Cellular regulation of nitrate uptake in denitrifying Flexibacter canadensis

1994 ◽  
Vol 40 (7) ◽  
pp. 576-582 ◽  
Author(s):  
Qitu Wu ◽  
Roger Knowles
Keyword(s):  
Nitrate Reductase ◽  
Nitrate Uptake ◽  
Inhibitory Effect ◽  
Nitrite Reduction ◽  
Nitrite Accumulation ◽  
Cellular Regulation ◽  
Oxygen Inhibition ◽  
Whole Cells ◽  
Nitrite Production ◽  
Carbonyl Cyanide

Nitrate uptake and its regulation were investigated using an ion-specific nitrate electrode for denitrifying Flexibacter canadensis under anaerobic conditions. Glucose supported a greater rate of nitrate uptake than did glycerol, glutamate, lactose, cellobiose, or ethanol. Nitrate uptake closely approximated Michaelis–Menten kinetics; the estimated Ks(glucose) and apparent Km(nitrate) for nitrate uptake were 21 and 44 μM, respectively. Nitrate disappearance was correlated with nitrite accumulation, and nitrate had an inhibitory effect on nitrite reduction. Oxygen inhibition of nitrate uptake increased as the percent air saturation increased, and reversed readily as the percent air saturation decreased. The minimal air saturation showing inhibition of nitrate uptake was about 2–4%. Azide and cyanide completely inhibited nitrate uptake. No nitrate uptake was observed in cells grown in the presence of 1 or 5 mM tungstate (no added molybdate). When molybdate (100–200μM) was present in the medium, nitrate uptake was exhibited by organisms grown with 1 mM, but not with 5 mM, tungstate, indicating that nitrate uptake was dependent on the presence of an active nitrate reductase, and that competition between tungsten and molybdenum occurred during the formation of nitrate reductase. Nitrite production from nitrate by whole cells but not cell-free extracts was inhibited by 2,4-dinitrophenol and carbonyl cyanide m-chlorophenylhydrazone, indicating that nitrate and (or) nitrite transport depended upon the electrochemical proton gradient.Key words: denitrification, nitrate uptake, Flexibacter canadensis.

scholarly journals Biogenic Fe(II-III) Hydroxycarbonate Green Rust Enhances Nitrate Removal and Decreases Ammonium Selectivity during Heterotrophic Denitrification

Minerals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 818
Author(s):  
Georges Ona-Nguema ◽  
Delphine Guerbois ◽  
Céline Pallud ◽  
Jessica Brest ◽  
Mustapha Abdelmoula ◽  
...  
Keyword(s):  
Nitrate Reduction ◽  
Nitrate Removal ◽  
Green Rust ◽  
Nitrite Reduction ◽  
Nitrite Accumulation ◽  
Bacterial Reduction ◽  
Water Treatment Process ◽  
Nitrite Production ◽  
Ammonium Production ◽  
Biogenic Iron

Nitrification-denitrification is the most widely used nitrogen removal process in wastewater treatment. However, this process can lead to undesirable nitrite accumulation and subsequent ammonium production. Biogenic Fe(II-III) hydroxycarbonate green rust has recently emerged as a candidate to reduce nitrite without ammonium production under abiotic conditions. The present study investigated whether biogenic iron(II-III) hydroxycarbonate green rust could also reduce nitrite to gaseous nitrogen during bacterial nitrate reduction. Our results showed that biogenic iron(II-III) hydroxycarbonate green rust could efficiently decrease the selectivity of the reaction towards ammonium during heterotrophic nitrate reduction by native wastewater-denitrifying bacteria and by three different species of Shewanella: S. putrefaciens ATCC 12099, S. putrefaciens ATCC 8071 and S. oneidensis MR-1. Indeed, in the absence of biogenic hydroxycarbonate green rust, bacterial reduction of nitrate converted 11–42% of the initial nitrate into ammonium, but this value dropped to 1–28% in the presence of biogenic hydroxycarbonate green rust. Additionally, nitrite accumulation did not exceed the 2–13% in the presence of biogenic hydroxycarbonate green rust, versus 0–28% in its absence. Based on those results that enhance the extent of denitrification of about 60%, the study proposes a water treatment process that couples the bacterial nitrite production with the abiotic nitrite reduction by biogenic green rust.

scholarly journals Light-Mediated Nitrite Accumulation during Denitrification by Pseudomonas sp. Strain JR12

