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<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:contributor>Christopher T. Mills</dc:contributor>
  <dc:contributor>Craig A. Johnson</dc:contributor>
  <dc:contributor>Thomas Rahn</dc:contributor>
  <dc:contributor>Chad Kinney</dc:contributor>
  <dc:creator>Kevin W. Mandernack</dc:creator>
  <dc:date>2009</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;In order to determine if the&amp;nbsp;&lt;/span&gt;&lt;i&gt;&amp;delta;&lt;/i&gt;&lt;sup&gt;15&lt;/sup&gt;&lt;span&gt;N and&amp;nbsp;&lt;/span&gt;&lt;i&gt;&amp;delta;&lt;/i&gt;&lt;sup&gt;18&lt;/sup&gt;&lt;span&gt;O values of N&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;O produced during co-oxidation of NH&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;&lt;span&gt;&amp;nbsp;by methanotrophic (methane oxidizing) bacteria can be isotopically distinguished from N&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;O produced either by autotrophic nitrifying or denitrifying bacteria, we conducted laboratory incubation experiments with pure cultures of methanotrophic bacteria that were provided NH&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;span&gt;Cl as an oxidation substrate. The N&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;O produced during NH&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;&lt;span&gt;&amp;nbsp;oxidation by methanotrophic bacteria showed nitrogen isotope fractionation between NH&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;&lt;span&gt;&amp;nbsp;and N&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;O (&lt;/span&gt;&lt;i&gt;&amp;epsilon;&lt;/i&gt;&lt;sub&gt;N&lt;sub&gt;2&lt;/sub&gt;O&amp;ndash;NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;&lt;/sub&gt;&lt;span&gt;) of &amp;minus;&amp;nbsp;48 and &amp;minus;&amp;nbsp;55&amp;permil; for&amp;nbsp;&lt;/span&gt;&lt;i&gt;Methylomonas methanica&lt;/i&gt;&lt;span&gt;&amp;nbsp;and&amp;nbsp;&lt;/span&gt;&lt;i&gt;Methylosinus trichosporium&lt;/i&gt;&lt;span&gt;, OB3b respectively. These large fractionations are similar to those previously measured for autotrophic nitrifying bacteria and consistent with N&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;O formation by multiple rate limiting steps that include NH&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;&lt;span&gt;oxidation by the methane monooxygenase enzyme and reduction of NO&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt;&lt;span&gt;&amp;nbsp;to N&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;O. Consequently, N&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;O formed by NH&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;&lt;span&gt;&amp;nbsp;oxidation via methanotrophic or autotrophic nitrifying bacteria might generally be characterized by lower&amp;nbsp;&lt;/span&gt;&lt;i&gt;&amp;delta;&lt;/i&gt;&lt;sup&gt;15&lt;/sup&gt;&lt;span&gt;N&lt;/span&gt;&lt;sub&gt;N&lt;sub&gt;2&lt;/sub&gt;O&lt;/sub&gt;&lt;span&gt;&amp;nbsp;values than that formed by denitrificaiton, although this also depends on the variability of&amp;nbsp;&lt;/span&gt;&lt;i&gt;&amp;delta;&lt;/i&gt;&lt;sup&gt;15&lt;/sup&gt;&lt;span&gt;N of available nitrogen sources (e.g., NH&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;&lt;span&gt;, NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt;&lt;span&gt;, NO&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt;&lt;span&gt;). Additional incubations with&amp;nbsp;&lt;/span&gt;&lt;i&gt;M. trichosporium&lt;/i&gt;&lt;span&gt;&amp;nbsp;OB3b at high and low CH&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;span&gt;&amp;nbsp;conditions in waters of different&amp;nbsp;&lt;/span&gt;&lt;i&gt;&amp;delta;&lt;/i&gt;&lt;sup&gt;18&lt;/sup&gt;&lt;span&gt;O values revealed that 19&amp;ndash;27% of the oxygen in N&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;O was derived from O&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;with the remainder from water. The biochemical mechanisms that could explain this amount of O&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;incorporation are discussed. The&amp;nbsp;&lt;/span&gt;&lt;i&gt;&amp;delta;&lt;/i&gt;&lt;sup&gt;18&lt;/sup&gt;&lt;span&gt;O of N&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;O formed under high CH&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;span&gt;&amp;nbsp;conditions was ~&amp;nbsp;+&amp;nbsp;15&amp;permil; more positive than that formed under lower CH&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;span&gt;&amp;nbsp;conditions. This enrichment resulted in part from the incorporation of O&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;into N&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;O that was enriched in&amp;nbsp;&lt;/span&gt;&lt;sup&gt;18&lt;/sup&gt;&lt;span&gt;O due to an isotope fractionation effect of &amp;minus;&amp;nbsp;16.1&amp;nbsp;&amp;plusmn;&amp;nbsp;2.0&amp;permil; and &amp;minus;&amp;nbsp;17.5&amp;nbsp;&amp;plusmn;&amp;nbsp;5.4&amp;permil; associated with O&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;&amp;nbsp;consumption during the high and low methane concentration incubations, respectively. Therefore, N&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;O formed by NH&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;&lt;span&gt;&amp;nbsp;oxidation via methanotrophic or autotrophic nitrifying bacteria can have very positive&amp;nbsp;&lt;/span&gt;&lt;i&gt;&amp;delta;&lt;/i&gt;&lt;sup&gt;18&lt;/sup&gt;&lt;span&gt;O&lt;/span&gt;&lt;sub&gt;N&lt;sub&gt;2&lt;/sub&gt;O&lt;/sub&gt;&lt;span&gt;&amp;nbsp;values if the O&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;incorporated is previously enriched in&amp;nbsp;&lt;/span&gt;&lt;sup&gt;18&lt;/sup&gt;&lt;span&gt;O from high rates of respiration. Nitrous oxide was collected from various depths in soils overlying a coal-bed methane seep where methanotrophic bacteria are naturally enriched. In one sampling when soil methane concentrations were very high, the&amp;nbsp;&lt;/span&gt;&lt;i&gt;&amp;delta;&lt;/i&gt;&lt;sup&gt;18&lt;/sup&gt;&lt;span&gt;O&lt;/span&gt;&lt;sub&gt;VSMOW&lt;/sub&gt;&lt;span&gt;&amp;nbsp;values of the N&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;O were highly enriched (+&amp;nbsp;50&amp;permil;), consistent with our laboratory experiments. Thus, soils overlying methane seeps could provide an&amp;nbsp;&lt;/span&gt;&lt;sup&gt;18&lt;/sup&gt;&lt;span&gt;O-enriched source of atmospheric N&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;O.&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1016/j.chemgeo.2009.06.008</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Elsevier</dc:publisher>
  <dc:title>The δ&lt;sup&gt;15&lt;/sup&gt;N and δ&lt;sup&gt;18&lt;/sup&gt;O values of N&lt;sub&gt;2&lt;/sub&gt;O produced during the co-oxidation of ammonia by methanotrophic bacteria</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>