Cedratvirus, a Double-Cork Structured Giant Virus, is a Distant Relative of Pithoviruses.

Julien Andreani,Fabrizio Di Pinto,Idir Bitam,Philippe Colson,Jacques Bou Khalil,Didier Raoult,Bernard La Scola,Sarah Aherfi

doi:10.3390/v8110300

Abstract

Most viruses are known for the ability to cause symptomatic diseases in humans and other animals. The discovery of Acanthamoeba polyphaga mimivirus and other giant amoebal viruses revealed a considerable and previously unknown area of uncharacterized viral particles. Giant viruses have been isolated from various environmental samples collected from very distant geographic places, revealing a ubiquitous distribution. Their morphological and genomic features are fundamental elements for classifying them. Herein, we report the isolation and draft genome of Cedratvirus, a new amoebal giant virus isolated in Acanthamoeba castellanii, from an Algerian environmental sample. The viral particles are ovoid-shaped, resembling Pithovirus sibericum, but differing notably in the presence of two corks at each extremity of the virion. The draft genome of Cedratvirus—589,068 base pairs in length—is a close relative of the two previously described pithoviruses, sharing 104 and 113 genes with P. sibericum and Pithovirus massiliensis genomes, respectively. Interestingly, analysis of these viruses’ core genome reveals that only 21% of Cedratvirus genes are involved in best reciprocal hits with the two pithoviruses. Phylogeny reconstructions and comparative genomics indicate that Cedratvirus is most closely related to pithoviruses, and questions their membership in an enlarged putative Pithoviridae family.

Highlights

For 13 years, high-throughput culture isolation strategies and genomic analyses have led to the discovery of a considerable diversity of amoeba-infecting giant viruses
Its remarkable features include its morphological properties, the size of its virions, the two cork virions compared to one cork in previously described pithoviruses, and its gene content with a high proportion of ORFans
It has greater coding density and GC% compared to these pithoviruses, and a large set of 449 new genes, not detected in P. sibericum and in P. massiliensis, even when we used a low value for significance threshold

Summary

Introduction

For 13 years, high-throughput culture isolation strategies and genomic analyses have led to the discovery of a considerable diversity of amoeba-infecting giant viruses. These discoveries have revolutionized the definition of viruses, and have raised questions on the role of eukaryotic viruses in the evolutionary history of living organisms [1]. These two latter viruses were isolated from 30,000-year-old permafrost, demonstrating a conserved infectious effect for amoebas [7,8]. We describe a new giant virus isolate, morphologically and genetically close to pithoviruses, which was named

Methods

Results

Conclusion