Archaeal Ammonia Oxidizers Dominate in Numbers, but Bacteria Drive Gross Nitrification in N-amended Grassland Soil

Abstract

Both ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) play an important role in nitrification in terrestrial environments. Most often AOA outnumber AOB, but the relative contribution of AOA and AOB to nitrification rates remains unclear. The aim of this experiment was to test the hypotheses that high nitrogen availability would favor AOB and result in high gross nitrification rates, while high carbon availability would result in low nitrogen concentrations that favor the activity of AOA. The hypotheses were tested in a microcosm experiment where sugars, ammonium, or amino acids were added regularly to a grassland soil for a period of 33 days. The abundance of amoA genes from AOB increased markedly in treatments that received nitrogen, suggesting that AOB were the main ammonia oxidizers here. However, AOB could not account for the entire ammonia oxidation activity observed in treatments where the soil was deficient in available nitrogen. The findings suggest that AOA are important drivers of nitrification under nitrogen-poor conditions, but that input of easily available nitrogen results in increased abundance, activity, and relative importance of AOB for gross nitrification in grassland soil.

Nitrification inhibitors effectively target N2O‐producing Nitrosospira spp. in tropical soil

“…This is thought to be linked to the enzymatic capabilities of different AOB and AOA species, with the former generating higher amounts of N 2 O through both abiotic (nitric oxide oxidation by O 2 ) and biotic (incomplete hydroxylamine oxidation and nitrifier denitrification) mechanisms, while the latter likely emits lower N 2 O using only an abiotic (nitric oxidation by O 2 ) mechanism (Harper et al, 2015;Kozlowski et al, 2016). These results support observations that the AOA Nitrososphaera is associated with low concentrations of ammonia linked to the stronger affinity of the archaeal ammonia monooxygenase for ammonia (Sterngren et al, 2015). More than five AOA Nitrososphaera 16S rRNA OTUs were identified compared to the two AOB Nitrosospira 16S rRNA OTUs; this supports the idea that the conditions in these unfertilized soils normally support the AOA Nitrososphaera rather than the AOB Nitrosospira or Nitrosomonas as the main ammonia oxidizers.…”

“…The Nitrosovibrio RY3C species was originally isolated from avocado rhizosphere and its nitrifying activity was susceptible to DCD (Matsuba et al, 2003). The Nitrosospira in general are widespread spiral soil bacteria with generally low specificity for ammonia and, thus, found in soils under high levels of ammonia (Jia and Conrad, 2009;Di et al, 2010a;Sterngren et al, 2015). as the N 2 Ogenerating AOB in tropical soil under sugarcane, and that study applied NH 4 NO 3 as the N source (Lourenço et al, 2018a).…”

Humus Forms and Soil Microbiological Parameters in a Mountain Forest: Upscaling to the Slope Scale

“…1900 m a.s.l., whereas Entic Podzols, Albic Podzols and Umbric Podzols are dominant in the forest above ( [34], according to [35]). descriptive information about soil quality [25], as they can compete for the same nutrients [26] and due to different pH dependencies of fungi, bacteria and archaea [27]. In order to understand spatial decomposition patterns in a high mountain environment, it would be useful if humus forms could be applied as indicators not only of the distribution of enchytraeid species [9,28], but also of microbiological parameters [29].…”

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

“…However, by characterising the conserved amoA gene, which encodes a subunit of the ammonia monooxygenase (AMO), it has been observed that the populations of ammonia oxidisers are largely controlled by soil type, NH 4 + concentration, pH and water content (Nicol et al 2008;Di et al 2009;Chen et al 2010;Norton and Stark 2011). In ammoniumrich soils, AOB abundance and activity increased whereas AOA abudance is unaffected or inhibited in response to a high concentration of ammonium fertilisers (Jia and Conrad 2009;Di et al 2009;Di and Cameron 2011;Sterngren et al 2015;Ouyang et al 2016). In unfertilised or acidic soils, AOA abundance and metabolic activity are much higher than those of AOB (Offre et al 2009;GubryRangin et al 2010;Zhang et al 2012).…”