The parasitic lifestyle of an archaeal symbiont

Abstract

DPANN Archaea are a diverse archaeal clade characterised by small cells and reduced genomes. To date, all cultivated DPANN Archaea are ectosymbionts that require direct cell cell interactions with a host archaeal species for proliferation. However, the dynamics of DPANN host interactions and the impacts of these interactions on host species are poorly understood. We show that the lifestyle of one DPANN archaeon (Candidatus Nanohaloarchaeum antarcticus) involves a cycle of attachment to host cells, invasion of the host cell cytoplasm, and subsequent lysis of the host cell. This is the first reported instance of such a predatory lifestyle amongst Archaea and indicates DPANN Archaea may be important players in microbial food webs across the biosphere. The internalisation of a symbiont cell within an archaeal host cell in the absence of phagocytotic machinery is relevant for models on the origin of the eukaryotic cell.

Selective lipid recruitment by an archaeal DPANN symbiont from its host

“…Nha. antarcticus appears to invade host cells during the process of interaction 26 and the preference for increased MK desaturation may similarly assist in survival during this stage of the symbiont’s lifecycle. The contrasting metabolic strategies employed by this nanohaloarchaeum compared to its host may therefore favor the selective acquisition of lipids seen in our data to maximize metabolic efficiency and survival.…”

“…In this study, we conducted a comprehensive analysis of the lipidome of the DPANN symbiont-host system consisting of Ca. Nanohaloarchaeum antarcticus – Halorubrum lacusprofundi 9, 26 . Ca.…”

“…Nha. antarcticus being a parasite that invades the host cytoplasm leading to host cell lysis 26 . Ca.…”

“…Purified cells were then pelleted by centrifugation at 20,000 g for 10 min and resuspended in 4 mL of DBCM2 media 54 . 100 µL of purified cells were stained with MitoTracker Green (as previously described 26 ) and Nile Red (1 µg/mL in 30% Salt Water (SW) mix 54 ) for 1 h and imaged on an Axio Imager M2 microscope to assess purity and possible contamination of cell debris. 100 uL of purified cells were pelleted, DNA extracted using a PeqGold DNA Blood and Tissue Extraction kit following the manufacturer's instructions (VWR), and PCR performed targeting both Ca.…”

“…Nha. antarcticus cells for use in co-culture experiments, nanohaloarchaeal cells were purified via filtration following previously described methods 26 . Briefly, 1 L of nanohaloarchaeal enrichment culture 9 was filtered sequentially through 0.8 µm (3x) and 0.2 µm (3x) polycarbonate filters (Isopore, Merck Scientific).…”