New Study Shines Light on Mysterious Giant Viruses

In recent years, giant viruses have been unearthed in several of the world's most mysterious locations, from the thawing permafrost of Siberia to locations unknown beneath the Antarctic ice. In a new study, a team of Michigan State University (MSU) scientists shed light on these enigmatic, yet captivating, giant microbes and key aspects of the process by which they infect cells. The study results were published online on May 8, 2020 in Cell. The article is titled "Structural and Proteomic Characterization of the Initiation of Giant Virus Infections." 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 diameter and can survive for many millennia. For comparison, the rhinovirus -- responsible for the common cold -- is roughly 30 nanometers in diameter. "Giant viruses are gargantuan in size and complexity," said principal investigator Kristin Parent, PhD, 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." 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 Tupan viruses -- 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.
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