Research on bacteriophages is extensive, but knowledge about viruses targeting archaea, especially non-extremophilic ones in mesophilic environments, is limited. This project focuses on viral infections of Methanoarchaea, aiming to bridge knowledge gaps by studying the interactions between M. mazei and MetSV, both genetically tractable, on molecular, mechanistic, and cellular levels. We will examine the virus replisome, the roles of viral and host proteins, and the host response to infection using genetical, imaging and biochemical approaches including structural analysis. Additionally, we aim to isolate novel methanoarchaeal viruses from a biogas reactor. Here our study builds on in-depth bioinformatics analysis of a comprehensive metagenomic dataset from a biogas reactor with a significant methanoarchaeal population. The biogas reactor was sampled over two years and metagenomic and metatranscriptomic datasets were generated. We aim to identify archaeal DNA and RNA viruses infecting methanoarchaeal hosts as well isolate specific viruses using the identified host for enrichments.