Nitrososphaera viennensis gen. nov., sp. nov., an aerobic and mesophilic, ammonia-oxidizing archaeon from soil and a member of the archaeal phylum Thaumarchaeota

<jats:p>A mesophilic, neutrophilic and aerobic, ammonia-oxidizing archaeon, strain EN76<jats:sup>T</jats:sup>, was isolated from garden soil in Vienna (Austria). Cells were irregular cocci with a diameter of 0.6–0.9 µm and possessed archaella and archaeal pili as cell appendages. Electron microscopy also indicated clearly discernible areas of high and low electron density, as well as tubule-like structures. Strain EN76<jats:sup>T</jats:sup>had an S-layer with p3 symmetry, so far only reported for members of the<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="order" xlink:type="simple"><jats:ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1601/nm.64" xlink:type="simple"><jats:italic>Sulfolobales</jats:italic></jats:ext-link></jats:named-content>. Crenarchaeol was the major core lipid. The organism gained energy by oxidizing ammonia to nitrite aerobically, thereby fixing CO<jats:sub>2</jats:sub>, but growth depended on the addition of small amounts of organic acids. The optimal growth temperature was 42 °C and the optimal pH was 7.5, with ammonium and pyruvate concentrations of 2.6 and 1 mM, respectively. The genome of strain EN76<jats:sup>T</jats:sup>had a DNA G+C content of 52.7 mol%. Phylogenetic analyses of 16S rRNA genes showed that strain EN76<jats:sup>T</jats:sup>is affiliated with the recently proposed phylum<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="phylum" xlink:type="simple"><jats:ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1601/nm.14437" xlink:type="simple"><jats:italic>Thaumarchaeota</jats:italic></jats:ext-link></jats:named-content>, sharing 85 % 16S rRNA gene sequence identity with the closest cultivated relative ‘<jats:italic>Candidatus</jats:italic>Nitrosopumilus maritimus’ SCM1, a marine ammonia-oxidizing archaeon, and a maximum of 81 % 16S rRNA gene sequence identity with members of the phyla<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="phylum" xlink:type="simple"><jats:ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1601/nm.2" xlink:type="simple"><jats:italic>Crenarchaeota</jats:italic></jats:ext-link></jats:named-content>and<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="phylum" xlink:type="simple"><jats:ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1601/nm.90" xlink:type="simple"><jats:italic>Euryarchaeota</jats:italic></jats:ext-link></jats:named-content>and any of the other recently proposed phyla (e.g. ‘<jats:italic>Korarchaeota</jats:italic>’ and ‘<jats:italic>Aigarchaeota</jats:italic>’). We propose the name<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="species" xlink:type="simple"><jats:ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1601/nm.22616" xlink:type="simple"><jats:italic>Nitrososphaera viennensis</jats:italic></jats:ext-link></jats:named-content>gen. nov., sp. nov. to accommodate strain EN76<jats:sup>T</jats:sup>. The type strain of<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="species" xlink:type="simple"><jats:ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1601/nm.22616" xlink:type="simple"><jats:italic>Nitrososphaera viennensis</jats:italic></jats:ext-link></jats:named-content>is strain EN76<jats:sup>T</jats:sup>( = DSM 26422<jats:sup>T</jats:sup> = JMC 19564<jats:sup>T</jats:sup>)<jats:italic>.</jats:italic>Additionally, we propose the family<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="family" xlink:type="simple"><jats:ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1601/nm.22613" xlink:type="simple"><jats:italic>Nitrososphaeraceae</jats:italic></jats:ext-link></jats:named-content>fam. nov., the order<jats:named-content xmlns:xlink="http://www.w3.org/1999/xlink" content-type="order" xlink:type="simple"><jats:ext-link ext-link-type="uri" xlink:href="http://dx.doi.org/10.1601/nm.22612" xlink:type="simple"><jats:italic>Nitrososphaerales</jats:italic></jats:ext-link></jats:named-content>ord. nov. and the class<jats:italic>Nitrososphaeria</jats:italic>classis nov.</jats:p>