The Nanoarchaeota: Physiology, Genomics and Phylogeny pp. 163-174
Authors: (Ana Casanueva, Marla Tuffin, Don A. Cowan, Institute for Microbial Biotechnology and Metagenomics, Department of Biotechnology, University of the Western Cape, Bellville, South Africa)
Abstract: The Nanoarchaeota, proposed as the fourth sub-division of the Archaea in 2002, are known from a single isolate, ―Nanoarchaeum equitans‖, which exists in a symbiotic association with the hyperthermophilic Crenarchaeote, Ignicoccus hospitalis. The sequencing of both genomes has provided clues on their unusual and very specific association. The discovery of nanoarchaeal sequences in diverse geographical hyperthermophilic locations, and most importantly the identification of nanoarchaeal phylotypes in mesophilic halophilic environments suggest the possibility of either free-living nanoarchaeotes or associations with novel hosts. The ―true‖ phylogenetic position of the Nanoarchaea is still a matter of debate, having been described originally as a separate phylum and later as a member of the phylum Euryarchaeota. The present review will discuss the recent discoveries on this hyperthermophilic organism and its association to Ignicoccus and will analyse the different views on the phylogenetic position of this unique organism.