If there was any doubt that viruses are basically microscopic machines, let this recreation of a T7 bacteriophage infecting an ecoli cell put those reservations to rest. In this animated video, the virus can be seen unfolding its six phage tail fibers as it latches on to an unsuspecting bacterium. Once stable and secure, it pierces the surface of the cell with its extended tail and injects its DNA directly into the cytoplasm. Following this genetic violation, the tail disassembles, allowing the cell's membrane to reseal. Mission accomplished.

This video comes courtesy of biologist Bo Hu, Ian Molineux, and their colleagues at the University of Texas at Austin and the University of Texas Health Science Center at Houston. Their latest paper shows the various ways in which the T7 phage remodels itself as it works to infect a cell.

They made this discovery by using a combination of genetics and cryo-electron tomography to image the infection process. Similar in process to a CT scan, cryo-electron tomography allows researchers to study objects with a diameter a thousandth the thickness of a human hair.


Their research, which was published in the journal Science, has dramatically changed our understanding of how a virus physically changes as it infects a cell.


For example, previous to this study, researchers didn't know that a bacteriophage's legs were bound to the virus head prior to coming into contact with the cell. As the model now shows, the legs are individually deployed as feelers, helping the virus to discover a suitable victim and then latch on.

In addition, the researchers have now confirmed that phages "walk" over a cell surface as it works to stabilize and properly align itself in preparation for the next phase, namely ejection of its DNA into the host.

Interestingly, this is the first time that scientists have captured an actual image showing a virus's tail extending directly into a cell.

You can read the entire study at Science.

Images: Bo Hu, Ian Molineux.