title: Evidence for the direct oxidation of organic nitrogen to N2 gas in the Arabian Sea.
abstract: We performed a suite of (15)N incubations ((15)NO(2)(-), (15)NO(3)(-) and (15)NH(4)(+)) with and without the organic-nitrogen (N) compound allylthiourea (ATU), in the suboxic waters of the Arabian Sea. Production of (29)N(2) in control (-ATU) incubations with either (15)NH(4)(+)+(14)NO(2)(-), or their analogues, (15)NO(2)(-)+(14)NH(4)(+), though small, confirmed the presence of anammox. In contrast, when we added ATU, along with (15)NO(2)(-) and (14)NH(4)(+), there was a much greater production of (29)N(2), with 92% of the (15)N-label being recovered as (29)N(2) on average. Such stimulated production of (29)N(2) could not be due to anammox, as the addition of ATU, along with (15)NH(4)(+)+(14)NO(2)(-), only produced (29)N(2) equivalent to that in the controls. The ratios of (29)N(2) to (30)N(2) produced also precluded stimulation of denitrification. We present this as evidence for a hitherto uncharacterised metabolism potentially capable of oxidising organic-N (e.g. NH(2) groups) directly to N(2) gas at the expense of NO(2)(-).
authors.affiliation: School of Biological and Chemical Sciences, Queen Mary University of London, London, UK. m.trimmer@qmul.ac.uk
authors.forename: Mark
authors.initials: M
authors.lastname: Trimmer
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Purdy
mesh_terms: D001419:Bacteria / Q000378:metabolism; D005740:Gases / Q000032:analysis / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D009587:Nitrogen Isotopes / Q000032:analysis / Q000378:metabolism; D009792:Oceans and Seas; D010084:Oxidation-Reduction; D014871:Water Microbiology
chemical_list: D005740:Gases; D009587:Nitrogen Isotopes; D009584:Nitrogen