s):  
Elisabeth Härtig ◽  
Walter G. Zumft
Keyword(s):  
Nitric Oxide ◽  
Nitrite Reductase ◽  
Sigma Factor ◽  
Pseudomonas Stutzeri ◽  
Nitrous Oxide Reductase ◽  
Null Mutant ◽  
Nitric Oxide Reductase ◽  
Structural Genes ◽  
Wild Type ◽  
Respiratory Nitrate Reductase

ABSTRACT The rpoN region of Pseudomonas stutzeri was cloned, and an rpoN null mutant was constructed. RpoN was not essential for denitrification in this bacterium but affected the expression levels and enzymatic activities of cytochromecd 1 nitrite reductase and nitric oxide reductase, whereas those of respiratory nitrate reductase and nitrous oxide reductase were comparable to wild-type levels. Since the transcription of the structural genes nirS andnorCB, coding for nitrite reductase and the nitric oxide reductase complex, respectively, proceeded unabated, our data indicate a posttranslational process for the two key enzymes of denitrification depending on RpoN.

scholarly journals Transcriptomic Response of Nitrosomonas europaea Transitioned from Ammonia- to Oxygen-Limited Steady-State Growth

mSystems ◽  
2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Christopher J. Sedlacek ◽  
Andrew T. Giguere ◽  
Michael D. Dobie ◽  
Brett L. Mellbye ◽  
Rebecca V. Ferrell ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Nitrous Oxide ◽  
Agricultural Soils ◽  
Nitrosomonas Europaea ◽  
Oxygen Limitation ◽  
Ammonia Oxidizing Bacteria ◽  
Content Type ◽  
Nitrifier Denitrification ◽  
Nitrous Oxide Production ◽  
Effect Of Oxygen

ABSTRACT Ammonia-oxidizing microorganisms perform the first step of nitrification, the oxidation of ammonia to nitrite. The bacterium Nitrosomonas europaea is the best-characterized ammonia oxidizer to date. Exposure to hypoxic conditions has a profound effect on the physiology of N. europaea, e.g., by inducing nitrifier denitrification, resulting in increased nitric and nitrous oxide production. This metabolic shift is of major significance in agricultural soils, as it contributes to fertilizer loss and global climate change. Previous studies investigating the effect of oxygen limitation on N. europaea have focused on the transcriptional regulation of genes involved in nitrification and nitrifier denitrification. Here, we combine steady-state cultivation with whole-genome transcriptomics to investigate the overall effect of oxygen limitation on N. europaea. Under oxygen-limited conditions, growth yield was reduced and ammonia-to-nitrite conversion was not stoichiometric, suggesting the production of nitrogenous gases. However, the transcription of the principal nitric oxide reductase (cNOR) did not change significantly during oxygen-limited growth, while the transcription of the nitrite reductase-encoding gene (nirK) was significantly lower. In contrast, both heme-copper-containing cytochrome c oxidases encoded by N. europaea were upregulated during oxygen-limited growth. Particularly striking was the significant increase in transcription of the B-type heme-copper oxidase, proposed to function as a nitric oxide reductase (sNOR) in ammonia-oxidizing bacteria. In the context of previous physiological studies, as well as the evolutionary placement of N. europaea’s sNOR with regard to other heme-copper oxidases, these results suggest sNOR may function as a high-affinity terminal oxidase in N. europaea and other ammonia-oxidizing bacteria. IMPORTANCE Nitrification is a ubiquitous microbially mediated process in the environment and an essential process in engineered systems such as wastewater and drinking water treatment plants. However, nitrification also contributes to fertilizer loss from agricultural environments, increasing the eutrophication of downstream aquatic ecosystems, and produces the greenhouse gas nitrous oxide. As ammonia-oxidizing bacteria are the most dominant ammonia-oxidizing microbes in fertilized agricultural soils, understanding their responses to a variety of environmental conditions is essential for curbing the negative environmental effects of nitrification. Notably, oxygen limitation has been reported to significantly increase nitric oxide and nitrous oxide production during nitrification. Here, we investigate the physiology of the best-characterized ammonia-oxidizing bacterium, Nitrosomonas europaea, growing under oxygen-limited conditions.

scholarly journals Nitrosomonas europaea Expresses a Nitric Oxide Reductase during Nitrification

