Question

how did diversity emerge

Answer 1

10 years after the serendipitous discovery of the first giant virus (i.e., easily visible by light microscopy) Acanthamoeba polyphaga Mimivirus1, 2, environmental sampling in search of other Acanthamoeba-infecting viruses only succeeded in the isolation of additional members of the Mimiviridaefamily3, 4. Then, when we returned in 2013 to the Chilean coastal area from where we previously isolated Megavirus chilensis3, we isolated the even bigger Pandoravirus salinus5. Its unique characteristics suggested the existence of a different family of giant viruses infecting Acanthamoeba. The worldwide distribution of this predicted virus family, the proposed Pandoraviridae, was quickly hinted by our subsequent isolation of Pandoravirus dulcis more than 15 000 km away, in a freshwater pond near Melbourne, Australia5. We also spotted pandoravirus-like particles in an article reporting micrographs of Acanthamoeba infected by an unidentified “endosymbiont”6, the genome sequence of which has recently become available as that of the German isolate Pandoravirus inopinatum7.

Here we describe three new members of the proposed Pandoraviridae family that were isolated from different environments and distant locations: Pandoravirus quercus, isolated from ground soil in Marseille (France); Pandoravirus neocaledonia, isolated from the brackish water of a mangrove near Noumea airport (New Caledonia); and Pandoravirus macleodensis, isolated from a freshwater pond near Melbourne (Australia), only 700 m away from where we previously isolated P. dulcis. Following the characterization of their replication cycles in Acanthamoeba castellanii by light and electron microscopy, we analyzed the five pandoravirus strains available in our laboratory through combined genomic, transcriptomic, and proteomic approaches. We then used these data (together with the genome sequence of P. inopinatum) in a comparative manner to build a global picture of the emerging family and refine the genome annotation of each individual strain. While the number of encoded proteins has been revised downward, we unraveled hundreds of previously unpredicted genes associated to non-coding transcripts. From the comparison of the six representatives at our disposal, the Pandoraviridae family appears quite diverse in terms of gene content, consistent with a family for which many members are still to be isolated. A large fraction of the pan-genome codes for proteins without homologs in cells or other viruses, raising the question of their origin. The purified virions are made of more than 200 different proteins, about half of which are shared by all tested strains in well-correlated relative abundances. This large core proteome is consistent with the highly similar early infection stages exhibited by the different isolates.

Answer 2

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• ✒In the ancient times, a man was a nomad. It was only years later that he started living a social life by mingling with other people of the society. This made man a social animal. People cannot fulfil all their needs on the own. We depend on each other and also on the social groups to fulfil our needs. This is how we are understanding diversity.

• ✒The backgrounds such as religion, social status, and economic status cannot become barriers in making friends. Inequality comes only when a person does not have the resources and opportunities that are available to other persons. This led to the emergence of diversity.