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Newly discovered complex viruses challenge what we think viruses are

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complex viruses/Abraho et al

As Peter Dockill explain at Science Alert,

Scientists have discovered two new kinds of virus in Brazil that display such size and genetic complexity we may need to rethink exactly what viruses are, scientists say.

The two new strains – dubbed Tupanvirus, after the Brazilian thunder god Tupã in Guaraní mythology – are as prodigious as their namesake, and while they’re not a threat to humans, their existence further challenges the scientific boundaries that define what a virus is.

Tupanvirus soda lake and Tupanvirus deep ocean, both named in relation to the extreme aquatic habitats in which they were discovered, aren’t just among the largest viruses ever found – they also contain the most protein-making machinery of any virus discovered to date.

Before Mimivirus, viruses were largely considered wholly separate from ‘living’ creatures, with their inability to synthesise proteins (and thus produce their own energy) being one of the reasons scientists excluded them from being classified among cellular life.

But Mimivirus’s genetic complexity – and that of other giant viruses that have subsequently been discovered – challenges this theoretical boundary, because they carry genes capable of things like DNA repair, DNA replication, transcription, and translation.

At Nature Communications:

Here we report the discovery of two Tupanvirus strains, the longest tailed Mimiviridae members isolated in amoebae. Their genomes are 1.44–1.51 Mb linear double-strand DNA coding for 1276–1425 predicted proteins. Tupanviruses share the same ancestors with mimivirus lineages and these giant viruses present the largest translational apparatus within the known virosphere, with up to 70 tRNA, 20 aaRS, 11 factors for all translation steps, and factors related to tRNA/mRNA maturation and ribosome protein modification. Moreover, two sequences with significant similarity to intronic regions of 18 S rRNA genes are encoded by the tupanviruses and highly expressed. In this translation-associated gene set, only the ribosome is lacking. At high multiplicity of infections, tupanvirus is also cytotoxic and causes a severe shutdown of ribosomal RNA and a progressive degradation of the nucleus in host and non-host cells. The analysis of tupanviruses constitutes a new step toward understanding the evolution of giant viruses.(public access) –
Jônatas Abrahão, Lorena Silva, Ludmila Santos Silva, Jacques Yaacoub Bou Khalil, Rodrigo Rodrigues, Thalita Arantes, Felipe Assis, Paulo Boratto, Miguel Andrade, Erna Geessien Kroon, Bergmann Ribeiro, Ivan Bergier, Herve Seligmann, Eric Ghigo, Philippe Colson, Anthony Levasseur, Guido Kroemer, Didier Raoult & Bernard La Scola, Tailed giant Tupanvirus possesses the most complete translational apparatus of the known virosphere, Nature Communicationsvolume 9, Article number: 749 (2018) doi:10.1038/s41467-018-03168-1 More.

See also: Should NASA look for viruses in space? Actually, it’s not clear that RNA came first. Nor is it clear that viruses precede life. A good case can doubtless be made for viruses being part of the scrap heap of existing life. But no matter. If you think you can find viruses in space, boldly go.

Why viruses are not considered to be alive

Another stab at whether viruses are alive

Phil Sci journal: Special section on understanding viruses

Why “evolution” is changing? Consider viruses

The Scientist asks, Should giant viruses be the fourth domain of life? Eukaryotes, prokaryotes, archaea… and viruses?

Viruses are alive.

and

Are viruses nature’s perfect machine? Or alive?

4 Replies to “Newly discovered complex viruses challenge what we think viruses are

  1. 1
    polistra says:

    Tupanvirus soda lake and Tupanvirus deep ocean …

    Isn’t this nomenclatural discrimination? Privileging the “living” with Latin species names and deprivileging the “non-living” with racist English? Get ready for a viral protest by viral rights protesters!

  2. 2
    News says:

    Yeah, polistra at 1: Sure to go viral. 😉

  3. 3
    critical rationalist says:

    How does this support ID?

    We were surprised? But, we expect to find various levels of replication fidelity, such as RNA viruses, which exhibit low fidelity and Eukaryotic cells with high-fidelity.

    IOW, this is yet another example of a gradation of replication fidelity actually found in nature.

  4. 4
    Peer says:

    Genetic Analysis will demonstrate we are dealing with bacteria, which acquired a virus-like coat. Like Mimivirus, which can be genetically tracked back to a soil bacterium. There is one law in biology: Everything goes as long as reproduction goes.

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