Bacteria and Archaea are two domains of prokaryotes, which are microscopic organisms. Prokaryotes lack a nucleus and only contain ribosomes as organelles. A single loop of double-stranded DNA in a nuclear area, or nucleoid, contains the genetic material. Viruses are common biological entities, with an estimated 1031 virus particles on the planet at any given time. They infect a wide range of organisms, including animals, plants, microbes, and archaea. By managing the composition of bacteria and archaea in water and soil, prokaryotic viruses such as phage and archaeal viruses play a vital role in balancing the global environment. Because the virus depends on the host for survival, identifying the viral host is critical for characterizing the virus.