A Brazilian Marseillevirus Is the Founding Member of a Lineage in Family Marseilleviridae.

Fábio Dornas,Bernard La Scola,Thalita Arantes,Philippe Colson,Sarah Aherfi,Felipe Assis,Jônatas Abrahão

doi:10.3390/v8030076

Abstract

In 2003, Acanthamoeba polyphaga mimivirus (APMV) was discovered as parasitizing Acanthamoeba. It was revealed to exhibit remarkable features, especially odd genomic characteristics, and founded viral family Mimiviridae. Subsequently, a second family of giant amoebal viruses was described, Marseilleviridae, whose prototype member is Marseillevirus, discovered in 2009. Currently, the genomes of seven different members of this family have been fully sequenced. Previous phylogenetic analysis suggested the existence of three Marseilleviridae lineages: A, B and C. Here, we describe a new member of this family, Brazilian Marseillevirus (BrMV), which was isolated from a Brazilian sample and whose genome was fully sequenced and analyzed. Surprisingly, data from phylogenetic analyses and comparative genomics, including mean amino acid identity between BrMV and other Marseilleviridae members and the analyses of the core genome and pan-genome of marseilleviruses, indicated that this virus can be assigned to a new Marseilleviridae lineage. Even if the BrMV genome is one of the smallest among Marseilleviridae members, it harbors the second largest gene content into this family. In addition, the BrMV genome encodes 29 ORFans. Here, we describe the isolation and genome analyses of the BrMV strain, and propose its classification as the prototype virus of a new lineage D within the family Marseilleviridae.

Highlights

Until recently, the concept of “giant viruses” was completely unrecognized
In 2001, the Phycodnaviridae family was linked to other viral families including Iridoviridae, Poxviridae and Asfarviridae, which comprised a monophyletic group of viruses known as nucleocytoplasmic large DNA viruses (NCLDV) [2]
It was noted that no replication of Brazilian Marseillevirus (BrMV) took place in any Acanthamoeba polyphaga strain tested, and its replication was restricted to the A. castellanii tested lineages

Summary

Introduction

The concept of “giant viruses” was completely unrecognized. It emerged in 1982 after the discovery of Paramecium bursaria chlorella virus 1, which was classified in the Phycodnaviridae family that included giant viruses infecting algae [1]. The concept of a giant virus dramatically expanded and gained notoriety in 2003 with the discovery of Acanthamoeba polyphaga mimivirus (APMV), the prototype species of the Mimivirus genus, Mimiviridae family, isolated from the water of a cooling tower in Bradford, England by co-culturing with Acanthamoeba polyphaga [3]. Following the APMV discovery, dozens of members of this family were isolated, mostly from water, soil and, recently, from pneumonia patients, which confirmed previous evidence of their possible involvement in pneumonia [4,5,6,7,8,9,10]. Scientists were surprised by the mimivirus isolates due to their unique biological and molecular features, mainly their particle and genome sizes

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