Nutrient availability affects optimal growth strategy in predatory DPANN

The DPANN archaea comprise a major microbial lineage that appears to be primarily host dependent. Despite the relative ubiquity of DPANN archaea across the biosphere, our understanding of their ecological role is limited due to the absence of cultivated representatives for most DPANN lineages. The majority of cultivated DPANN species are characterized as mildly parasitic ectosymbionts due to reliance on physical interactions with host cells. However, Candidatus Nanohaloarchaeum antarcticus has been reported to adopt a predatory lifestyle, resulting in the lysis of large numbers of host cells. The factors influencing DPANN-host interactions that drive Ca. Nha. antarcticus to adopt an aggressive lifestyle, although other DPANN appear not to, remain unclear. Here, I present a framework for understanding the ecological pressures specific to the Ca. Nha. antarcticus-Halorubrum lacusprofundi system and why a more aggressive, predatory lifestyle improves population persistence compared with a lifestyle more similar to other DPANN.