Isotopic signatures of N2O produced by ammonia-oxidizing archaea from soils

Abstract

N 2 O gas is involved in global warming and ozone depletion. The major sources of N 2 O are soil microbial processes. Anthropogenic inputs into the nitrogen cycle have exacerbated these microbial processes, including nitrification. Ammonia-oxidizing archaea (AOA) are major members of the pool of soil ammonia-oxidizing microorganisms. This study investigated the isotopic signatures of N 2 O produced by soil AOA and associated N 2 O production processes. All five AOA strains (I.1a, I.1a-associated and I.1b clades of Thaumarchaeota) from soil produced N 2 O and their yields were comparable to those of ammonia-oxidizing bacteria (AOB). The levels of site preference (SP), d 15 N bulk and d 18 O -N 2 O of soil AOA strains were 13-30%, À 13 to À 35% and 22-36%, respectively, and strains MY1-3 and other soil AOA strains had distinct isotopic signatures. A 15 N-NH 4 þ -labeling experiment indicated that N 2 O originated from two different production pathways (that is, ammonia oxidation and nitrifier denitrification), which suggests that the isotopic signatures of N 2 O from AOA may be attributable to the relative contributions of these two processes. The highest N 2 O production yield and lowest site preference of acidophilic strain CS may be related to enhanced nitrifier denitrification for detoxifying nitrite. Previously, it was not possible to detect N 2 O from soil AOA because of similarities between its isotopic signatures and those from AOB. Given the predominance of AOA over AOB in most soils, a significant proportion of the total N 2 O emissions from soil nitrification may be attributable to AOA.

Glyphosate Use Predicts Healthcare Utilization for ADHD in the Healthcare Cost and Utilization Project net (HCUPnet): A Two-Way Fixed-Effects Analysis

“…It has also been suggested that N 2 O is emitted as a spontaneous metabolic AO intermediate [73]. Recent research reveals that ammonia-oxidizing archaea are underestimated contributors to N 2 O emissions in soil [77], and this discovery is consistent with changing glyphosate dynamics. N 2 O and ADHD N 2 O has been used as an anesthetic agent in health care settings, primarily dentistry.…”

Pathways and key intermediates required for obligate aerobic ammonia-dependent chemolithotrophy in bacteria and Thaumarchaeota

“…The authors concluded that NO was either released as a free intermediate during ammonia oxidation by N. maritimus, or it could serve a functional role as an electron delivery mechanism to ammonia monooxygenase, an idea that has been proposed previously . Although the detection of nitrous oxide (N 2 O) has been reported for both enrichments and pure cultures of Thaumarchaea engaged in ammonia oxidation (Santoro et al, 2011;Loscher et al, 2012;Jung et al, 2014;Stieglmeier et al, 2014b), the isotope data reported by Stieglmeier et al (2014b) revealed that ammonia-oxidizing Thaumarchaea cannot enzymatically reduce NO 2 − to N 2 O via NO in the pathway known as 'nitrifier denitrification'. Several publications have suggested that ammoniaoxidizing Thaumarchaea are a major source of N 2 O to the environment based on their relative abundance in oxic environments, the isotopic signature of the detected N 2 O, and that the authors failed to detect known bacterial denitrification genes and pertinent activities (Santoro et al, 2011;Loscher et al, 2012;Jung et al, 2014).…”

Nitrogen fertiliser-induced changes in N2O emissions are attributed more to ammonia-oxidising bacteria rather than archaea as revealed using 1-octyne and acetylene inhibitors in two arable soils

“…Nitrification-related processes (the oxidation of NH 2 OH and NO 2 − reduction) mediated by AOB are recognised to be a main pathway of N 2 O emission from arable soils (G dde and Conrad 1999;Zhu et al 2013;Huang et al 2014a). The traditional viewpoint that soil ammonia oxidation and associated N 2 O emission is exclusively carried out by AOB has been challenged by the discovery of amoA and nirK genes in AOA strains (Venter et al 2004;Lund et al 2012) and by the demonstration of the N 2 O production capacity of AOA enriched or isolated from arable soils and marine ecosystem (Jung et al 2011(Jung et al , 2014Santoro et al 2011;Loscher et al 2012). In most soils, AOA outnumbers AOB abundance, a common feature in multiple ecosystems (Leininger et al 2006;He et al 2007;Hu et al 2013), and a high AOA ammonia oxidation activity has been assessed in certain soils (Yao et al 2011;Zhang et al 2012;Hu et al 2015).…”