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Oxidation of urea‐derived nitrogen by thaumarchaeota‐dominated marine nitrifying communities
Author(s) -
Tolar Bradley B.,
Wallsgrove Natalie J.,
Popp Brian N.,
Hollibaugh James T.
Publication year - 2017
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.13457
Subject(s) - nitrification , urea , biology , ammonium , ammonia , thaumarchaeota , nitrogen , temperate climate , environmental chemistry , zoology , ecology , biochemistry , chemistry , archaea , gene , organic chemistry
Summary 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 −1 d −1 , Mann‐Whitney U‐test p < 0.0001), and the South Atlantic Bight (20 ± 8.8 versus 2.2 ± 1.7 nmol L −1 d −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 −1 d −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 of 15 NH 3 suggest 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.