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

Spiro, Stephen

doi:10.1098/rstb.2011.0309

Cited by 111 publications

(94 citation statements)

References 74 publications

(110 reference statements)

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“…6), while the other factors contributed considerably less to explain the observed N 2 emissions. The dominance of WFPS is in line with common knowledge about the functioning of denitification, given that N 2 production is catalyzed by the enzyme N 2 O-reductase, which in turn is up-regulated by low oxygen concentrations (Spiro, 2012). From calculating fractions it is clear that N 2 is the dominant compound of gaseous losses, often exceeding N 2 O and NO emissions by several magnitudes (Table 3).…”

Section: N 2 Emissions and Total Gaseous Nitrogen Lossessupporting

confidence: 64%

N2O, NO, N2 and CO2 emissions from tropical savanna and grassland of northern Australia: an incubation experiment with intact soil cores

et al. 2014

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Abstract. Strong seasonal variability of hygric and thermal soil conditions are a defining environmental feature in northern Australia. However, how such changes affect the soil-atmosphere exchange of nitrous oxide (N 2 O), nitric oxide (NO) and dinitrogen (N 2 ) is still not well explored. By incubating intact soil cores from four sites (three savanna, one pasture) under controlled soil temperatures (ST) and soil moisture (SM) we investigated the release of the trace gas fluxes of N 2 O, NO and carbon dioxide (CO 2 ). Furthermore, the release of N 2 due to denitrification was measured using the helium gas flow soil core technique. Under dry pre-incubation conditions NO and N 2 O emissions were very low (< 7.0±5.0 µg NO-N m −2 h −1 ; < 0.0±1.4 µg N 2 O-N m −2 h −1 ) or in the case of N 2 O, even a net soil uptake was observed. Substantial NO (max: 306.5 µg N m −2 h −1 ) and relatively small N 2 O pulse emissions (max: 5.8 ± 5.0 µg N m −2 h −1 ) were recorded following soil wetting, but these pulses were short lived, lasting only up to 3 days. The total atmospheric loss of nitrogen was generally dominated by N 2 emissions (82.4-99.3 % of total N lost), although NO emissions contributed almost 43.2 % to the total atmospheric nitrogen loss at 50 % SM and 30 • C ST incubation settings (the contribution of N 2 at these soil conditions was only 53.2 %). N 2 O emissions were systematically higher for 3 of 12 sample locations, which indicates substantial spatial variability at site level, but on average soils acted as weak N 2 O sources or even sinks. By using a conservative upscale approach we estimate total annual emissions from savanna soils to average 0.12 kg N ha −1 yr −1 (N 2 O), 0.68 kg N ha −1 yr −1 (NO) and 6.65 kg N ha −1 yr −1 (N 2 ). The analysis of longterm SM and ST records makes it clear that extreme soil saturation that can lead to high N 2 O and N 2 emissions only occurs a few days per year and thus has little impact on the annual total. The potential contribution of nitrogen released due to pulse events compared to the total annual emissions was found to be of importance for NO emissions (contribution to total: 5-22 %), but not for N 2 O emissions. Our results indicate that the total gaseous release of nitrogen from these soils is low and clearly dominated by loss in the form of inert nitrogen. Effects of seasonally varying soil temperature and moisture were detected, but were found to be low due to the small amounts of available nitrogen in the soils (total nitrogen < 0.1 %).

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Section: N 2 Emissions and Total Gaseous Nitrogen Lossessupporting

confidence: 64%

N2O, NO, N2 and CO2 emissions from tropical savanna and grassland of northern Australia: an incubation experiment with intact soil cores

et al. 2014

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“…These results would exclude N 2 O as a regulator of nosZ transcription in B. japonicum. Consistent with this, it has been reported that N 2 O does not appear to regulate the expression of any denitrification gene (5).…”

supporting

confidence: 76%

“…Soybean nodules emit N 2 O under field conditions in the late growth period (1)(2)(3). While N 2 O generation is due to a diversity of microbial enzymes, N 2 O consumption appears to be due exclusively to N 2 O reductase (Nos) (4)(5)(6). Nos catalyzes the two-electron reduction of N 2 O to N 2 .…”

mentioning

confidence: 99%

Linked Expressions of nap and nos Genes in a Bradyrhizobium japonicum Mutant with Increased N ₂ O Reductase Activity

