Unexpected diversity and ecological significance of uncultivable large virus-like particles in aquatic environments

Abstract

The discovery of Jumbo phages and giant viruses of microeukaryotes has transformed our perception of the virosphere. Metagenomic and metatranscriptomic data further highlight their diversity and ecological impact. Nevertheless, sequence-based approaches fail to take into account the morphological diversity of non-cultivated viruses, resulting in our fragmented understanding of their nature and role in the environment. Here, we combined flow cytometry and electron microscopy to uncover both previously unsuspected morphological diversity as well as significant abundances of large viruses in aquatic environments. We discovered four new viral morphotypes, all of which were associated with microeukaryotes. We also obtained insights into the multi-year dynamics of the abundances of both giant microeukaryotic viruses and Jumbo phages. This work deepens our understanding of large viruses and reveals their key role as regulators of microbial communities.