2004 ◽  
Vol 186 (13) ◽  
pp. 4417-4421 ◽  
Author(s):  
Hubertus J. E. Beaumont ◽  
Bas van Schooten ◽  
Sylvia I. Lens ◽  
Hans V. Westerhoff ◽  
Rob J. M. van Spanning
Keyword(s):  
Nitric Oxide ◽  
Nitrous Oxide ◽  
Gene Cluster ◽  
Nitrosomonas Europaea ◽  
Nitric Oxide Reductase ◽  
Wild Type ◽  
Aerobic Growth ◽  
No Consumption ◽  
Dependent Activity ◽  
Alternative Site

ABSTRACT In this paper, we report the identification of a norCBQD gene cluster that encodes a functional nitric oxide reductase (Nor) in Nitrosomonas europaea. Disruption of the norB gene resulted in a strongly diminished nitric oxide (NO) consumption by cells and membrane protein fractions, which was restored by the introduction of an intact norCBQD gene cluster in trans. NorB-deficient cells produced amounts of nitrous oxide (N2O) equal to that of wild-type cells. NorCB-dependent activity was present during aerobic growth and was not affected by the inactivation of the putative fnr gene. The findings demonstrate the presence of an alternative site of N2O production in N. europaea.

scholarly journals Effect of Nitroxides on Swarming Motility and Biofilm Formation, Multicellular Behaviors in Pseudomonas aeruginosa

2013 ◽  
Vol 57 (10) ◽  
pp. 4877-4881 ◽  
Author(s):  
César de la Fuente-Núñez ◽  
Fany Reffuveille ◽  
Kathryn E. Fairfull-Smith ◽  
Robert E. W. Hancock
Keyword(s):  
Nitric Oxide ◽  
Pseudomonas Aeruginosa ◽  
Biofilm Formation ◽  
Wild Type ◽  
Planktonic Cells ◽  
Swarming Motility ◽  
Content Type ◽  
Exogenous Addition ◽  
Biofilm Dispersion ◽  
Dispersal Activity

ABSTRACTThe ability of nitric oxide (NO) to induce biofilm dispersion has been well established. Here, we investigated the effect of nitroxides (sterically hindered nitric oxide analogues) on biofilm formation and swarming motility inPseudomonas aeruginosa. A transposon mutant unable to produce nitric oxide endogenously (nirS) was deficient in swarming motility relative to the wild type and the complemented strain. Moreover, expression of thenirSgene was upregulated by 9.65-fold in wild-type swarming cells compared to planktonic cells. Wild-type swarming levels were substantially restored upon the exogenous addition of nitroxide containing compounds, a finding consistent with the hypothesis that NO is necessary for swarming motility. Here, we showed that nitroxides not only mimicked the dispersal activity of NO but also prevented biofilms from forming in flow cell chambers. In addition, anirStransposon mutant was deficient in biofilm formation relative to the wild type and the complemented strain, thus implicating NO in the formation of biofilms. Intriguingly, despite its stand-alone action in inhibiting biofilm formation and promoting dispersal, a nitroxide partially restored the ability of anirSmutant to form biofilms.

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 Functional interactions between nitrite reductase and nitric oxide reductase from Paracoccus denitrificans

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Ingrid Albertsson ◽  
Johannes Sjöholm ◽  
Josy ter Beek ◽  
Nicholas J. Watmough ◽  
Jerker Widengren ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Nitrite Reductase ◽  
Paracoccus Denitrificans ◽  
Affinity Constant ◽  
Nitric Oxide Reductase ◽  
Terminal Electron Acceptor ◽  
Model Soil ◽  
Transient Interactions ◽  
Electron Donation