Sánchez¹,

Itakura²,

Mitsui³

et al. 2013

Appl Environ Microbiol

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To understand the mechanisms underlying the increased N 2 O reductase activity in the Bradyrhizobium japonicum 5M09 mutant from enrichment culture under N 2 O respiration, we analyzed the expression of genes encoding denitrification reductases and regulators. Our results suggest a common regulation of nap (encoding periplasmic nitrate reductase) and nos (encoding N 2 O reductase). N itrous oxide (N 2 O) is a key greenhouse gas that also damages the ozone layer. Soybean nodules emit N 2 O under field conditions in the late growth period (1-3). While N 2 O generation is due to a diversity of microbial enzymes, N 2 O consumption appears to be due exclusively to N 2 O reductase (Nos) (4-6). Nos catalyzes the two-electron reduction of N 2 O to N 2 . In strain USDA110 of the soybean symbiont Bradyrhizobium japonicum, the complete reduction of nitrate to N 2 depends on napEDABC (which encode periplasmic nitrate reductase [Nap]), nirK (copper-containing nitrite reductase [NirK]), norCBQD (c-type nitric oxide reductase [cNor]), and nosRZDYFLX (Nos) (7).A B. japonicum mutant, 5M09, with increased N 2 O reductase activity (Nos ϩϩ ) was isolated through the impairment of proofreading activity and the use of enrichment culture under selection pressure for N 2 O respiration (8). Recently, it was shown that postharvest N 2 O emissions from soybean fields can be mitigated by inoculation with 5M09 at the field scale (9). Because the mechanisms underlying the increased Nos activity in 5M09 remain unclear, the main objective of this work was to evaluate the expression of genes encoding denitrification reductases and regulators in 5M09. A B. japonicum mutant (PRNOS) that overexpresses the nos genes as controlled by the rRNA gene promoter (9) was used as a Nos ϩϩ reference. B. japonicum USDA110 (United States Department of Agriculture, Beltsville, MD) and the mutant derivative strains 5M09 (8) and PRNOS (9) were used in this study. The bacterial strains and plasmids used in this work are listed in Table S1 in the supplemental material. Cells were routinely cultured at 30°C in HM salt medium (10) supplemented with 0.1% arabinose, 0.025% (wt/vol) yeast extract, and trace metals (HMM medium) (11). For ␤-galactosidase assays, methyl viologen (MV)-dependent nitrate reductase assays, and RNA isolation, aerobically grown cells were collected and washed twice. They were then adjusted to an optical density at 660 nm of about 0.1 by the addition of HMM medium. Cells (10 ml) were incubated for 24 h in 120-ml airtight vials with air (aerobic conditions) or N 2 (anaerobic conditions). Where appropriate, either N 2 O (1%, 5%, 20%, or 25% [vol/vol]) or KNO 3 (10 or 20 mM) was added.For ␤-galactosidase assays, we used chromosomally integrated transcriptional lacZ fusions with the napE, nirK, norC, and nosZ promoters. The plasmids pBG0614 (12), pRJ2498 (13), pRJ2499 (13), and pNOSLZch were integrated by homologous recombination into the chromosome of each of USDA110 and 5M09. ␤-Galactosidase activity was determined with permeabilized cells as descri...

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“…One regulator that mediates this de-repression is the NO-binding protein NsrR. In E. coli, NsrR regulates some 20 genes, including that for flavohaemoglobin (Hmp) which converts NO to N 2 O under anoxic conditions [42].…”

Section: Biological Production and Consumption Of Nitrous Oxidementioning

confidence: 99%

“…(b) Microbiological aspects Of the many factors that contribute to the emission of N 2 O from bacterial populations, one important determinant is the cellular abundance and another is the activities of the enzymes that produce and consume N 2 O [42]. Enzyme abundance is governed by expression of the corresponding genes of regulatory systems and signal transduction pathways that respond to intra-or extracellular signals.…”

Section: Biological Production and Consumption Of Nitrous Oxidementioning

confidence: 99%

Biological sources and sinks of nitrous oxide and strategies to mitigate emissions

Thomson

Giannopoulos

Pretty

et al. 2012

Phil. Trans. R. Soc. B

419

282

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Nitrous oxide (N 2 O) is a powerful atmospheric greenhouse gas and cause of ozone layer depletion. Global emissions continue to rise. More than two-thirds of these emissions arise from bacterial and fungal denitrification and nitrification processes in soils, largely as a result of the application of nitrogenous fertilizers. This article summarizes the outcomes of an interdisciplinary meeting, ‘Nitrous oxide (N 2 O) the forgotten greenhouse gas’, held at the Kavli Royal Society International Centre, from 23 to 24 May 2011. It provides an introduction and background to the nature of the problem, and summarizes the conclusions reached regarding the biological sources and sinks of N 2 O in oceans, soils and wastewaters, and discusses the genetic regulation and molecular details of the enzymes responsible. Techniques for providing global and local N 2 O budgets are discussed. The findings of the meeting are drawn together in a review of strategies for mitigating N 2 O emissions, under three headings, namely: (i) managing soil chemistry and microbiology, (ii) engineering crop plants to fix nitrogen, and (iii) sustainable agricultural intensification.

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

Cited by 111 publications

References 74 publications

N<sub>2</sub>O, NO, N<sub>2</sub> and CO<sub>2</sub> emissions from tropical savanna and grassland of northern Australia: an incubation experiment with intact soil cores

N<sub>2</sub>O, NO, N<sub>2</sub> and CO<sub>2</sub> emissions from tropical savanna and grassland of northern Australia: an incubation experiment with intact soil cores

Linked Expressions of nap and nos Genes in a Bradyrhizobium japonicum Mutant with Increased N ₂ O Reductase Activity

Biological sources and sinks of nitrous oxide and strategies to mitigate emissions

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

Cited by 111 publications

References 74 publications

N&lt;sub&gt;2&lt;/sub&gt;O, NO, N&lt;sub&gt;2&lt;/sub&gt; and CO&lt;sub&gt;2&lt;/sub&gt; emissions from tropical savanna and grassland of northern Australia: an incubation experiment with intact soil cores

N&lt;sub&gt;2&lt;/sub&gt;O, NO, N&lt;sub&gt;2&lt;/sub&gt; and CO&lt;sub&gt;2&lt;/sub&gt; emissions from tropical savanna and grassland of northern Australia: an incubation experiment with intact soil cores

Linked Expressions of nap and nos Genes in a Bradyrhizobium japonicum Mutant with Increased N 2 O Reductase Activity

Biological sources and sinks of nitrous oxide and strategies to mitigate emissions

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Product

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N<sub>2</sub>O, NO, N<sub>2</sub> and CO<sub>2</sub> emissions from tropical savanna and grassland of northern Australia: an incubation experiment with intact soil cores

N<sub>2</sub>O, NO, N<sub>2</sub> and CO<sub>2</sub> emissions from tropical savanna and grassland of northern Australia: an incubation experiment with intact soil cores

Linked Expressions of nap and nos Genes in a Bradyrhizobium japonicum Mutant with Increased N ₂ O Reductase Activity