1998 ◽  
Vol 64 (3) ◽  
pp. 813-817 ◽  
Author(s):  
Yoram Barak ◽  
Yossi Tal ◽  
Jaap van Rijn
Keyword(s):  
Nitrate Reduction ◽  
Electron Flow ◽  
Inhibitory Effect ◽  
Nitrite Reduction ◽  
Aerobic Respiration ◽  
Nitrite Accumulation ◽  
Respiratory Pathway ◽  
Low Light ◽  
Light Inhibition ◽  
Effect Of Light

ABSTRACT The effect of light on the denitrifying characteristics of a nonphotosynthetic denitrifier, Pseudomonas sp. strain JR12, was examined. Already at low light intensities, nitrite accumulated as a result of light inhibition of nitrite but not of nitrate reduction rates. Exposure of this bacterium to light caused a photooxidation of cytochrome c, an intermediate electron carrier in its respiratory pathway. Photoinhibition of nitrite reduction was reversible, as nitrite reduction rates returned to preillumination levels when light-exposed cells were returned to dark conditions. Antimycin A reversed the inhibitory effect of light on nitrite reduction by preventing a reversed electron flow. Aerobic respiration by this bacterium was not affected by light.

Effect of Herbicides on In Vivo Nitrate and Nitrite Reduction

Weed Science ◽  
1977 ◽  
Vol 25 (1) ◽  
pp. 18-22 ◽  
Author(s):  
R.L. Finke ◽  
R.L. Warner ◽  
T.J. Muzik
Keyword(s):  
Hordeum Vulgare ◽  
Nitrate Reductase ◽  
Nitrate Reduction ◽  
Amaranthus Retroflexus ◽  
Nitrite Reduction ◽  
Nitrite Accumulation ◽  
Inhibitory Effects ◽  
Potassium Azide ◽  
Nitrate And Nitrite

The effects of herbicides on in vivo nitrate and nitrite reduction were determined by vacuum infiltrating sections of barley (Hordeum vulgareL.) or bean (Phaseolus vulgarisL.) leaves with solutions containing nitrate and herbicides. Herbicides causing a reduction of nitrite accumulation in the dark were considered to have inhibitory effects upon nitrate reduction and those causing an accumulation of nitrite in the light were considered to inhibit nitrite reduction. Only dinoseb (2-sec-butyl-4,6-dinitrophenol) and potassium azide significantly reduced nitrate reduction in both barley and bean. All of the herbicides which inhibit photosynthesis inhibited nitrite reduction but had no significant effect on nitrate reduction in barley and bean. Nitrite reduction in an atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] resistant pigweed (Amaranthus retroflexusL.) biotype was not affected by any triazine tested. However, these triazines significantly inhibited nitrite reduction in barley, bean, and the susceptible pigweed biotype. The results suggest that the in vivo nitrate reductase technique may be a useful technique for identifying chemicals which inhibit the flow of electrons to ferredoxin, thereby inhibiting nitrite reduction in light.

scholarly journals Insulin inhibits hepatocyte iNOS expression induced by cytokines by an Akt-dependent mechanism

2012 ◽  
Vol 302 (1) ◽  
pp. G116-G122 ◽  
Author(s):  
Brian G. Harbrecht ◽  
Ikenna Nweze ◽  
Jason W. Smith ◽  
Baochun Zhang
Keyword(s):  
Cyclic Adenosine Monophosphate ◽  
Rat Hepatocytes ◽  
Adenosine Monophosphate ◽  
Inhibitory Effect ◽  
Akt Signaling ◽  
Inos Expression ◽  
Dominant Negative ◽  
Nitrite Accumulation ◽  
Dependent Manner ◽  
Nitrite Production

Hepatocyte inducible nitric oxide synthese (iNOS) expression is a tightly controlled pathway that mediates hepatic inflammation and hepatocyte injury in a variety of disease states. We have shown that cyclic adenosine monophosphate (cAMP) regulates cytokine-induced hepatocyte iNOS expression through mechanisms that involve protein kinase B/Akt. We hypothesized that insulin, which activates Akt signaling in hepatocytes, as well as signaling through p38 and MAPK p42/p44, would regulate iNOS expression during inflammation. In primary rat hepatocytes, insulin inhibited cytokine-stimulated nitrite accumulation and iNOS expression in a dose-dependent manner. Inhibition of MAPK p42/p44 with PD98059 had no effect on iNOS activation, whereas SB203580 to block p38 reversed insulin's inhibitory effect. However, insulin did not increase p38 activation and inhibition of p38 signaling with a dominant negative p38 plasmid had no effect on cytokine- or insulin-mediated effects on iNOS. We found that SB203580 blocked insulin-induced Akt activation. Inhibition of Akt signaling with LY294002 or a dominant negative Akt plasmid increased cytokine-stimulated nitrite production and iNOS protein expression and blocked the inhibitory effects of insulin. NF-κB induces iNOS expression and can be regulated by Akt, but insulin had no effect on cytokine-mediated IκBα levels or NF-κB p65 translocation. Our data demonstrate that insulin inhibits cytokine-stimulated hepatocyte iNOS expression and does so through effects on Akt-mediated signaling.

