Journal Article

moderately thermophilic ammonia-oxidizing crenarchaeote from a hot spring

Spieck, Eva, Daims, Holger, Stoecker, Kilian, Hatzenpichler, Roland, Lebedeva, Elena V, Wagner, Michael, Richter, Andreas

2008

Overview

The recent discovery of ammonia-oxidizing archaea (AOA) dramatically changed our perception of the diversity and evolutionary history of microbes involved in nitrification. In this study, a moderately thermophilic (46°C) ammonia-oxidizing enrichment culture, which had been seeded with biomass from a hot spring, was screened for ammonia oxidizers. Although gene sequences for crenarchaeotal 16S rRNA and two subunits of the ammonia monooxygenase (amoA and amoB) were detected via PCR, no hints for known ammonia-oxidizing bacteria were obtained. Comparative sequence analyses of these gene fragments demonstrated the presence of a single operational taxonomic unit and thus enabled the assignment of the amoA and amoB sequences to the respective 16S rRNA phylotype, which belongs to the widely distributed group I.1b (soil group) of the CRENARCHAEOTA: Catalyzed reporter deposition (CARD)-FISH combined with microautoradiography (MAR) demonstrated metabolic activity of this archaeon in the presence of ammonium. This finding was corroborated by the detection of amoA gene transcripts in the enrichment. CARD-FISH/MAR showed that the moderately thermophilic AOA is highly active at 0.14 and 0.79 mM ammonium and is partially inhibited by a concentration of 3.08 mM. The enriched AOA, which is provisionally classified as \"Candidatus Nitrososphaera gargensis,\" is the first described thermophilic ammonia oxidizer and the first member of the crenarchaeotal group I.1b for which ammonium oxidation has been verified on a cellular level. Its preference for thermophilic conditions reinvigorates the debate on the thermophilic ancestry of AOA.

• Publisher: National Academy of Sciences,National Acad Sciences
• Subject: Ammonia / Ammonia - metabolism / ammonia monooxygenase / Ammonium / ancestry / Archaea / Archaea - genetics / Archaea - metabolism / bacteria / Biodiversity / Biological Sciences / Biomass / Catalysis / Comparative analysis / Crenarchaeota / enrichment culture / genes / Hot springs / Hot Temperature / In Situ Hybridization, Fluorescence / messenger RNA / Molecular Sequence Data / Nitrification / Nitrites / nucleotide sequences / oxidants / Oxidation / Oxidation-Reduction / Oxidizers / Phylogeny / phylotype / Polymerase chain reaction / Product category rules / Quaternary ammonium compounds / Reverse Transcriptase Polymerase Chain Reaction / ribosomal RNA / RNA, Messenger - genetics / RNA, Ribosomal, 16S - genetics / rRNA genes / Sedimentary soils / sequence analysis / soil / Studies / Water Microbiology