Coevolution and cross-infection patterns between viruses and their host methanogens in paddy soils

Methanogens play a critical role in global methane (CH₄) emissions from rice paddy ecosystems. Through the integration of metagenomic analysis and meta-analysis, we constructed a CRISPR spacer database comprising 14 475 spacers derived from 351 methanogenic genomes. This enabled the identification of viruses targeting key methanogenic families prevalent in rice paddies, including Methanosarcinaceae, Methanotrichaceae, Methanobacteriaceae, Methanocellaceae, and Methanomassiliicoccaceae. We identified 419 virus-host linkages involving 56 methanogenic host species and 189 viruses, spanning the families Straboviridae, Salasmaviridae, Kyanoviridae, Herelleviridae, and Demerecviridae, along with 126 unclassified viral entities. These findings highlight a virome composition that is markedly distinct from those observed in gut environments. Cross-infection patterns were supported by the presence of specific viruses predicted to infect multiple closely related methanogenic species. Evidence for potential virus-host coevolution was observed in 24 viruses encoding anti-CRISPR proteins, likely facilitating evasion of host CRISPR-mediated immunity. Collectively, this study reveals a complex and dynamic network of virus-host interactions shaping methanogen communities in rice paddy ecosystems.