Simon Roux

Sullivan Lab, Department of Microbiology, Ohio State University
 

The ecological importance of viruses is now widely recognized, yet our
limited knowledge of viral sequence space and virus‑host interactions precludes accurate
prediction of their roles and impacts. Notably, while studies of microbial
taxonomic diversity and ecology were transformed by the emergence of 16S
rRNA sequencing, viruses lack such a universally‑conserved marker gene. Combined
with the difficulty of isolating environmental viruses in the lab (with the
vast majority of potential hosts not cultivated), this leads our current
description of the global viral diversity to be largely incomplete. Pragmatically, studies of environmental viral
diversity all highlighted the high level of genetic novelty found in viral
genomes and, through sample‑to‑sample comparisons, revealed ecological
drivers of this viral diversity, but were limited until very recently to gene‑level
analysis. In the last years, genome‑level information on viral diversity
has been progressively uncovered, especially through (i) the mining of viral
signal from microbial genomes, and (ii) viral metagenomics approaches allowing
for a comprehensive characterization of a sample viral diversity. In both cases,
working with genomes allows for a robust definition and classification of
viral genotypes, and provides glimpses into long‑term evolutionary interactions
between viruses and host cells. A more detailed view of viruses infection
modes, regulations, and potential co‑infection patterns can also be gained
from the viral signal in microbial genomes, while viral metagenomes provide a
broader picture of viral diversity, with the possibility to identify keys
players in environmental communities and new means by which viruses can
impact their host cell metabolism. Overall, these large‑scale sequence analysis
associated with the development of new virus‑host model systems and
techniques such as single‑virus genomics should help us progress toward a
comprehensive characterization of viruses of microbes, direly needed in order to include
viruses, the most abundant biological entities on Earth, into global ecosystem models.