title: Aerobic nitrous oxide production through N-nitrosating hybrid formation in ammonia-oxidizing archaea.
abstract: Soil emissions are largely responsible for the increase of the potent greenhouse gas nitrous oxide (N2O) in the atmosphere and are generally attributed to the activity of nitrifying and denitrifying bacteria. However, the contribution of the recently discovered ammonia-oxidizing archaea (AOA) to N2O production from soil is unclear as is the mechanism by which they produce it. Here we investigate the potential of Nitrososphaera viennensis, the first pure culture of AOA from soil, to produce N2O and compare its activity with that of a marine AOA and an ammonia-oxidizing bacterium (AOB) from soil. N. viennensis produced N2O at a maximum yield of 0.09% N2O per molecule of nitrite under oxic growth conditions. N2O production rates of 4.6±0.6 amol N2O cell(-1) h(-1) and nitrification rates of 2.6±0.5 fmol NO2(-) cell(-1) h(-1) were in the same range as those of the AOB Nitrosospira multiformis and the marine AOA Nitrosopumilus maritimus grown under comparable conditions. In contrast to AOB, however, N2O production of the two archaeal strains did not increase when the oxygen concentration was reduced, suggesting that they are not capable of denitrification. In (15)N-labeling experiments we provide evidence that both ammonium and nitrite contribute equally via hybrid N2O formation to the N2O produced by N. viennensis under all conditions tested. Our results suggest that archaea may contribute to N2O production in terrestrial ecosystems, however, they are not capable of nitrifier-denitrification and thus do not produce increasing amounts of the greenhouse gas when oxygen becomes limiting.
authors.affiliation: Department of Ecogenomics and Systems Biology, Archaea Biology and Ecogenomics Division, University of Vienna, Vienna, Austria.
authors.forename: Michaela
authors.initials: M
authors.lastname: Stieglmeier
authors.affiliation: Department of Microbiology and Ecosystem Science, Division of Terrestrial Ecosystem Research, University of Vienna, Vienna, Austria.
authors.forename: Maria
authors.initials: M
authors.lastname: Mooshammer
authors.affiliation: Federal Research and Training Centre for Forests, Natural Hazards and Landscape, Unit of Soil Biology, Vienna, Austria.
authors.forename: Barbara
authors.initials: B
authors.lastname: Kitzler
authors.affiliation: Department of Microbiology and Ecosystem Science, Division of Terrestrial Ecosystem Research, University of Vienna, Vienna, Austria.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wanek
authors.affiliation: 1] Federal Research and Training Centre for Forests, Natural Hazards and Landscape, Unit of Soil Biology, Vienna, Austria [2] University of Natural Resources and Life Sciences, Institute of Soil Research, Vienna, Austria.
authors.forename: Sophie
authors.initials: S
authors.lastname: Zechmeister-Boltenstern
authors.affiliation: Department of Microbiology and Ecosystem Science, Division of Terrestrial Ecosystem Research, University of Vienna, Vienna, Austria.
authors.forename: Andreas
authors.initials: A
authors.lastname: Richter
authors.affiliation: Department of Ecogenomics and Systems Biology, Archaea Biology and Ecogenomics Division, University of Vienna, Vienna, Austria.
authors.forename: Christa
authors.initials: C
authors.lastname: Schleper
mesh_terms: D000641:Ammonia / Q000378:metabolism; D001105:Archaea / Q000378:metabolism*; D001419:Bacteria / Q000378:metabolism; D058440:Denitrification; D017753:Ecosystem; D058465:Nitrification; D009609:Nitrous Oxide / Q000378:metabolism*; D010084:Oxidation-Reduction; D012988:Soil Microbiology
chemical_list: D000641:Ammonia; D009609:Nitrous Oxide