Direct biological fixation provides a freshwater sink for N2O

Si, Yueyue; Zhu, Yizhu; Sanders, Ian; Kinkel, Dorothee B.; Purdy, Kevin J.; Trimmer, Mark

doi:10.1038/s41467-023-42481-2

Cited by 4 publications

(1 citation statement)

References 76 publications

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“…N2O consumption via denitrification is more sensitive to oxygen than N2O production via denitrification (Farías et al 2009;Dalsgaard et al 2014;Babbin et al 2015;Frey et al 2020), although the oxygen inhibition constant for N2O consumption remains difficult to define (Sun et al 2021b). N2O may also be consumed through N2O fixation, although the importance of N2O fixation in the ocean has yet to be determined (Farías et al 2013;Si et al 2023).…”

Section: Introductionmentioning

confidence: 99%

Isotopomer labeling and oxygen dependence of hybrid nitrous oxide production

Kelly,

Travis,

Baya

et al. 2023

Preprint

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Abstract. Nitrous oxide (N2O) is a potent greenhouse gas and ozone depletion agent, with a significant natural source from marine oxygen deficient zones (ODZs). Open questions remain, however, about the microbial processes responsible for this N2O production, especially hybrid N2O production when ammonia-oxidizing archaea are present. Using 15N-labeled tracer incubations, we measured the rates of N2O production from ammonium (NH4+), nitrite (NO2-), and nitrate (NO3-) in the Eastern Tropical North Pacific ODZ, as well as the isotopic labeling of the central (α) and terminal (β) nitrogen atoms of the N2O molecule. We observed production of both doubly- and singly labeled N2O from each tracer, with the highest rates of labeled N2O production at the same depths as the near-surface N2O concentration maximum. At most stations and depths, the production of 45N2Oα and 45N2Oβ were statistically indistinguishable, but at a few depths, there were significant differences in the labelling of the two nitrogen atoms in the N2o molecule. Implementing the rates of labeled N2O production in a forward-running model, we found that N2O production from NO3- dominated at most stations and depths, with rates as high as 1.6±0.2 nM N2O/day. Hybrid N2O production, one of the mechanisms by which ammonia-oxidizing archaea produce N2O, had rates as high as 0.23±0.08 nM N2O/day that peaked in both the near-surface and deep N2O concentration maxima. We inferred from the 45N2Oα and 45N2Oβ data that hybrid N2O production by ammonia-oxidizing archaea may have a variable site preference that depends on the 15N content of each substrate. We also found that the rates and yields of hybrid N2O production exhibited a clear [O2] inhibition curve, with the hybrid N2O yields as high as 20 % at depths where dissolved [O2] was 0 µM but nitrification was still active. Finally, we identified a few incubations with dissolved [O2] up to 20 µM where N2O production from NO3- was still active. A relatively high O2 tolerance for N2O production via denitrification has implications for the feedbacks between marine deoxygenation and greenhouse gas cycling.

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Section: Introductionmentioning

confidence: 99%

Isotopomer labeling and oxygen dependence of hybrid nitrous oxide production

Kelly,

Travis,

Baya

et al. 2023

Preprint

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4d–2p–4f Gradient Orbital Coupling Enables Tandem Catalysis for Simultaneous Abatement of N₂O and CO on Atomically Dispersed Rh/CeO₂ Catalyst

Liu,

Yang,

et al. 2024

Environ. Sci. Technol.

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Unraveling the genetic potential of nitrous oxide reduction in wastewater treatment: insights from metagenome-assembled genomes

Schacksen,

Nielsen

2024

Appl Environ Microbiol

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This study explores the genetic landscape of nitrous oxide (N 2 O) reduction in wastewater treatment plants (WWTPs) by profiling 1,083 high-quality metagenome-assembled genomes (HQ MAGs) from 23 Danish full-scale WWTPs. The focus is on the distribution and diversity of nitrous oxide reductase ( nosZ ) genes and their association with other nitrogen metabolism pathways. A custom pipeline for clade-specific nosZ gene identification with higher sensitivity revealed 503 nosZ sequences in 489 of these HQ MAGs, outperforming existing Kyoto Encyclopedia of Genes and Genomes (KEGG) module-based methods. Notably, 48.7% of the total 1,083 HQ MAGs harbored nosZ genes, with clade II being predominant, accounting for 93.7% of these genes. Taxonomic profiling highlighted the prevalence of nosZ -containing taxa within Bacteroidota and Pseudomonadota. Chloroflexota exhibited unexpected affiliations with both the sec and tat secretory pathways, and all were found to contain the accessory nosB gene, underscoring the importance of investigating the secretory pathway. The majority of non-denitrifying N 2 O reducers were found within Bacteroidota and Chloroflexota . Additionally, HQ MAGs with genes for dissimilatory nitrate reduction to ammonium and assimilatory nitrate reduction frequently co-occurred with the nosZ gene. Traditional primers targeting nosZ often focus on short-length amplicons. Therefore, we introduced custom-designed primer sets targeting near-full-length nosZ sequences. These new primers demonstrate efficacy in capturing diverse and well-characterized sequences, providing a valuable tool with higher resolution for future research. In conclusion, this comprehensive analysis enhances our understanding of N 2 O-reducing organisms in WWTPs, highlighting their potential as N 2 O sinks with the potential for optimizing wastewater treatment processes and mitigating greenhouse gas emissions. IMPORTANCE This study provides critical insights into the genetic diversity of nitrous oxide reductase (nosZ) genes and the microorganisms harboring them in wastewater treatment plants (WWTPs) by exploring 1,083 high-quality metagenome-assembled genomes (MAGs) from 23 Danish full-scale WWTPs. Despite the pivotal role of nosZ-containing organisms, their diversity remains largely unexplored in WWTPs. Our custom pipeline for detecting nosZ provides near-full-length genes with detailed information on secretory pathways and accessory nos genes. Using these genes as templates, we developed taxonomically diverse clade-specific primers that generate nosZ amplicons for phylogenetic annotation and gene-to-MAG linkage. This approach improves detection and expands the discovery of novel sequences, highlighting the prevalence of non-denitrifying N 2 O reducers and their potential as N 2 O sinks. These findings have the potential to optimize nitrogen removal processes and mitigate greenhouse gas emissions from WWTPs by fully harnessing the capabilities of the microbial communities.

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Direct biological fixation provides a freshwater sink for N2O

Cited by 4 publications

References 76 publications

Isotopomer labeling and oxygen dependence of hybrid nitrous oxide production

Isotopomer labeling and oxygen dependence of hybrid nitrous oxide production

4d–2p–4f Gradient Orbital Coupling Enables Tandem Catalysis for Simultaneous Abatement of N₂O and CO on Atomically Dispersed Rh/CeO₂ Catalyst

Unraveling the genetic potential of nitrous oxide reduction in wastewater treatment: insights from metagenome-assembled genomes

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Direct biological fixation provides a freshwater sink for N2O

Cited by 4 publications

References 76 publications

Isotopomer labeling and oxygen dependence of hybrid nitrous oxide production

Isotopomer labeling and oxygen dependence of hybrid nitrous oxide production

4d–2p–4f Gradient Orbital Coupling Enables Tandem Catalysis for Simultaneous Abatement of N2O and CO on Atomically Dispersed Rh/CeO2 Catalyst

Unraveling the genetic potential of nitrous oxide reduction in wastewater treatment: insights from metagenome-assembled genomes

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4d–2p–4f Gradient Orbital Coupling Enables Tandem Catalysis for Simultaneous Abatement of N₂O and CO on Atomically Dispersed Rh/CeO₂ Catalyst