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

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 and significant abundances of large virus-like particles in aquatic environments. We discovered new viral morphotypes, all likely to be associated with microeukaryotes. We also obtained insights into the multi-year dynamics of the abundances of both giant microeukaryotic virus-like particles and jumbo phage-like particles. This work deepens our understanding of large virus and reveals their key role as regulators of microbial communities.