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  • Proceedings of the National Academy of Sciences  (5)
  • 1
    Online Resource
    Online Resource
    Revising the nitrogen cycle in the Peruvian oxygen minimum zone
    Proceedings of the National Academy of Sciences ; 2009
    In:  Proceedings of the National Academy of Sciences Vol. 106, No. 12 ( 2009-03-24), p. 4752-4757
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 106, No. 12 ( 2009-03-24), p. 4752-4757
    Abstract: The oxygen minimum zone (OMZ) of the Eastern Tropical South Pacific (ETSP) is 1 of the 3 major regions in the world where oceanic nitrogen is lost in the pelagic realm. The recent identification of anammox, instead of denitrification, as the likely prevalent pathway for nitrogen loss in this OMZ raises strong questions about our understanding of nitrogen cycling and organic matter remineralization in these waters. Without detectable denitrification, it is unclear how NH 4 + is remineralized from organic matter and sustains anammox or how secondary NO 2 − maxima arise within the OMZ. Here we show that in the ETSP-OMZ, anammox obtains 67% or more of NO 2 − from nitrate reduction, and 33% or less from aerobic ammonia oxidation, based on stable-isotope pairing experiments corroborated by functional gene expression analyses. Dissimilatory nitrate reduction to ammonium was detected in an open-ocean setting. It occurred throughout the OMZ and could satisfy a substantial part of the NH 4 + requirement for anammox. The remaining NH 4 + came from remineralization via nitrate reduction and probably from microaerobic respiration. Altogether, deep-sea NO 3 − accounted for only ≈50% of the nitrogen loss in the ETSP, rather than 100% as commonly assumed. Because oceanic OMZs seem to be expanding because of global climate change, it is increasingly imperative to incorporate the correct nitrogen-loss pathways in global biogeochemical models to predict more accurately how the nitrogen cycle in our future ocean may respond.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.0812444106
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2009
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 2
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    Online Resource
    Nitrogen isotope effects induced by anammox bacteria
    Proceedings of the National Academy of Sciences ; 2013
    In:  Proceedings of the National Academy of Sciences Vol. 110, No. 47 ( 2013-11-19), p. 18994-18999
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 110, No. 47 ( 2013-11-19), p. 18994-18999
    Abstract: Nitrogen (N) isotope ratios ( 15 N/ 14 N) provide integrative constraints on the N inventory of the modern ocean. Anaerobic ammonium oxidation (anammox), which converts ammonium and nitrite to dinitrogen gas (N 2 ) and nitrate, is an important fixed N sink in marine ecosystems. We studied the so far unknown N isotope effects of anammox in batch culture experiments. Anammox preferentially removes 14 N from the ammonium pool with an isotope effect of +23.5‰ to +29.1‰, depending on factors controlling reversibility. The N isotope effects during the conversion of nitrite to N 2 and nitrate are ( i ) inverse kinetic N isotope fractionation associated with the oxidation of nitrite to nitrate (−31.1 ± 3.9‰), ( ii ) normal kinetic N isotope fractionation during the reduction of nitrite to N 2 (+16.0 ± 4.5‰), and ( iii ) an equilibrium N isotope effect between nitrate and nitrite (−60.5 ± 1.0‰), induced when anammox is exposed to environmental stress, leading to the superposition of N isotope exchange effects upon kinetic N isotope fractionation. Our findings indicate that anammox may be responsible for the unresolved large N isotope offsets between nitrate and nitrite in oceanic oxygen minimum zones. Irrespective of the extent of N isotope exchange between nitrate and nitrite, N removed from the combined nitrite and nitrate (NO x ) pool is depleted in 15 N relative to NO x . This net N isotope effect by anammox is superimposed on the N isotope fractionation by the co-occurring reduction of nitrate to nitrite in suboxic waters, possibly enhancing the overall N isotope effect for N loss from oxygen minimum zones.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1310488110
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2013
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
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  • 3
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    Online Resource
    Massive nitrogen loss from the Benguela upwelling system through anaerobic ammonium oxidation
    Proceedings of the National Academy of Sciences ; 2005
    In:  Proceedings of the National Academy of Sciences Vol. 102, No. 18 ( 2005-05-03), p. 6478-6483
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 102, No. 18 ( 2005-05-03), p. 6478-6483
