[Enigmatic archaeal viruses].

Viruses infecting microorganisms of the third domain of life, Archaea, are still poorly characterized: to date, only about fifty of these viruses have been isolated. Their hosts are hyperthermophilic, acidothermophilic, and extreme halophilic or methanogenic archaea. Their morphotypes are highly diverse and their gene content is very specific. Some of these viruses have developed extraordinary mechanisms to open the cell wall thanks to the formation of exceptional pyramidal nanostructures. The still limited knowledge about the biology of archaeoviruses should develop rapidly in the coming years.