Nitrification of archaeal ammonia oxidizers in a high-temperature hot spring

作者：Chen Shun; Peng Xiaotong; Xu Hengchao; Ta Kaiwen

来源：Biogeosciences, 2016, 13(7): 2051-2060.

DOI：10.5194/bg-13-2051-2016

<jats:p>&lt;p&gt;&lt;strong&gt;Abstract.&lt;/strong&gt; The oxidation of ammonia by microbes has been shown to occur in diverse natural environments. However, the link of in situ nitrification activity to taxonomic identities of ammonia oxidizers in high-temperature environments remains poorly understood. Here, we studied in situ ammonia oxidation rates and the diversity of ammonia-oxidizing Archaea (AOA) in surface and bottom sediments at 77&lt;span class="thinspace"&gt;&lt;/span&gt;°C in the Gongxiaoshe hot spring, Tengchong, Yunnan, China. The in situ ammonia oxidation rates measured by the &lt;sup&gt;15&lt;/sup&gt;N-NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;−&lt;/sup&gt; pool dilution technique in the surface and bottom sediments were 4.80 and 5.30&lt;span class="thinspace"&gt;&lt;/span&gt;nmol&lt;span class="thinspace"&gt;&lt;/span&gt;N&lt;span class="thinspace"&gt;&lt;/span&gt;g&lt;sup&gt;−1&lt;/sup&gt;&lt;span class="thinspace"&gt;&lt;/span&gt;h&lt;sup&gt;−1&lt;/sup&gt;, respectively. Real-time quantitative polymerase chain reaction (qPCR) indicated that the archaeal 16S rRNA genes and &lt;i&gt;amoA&lt;/i&gt; genes were present in the range of 0.128 to 1.96&lt;span class="thinspace"&gt;&lt;/span&gt; × &lt;span class="thinspace"&gt;&lt;/span&gt;10&lt;sup&gt;8&lt;/sup&gt; and 2.75 to 9.80&lt;span class="thinspace"&gt;&lt;/span&gt; × &lt;span class="thinspace"&gt;&lt;/span&gt;10&lt;sup&gt;5&lt;/sup&gt;&lt;span class="thinspace"&gt;&lt;/span&gt;gene&lt;span class="thinspace"&gt;&lt;/span&gt;copies&lt;span class="thinspace"&gt;&lt;/span&gt;g&lt;sup&gt;−1&lt;/sup&gt; sediment, respectively, while bacterial &lt;i&gt;amoA&lt;/i&gt; was not detected. Phylogenetic analysis of 16S rRNA genes showed high sequence similarity to thermophilic &lt;i&gt;Candidatus&lt;/i&gt; Nitrosocaldus yellowstonii, which represented the most abundant operational taxonomic units (OTU) in both surface and bottom sediments. The archaeal predominance was further supported by fluorescence in situ hybridization (FISH) visualization. The cell-specific rate of ammonia oxidation was estimated to range from 0.410 to 0.790&lt;span class="thinspace"&gt;&lt;/span&gt;fmol&lt;span class="thinspace"&gt;&lt;/span&gt;N&lt;span class="thinspace"&gt;&lt;/span&gt;archaeal&lt;span class="thinspace"&gt;&lt;/span&gt;cell&lt;sup&gt;−1&lt;/sup&gt;&lt;span class="thinspace"&gt;&lt;/span&gt;h&lt;sup&gt;−1&lt;/sup&gt;, higher than those in the two US Great Basin hot springs. These results suggest the importance of archaeal rather than bacterial ammonia oxidation in driving the nitrogen cycle in terrestrial geothermal environments.&lt;/p&gt;
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• 出版日期2016