"Mythological Beast of a Virus" Found in Californian Hot Spring

By Sarah Zhang | April 23, 2012 10:37 am

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The lair of the “beast” in Lassen Volcanic National Park

It’s not often that a scientist will say “mythological beast” with a straight face, but that’s exactly what virologist Ken Stedman told Nature News about a new virus. In a recent paper in Biology Direct, Stedman and his research team describe a genetic sequence that suggests the existence of a DNA-RNA chimera virus.

RNA and DNA viruses, referring to the type of nucleic acid they use to store genetic information, are two very distinct groups—probably more evolutionary distant than a lion and a snake. That’s why researchers were so surprised when they found a DNA virus sequence encoding a protein only ever found in RNA viruses. The sample came from a Lassen Volcanic National Park hotspring, where viruses prey on the bacteria living in the acidic water.

As reported by Nature News, the researchers see two possible explanations for the hybrid virus:

In one scenario, an RNA virus, a DNA virus and a retrovirus infected the same cell at the same time; the retrovirus used its reverse transcriptase enzyme to translate the RNA gene into a DNA copy, which got lumped in with the DNA virus genome. Such a scenario might also work if there was free-floating reverse transcriptase present in the environment. Alternatively, a special kind of viral ligase protein — which glues nucleic acids together — may have joined the dissimilar DNA and RNA strands, with the resultant hybrid code then replicated into DNA. Both scenarios are possible, if a bit far-fetched, says Stedman.

If either of those scenarios are true, it suggests that viral evolution and the ability of different viruses to swap genes is more widespread and general than we had thought. Moreover, the authors looked at other viral sequences and suggest that this hybridization may have occurred independently in viruses elsewhere too. If so, that makes the existence of this “mythological beast” is not so unique or mythological after all.

But considering how novel a DNA-RNA chimera virus would be, we should probably wait to hear confirmation on the discovery. This study relies on sequencing from an environmental sample that contain many different types of viruses. In this method, all DNA in the sample is chopped up, sequenced, and then individual viral genomes reconstructed using computer algorithms—a process that is not always perfect.

[via Nature News]

Image via Flickr / jankgo


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