title: Oxidation of urea-derived nitrogen by thaumarchaeota-dominated marine nitrifying communities.
abstract: Urea nitrogen has been proposed to contribute significantly to nitrification by marine thaumarchaeotes. These inferences are based on distributions of thaumarchaeote urease genes rather than activity measurements. We found that ammonia oxidation rates were always higher than oxidation rates of urea-derived N in samples from coastal Georgia, USA (means ± SEM: 382 ± 35 versus 73 ± 24 nmol L-1d-1, Mann-Whitney U-test p < 0.0001), and the South Atlantic Bight (20 ± 8.8 versus 2.2 ± 1.7 nmol L-1d-1, p = 0.026) but not the Gulf of Alaska (8.8 ± 4.0 versus 1.5 ± 0.6, p > 0.05). Urea-derived N was relatively more important in samples from Antarctic continental shelf waters, though the difference was not statistically significant (19.4 ± 4.8 versus 12.0 ± 2.7 nmol L-1d-1, p > 0.05). We found only weak correlations between oxidation rates of urea-derived N and the abundance or transcription of putative Thaumarchaeota ureC genes. Dependence on urea-derived N does not appear to be directly related to pH or ammonium concentrations. Competition experiments and release of15NH3suggest that urea is hydrolyzed to ammonia intracellularly, then a portion is lost to the dissolved pool. The contribution of urea-derived N to nitrification appears to be minor in temperate coastal waters, but may represent a significant portion of the nitrification flux in Antarctic coastal waters.
authors.affiliation: Department of Marine Sciences, University of Georgia, Athens, GA, 30602, USA.|Department of Microbiology, University of Georgia, Athens, GA, 30602, USA.
authors.forename: Bradley B
authors.initials: BB
authors.lastname: Tolar
authors.affiliation: Department of Geology and Geophysics, University of Hawai'i, Honolulu, HI, 96822, USA.
authors.forename: Natalie J
authors.initials: NJ
authors.lastname: Wallsgrove
authors.affiliation: Department of Geology and Geophysics, University of Hawai'i, Honolulu, HI, 96822, USA.
authors.forename: Brian N
authors.initials: BN
authors.lastname: Popp
authors.affiliation: Department of Marine Sciences, University of Georgia, Athens, GA, 30602, USA.
authors.forename: James T
authors.initials: JT
authors.lastname: Hollibaugh
mesh_terms: D000413:Alaska; D000641:Ammonia / Q000378:metabolism*; D064751:Ammonium Compounds / Q000378:metabolism*; D000864:Antarctic Regions; D001105:Archaea / Q000235:genetics / Q000378:metabolism*; D058465:Nitrification; D009584:Nitrogen / Q000737:chemistry; D058458:Nitrogen Cycle / Q000502:physiology; D010084:Oxidation-Reduction; D014508:Urea / Q000737:chemistry*; D014510:Urease / Q000378:metabolism
chemical_list: D064751:Ammonium Compounds; D000641:Ammonia; D014508:Urea; D014510:Urease; D009584:Nitrogen