Autotrophic ammonia oxidation by soil thaumarchaea
Li-Mei Zhang1, Pierre R Offre, Ji-Zheng He
1Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 3UU, United Kingdom.
Summary
Archaeal ammonia oxidizers, previously unconfirmed in soils, were shown to fix inorganic carbon and grow autotrophically. This study provides direct evidence for archaea
Area of Science:
- Microbiology
- Environmental Science
- Biogeochemistry
Background:
- Nitrification is crucial to the nitrogen cycle, impacting fertilizer use, greenhouse gas emissions, and water quality.
- Ammonia oxidation, the initial nitrification step, was historically attributed to bacteria, but archaea are now recognized as ammonia oxidizers.
- The role of bacteria versus archaea in soil nitrification and whether archaea are autotrophic or heterotrophic remains unclear.
Purpose of the Study:
- To investigate the role of archaea in soil nitrification.
- To determine if soil ammonia-oxidizing archaea (AOA) grow autotrophically using inorganic carbon.
- To provide direct evidence for archaeal ammonia oxidation in soil environments.
Main Methods:
- Stable isotope probing with (13)C-enriched carbon dioxide in soil microcosms.
- Quantification and sequencing of archaeal and bacterial amoA genes.
- Analysis of archaeal hcd gene abundance, involved in autotrophic carbon fixation.
Main Results:
- Incorporation of (13)C into thaumarchaeal DNA containing amoA and hcd genes was observed.
- Archaeal amoA gene abundance increased, with detected (13)C-labeled genes, indicating inorganic CO2 fixation.
- Bacterial amoA genes showed no significant changes or (13)C incorporation.
- Coordinate increases in (13)C-labeled amoA and hcd gene abundance supported autotrophic archaeal growth.
Conclusions:
- Provides direct evidence for the significant role of archaea in soil ammonia oxidation.
- Demonstrates autotrophic growth of ammonia-oxidizing archaea in soil environments.
- Highlights the importance of archaea in the soil nitrogen cycle and carbon fixation.
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