gen. nov., sp. nov., a thermophilic sulfur- and iron-reducing archaeon, and proposal of fam. nov., ord. nov., and class. nov. in the phylum .

A thermoacidophilic, anaerobic, and iron- and sulfur-reducing archaeon, strain NAS-02, was isolated from a terrestrial hot spring in Japan, as previously reported. This organism is the first non-ammonia-oxidizing isolate in the phylum . Here, we propose gen. nov., sp. nov. to accommodate this strain. The type strain of the type species is NAS-02 (=JCM 31663=DSM 105898). The values of 16S rRNA gene similarity and average amino acid identity between NAS-02 and its closest relatives are <86 and <42 %, respectively. Based on the phylogeny and physiology, we propose the family fam. nov., the order ord. nov. and the class class. nov. to accommodate the novel genus.