AbstractDenitrification is a microbial pathway that constitutes an important part of the nitrogen cycle on earth. Denitrifying organisms use nitrate as a terminal electron acceptor and reduce it stepwise to nitrogen gas, a process that produces the toxic nitric oxide (NO) molecule as an intermediate. In this work, we have investigated the possible functional interaction between the enzyme that produces NO; the cd1 nitrite reductase (cd1NiR) and the enzyme that reduces NO; the c-type nitric oxide reductase (cNOR), from the model soil bacterium P. denitrificans. Such an interaction was observed previously between purified components from P. aeruginosa and could help channeling the NO (directly from the site of formation to the side of reduction), in order to protect the cell from this toxic intermediate. We find that electron donation to cNOR is inhibited in the presence of cd1NiR, presumably because cd1NiR binds cNOR at the same location as the electron donor. We further find that the presence of cNOR influences the dimerization of cd1NiR. Overall, although we find no evidence for a high-affinity, constant interaction between the two enzymes, our data supports transient interactions between cd1NiR and cNOR that influence enzymatic properties of cNOR and oligomerization properties of cd1NiR. We speculate that this could be of particular importance in vivo during metabolic switches between aerobic and denitrifying conditions.

scholarly journals Novel nitrite reductase domain structure suggests a chimeric denitrification repertoire in Phylum Chloroflexi

2021 ◽  
Author(s):  
Sarah Schwartz ◽  
Lily Momper ◽  
L. Thiberio Rangel ◽  
Cara Magnabosco ◽  
Jan Amend ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Nitrite Reductase ◽  
Phylogenetic Analyses ◽  
Domain Architecture ◽  
Terrestrial Ecosystems ◽  
Genomic Diversity ◽  
Nitric Oxide Reductase ◽  
Fusion Event ◽  
Ecological Carrying Capacity ◽  
Global Nitrogen Cycle

Denitrification plays a central role in the global nitrogen cycle, reducing and removing nitrogen from marine and terrestrial ecosystems. The flux of nitrogen species through this pathway has a widespread impact, affecting ecological carrying capacity, agriculture, and climate. Nitrite reductase (Nir) and nitric oxide reductase (NOR) are the two central enzymes in this pathway. Here we present a previously unreported Nir domain architecture in members of Phylum Chloroflexi. Phylogenetic analyses of protein domains within Nir indicate that an ancestral horizontal transfer and fusion event produced this chimeric domain architecture. We also identify an expanded genomic diversity of a rarely reported nitric oxide reductase subtype, eNOR. Together, these results suggest a greater diversity of denitrification enzyme arrangements exist than have been previously reported.

scholarly journals Determining Roles of Accessory Genes in Denitrification by Mutant Fitness Analyses

2015 ◽  
Vol 82 (1) ◽  
pp. 51-61 ◽  
Author(s):  
Brian J. Vaccaro ◽  
Michael P. Thorgersen ◽  
W. Andrew Lancaster ◽  
Morgan N. Price ◽  
Kelly M. Wetmore ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Nitrous Oxide ◽  
Electron Acceptor ◽  
Pseudomonas Stutzeri ◽  
Basic Function ◽  
Nitric Oxide Reductase ◽  
Content Type ◽  
Nitric Oxide Release ◽  
Peripheral Proteins ◽  
Cofactor Biosynthesis

ABSTRACTEnzymes of the denitrification pathway play an important role in the global nitrogen cycle, including release of nitrous oxide, an ozone-depleting greenhouse gas. In addition, nitric oxide reductase, maturation factors, and proteins associated with nitric oxide detoxification are used by pathogens to combat nitric oxide release by host immune systems. While the core reductases that catalyze the conversion of nitrate to dinitrogen are well understood at a mechanistic level, there are many peripheral proteins required for denitrification whose basic function is unclear. A bar-coded transposon DNA library fromPseudomonas stutzeristrain RCH2 was grown under denitrifying conditions, using nitrate or nitrite as an electron acceptor, and also under molybdenum limitation conditions, with nitrate as the electron acceptor. Analysis of sequencing results from these growths yielded gene fitness data for 3,307 of the 4,265 protein-encoding genes present in strain RCH2. The insights presented here contribute to our understanding of how peripheral proteins contribute to a fully functioning denitrification pathway. We propose a new low-affinity molybdate transporter, OatABC, and show that differential regulation is observed for two MoaA homologs involved in molybdenum cofactor biosynthesis. We also propose that NnrS may function as a membrane-bound NO sensor. The dominant HemN paralog involved in heme biosynthesis is identified, and a CheR homolog is proposed to function in nitrate chemotaxis. In addition, new insights are provided into nitrite reductase redundancy, nitric oxide reductase maturation, nitrous oxide reductase maturation, and regulation.

Sign in / Sign up

Export Citation Format

Share Document