Ammonia oxidation coupled to CO2 fixation by archaea and bacteria in an agricultural soil

Jennifer Pratscher, Marc G. Dumont, Ralf Conrad

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154 Citations (Scopus)

Abstract

Ammonia oxidation is an essential part of the global nitrogen cycling and was long thought to be driven only by bacteria. Recent findings expanded this pathway also to the archaea. However, most questions concerning the metabolism of ammonia-oxidizing archaea, such as ammonia oxidation and potential CO 2 fixation, remain open, especially for terrestrial environments. Here, we investigated the activity of ammonia-oxidizing archaea and bacteria in an agricultural soil by comparison of RNA- and DNA-stable isotope probing (SIP). RNA-SIP demonstrated a highly dynamic and diverse community involved in CO 2 fixation and carbon assimilation coupled to ammonia oxidation. DNA-SIP showed growth of the ammonia-oxidizing bacteria but not of archaea. Furthermore, the analysis of labeled RNA found transcripts of the archaeal acetyl-CoA/propionyl-CoA carboxylase (accA/pccB) to be expressed and labeled. These findings strongly suggest that ammoniaoxidizing archaeal groups in soil autotrophically fix CO2 using the 3-hydroxypropionate-4- hydroxybutyrate cycle, one of the two pathways recently identified for CO 2 fixation in Crenarchaeota. Catalyzed reporter deposition (CARD)-FISH targeting the gene encoding subunit A of ammonia monooxygenase (amoA) mRNA and 16S rRNA of archaea also revealed ammonia-oxidizing archaea to be numerically relevant among the archaea in this soil. Our results demonstrate a diverse and dynamic contribution of ammonia-oxidizing archaea in soil to nitrification and CO2 assimilation and that their importance to the overall archaeal community might be larger than previously thought.

Original languageEnglish
Pages (from-to)4170-4175
Number of pages6
JournalProceedings of the National Academy of Sciences
Volume108
Issue number10
DOIs
Publication statusPublished - 8 Mar 2011

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