Extremophile Virus SIRV2 Could Help Kill Anthrax, Other Pathogens

An unusual virus called Sulfolobus islandicus Rod-shaped Virus 2 (SIRV2 for short) could be a new weapon in the fight against pathogens, says an international group of researchers co-led by Dr David Prangishvili of Institut Pasteur in France and Dr Edward Egelman of the University of Virginia School of Medicine.

Transmission electron micrograph (false-color) of negatively stained SIRV2 particles. Image credit: Nicole Steinmetz et al.

SIRV2 belongs to a common crenarchaeal virus family, the Rudiviridae. It was first discovered in 1998 in the hot acidic sulfurous springs of Iceland.

According to previous studies, SIRV2 infects Sulfolobus islandicus, a single-celled microorganism that grows optimally at 80 degrees Celsius and at pH 3. The virus has a very stable rod-shaped viral capsule, about 900 nm long and 23 nm in width.

Now, Dr Prangishvili, Dr Egelman and their colleagues have used cryo-electron microscopy to generate a 3D reconstruction of the SIRV2 virion, which revealed a previously unknown form of virion organization.

The team identified surprising similarities between SIRV2 and the spores bacteria form to survive in inhospitable environments.

“Some of these spores are responsible for very, very horrific diseases that are hard to treat, like anthrax. So we show in this study that this virus actually functions in a similar way to some of the proteins present in bacterial spores,” said Dr Egeleman, who is the senior author on the paper published in thejournal Science.

“Understanding how these bacterial spores work gives us potentially new abilities to destroy them,” he said.

Dr Egeleman and co-authors also found that SIRV2 survives the inhospitable conditions by forcing its DNA into what is called A-form, a structural state identified by pioneering DNA researcher Rosalind Franklin more than a half-century ago.

“This is, I think, going to highlight once again the contributions she made, because many people have felt that this A-form of DNA is only found in the laboratory under very non-biological conditions, when DNA is dehydrated or dry. Instead, it appears to be a general mechanism in biology for protecting DNA,” Dr Egelman said.

References

Frank DiMaio et al. 2015. A virus that infects a hyperthermophile encapsidat es A-form DNA. Science, vol. 348, no. 6237, pp. 914-917; doi: 10.1126/science.aaa4181May 27, 2015 by Sci-News.com

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