Four years of experimental climate change modifies the microbial drivers of N O
Amélie CantarelJuliette BloorThomas PommierNadine GuillaumaudCaroline MoirotJean‐François SoussanaFranck Poly
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Abstract Emissions of the trace gas nitrous oxide ( N 2 O ) play an important role for the greenhouse effect and stratospheric ozone depletion, but the impacts of climate change on N 2 O fluxes and the underlying microbial drivers remain unclear. The aim of this study was to determine the effects of sustained climate change on field N 2 O fluxes and associated microbial enzymatic activities, microbial population abundance and community diversity in an extensively managed, upland grassland. We recorded N 2 O fluxes, nitrification and denitrification, microbial population size involved in these processes and community structure of nitrite reducers ( nir K) in a grassland exposed for 4 years to elevated atmospheric CO 2 (+200 ppm), elevated temperature (+3.5 °C) and reduction of summer precipitations (−20%) as part of a long‐term, multifactor climate change experiment. Our results showed that both warming and simultaneous application of warming, summer drought and elevated CO 2 had a positive effect on N 2 O fluxes, nitrification, N 2 O release by denitrification and the population size of N 2 O reducers and NH 4 oxidizers. In situ N 2 O fluxes showed a stronger correlation with microbial population size under warmed conditions compared with the control site. Specific lineages of nir K denitrifier communities responded significantly to temperature. In addition, nir K community composition showed significant changes in response to drought. Path analysis explained more than 85% of in situ N 2 O fluxes variance by soil temperature, denitrification activity and specific denitrifying lineages. Overall, our study underlines that climate‐induced changes in grassland N 2 O emissions reflect climate‐induced changes in microbial community structure, which in turn modify microbial processes.Keywords:
Nitrous oxide
Nitrogen Cycle
Denitrification is an important biological mechanism in wastewater treatment process because this process is technically to remove nitrogen from water to air. There have been lots of study about denitrification engineering and molecular biological research about denitrifying bacteria, respectively. However, combination of these researches was unusual and rare. This study is about the correlation between quantity of denitrifying bacteria and denitrification potential, and consists of NUR batch test as analysis method of denitrification potential and quantitative molecular analysis for denitrifying bacteria. Three reactors (A/O, MLE and A/O of nitrogen deficiency) are operated to get activated sludge with various denitrification potential. All samples which were acquired from reactors were measured denitrification potential by NUR test and NUiR test. Also, Real-time PCR was conducted for quantification of denitrifying bacteria composition in activated sludge. The various denitrification potentials were measured in the reactors. The denitrifiaction potential was the highest in MLE process and the reactor of the nitrogen deficiency showed the lowest. Genomic DNA of activated sludge was obtained and consequently, real-time PCRuse the primer sets of nirK and nirS were conducted to quantify genes involving denitrification reductase production. As the result of real-time PCR, nirK gene showed more significant influence on denitrification potential comapred with nirS gene.
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Abstract Although numerous studies of denitrification in surface soils have been reported, few attempts have been made to study denitrifying activity in subsurface soils. We collected samples of four Iowa soil profiles to a depth of 3 m and measured their population of denitrifying bacteria and their capacity and potential for denitrification. Their denitrification capacity was assessed from their ability to reduce nitrate when incubated anaerobically (helium atmosphere) at 30°C for 72 hours after treatment with nitrate, and their denitrification potential was assessed from their corresponding ability when incubated anaerobically after treatment with both nitrate and organic carbon (as glucose). We found that the denitrification potentials of the subsurface samples studied greatly exceeded their denitrification capacities and that whereas both the population of denitrifying bacteria and the denitrification capacity of the samples decreased appreciably with depth in the profile, the denitrification potential of the samples did not decrease with depth. These findings indicate that the slow rate of denitrification in Iowa subsoils is not due to a lack of denitrifying microorganisms but to a lack of organic carbon that can by utilized by these microorganisms for reduction of nitrate.
