DENITRIFICATION, DENITRIFYING BACTERIA, AND IRON REDUCTION IN A SOIL SUPPLEMENTED WITH SULFIDE AND ACETYLENE

1986 ◽  
Vol 66 (4) ◽  
pp. 633-639 ◽  
Author(s):  
ANNE M. ADKINS ◽  
ROGER KNOWLES
Keyword(s):  
Nitrous Oxide ◽  
Iron Reduction ◽  
Enrichment Culture ◽  
Denitrifying Bacteria ◽  
Sterile Soil ◽  
Culture Methods ◽  
Untreated Soil ◽  
Nitrous Oxide Reduction ◽  
Key Words Denitrification ◽  
Nitrate And Nitrite

Populations of denitrifying bacteria were estimated using MPN enrichment culture methods with nitrate, nitrite, and nitrous oxide (N2O) as electron acceptors. Nitrate and nitrite respirers predominated in untreated soil, and anaerobic preincubation with glucose and nitrate stimulated nitrate respirers 10-fold. During subsequent incubation with N2O and various combinations of acetylene (C2H2) and sulfide the numbers of nitrate and nitrite reducers decreased, and N2O reducers increased in treatments in which N2O reduction occurred. In the presence of N2O and C2H2 without sulfide there was no reduction of N2O and no change in the N2O-utilizing population. Incubation with N2O, C2H2, and sulfide caused a marked enrichment of N2O reducers in the denitrifying population. The addition of sulfide to anaerobic non-sterile or sterile soil caused an increase in reduced iron (Fe2+) and there was a relatively rapid conversion of free to acid-soluble sulfide. Key words: Denitrification, denitrifiers, sulfide, iron reduction, nitrous oxide reduction

Sulfide alleviation of acetylene inhibition of nitrous oxide reduction by Flexibacter Canadensis

1992 ◽  
Vol 38 (2) ◽  
pp. 143-148 ◽  
Author(s):  
Alison M. Jones ◽  
Roger Knowles
Keyword(s):  
Nitrous Oxide ◽  
Pseudomonas Stutzeri ◽  
Sulfide Concentration ◽  
Oxide Reduction ◽  
Acetylene Inhibition ◽  
Experimental Conditions ◽  
Nitrous Oxide Reduction ◽  
Pure Cultures ◽  
Dissolved Sulfide ◽  
Key Words Denitrification

The role of sulfide in the relief of acetylene inhibition of nitrous oxide reduction by Flexibacter canadensis was studied. In this organism, the reversal of acetylene inhibition of nitrous oxide reduction is correlated with a 90% decrease in the dissolved sulfide concentration. The fate of this sulfide is not known, since there was no concomitant increase in acid-soluble sulfide and volatile sulfur compounds were not detectable by flame photometric gas chromatography. Of the other sulfur-containing compounds tested (sulfate, sulfite, thiosulfate, cysteine, methionine, dithionite, dithionate, and glutathione), only cysteine relieved the acetylene block of nitrous oxide reduction by F. canadensis. Under similar experimental conditions, other denitrifiers tested (Azospirillum brasilense, Pseudomonas stutzeri, and a Flavobacterium isolate) failed to reduce nitrous oxide in the presence of sulfide and an inhibitory concentration of acetylene. It is concluded that both biological and abiological factors contribute to the sulfide relief of acetylene inhibition of nitrous oxide by pure cultures of F. canadensis. Key words: denitrification, nitrous oxide, acetylene, sulfide, Flexibacter canadensis.

Effects of sulfide and acetylene on nitrous oxide reduction by soil and by Pseudomonas aeruginosa

1979 ◽  
Vol 25 (10) ◽  
pp. 1133-1138 ◽  
Author(s):  
Tat-Yee Tam ◽  
Roger Knowles
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Nitrous Oxide ◽  
Sodium Sulfide ◽  
Sodium Thiosulfate ◽  
Cell Suspensions ◽  
Inhibition Assay ◽  
Sterile Soil ◽  
Washed Cell ◽  
Complete Reduction ◽  
Nitrous Oxide Reduction

The production and reduction of nitrous oxide (N2O) after the addition of N2O, nitrite (NO2−), or nitrate (NO3−) was studied in non-sterile soil, in sterilized soil inoculated with Pseudomonas aeruginosa, and in washed cell suspensions of this organism. Sodium sulfide (8 μmol S2− mL−1 or g−1) inhibited N2O reduction markedly in cell suspensions and also in soil, an effect which may cause sulfidic habitats to act as sources of N2O. Sodium thiosulfate (up to 64 μmol S2O32− g−1) showed no such effect. Acetylene (0.02 atm C2H2) completely inhibited the reduction of N2O by soil, but the combination of C2H2 with 8 μmol S2− g−1 permitted the complete reduction of 2 μmol added N2O g−1 within 3 days under the most favourable conditions. Under the same conditions, 8 μmol S2O32− g−1 permitted complete reduction of the N2O within 6 days. The rate of such reduction of N2O was decreased, but not inhibited completely, by raising the C2H2 concentration to 0.11 atm. The data have important implications for the effectiveness of the C2H2 inhibition assay of denitrification in highly anaerobic environments.

