Unraveling the diversity, function, and virus-host interactions of archaeal proviruses

Archaea, the third domain of life, play critical roles in global biogeochemical cycles. However, archaeal proviruses integrated into host genomes remain largely unexplored. To bridge this gap, we conducted a large-scale mining of genomes spanning all presently known 21 archaeal phyla for their proviruses. We identified 770 archaeal proviruses across 12 archaeal phyla and 84 families, which clustered into 655 viral operational taxonomic units (vOTUs). Among these, 86.1% of the vOTUs were novel at the species level, and 69.3% could not be classified at the family level, substantially expanding the known diversity of archaeal viruses. Additionally, phylogenomic analysis supported the proposal of 16 putative novel viral families, further extending the current taxonomy landscape of archaeal viruses. Notably, 21.8% of the identified proviruses were predicted to adopt a lytic lifestyle, suggesting that these proviruses may retain the capacity to enter the lytic cycle under appropriate conditions. Host prediction indicated only 14 out of the 655 vOTUs might have potential across-lineage infection abilities. We detected 63 anti-defense genes encoded by 61 provirus genomes, such as anti-CRISPR and anti-RM, suggesting an ongoing evolutionary arms race between hosts and proviruses. However, only 10 auxiliary metabolic genes (AMGs) were identified, suggesting a limited impact of proviruses in the modulation of host metabolism through AMGs. This study establishes a systematic global genomic atlas of archaeal proviruses, advancing our understanding of their distribution and diversity while providing a foundation for future research into how proviruses regulate archaeal metabolism and ecosystem functioning.