Abstract
We performed a suite of 15N incubations (15NO2−, 15NO3− and 15NH4+) with and without the organic-nitrogen (N) compound allylthiourea (ATU), in the suboxic waters of the Arabian Sea. Production of 29N2 in control (-ATU) incubations with either 15NH4++14NO2−, or their analogues, 15NO2−+14NH4+, though small, confirmed the presence of anammox. In contrast, when we added ATU, along with 15NO2− and 14NH4+, there was a much greater production of 29N2, with 92% of the 15N-label being recovered as 29N2 on average. Such stimulated production of 29N2 could not be due to anammox, as the addition of ATU, along with 15NH4++14NO2−, only produced 29N2 equivalent to that in the controls. The ratios of 29N2 to 30N2 produced also precluded stimulation of denitrification. We present this as evidence for a hitherto uncharacterised metabolism potentially capable of oxidising organic-N (e.g. NH2 groups) directly to N2 gas at the expense of NO2−.
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Acknowledgements
We thank the crew on board the RRS Charles Darwin and CA Davies, JC Nicholls and J Petersen for help with the sampling, experiment and analysis at sea. This research has been supported by a Natural Environment Research Council grant (NER/A/S/2001/01196) to MT.
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Trimmer, M., Purdy, K. Evidence for the direct oxidation of organic nitrogen to N2 gas in the Arabian Sea. ISME J 6, 1798–1800 (2012). https://doi.org/10.1038/ismej.2012.18
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DOI: https://doi.org/10.1038/ismej.2012.18
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