scholarly journals Nitrogen and oxygen availabilities control water column nitrous oxide production during seasonal anoxia in the Chesapeake Bay

2018 ◽  
Vol 15 (20) ◽  
pp. 6127-6138 ◽  
Author(s):  
Qixing Ji ◽  
Claudia Frey ◽  
Xin Sun ◽  
Melanie Jackson ◽  
Yea-Shine Lee ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Chesapeake Bay ◽  
Water Column ◽  
N2o Emissions ◽  
N2o Production ◽  
Isotope Tracer ◽  
Relative Contribution ◽  
Environmental Controls ◽  
Long Run ◽  
Nitrate And Nitrite

Abstract. Nitrous oxide (N2O) is a greenhouse gas and an ozone depletion agent. Estuaries that are subject to seasonal anoxia are generally regarded as N2O sources. However, insufficient understanding of the environmental controls on N2O production results in large uncertainty about the estuarine contribution to the global N2O budget. Incubation experiments with nitrogen stable isotope tracer were used to investigate the geochemical factors controlling N2O production from denitrification in the Chesapeake Bay, the largest estuary in North America. The highest potential rates of water column N2O production via denitrification (7.5±1.2 nmol-N L−1 h−1) were detected during summer anoxia, during which oxidized nitrogen species (nitrate and nitrite) were absent from the water column. At the top of the anoxic layer, N2O production from denitrification was stimulated by addition of nitrate and nitrite. The relative contribution of nitrate and nitrite to N2O production was positively correlated with the ratio of nitrate to nitrite concentrations. Increased oxygen availability, up to 7 µmol L−1 oxygen, inhibited both N2O production and the reduction of nitrate to nitrite. In spring, high oxygen and low abundance of denitrifying microbes resulted in undetectable N2O production from denitrification. Thus, decreasing the nitrogen input into the Chesapeake Bay has two potential impacts on the N2O production: a lower availability of nitrogen substrates may mitigate short-term N2O emissions during summer anoxia; and, in the long-run (timescale of years), eutrophication will be alleviated and subsequent reoxygenation of the bay will further inhibit N2O production.

scholarly journals Comparing the Yield of Staphylococcus aureus Recovery with Static versus Agitated Broth Incubation

2018 ◽  
Vol 2018 ◽  
pp. 1-3
Author(s):  
Carol E. Muenks ◽  
Patrick G. Hogan ◽  
Carey-Ann D. Burnham ◽  
Stephanie A. Fritz
Keyword(s):  
Staphylococcus Aureus ◽  
Enrichment Culture ◽  
Culture Method ◽  
Ambient Air ◽  
Built Environments ◽  
Culture Methods ◽  
Semiquantitative Assessment ◽  
Direct Plating ◽  
Static Conditions ◽  
Broth Enrichment

Given the lack of standardization of methodologies for microbial recovery from built environments, we sought to compare the yield of Staphylococcus aureus with a broth enrichment method when incubated in agitated versus static conditions. Five unique strains of S. aureus at five different concentrations were cultured to compare direct plating, agitated broth enrichment, and static broth enrichment culture methods. All samples were incubated at 35° in ambient air. The lowest concentration recovered across three replicates and five strains did not differ between culture methods (Fisher’s exact test, p=0.50); notably, recovery of S. aureus was equivalent between static and agitated broth incubation. When broth enrichment was used (both static and agitated), the burden of S. aureus growth was higher (by semiquantitative assessment of 4-quadrant streaking) compared to the direct plating culture method. Optimizing strategies for microbial recovery is essential, particularly in areas of lower biomass, given the paucity of research concerning microbial communities of built environments. The results of this study, in conjunction with other experiments investigating microbiomes of built environments, can help inform protocols for standardizing culturing methods within built environments.

scholarly journals Nitrous oxide production and consumption: regulation of gene expression by gas-sensitive transcription factors

2012 ◽  
Vol 367 (1593) ◽  
pp. 1213-1225 ◽  
Author(s):  
Stephen Spiro
Keyword(s):  
Nitrous Oxide ◽  
Transcription Initiation ◽  
Regulatory Networks ◽  
Regulation Of Gene Expression ◽  
Environmental Signals ◽  
Production And Consumption ◽  
Genes Encoding ◽  
Nitrous Oxide Production ◽  
Biochemical Mechanisms ◽  
Nitrate And Nitrite

Several biochemical mechanisms contribute to the biological generation of nitrous oxide (N 2 O). N 2 O generating enzymes include the respiratory nitric oxide (NO) reductase, an enzyme from the flavo-diiron family, and flavohaemoglobin. On the other hand, there is only one enzyme that is known to use N 2 O as a substrate, which is the respiratory N 2 O reductase typically found in bacteria capable of denitrification (the respiratory reduction of nitrate and nitrite to dinitrogen). This article will briefly review the properties of the enzymes that make and consume N 2 O, together with the accessory proteins that have roles in the assembly and maturation of those enzymes. The expression of the genes encoding the enzymes that produce and consume N 2 O is regulated by environmental signals (typically oxygen and NO) acting through regulatory proteins, which, either directly or indirectly, control the frequency of transcription initiation. The roles and mechanisms of these proteins, and the structures of the regulatory networks in which they participate will also be reviewed.