O2 regulation of denitrification in Flexibacter canadensis

1994 ◽  
Vol 40 (11) ◽  
pp. 916-921 ◽  
Author(s):  
Qitu Wu ◽  
Roger Knowles ◽  
Donald F. Niven
Keyword(s):  
Nitric Oxide ◽  
Nitrous Oxide ◽  
Nitrate Reductase ◽  
Reductase Activity ◽  
Inhibitory Effect ◽  
Nitrate Transport ◽  
Intact Cells ◽  
Benzyl Viologen ◽  
Whole Cells ◽  
Nitrate And Nitrite

We studied the sensitivity to oxygen of the reductases involved in denitrification by whole cells and membrane fractions of Flexibacter canadensis. All of the nitrate reductase activity was found in the membrane fraction, suggesting that the nitrate reductase of F. canadensis is largely or entirely a membrane-bound enzyme. Methyl viologen and benzyl viologen were good electron donors to nitrate reductase in both whole cells and membrane fractions, whereas glucose and glycerol were effective in whole cells but, as expected, not in membrane fractions. Oxygen, generated by means of H2O2 plus catalase, inhibited the production of nitrite from nitrate by intact cells but not by membrane fractions, suggesting that O2 exerts its inhibitory effect at the level of nitrate transport rather than nitrate reduction. In intact cells, the rates of nitric oxide accumulation during reduction of nitrite in the presence of 20 μM carbonyl cyanide m-chlorophenylhydrazone, and consumption of nitric oxide and nitrous oxide, decreased as the concentration of H2O2 was increased. The concentrations of H2O2 giving 50% inhibition of reduction of nitrate and nitrite were 0.34 and 0.12 mM, respectively. In contrast, the rates of nitric oxide and nitrous oxide consumption were inhibited by only 36 and 32% at a concentration of H2O2 of 3.99 mM. These results indicate that the reduction of both nitric oxide and nitrous oxide is relatively tolerant to oxygen, and that nitrite reductase is much more sensitive to oxygen than the other reductases.Key words: nitrate reductase, nitrate transport, denitrification, O2 inhibition, Flexibacter canadensis.

Nitrification potential in an alder plantation

1984 ◽  
Vol 14 (4) ◽  
pp. 543-546 ◽  
Author(s):  
O. Hendrickson ◽  
L. Chatarpaul
Keyword(s):  
Inhibitory Effect ◽  
Nitrification Potential ◽  
Nitrite Production ◽  
Conifer Needles

Nitrification rates in soil from an alder plantation were measured by nitrite production in chlorate-amended slurries. Rates were stimulated by increased pH, ammonium, and phosphate levels. Alder roots did not have an inhibitory effect on nitrification. Conifer needles totally suppressed nitrite production in the slurries. If conifer needles were added 6 h after the start of incubation, nitrite levels declined rapidly. This decline was attributed to denitrification or microbial assimilation rather than to leakage through the chlorate block.

Effects of pH and alkalinity on sulfur-denitrification in a biological granular filter

1996 ◽  
Vol 34 (1-2) ◽  
pp. 355-362 ◽  
Author(s):  
Hiroaki Furumai ◽  
Hideki Tagui ◽  
Kenji Fujita
Keyword(s):  
Enrichment Culture ◽  
Nitrite Reduction ◽  
The Other ◽  
Nitrite Accumulation ◽  
Ph Dependency ◽  
Effects Of Ph ◽  
Rapid Removal ◽  
Nitrate And Nitrite ◽  
The Relationship ◽  
Biological Filters

