Diverse viruses have restricted biogeography in deep-sea hydrothermal vent fluids

Abstract:

Marine viruses regulate biogeochemical cycling, alter microbial population structure, and manipulate microbial genetic potential. While previous research has found deep-sea hydrothermal vents to host diverse and abundant populations of chemolithoautotrophic bacteria and archaea, relatively little is known about the viruses that inhabit diffuse vent fluids. We examined viral diversity, abundance, and virus-host interactions in three hydrothermal vent fields: Piccard vent field and Von Damm vent field at the Mid-Cayman Rise in the Caribbean Sea, and Axial Seamount in the Pacific Ocean. These vent fields are not only geographically distant, they also host geochemically distinct venting fluids. Through a metagenome-based analysis, we found a high diversity of viruses with very few viruses shared between vent fields, as well as an abundance of lysogenic viruses. Over 40% of metagenome-assembled genomes contained a putative prophage, emphasizing the importance of the lysogenic viral life cycle at these vents. Using virus-host interaction networks based upon CRISPR sequences, we found viral infection to be highly host-specific and spatially restricted; viruses rarely infected different microbial lineages or microbial hosts at multiple vents. However, virus-host interactions were often conserved over multiple years. Thus, while viruses appear to be diverse, abundant, and active at the Mid-Cayman Rise and Axial Seamount vents, their role in mediating horizontal gene transfer between vents and hosts is relatively restricted. Future work examining viral diversity and distribution across higher resolution transects over space and time should reveal further insights into the extent of the viral influence in deep-sea hydrothermal vents.