THE DEEP VIROSPHERE: ASSESSING THE VIRAL IMPACT ON MICROBIAL COMMUNITIES IN THE DEEP SUBSURFACE

There is little information on the nature of viral impact on microbial communities in deep subsurface environments. Yet the few details emerging, provide evidence for a high incidence of viruses in some deep subsurface environments and that their influence on the microbial communities could be profound on many levels. Viral infection may significantly impact biogeochemical cycling in he subsurface through lysis of cells, releasing nutrients and organic compounds that would otherwise be entrained in biomass. Viruses are also known to alter the structure of the microbial communities they infect, potentially increasing overall diversity through lysis of cells that become most abundant. Moreover, through the process of lysogeny (the viral genome is incorporated into the host genome) and transduction (viral mediated transfer of genes to the host), viruses may manipulate the genomes and gene expression of the hosts they infect throughout the subsurface, effectively resulting in mutualistic, symbiotic relationships between host and virus that transcends the common notion of viruses as parasites. Single or multiple viral genomes incorporated into host genomes (genomic islands) can impart new physiological traits including energy yielding metabolisms and ability to enter into mutualistic and parasitic interactions with other organisms. Indeed, the role of virus as parasite, as mutualist, and as a sharer of information through gene transfer may be a fundamental underpinning of life in the deep subsurface that extends back in time to the dawn of life itself.

In this presentation, we will provide an overview of viral life cycles, the types of viruses in the deep subsurface, and the potential role of viruses in different subsurface environments with a focus on the marine subsurface.