EXPANDING THE SAMPLE. “Additional genomic exploration among the still largely uncharacterized TACK and DPANN archaea (a newly recognized monophyletic superphylum) cannot but further narrow the prokaryote–eukaryote gap.” (TACK = phyla comprising Thaumarchaeota, Aigarchaeota, Crenarchaeota, and Korarchaeota).
http://www.pnas.org/content/112/33/10278.full