Siberian permafrost [image credit: Julian Murton / BBC]
Since viruses – and not much else – are in the news these days, here’s a reminder that they’re nothing new. If anything they’re less scary than in the distant past, judging by this story.
– – –
Giant viruses known as “Girus”, frozen in the permafrost from the remote landscapes of Siberia and the Antarctic are being studied by Michigan State University, reports HeritageDaily – Archaeology News.
The researchers have shed light on these enigmatic, yet captivating giant microbes and key aspects of the process by which they infect cells.
“Giant viruses are gargantuan in size and complexity,” said principal investigator Kristin Parent, associate professor of Biochemistry and Molecular Biology at MSU.
“The giant viruses recently discovered in Siberia retained the ability to infect after 30,000 years in permafrost.”
With the help of cutting-edge imaging technologies, this study developed a reliable model for studying giant viruses and is the first to identify and characterize several key proteins responsible for orchestrating infection.
Giant viruses are bigger than 300 nanometers in size and can survive for many millennia. For comparison, the rhinovirus — responsible for the common cold — is roughly 30 nanometers.
The outer shells — or capsids — are rugged and able to withstand harsh environments, protecting the viral genome inside. The capsids of the species analyzed in this study — mimivirus, Antarctica virus, Samba virus and the newly discovered Tupanviruses — are icosahedral, or shaped like a twenty-sided die.
These species have a unique mechanism for releasing their viral genome. A starfish-shaped seal sits atop one of the outer shell vertices. This unique vertex is known as the ‘stargate.’ During infection, the ‘starfish’ and ‘stargate’ open to release the viral genome.
During the study, several roadblocks needed to be addressed. “Giant viruses are difficult to image due to their size and previous studies relied on finding the ‘one-in-a-million’ virus in the correct state of infection,” Parent said.
To solve this issue, Parent’s graduate student Jason Schrad developed a novel method for mimicking infection stages. Using the university’s new Cryo-Electron Microscopy microscope and the university’s Scanning Electron Microscope, Parent’s group subjected various species to an array of harsh chemical and environmental treatments designed to simulate conditions a virus might experience during the infection process.
“Cryo-EM allows us to study viruses and protein structures at the atomic level and to capture them in action,” Parent said. “Access to this technology is very important and the new microscope at MSU is opening new doors for research on campus.”
The results revealed three environmental conditions that successfully induced stargate opening: low pH, high temperature and high salt. Even more, each condition induced a different stage of infection.
With this new data, Parent’s group designed a model to effectively and reliably mimic stages of infection for study.
“This new model now allows scientists to mimic the stages reliably and with high frequency, opening the door for future study and dramatically simplifying any studies aimed at the virus,” Parent said.
Full report here.
via Tallbloke’s Talkshop
May 10, 2020 at 01:54PM
Iowa Climate Science Education 