Newly discovered viral genome has implications for theories of viral evolution

A ‘fishing expedition’ in an acidic, high temperature lake has led to the discovery of a previously unknown group of viruses, which might change the way we think about viral evolution.

Publishing today in Biology Direct, Kenneth Stedman and colleagues describe their metagenomic approach to investigating viral diversity in Boiling Springs Lake in Lassen National Park, California, which sustains a purely microbial ecosystem in water between 52-95°C, and at a pH of ~2.5. Here they found a unique viral genome: a circular, single-stranded DNA virus which encodes a major capsid protein, a protein which until now has only been seen in RNA viruses.

This unusual genome appears to be the result of a recombination event between unrelated RNA and DNA viruses, where at some point in evolution a DNA virus genome has incorporated the gene encoding the capsid protein, suggesting that recombination can occur between significantly diverse viral lineages.

As no mechanisms for interviral RNA-DNA recombination have yet been identified, observation of this group of viruses throws new light on theories of virus evolution.

Lead author Stedman said, “As more viral metagenomic data are generated and analyzed, additional evidence of recombination between RNA and DNA virus groups will likely be discovered. The discovery that novel virus groups can emerge via recombination between highly disparate virus types will have broad implications for the early evolution of viruses and extends the modular theory of virus evolution to encompass a much broader range of possibilities than previously thought.”

Stedman and colleagues go on to compare this novel virus genome with other metagenomic DNA sequences from the Global Ocean Survey, and found strong evidence to suggest that previously undetected viruses of this kind could well be widespread. Eugene Koonin, co-Editor-in-Chief of Biology Direct comments in his review of the work that “one cannot help wondering how many of such unexpected wonders of the virus world await in all kinds of environments”.

Koonin’s review of the research is available in full as part of the article – Biology Direct’s novel
approach to peer review requires that the comments of the reviewers (who are selected from the Editorial Board by the authors) are both public and named, with the aim of increasing the responsibility of the referees and eliminating sources of abuse in the refereeing process. More information on Biology Direct’s scheme of peer review are outlined in the launch Editorial, and in the journal information pages.

Boiling Springs Lake, Lassen National Park, USA. Original image here: http://en.wikipedia.org/wiki/File:Boiling_Springs_Lake_Lassen_NP.jpg 

Image:  Boiling Springs Lake, Lassen National Park, USA. Creative commons.

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