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.

scholarly journals Continuous measurements of nitrous oxide isotopomers during incubation experiments

2016 ◽  
Author(s):  
Malte Winther ◽  
David Balslev-Harder ◽  
Søren Christensen ◽  
Anders Priemé ◽  
Bo Elberling ◽  
...  
Keyword(s):  
Nitrous Oxide ◽  
Greenhouse Gas ◽  
Isotope Effect ◽  
Atmospheric Chemistry ◽  
Isotope Effects ◽  
Denitrifying Bacteria ◽  
Central Position ◽  
Site Preference ◽  
Continuous Measurements ◽  
Incubation Experiments

Abstract. Nitrous oxide (N2O) is an important and strong greenhouse gas in the atmosphere and part of a feed-back loop with climate. N2O is produced by microbes during nitrification and denitrification in terrestrial and aquatic ecosystems. The main sinks for N2O are turnover by denitrification and photolysis and photo-oxidation in the stratosphere. The position of the isotope 15N in the linear N = N = O molecule can be distinguished between the central or terminal position (isotopomers of N2O). It has been demonstrated that nitrifying and denitrifying microbes have a different relative preference for the terminal and central position. Therefore, measurements of the site preference in N2O can be used to determine the source of N2O i.e. nitrification or denitrification. Recent instrument development allows for continuous (on the order of days) position dependent δ15N measurements at N2O concentrations relevant for studies of atmospheric chemistry. We present results from continuous incubation experiments with denitrifying bacteria, Pseudomonas fluorescens (producing and reducing N2O) and P. chlororaphis (only producing N2O). The continuous position dependent measurements reveal the transient pattern (KNO3 to N2O and N2, respectively), which can be compared to previous reported site preference (SP) values. We find bulk isotope effects of −5.5 ‰ ± 0.9 for P. chlororaphis. For P. fluorescens, the bulk isotope effect during production of N2O is −50.4 ‰ ± 9.3 and 8.5 ‰ ± 3.7 during N2O reduction. The values for P. fluorescens are in line with earlier findings, whereas the values for P. chlororaphis are larger than previously published δ15Nbulk measurements from production. The calculations of the SP isotope effect from the measurements of P. chlororaphis result in values of −6.6 ‰ ± 1.8. For P. fluorescens, the calculations results in SP values of −5.7 ‰ ± 5.6 during production of N2O and 2.3 ‰ ± 3.2 during reduction of N2O. In summary, we implemented continuous measurements of N2O isotopomers during incubation of denitrifying bacteria and believe that similar experiments will lead to a better understanding of denitrifying bacteria and N2O turnover in soils and sediments and ultimately hands-on knowledge on the biotic mechanisms behind greenhouse gas exchange of the Globe.

Release of nitrous oxide (N2O) from denitrifying activated sludge caused by H2S-containing wastewater: quantification and application of a new mathematical model

1998 ◽  
Vol 38 (1) ◽  
pp. 237-246 ◽  
Author(s):  
Barbara Schönharting ◽  
Ruxandra Rehner ◽  
Jörg W. Metzger ◽  
Karlheinz Krauth ◽  
Manfred Rizzi
Keyword(s):  
Mathematical Model ◽  
Nitrous Oxide ◽  
Hydrogen Sulfide ◽  
Activated Sludge ◽  
Sulfide Concentration ◽  
Oxide Reduction ◽  
Strong Inhibition ◽  
Wide Range ◽  
Nitrous Oxide Reduction ◽  
Denitrification Process

A new mathematical model is presented which describes the denitrification process by dynamic material balance equations. In this approach the kinetic rate expressions of the single denitrification steps and the observed strong inhibition of nitrate on nitrite and nitrous oxide reduction are based exclusively on fundamental enzyme kinetics. This allows a prediction of the denitrification process in a wide range of wastewater-relevant nitrate concentrations. The model was successfully applied to the description of the kinetic behavior of a standardized denitrifying activated sludge system. Furthermore the experimentally investigated influence of hydrogen sulfide was quantified by extending the model with a non-competitive inhibition mechanism involving all steps of the denitrification process. The inhibitory effect was related to the free membrane-permeable hydrogen sulfide concentration. This means that the extent of its inhibition depends additionally on the pH-value. Even very low hydrogen sulfide concentrations lead to a strong inhibition of nitrous oxide reduction and therefore to a high release of nitrous oxide from wastewater treatment plants.

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