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

Sterngren AE, Hallin S, Bengtson P - Front Microbiol (2015)

Bottom Line: 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 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.

View Article: PubMed Central - PubMed

Affiliation: Microbial Ecology, Department of Biology, Lund University Lund, Sweden.

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.

No MeSH data available.


Related in: MedlinePlus

Abundance of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in different treatments after 5, 19, and 33 days of incubation.(A) Archaeal amoA genes copies per g dry soil. Treatment: F = 2.47, p = 0.11; sampling time: F = 0.20, p = 0.82. (B) Bacterial amoA genes copies per g dry soil. Treatment: F = 74.85, p < 0.001; sampling time: F = 16.72, p < 0.001; interaction F = 11.40, p < 0.001. (C) Ratio between archaeal and bacterial amoA genes. Treatment: F = 19.07, p < 0.001; sampling time: F = 13.54, p < 0.001; interaction F = 10.86, p < 0.001. Boxes represent the 25 and 75% percentiles, whiskers the 5 and 95% percentile and the horizontal line in each box the median value.
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Figure 1: Abundance of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in different treatments after 5, 19, and 33 days of incubation.(A) Archaeal amoA genes copies per g dry soil. Treatment: F = 2.47, p = 0.11; sampling time: F = 0.20, p = 0.82. (B) Bacterial amoA genes copies per g dry soil. Treatment: F = 74.85, p < 0.001; sampling time: F = 16.72, p < 0.001; interaction F = 11.40, p < 0.001. (C) Ratio between archaeal and bacterial amoA genes. Treatment: F = 19.07, p < 0.001; sampling time: F = 13.54, p < 0.001; interaction F = 10.86, p < 0.001. Boxes represent the 25 and 75% percentiles, whiskers the 5 and 95% percentile and the horizontal line in each box the median value.

Mentions: The numbers of archaeal amoA gene copies per g dry soil only varied between 4.8 × 107 and 7.2 × 107, whereas the numbers of bacterial amoA gene copies showed a much broader range (1.3 × 106–1.2 × 107; Figures 1A,B). In the control and sugar treatment, the abundance of bacterial amoA genes remained constant, with a tendency to decrease with time, whereas a significant increase was observed when ammonium or amino acids were added (F = 16.72, p < 0.001, Figure 1B). The effect was more pronounced when ammonium was added compared to the amino-acid treatment, even though the same amount of nitrogen was added. By contrast, there was no difference in archaeal amoA gene copy numbers between treatments (F = 2.47, p ≥ 0.05) or over time (F = 0.20, p ≥ 0.05, Figure 1A).


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

Sterngren AE, Hallin S, Bengtson P - Front Microbiol (2015)

Abundance of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in different treatments after 5, 19, and 33 days of incubation.(A) Archaeal amoA genes copies per g dry soil. Treatment: F = 2.47, p = 0.11; sampling time: F = 0.20, p = 0.82. (B) Bacterial amoA genes copies per g dry soil. Treatment: F = 74.85, p < 0.001; sampling time: F = 16.72, p < 0.001; interaction F = 11.40, p < 0.001. (C) Ratio between archaeal and bacterial amoA genes. Treatment: F = 19.07, p < 0.001; sampling time: F = 13.54, p < 0.001; interaction F = 10.86, p < 0.001. Boxes represent the 25 and 75% percentiles, whiskers the 5 and 95% percentile and the horizontal line in each box the median value.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4663241&req=5

Figure 1: Abundance of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in different treatments after 5, 19, and 33 days of incubation.(A) Archaeal amoA genes copies per g dry soil. Treatment: F = 2.47, p = 0.11; sampling time: F = 0.20, p = 0.82. (B) Bacterial amoA genes copies per g dry soil. Treatment: F = 74.85, p < 0.001; sampling time: F = 16.72, p < 0.001; interaction F = 11.40, p < 0.001. (C) Ratio between archaeal and bacterial amoA genes. Treatment: F = 19.07, p < 0.001; sampling time: F = 13.54, p < 0.001; interaction F = 10.86, p < 0.001. Boxes represent the 25 and 75% percentiles, whiskers the 5 and 95% percentile and the horizontal line in each box the median value.
Mentions: The numbers of archaeal amoA gene copies per g dry soil only varied between 4.8 × 107 and 7.2 × 107, whereas the numbers of bacterial amoA gene copies showed a much broader range (1.3 × 106–1.2 × 107; Figures 1A,B). In the control and sugar treatment, the abundance of bacterial amoA genes remained constant, with a tendency to decrease with time, whereas a significant increase was observed when ammonium or amino acids were added (F = 16.72, p < 0.001, Figure 1B). The effect was more pronounced when ammonium was added compared to the amino-acid treatment, even though the same amount of nitrogen was added. By contrast, there was no difference in archaeal amoA gene copy numbers between treatments (F = 2.47, p ≥ 0.05) or over time (F = 0.20, p ≥ 0.05, Figure 1A).

Bottom Line: 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 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.

View Article: PubMed Central - PubMed

Affiliation: Microbial Ecology, Department of Biology, Lund University Lund, Sweden.

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.

No MeSH data available.


Related in: MedlinePlus