Prof. Edward C. HOLMES
NHMRC Australia Fellow,
University of Sydney, Australia
Redefining the Virosphere
Our knowledge of RNA virus biodiversity is both biased and fragmentary. Here I will describe a meta-transcriptomic study of ~220 invertebrate species sampled across nine animal phyla. This revealed the presence of 1445 novel RNA viruses, including some sufficiently divergent to comprise new families. Strikingly, viruses comprised a substantial proportion of total RNA in many of the invertebrates sampled. The newly identified viruses filled major gaps in the RNA virus phylogeny, and revealed an evolutionary history characterized by both host switching and co-divergence that likely extends for more than a billion years. The invertebrate virome was also characterized by remarkable genomic flexibility, including frequent recombination, lateral gene transfer among viruses and hosts, gene gain and loss, and complex genomic rearrangements. Together, these data present a view of the virosphere that is more phylogenetically and genomically diverse than depicted in current classification schemes.