Current knowledge and clinical perspectives for a unique new phylum: Nanaorchaeota

Nanoarchaea measuring less than 500 nm and encasing an average 600-kb compact genome have been studied for twenty years, after an estimated 4193-million-year evolution. Comprising only four co-cultured representatives, these symbiotic organisms initially detected in deep-sea hydrothermal vents and geothermal springs, have been further distributed in various environmental ecosystems worldwide. Recent isolation by co-culture of Nanopusillus massiliensis from the unique ecosystem of the human oral cavity, prompted us to review the evolutionary diversity of nanaorchaea resulting in a rapidly evolving taxonomiy. Regardless of their ecological niche, all nanoarchaea share limited metabolic capacities correlating with an obligate ectosymbiotic or parasitic lifestyle; focusing on the dynamics of nanoarchaea-bacteria nanoarchaea-archaea interactions at the morphological and metabolic levels; highlighting proteins involved in nanoarchaea attachment to the hosts, as well metabolic exchanges between both organisms; and highlighting clinical nanoarchaeology, an emerging field of research in the frame of the recent discovery of Candidate Phyla radiation (CPR) in human microbiota. Future studies in clinical nanobiology will expand knowledge of the nanaorchaea repertoire associated with human microbiota and diseases, to improve our understanding of the diversity of these nanoorganims and their intreactions with microbiota and host tissues.