The deep-ocean accounts for the majority of the water on our planet. While the cold deep-ocean is the dominant nutrient-challenged ecosystem, hydrothermal vents represent oases along tectonically active areas of the seafloor. Hydrothermal vents and the surrounding cold deep-ocean each support unique communities of microbes and viruses that have become highly adapted to local conditions. Through cycles of infection and host cell lysis, bacteriophages (viruses that specifically infect...