blogging the latest developments in microbiology

Guest post: A wolf in sheep’s clothing (kind of)

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ResearchBlogging.orgLike bacteria, viruses have existed for millions of years, yet even after all this time we still don’t really know when or how they evolved. Viruses are grouped into families based on their genome, which can be either DNA or RNA.

Like all other organisms on Earth, viruses evolve, and they mix their genomes with each other in the environment to form new strains – which is why new flu strains appear each year. It was thought that viruses only mixed with others of the same family or with their close relatives, but researchers have discovered a new virus that seems to be a bit of a rule-breaker…

This virus, provisionally named BSL RDHV (Boiling Springs Lake RNA–DNA hybrid virus), is unusual because it seems to be a mix of both DNA and RNA viruses. A typical virus consists of genetic material (DNA or RNA) surrounded by a protein shell; the genetic material in this newly discovered virus is DNA, yet its shell contains a protein similar to those found in RNA viruses.

Through an unusual recombination event, the DNA virus seems to have picked up a gene from an RNA virus. Whereas DNA–DNA and RNA–RNA recombinations are well understood, we don’t understand how DNA–RNA recombinations work.

The new virus was discovered by researchers in the acidic Boiling Springs Lake at Lassen Volcanic National Park, USA. The researchers collected and analysed samples of DNA from the lake’s sediment, identifying the virus and its unusual RNA-derived gene. This technique, known as metagenomics, allows scientists to investigate genetic material from environmental microorganisms directly, instead of first growing them in the lab.

This new discovery is an important step in understanding virus evolution: it seems likely that RNA viruses evolutionarily preceded DNA viruses, so the authors speculate that the incorporation of RNA genes by DNA viruses might help to explain this branch of evolution.

Sruthi Raghavan

Sruthi is a freelance science writer

Diemer, G., & Stedman, K. (2012). A novel virus genome discovered in an extreme environment suggests recombination between unrelated groups of RNA and DNA viruses Biology Direct, 7 (1) DOI: 10.1186/1745-6150-7-13

Image Credit: Dave Faris on Flickr

Written by microbelog

07/06/2012 at 1:05 pm

One Response

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  1. Quote from the conclusion section of the article: “Any instance in which an RNA cistron is converted into DNA and then integrated into a DNA genome presumably involves a reverse-transcriptase (RT)
    mechanism. However, no trace of a RT module exists in the BSL RDHV.”

    Couldn’t it be that the RNA cistron was first horizontally transferred to a retrovirus, where the reverse-transcription occured, and then the reverse-transcribed sequence was again horizontally transferred to BSL RDHV where the recombination into its genome happened?

    Ilkka Nousiainen

    08/06/2012 at 7:07 pm

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