    Abstract: In many oceanic regions, growth of phytoplankton is nitrogen-limited because fixation of N 2 cannot make up for the removal of fixed inorganic nitrogen (NH + 4 , NO - 2 , and NO - 3 ) by anaerobic microbial processes. Globally, 30-50% of the total nitrogen loss occurs in oxygen-minimum zones (OMZs) and is commonly attributed to denitrification (reduction of nitrate to N 2 by heterotrophic bacteria). Here, we show that instead, the anammox process (the anaerobic oxidation of ammonium by nitrite to yield N 2 ) is mainly responsible for nitrogen loss in the OMZ waters of one of the most productive regions of the world ocean, the Benguela upwelling system. Our in situ experiments indicate that nitrate is not directly converted to N 2 by heterotrophic denitrification in the suboxic zone. In the Benguela system, nutrient profiles, anammox rates, abundances of anammox cells, and specific biomarker lipids indicate that anammox bacteria are responsible for massive losses of fixed nitrogen. We have identified and directly linked anammox bacteria to the removal of fixed inorganic nitrogen in the OMZ waters of an open-ocean setting. We hypothesize that anammox could also be responsible for substantial nitrogen loss from other OMZ waters of the ocean.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.0502088102
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2005
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
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  • 4
    Online Resource
    Online Resource
    Multiheme hydroxylamine oxidoreductases produce NO during ammonia oxidation in methanotrophs
    Proceedings of the National Academy of Sciences ; 2020
    In:  Proceedings of the National Academy of Sciences Vol. 117, No. 39 ( 2020-09-29), p. 24459-24463
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 117, No. 39 ( 2020-09-29), p. 24459-24463
    Abstract: Aerobic and nitrite-dependent methanotrophs make a living from oxidizing methane via methanol to carbon dioxide. In addition, these microorganisms cometabolize ammonia due to its structural similarities to methane. The first step in both of these processes is catalyzed by methane monooxygenase, which converts methane or ammonia into methanol or hydroxylamine, respectively. Methanotrophs use methanol for energy conservation, whereas toxic hydroxylamine is a potent inhibitor that needs to be rapidly removed. It is suggested that many methanotrophs encode a hydroxylamine oxidoreductase (mHAO) in their genome to remove hydroxylamine, although biochemical evidence for this is lacking. HAOs also play a crucial role in the metabolism of aerobic and anaerobic ammonia oxidizers by converting hydroxylamine to nitric oxide (NO). Here, we purified an HAO from the thermophilic verrucomicrobial methanotroph Methylacidiphilum fumariolicum SolV and characterized its kinetic properties. This mHAO possesses the characteristic P 460 chromophore and is active up to at least 80 °C. It catalyzes the rapid oxidation of hydroxylamine to NO. In methanotrophs, mHAO efficiently removes hydroxylamine, which severely inhibits calcium-dependent, and as we show here, lanthanide-dependent methanol dehydrogenases, which are more prevalent in the environment. Our results indicate that mHAO allows methanotrophs to thrive under high ammonia concentrations in natural and engineered ecosystems, such as those observed in rice paddy fields, landfills, or volcanic mud pots, by preventing the accumulation of inhibitory hydroxylamine. Under oxic conditions, methanotrophs mainly oxidize ammonia to nitrite, whereas in hypoxic and anoxic environments reduction of both ammonia-derived nitrite and NO could lead to nitrous oxide (N 2 O) production.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.2011299117
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2020
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
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  • 5
    Online Resource
    Online Resource
    Archaea catalyze iron-dependent anaerobic oxidation of methane
    Proceedings of the National Academy of Sciences ; 2016
    In:  Proceedings of the National Academy of Sciences Vol. 113, No. 45 ( 2016-11-08), p. 12792-12796
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 113, No. 45 ( 2016-11-08), p. 12792-12796
    Abstract: Anaerobic oxidation of methane (AOM) is crucial for controlling the emission of this potent greenhouse gas to the atmosphere. Nitrite-, nitrate-, and sulfate-dependent methane oxidation is well-documented, but AOM coupled to the reduction of oxidized metals has so far been demonstrated only in environmental samples. Here, using a freshwater enrichment culture, we show that archaea of the order Methanosarcinales , related to “ Candidatus Methanoperedens nitroreducens,” couple the reduction of environmentally relevant forms of Fe 3+ and Mn 4+ to the oxidation of methane. We obtained an enrichment culture of these archaea under anaerobic, nitrate-reducing conditions with a continuous supply of methane. Via batch incubations using [ 13 C]methane, we demonstrated that soluble ferric iron (Fe 3+ , as Fe-citrate) and nanoparticulate forms of Fe 3+ and Mn 4+ supported methane-oxidizing activity. CO 2 and ferrous iron (Fe 2+ ) were produced in stoichiometric amounts. Our study connects the previous finding of iron-dependent AOM to microorganisms detected in numerous habitats worldwide. Consequently, it enables a better understanding of the interaction between the biogeochemical cycles of iron and methane.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1609534113
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2016
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
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    Online Resource
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