Estimation of isotopologue variation of N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O during denitrification by &amp;lt;i&amp;gt;Pseudomonas aureofaciens&amp;lt;/i&amp;gt; and &amp;lt;i&amp;gt;Pseudomonas&amp;lt;/i&amp;gt; chlororaphis: Implications for N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O source apportionment