Ammonia-oxidizing bacteria and archaea grow under contrasting soil nitrogen conditions

Abstract

Nitrification is a key process of the nitrogen (N) cycle in soil with major environmental implications. The recent discovery of ammonia-oxidizing archaea (AOA) questions the traditional assumption of the dominant role of ammoniaoxidizing bacteria (AOB) in nitrification. We investigated AOB and AOA growth and nitrification rate in two different layers of three grassland soils treated with animal urine substrate and a nitrification inhibitor [dicyandiamide (DCD)]. We show that AOB were more abundant in the topsoils than in the subsoils, whereas AOA were more abundant in one of the subsoils. AOB grew substantially when supplied with a high dose of urine substrate, whereas AOA only grew in the Controls without the urine-N substrate. AOB growth and the amoA gene transcription activity were significantly inhibited by DCD. Nitrification rates were much higher in the topsoils than in the subsoils and were significantly related to AOB abundance, but not to AOA abundance. These results suggest that AOB and AOA prefer different soil N conditions to grow: AOB under high ammonia (NH 3 ) substrate and AOA under low NH 3 substrate conditions.

Effects of dicyandiamide and acetylene on N2O emissions and ammonia oxidizers in a fluvo-aquic soil applied with urea

“…3a), which was in agreement with previous studies in a large number of agricultural soils (Wu et al 2011;Habteselassie et al 2013;Chen et al 2015). It has been reported that AOB growth is favored by high-N soil conditions (Jia and Conrad 2009;Verhamme et al 2011;Taylor et al 2012), whereas AOA growth is not affected (Di et al 2009(Di et al , 2010a. The stronger suppression of the AOB population size by C 2 H 2 than DCD was observed, suggesting a coincidence of dynamics between the AOB population and N 2 O emission.…”

“…C 2 H 2 is another effective inhibitor and works on autotrophic nitrification at a low concentration (10-100 Pa) (Zhu et al 2013). These compounds inhibit nitrification by deactivating ammonia monooxygenase (AMO) and blocking the growth of AOB and AOA (Di et al 2010a;Hink et al 2016). DCD or C 2 H 2 was reported to be more effective in inhibiting AOA compared with AOB in low-pH soils (Gubry-Rangin et al 2010;Zhang et al 2012), and vice verse in nitrogen-rich soils (Di et al 2009;Jia and Conrad 2009;Dai et al 2013;Chen et al 2015).…”

Effect of nitrogen fertilizer on nitrogen pools and soil communities under grazed pastures

“…Several studies have suggested the AOA play a significant role in ammonium oxidation in soil (Leininger et al 2006;Francis et al 2007;Prosser & Nichol 2008). For a N rich soil, however, AOA did not respond to application of ammonium-N, in contrast to the response of the AOB; therefore AOA may prefer low ammonium-N conditions (Di et al 2009(Di et al , 2010.…”

“…soil fungal:bacterial ratio, and the DNA and RNA profiles of specific microbial groups) and larger soil invertebrates. We hypothesized that, because these pasture systems respond readily to N, changes in the below-ground system would also change in concert with increased soil N availability, particularly the abundances of AOB which appear to be sensitive to labile N. We test whether AOB and AOA respond differently to N additions in the field, as suggested in laboratory studies (Di et al 2010). Implications for N leaching under grazed pastures are discussed.…”

Ammonia-oxidizing microorganisms: key players in the promotion of plant growth

“…AOB thrive under conditions of high NH 3 availability, whereas AOA prefer low NH 3 conditions (Di et al, 2010). The response of nitrification to the availability of NH 4 + availability can be ascertained by Michaelis-Menten kinetics, and this model has been used to characterize some nitrifiers in soil (Stark and Firestone, 1996).…”