title: Novel genes for nitrite reductase and Amo-related proteins indicate a role of uncultivated mesophilic crenarchaeota in nitrogen cycling.
abstract: Mesophilic crenarchaeota are frequently found in terrestrial and marine habitats worldwide, but despite their considerable abundance the physiology of these as yet uncultivated archaea has remained unknown. From a 1.2 Gb large-insert environmental fosmid library of a calcareous grassland soil, a 43 kb genomic fragment was isolated with a ribosomal RNA that shows its affiliation to group 1.1b of crenarchaeota repeatedly found in soils. The insert encoded a homologue of a copper-containing nitrite reductase with an unusual C-terminus that encoded a potential amicyanin-like electron transfer domain as well as two proteins related to subunits of ammonia monooxygenases or particulate methane monooxygenases (AmoAB/PmoAB) respectively. Expression of nirK and the amoA-like gene was shown by reverse transcription polymerase chain reaction (PCR) analyses in soil samples, the latter being found at higher levels when the soil was incubated with ammonia (measured by quantitative PCR). Further variants of both genes were amplified from soil samples and were found in the environmental database from the Sargasso Sea plankton. Taken together, our findings suggest that mesophilic terrestrial and marine crenarchaeota might be capable of ammonia oxidation under aerobic and potentially also under anaerobic conditions.
authors.affiliation: University of Bergen, Department of Biology, Jahnebakken 5, N-5020 Bergen, Norway.
authors.forename: Alexander H
authors.initials: AH
authors.lastname: Treusch
authors.forename: Sven
authors.initials: S
authors.lastname: Leininger
authors.forename: Arnulf
authors.initials: A
authors.lastname: Kletzin
authors.forename: Stephan C
authors.initials: SC
authors.lastname: Schuster
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Klenk
authors.forename: Christa
authors.initials: C
authors.lastname: Schleper
mesh_terms: D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000235:genetics*; D019615:Crenarchaeota / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009572:Nitrite Reductases / Q000235:genetics*; D009584:Nitrogen / Q000378:metabolism*; D010088:Oxidoreductases / Q000235:genetics*; D010105:Oxygenases / Q000235:genetics; D016415:Sequence Alignment; D012988:Soil Microbiology; D013045:Species Specificity
chemical_list: D019843:Archaeal Proteins; D010088:Oxidoreductases; D010105:Oxygenases; C021555:methane monooxygenase; D009572:Nitrite Reductases; C045582:ammonia monooxygenase; D009584:Nitrogen