The parasitic lifestyle of an archaeal symbiont

DPANN Archaea are a diverse group of organisms typically characterised by small cells and reduced genomes. To date, all cultivated DPANN Archaea are ectosymbionts that require direct cell contact with an archaeal host species for proliferation. However, the dynamics of DPANN – host interactions and the impacts of these interactions on the host species are poorly understood. Here, we show that one DPANN archaeon ( Candidatus Nanohaloarchaeum antarcticus) engages in parasitic interactions with its host ( Halorubrum lacusprofundi ) that result in host cell lysis. Our data also suggest that these interactions involve invasion of the host cell by the nanohaloarchaeon. This is the first reported instance of such a predatory-like lifestyle amongst Archaea and indicates that some DPANN Archaea may interact with host populations in a manner similar to viruses.