First evidence of host range expansion in virophages and its potential impact on giant viruses and host cells

Said Mougari; Nisrine Chelkha; Dehia Sahmi-Bounsiar; Fabrizio Di Pinto; Philippe Colson; Jonatas Abrahao; Bernard La Scola

After the lysis of host cells coinfected with Guarani and Tupanvirus Deep Ocean or Tupanvirus Soda Lake, each culture supernatant was filtered through 0.22-µm-pore filters to remove giant virus particles. The obtained supernatants containing only Guarani particles were subsequently used to infect fresh A. castellanii cells simultaneously inoculated with Tupanvirus Deep Ocean or Tupanvirus Soda Lake. The replication of the virophage was then measured by qPCR. In these assays, Guarani remarkably infected and successfully replicated with both Tupanvirus Deep Ocean and Tupanvirus Soda Lake after only one passage with each virus (Fig. 2a and 2b) . We interpreted this phenomenon as the result of a mechanism of host range expansion that allowed Guarani to replicate with new viral hosts previously resistant to this virophage. A small fraction of the Guarani population in our stocks was likely composed of an emergent mutant able to infect Tupanvirus. We found that Guarani isolated author/funder. All rights reserved. No reuse allowed without permission.