In a rare first, scientists have captured images of a virus in the very act of infecting an E. coli bug, and the structural changes that it undergoes.

A virus must be able to find a suitable cell and then eject its genetic material into its host to infect it. This process has been observed in a virus called T7 and visualised by researchers at the University of Texas. Researchers used a combination of genetics and cryo-electron tomography to image the infection process. It is similar to a CT scan, but it is scaled to study objects a thousand times thinner than human hair.

How T7 infects

The image showed that when searching for its prey, the virus briefly extends one or two of six ultra-thin fibres it normally keeps folded at the base of its head.

Once a suitable host has been located, the virus extends these fibres to walk across the surface of the cell and find an optimal site for infection. Once they do, the virus alters its structure and transfers its genetic material into the host.

After this the protein path collapses and the infected cell membrane reseals.

How important is this?

“The overall process completely changes our understanding of how a virus infects a cell.” Researchers now know that most of the fibres are usually bound to the virus head rather than extended, as was previously thought.IANS