Morphologic and Genomic Analyses of New Isolates Reveal a Second Lineage of Cedratviruses

Abstract

Giant viruses have been isolated and characterized in different environments, expanding our knowledge about the biology of these unique microorganisms. In the last 2 years, a new group was discovered, the cedratviruses, currently composed of only two isolates and members of a putative new family, "Pithoviridae," along with previously known pithoviruses. Here we report the isolation and biological and genomic characterization of two novel cedratviruses isolated from samples collected in France and Brazil. Both viruses were isolated using as a host cell and exhibit ovoid particles with corks at either extremity of the particle. Curiously, the Brazilian cedratvirus is ∼20% smaller and presents a shorter genome of 460,038 bp, coding for fewer proteins than other cedratviruses. In addition, it has a completely asyntenic genome and presents a lower amino acid identity of orthologous genes (∼73%). Pangenome analysis comprising the four cedratviruses revealed an increase in the pangenome concomitant with a decrease in the core genome with the addition of the two novel viruses. Finally, phylogenetic analyses clustered the Brazilian virus in a separate branch within the group of cedratviruses, while the French isolate is closer to the previously reported Taking all together, we propose the existence of a second lineage of this emerging viral genus and provide new insights into the biodiversity and ubiquity of these giant viruses. Various giant viruses have been described in recent years, revealing a unique part of the virosphere. A new group among the giant viruses has recently been described, the cedratviruses, which is currently composed of only two isolates. In this paper, we describe two novel cedratviruses isolated from French and Brazilian samples. Biological and genomic analyses showed viruses with different particle sizes, genome lengths, and architecture, revealing the existence of a second lineage of this new group of giant viruses. Our results provide new insights into the biodiversity of cedratviruses and highlight the importance of ongoing efforts to prospect for and characterize new giant viruses.

The DNA methylation landscape of giant viruses

“…Cedratviruses are giant viruses morphologically and to some extant genetically related to pithoviruses 31 . Four completely sequenced genomes are available today: cedratvirus A11 21 , cedratvirus zaza 44 , cedratvirus lausannensis 31 , and brazilian cedratvirus 44 . We isolated a new strain of cedratvirus (named cedratvirus kamchatka) from a muddy grit soil sample collected near a lake at kizimen volcano, Kamchatka (Russian Federation N 55°05'50 E 160°20'58) (see Methods).…”

Discovery and Further Studies on Giant Viruses at the IHU Mediterranee Infection That Modified the Perception of the Virosphere

“…New members of the putative “ Pithoviridae ” family were isolated from Algerian, French, and Brazilian samples and named Cedratviruses [22,120,121]. Cedratviruses have elipsoid particles of ~1.0 µm but present some differences compared to other pithoviruses.…”

“…Cedratviruses replicate in Acanthamoeba cells, entering through phagocytosis and establishing a viral factory in the host cytoplasm, wherein a complex process of morphogenesis occurs, generating a viral progeny that is released mostly by cell lysis, although exocytosis is also possible [122]. Similar to pithoviruses, the cedratviruses have a large particle containing a relatively small circular genome (from 460,038 bp for Brazilian Cedratvirus to 589,068 for Cedratvirus A11), and are possible exceptions to the allometric law involving virion volume and genome length [121]. Those exceptions raised questions about DNA compaction and about macromolecules contained inside the particle particularly, where a lower density than the Mimivirus particle could be detected in Pithovirus [118].…”

“…Given the genomic variations we observed between Cedratvirus lineages, this particle size could be a powerful adaptation mechanism in light of evolution where the volume of the capsid does not become a constraint for the selection process and for genomic evolution. There are currently two lineages of Cedratviruses , a possible new genus of the expanding “ Pithoviridae ” family [121].…”

The DNA Methylation Landscape of Giant Viruses

“…Cedratviruses are giant viruses morphologically and to some extant genetically related to Pithoviruses (38). Four completely sequenced genomes are available today: Cedratvirus A11 (27), Cedratvirus zaza (54), Cedratvirus lausannensis (38) and Brazilian Cedratvirus (54). We recently isolated a new strain of Cedratvirus (named "Cedratvirus kamchatka") from a muddy grit soil sample collected near a lake at kizimen volcano, Kamchatka (Russian Federation N 55°05'50 E 160°20'58) (see Methods).…”