To infect a cell, a virus must be able to first find a suitable cell and then eject its genetic material into its host. This robot-like process has been observed in a virus called T7 and visualized by Ian Molineux, professor of biology at The University of Texas at Austin, and his colleagues.
Researchers found that the T7 virus has six tail fibers that are folded back against its capsid. The fibers extend as the virus locates a suitable host and as it “walks” across its host cell surface to find a site to infect.
Credit: From Hu et. al. 2013. Science Express.
The researchers show that when searching for its prey, the virus briefly extends — like feelers — one or two of six ultra-thin fibers it normally keeps folded at the base of its head.
Once a suitable host has been located, the virus behaves a bit like a planetary rover, extending these fibers to walk randomly across the surface of the cell and find an optimal site for infection.
At the preferred infection site, the virus goes through a major change in structure in which it ejects some of its proteins through the bacterium's cell membrane, creating a path for the virus's genetic material to enter the host.
After the viral DNA has been ejected, the protein path collapses and the infected cell membrane reseals.
"Although many of these details are specific to T7," said Molineux, "the overall process completely changes our understanding of how a virus infects a cell."
For example, the researchers now know that most of the fibers are usually bound to the virus head rather than extended, as was previously thought. That those fibers are in a dynamic equilibrium between bound and extended states is also new.
Molineux said that the idea that phages "walk" over the cell surface was previously proposed, but their paper provides the first experimental evidence that this is the case.
This is also the first time that scientists have made actual images showing how the virus's tail extends into the host — the very action that allows it to infect a cell with its DNA.
"I first hypothesized that T7 made an extended tail more than 10 years ago," said Molineux, "but this is the first irrefutable experimental evidence for the idea and provides the first images of what it looks like."
The researchers used a combination of genetics and cryo-electron tomography to image the infection process. Cryo-electron tomography is a process similar to a CT scan, but it is scaled to study objects with a diameter a thousandth the thickness of a human hair.
Molineux's co-authors are Bo Hu, William Margolin and Jun Liu from UT Health.
Additional contacts:Ian Molineux, Professor
Lee Clippard | EurekAlert!
Nesting aids make agricultural fields attractive for bees
20.07.2017 | Julius-Maximilians-Universität Würzburg
The Kitchen Sponge – Breeding Ground for Germs
20.07.2017 | Hochschule Furtwangen
Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.
For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...
What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.
To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...
The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....
A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...
Physics supports biology: Researchers from PTB have developed a model system to investigate friction phenomena with atomic precision
Friction: what you want from car brakes, otherwise rather a nuisance. In any case, it is useful to know as precisely as possible how friction phenomena arise –...
19.07.2017 | Event News
12.07.2017 | Event News
12.07.2017 | Event News
20.07.2017 | Information Technology
20.07.2017 | Materials Sciences
20.07.2017 | Physics and Astronomy