Virus caught in the act of infecting a cell (w/ video)

Jan 10, 2013

The detailed changes in the structure of a virus as it infects an E. coli bacterium have been observed for the first time, report researchers from The University of Texas at Austin and The University of Texas Health Science Center at Houston (UT Health) Medical School this week in Science Express.

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.

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.

This video is not supported by your browser at this time.
Animation of T7 infection. Credit: Science, AAAS.

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 , creating a path for the virus's genetic material to enter the host.

After the 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 that this is the case.

This is also the first time that scientists have made actual images showing how the '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.

Explore further: Researchers successfully clone adult human stem cells

More information: Paper: "The Bacteriophage T7 Virion Undergoes Extensive Structural Remodeling During Infection," by B. Hu et al: www.sciencemag.org/content/early/2013/01/09/science.1231887

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User comments : 3

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Caliban
1 / 5 (1) Jan 11, 2013
I dunno,

That animation looks more like them damn Nazis invading the Sudetenland, to me.

Who knew Hitler was really a virus?

That must be how they was able to replicate his ass down there in Brazil...

Caliban
not rated yet Jan 11, 2013
@Caliban: Whole Internet is full of bored kids, who are just replacing their qualification for matter-of-fact discussion with unflagging sense of humor. Such a silly attempts for joke are rather worth of reddit or Facebook comment section. You can see the real-life TEM video at http://www.scienc...uppl/DC1


Thanks for the link.

Unfortunately, I'm not keen on downloading unkown file types to my computer. I'm sure you are aware of the risks.

Too bad you didn't appreciate my little joke. I had a purpose in mind when posting it here rather than reddit, or some such.

RealScience
not rated yet Jan 11, 2013
@natello - thanks for the link.
I see that you have 'lite' disease - a reflexive '1' rating from 'lite' even when you post something useful. Here's a '5' to even the score.

I chanced the video, and I an attest that the cartoon animation is a pretty good animation of what the electron microscope video shows.

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