Pera virus mimics bacteria to infect Pedopumella sp. a freshwater heterotrophic Chrysophyceae

Heterotrophic Chrysophyceae play a key role in the functioning of many aquatic food webs as primary predators of prokaryotes, but their top-down regulatory factors are poorly understood. To date, no virus isolates from heterotrophic Chrysophyceae have been described in the literature. Here we describe Pera virus, a giant virus infecting the heterotrophic Chrysophyceae Pedospumella sp.. Pera virus have an icosahedral capsid-vesicle morphology, a feature unprecedented in viruses. We hypothesize that this vesicle mimics the shape of bacteria so that the virus is recognized as such by its bacteriophage protist host. This constitutes a morphological evolution of viruses that promotes infection of their heterotrophic host. The capside measures 414 nm in diameter. The vesicle has a variable diameter ranging from 231 to 587 nm. The virion as a whole can reach 1008 nm in length. We searched for this new type of virus under environmental conditions during time series studies in hyper-eutrophic freshwater lakes. Surprisingly, we report the existence of Pera virus-like particles (PVLs) of various shapes and size that can reach 5 {micro}m illustrating the hidden diversity of this undescribed virus types. The dynamics of PVLs, which can reach 2.4 x 105 PVL.mL-1, are closely associated with those of unicellular heterotrophic eukaryotes, acting as major regulatory agents of protozoan bacterivory in freshwater. This pair provides a new model for understanding the evolution of giant viruses and their ecological role.