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Denitrification is the major biological process through which fixed nitrogen (N) is returned from the soil to the atmosphere. The general requirements for denitrification are the presence of bacteria possessing the metabolic capacity; suitable electron donors such as organic carbon compounds, reduced sulphur compounds, or molecular hydrogen; anaerobic conditions or restricted oxygen availability; and N oxides. The capacity to denitrify has been reported to be present in about 23 genera of bacteria. This chapter presents a list of denitrifying genera including 13 genera for which there is confirmed or multiple documentation. Most denitrifying bacteria are chemoheterotrophs. Denitrification supports bacterial life through respiration. It is well established that denitrification in soil is strongly dependent on the availability of organic compounds as electron donors and as sources of cellular material. Nitrate reduction during denitrification in soil is an enzyme catalyzed reaction.
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Denitrification is an important biological mechanism in wastewater treatment process because this process is technically to remove nitrogen from water to air. There have been lots of study about denitrification engineering and molecular biological research about denitrifying bacteria, respectively. However, combination of these researches was unusual and rare. This study is about the correlation between quantity of denitrifying bacteria and denitrification potential, and consists of NUR batch test as analysis method of denitrification potential and quantitative molecular analysis for denitrifying bacteria. Three reactors (A/O, MLE and A/O of nitrogen deficiency) are operated to get activated sludge with various denitrification potential. All samples which were acquired from reactors were measured denitrification potential by NUR test and NUiR test. Also, Real-time PCR was conducted for quantification of denitrifying bacteria composition in activated sludge. The various denitrification potentials were measured in the reactors. The denitrifiaction potential was the highest in MLE process and the reactor of the nitrogen deficiency showed the lowest. Genomic DNA of activated sludge was obtained and consequently, real-time PCRuse the primer sets of nirK and nirS were conducted to quantify genes involving denitrification reductase production. As the result of real-time PCR, nirK gene showed more significant influence on denitrification potential comapred with nirS gene.
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ABSTRACT In contrast to most denitrifiers studied so far, Pseudomonas stutzeri TR2 produces low levels of nitrous oxide (N 2 O) even under aerobic conditions. We compared the denitrification activity of strain TR2 with those of various denitrifiers in an artificial medium that was derived from piggery wastewater. Strain TR2 exhibited strong denitrification activity and produced little N 2 O under all conditions tested. Its growth rate under denitrifying conditions was near comparable to that under aerobic conditions, showing a sharp contrast to the lower growth rates of other denitrifiers under denitrifying conditions. Strain TR2 was tolerant to toxic nitrite, even utilizing it as a good denitrification substrate. When both nitrite and N 2 O were present, strain TR2 reduced N 2 O in preference to nitrite as the denitrification substrate. This bacterial strain was readily able to adapt to denitrifying conditions by expressing the denitrification genes for cytochrome cd 1 nitrite reductase (NiR) ( nirS ) and nitrous oxide reductase (NoS) ( nosZ ). Interestingly, nosZ was constitutively expressed even under nondenitrifying, aerobic conditions, consistent with our finding that strain TR2 preferred N 2 O to nitrite. These properties of strain TR2 concerning denitrification are in sharp contrast to those of well-characterized denitrifiers. These results demonstrate that some bacterial species, such as strain TR2, have adopted a strategy for survival by preferring denitrification to oxygen respiration. The bacterium was also shown to contain the potential to reduce N 2 O emissions when applied to sewage disposal fields.
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Denitrification plays an important role in wastewater treatment systems for the reason that the nitrate or nitrite was reduced, and some gases such as NO, N_2O or N_2 were released. The application of denitrification in wastewater, the mechanism of denitrification, and the effect factors of denitrification were introduced in this paper. The communities of Denitrifying bacteria, and some key enzymes of denitrification were also introduced. The discovery of aerobic denitrifying bacteria, autotrophic denitrifying bacteria, and denitrifying Phosphorus-removing Bacteria were also mentioned in this paper.
Aerobic denitrification
Autotroph
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This paper studied the abilities of denitrification and kinetics of denitrification of heterotrophic denitrifying bacteria. And the results showed that several denitrifying bacteria selected all had the abilities of denitrification, but the abilities differed with different Bacteria, and that two of them, 12E and 22A, not only had strongest abilities of denitrification, also reproduced fastest.
Aerobic denitrification
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