In order to map one of the world’s largest viruses, scientists took a DIY approach to build a retrofitted cryo-electron microscope.
“If the common cold virus is scaled to the size of a ladder, then the Giant Samba Virus is bigger than the Washington Monument,” says Kristin Parent, assistant professor of biochemistry and molecular biology at Michigan State University and coauthor of the paper in the journal Viruses. “Cryo-EM allowed us to map this virus’ structure and observe the proteins it uses to enter, or attack, cells.”
It seems counterintuitive that bigger organisms are harder to see, but they are when using cryo-electron microscopy. That’s because scientists usually use these microscopes to look at thin specimens. The microscopes can’t decipher larger organisms to reveal their biological mechanisms. For thick samples, scientists see only dark gray or black blobs instead of seeing the molecular framework.
Cryo-EM allowed Parent’s team to image the giant Samba virus and understand the structures that allow it to enter an amoeba. Once inside, Samba opens one of its capsid layers and releases its nucleocapsid—which carries the genetic cargo that sparks an infection. While Samba isn’t known to cause any diseases in humans, its cousin, the mimivirus, may be a culprit for causing some respiratory ailments in humans.
Posted by Dr. Tim Sandle