Two laboratory-scale biological filters were operated to investigate the effects of alkalinity and pH on removal of nitrate and nitrite in sulfur denitrification filter processes. The concentration of sodium bicarbonate in the feed media was changed from 120 to 240 mg/l during about 3 months in a filter (Run A). The other filter was initially fed with 300 mg/l and then with 240 mg/l (Run B). The performance of the filter was monitored by measuring pH, nitrate, nitrite, sulfate, alkalinity, and thiosulfate. Nitrate concentration in effluent rapidly decreased to lower levels within several days for both filters after inoculation of enrichment culture of sulfur denitrifiers. However there was a large difference in removal of nitrite. When rapid removal of nitrate took place, nitrite accumulation was observed and remained while the bicarbonate concentration was 120 and 150 mg/l. On the other hand the nitrite accumulation disappeared when more bicarbonate (240 and 300 mg/l) was supplied. The experimental results indicated that the nitrite accumulation was closely related to pH condition and alkalinity level in the filter. The stable data of effluent water quality for 5 cases were collected and the relationship discussed between nitrite concentration and pH in effluents. The relationship indicated a strong pH dependency on nitrite accumulation below pH of 7.4. The pH condition around 7 is not so inhibitory to biological activity. Therefore, the pH within the biofilm would be low enough to suppress the nitrite reduction by sulfur denitrifiers, while the pH in effluent was not in the inhibitory range. It was recommended to keep the pH higher than 7.4 to prevent nitrite accumulation in the sulfur denitrification filter.

Hydrogen Evolution Catalyzed by Hydrogenase in Cultures of Cyanobacteria

1981 ◽  
Vol 36 (1-2) ◽  
pp. 87-92 ◽  
Author(s):  
Patrick C. Hallenbeck ◽  
Leon V. Kochian ◽  
John R. Benemann
Keyword(s):  
Hydrogen Production ◽  
Hydrogen Evolution ◽  
High Frequency ◽  
Nitrogenase Activity ◽  
Inhibitory Effect ◽  
Hydrogenase Activity ◽  
Oxygen Inhibition ◽  
Oxygen Sensitive

Abstract Cultures of Anabaena cylindrica, grown on media containing 5 mᴍ NH4Cl (which represses heterocyst formation), evolved hydrogen after a period of dark incubation under an argon atmosphere. This hydrogen production was not due to nitrogenase activity, which was nearly undetectable, but was due to a hydrogenase. Cultures grown on media with tungsten substituted for molybdenum had a high frequency of heterocysts (15%) and inactive nitrogenase after nitrogen starvation. The hydrogenase activity of these cultures was three-fold greater than the activity of non-heterocystous cultures. The effects of oxygen inhibition on hydrogen evolution by hetero-cystous cultures suggest that two pools of hydrogenase activity exist - an oxygen sensitive hydrogen evolution in vegetative cells and a relatively oxygen-resistent hydrogen evolution in heterocysts. In either case, inhibition by oxygen was reversible. Light had an inhibitory effect on net hydrogen evolution. Hydrogen production in vitro was much higher than in vivo, indicating that in vivo hydrogenase activity is limited by endogenous reductant supply.

Effect of organic compounds on nitrite accumulation during the nitrification process for coking wastewater

2010 ◽  
Vol 62 (9) ◽  
pp. 2096-2105 ◽  
Author(s):  
H. B. Li ◽  
H. B. Cao ◽  
Y. P. Li ◽  
Y. Zhang ◽  
H. R. Liu
Keyword(s):  
Organic Compounds ◽  
Ammonia Oxidation ◽  
Industrial Effluents ◽  
Reaction Rates ◽  
Inhibitory Effect ◽  
Nitrite Accumulation ◽  
Coking Wastewater ◽  
Batch Bioreactor ◽  
The Difference ◽  
High Concentrations

Coking wastewater is one of the most toxic industrial effluents since it contains high concentrations of ammonia and toxic organic compounds. Nitrification might be upset by the inhibitory effect of organic compounds during the biological treatment of the wastewater. In this study, shortcut nitrification was obtained in a sequencing batch bioreactor (SBR) and the inhibitory effect of organic compounds on the nitrification was examined when temperature was 30±1°C, pH was 7.0–8.5, and dissolved oxygen concentration was 2.0–3.0 mg L−1. The inhibitory effect of organic compounds was presumed to be one of the main factors to obtain satisfactory nitrite accumulation. The effect of organic compounds on nitrification was examined in the SBR with initial inhibitor concentrations ranging from 0 to 80 mg L−1, including phenol, pyrocatechol, resorcin, benzene, quinoline, pyridine and indole. The inhibitory effect became stronger with the increase in the concentration, and it was presumed to take place through a direct mechanism resulting from biological toxicity of the inhibitor itself. Furthermore, the inhibitory effect on ammonia oxidation was slighter than that on nitrite oxidation, and the nitrite accumulation ratio during the nitrification was determined by the difference between the reaction rates of above two processes.

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