Archaea rather than bacteria control nitrification in two agricultural acidic soils
Cécile Gubry-Rangin1, Graeme W Nicol, James I Prosser
1Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, UK. c.rangin@abdn.ac.uk
FEMS Microbiology Ecology
|November 3, 2010
Summary
Ammonia-oxidizing archaea (AOA) control nitrification in acidic soils, not ammonia-oxidizing bacteria (AOB). Studies show AOA growth and activity are key drivers of this crucial nitrogen cycle process in these environments.
Area of Science:
- Environmental Microbiology
- Biogeochemistry
- Soil Science
Background:
- Nitrification is a key process in the global nitrogen cycle.
- Ammonia oxidation, the initial step, is carried out by ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) in soils.
- Soil pH is hypothesized to influence the relative abundance and activity of AOA and AOB.
Purpose of the Study:
- To investigate the roles of AOA and AOB in ammonia oxidation in two agricultural acidic Scottish soils.
- To determine the contribution of AOA and AOB to nitrification rates under varying pH conditions.
- To assess the impact of a nitrification inhibitor on AOA and AOB communities.
Main Methods:
- Incubation of soil microcosms with and without acetylene (nitrification inhibitor) at 20°C for 1 month.
- Quantification of amoA genes to assess AOA and AOB growth.
- Measurement of nitrification rates.
- Analysis of AOA and AOB transcriptional activity.
Main Results:
- High nitrification rates were observed in both acidic soils without acetylene.
- Significant growth of AOA, but not AOB, was detected.
- Nitrification rates positively correlated with AOA growth, but not AOB growth.
- Acetylene significantly inhibited AOA growth and decreased AOA transcriptional activity, with no effect on AOB.
Conclusions:
- Ammonia-oxidizing archaea (AOA), not ammonia-oxidizing bacteria (AOB), are the primary drivers of nitrification in these acidic agricultural soils.
- Soil acidity influences the dominance of AOA over AOB in ammonia oxidation.
- AOA play a critical role in the nitrogen cycle in acidic terrestrial ecosystems.
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