An Overview of Viruses for Light Microscopists
A 3D modelling article
by Mol Smith 2010
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  Scale  Herpes Virus  T4 Virus  Influenza Virus   Resources and external links
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The T4 Virus
This is often the typical virus shown in school text books. What a formidable looking structure it has - like something out of a country's military weapon's system. This is a Bacteriophage Virus - one that invades bacteria rather than animal cells directly - and it one of a variant of the T4 classification group. This one typically attacks the e-coli bacterium.








Below is a diagram I made using a 3D model of a T4 virus invading a bacterium cell. The various elements of the structure have been correctly labeled. The internal DNA/RNA genetic material is not visible in this diagram. Bacteriophages do not just adhere randomly to the host cell's exterior wall. They 'home-in' on and are attracted to specific receptor sites. These sites will differ from phage to phage but can include any part of the bacterium cell, including flagella and pili.


Once the virus has 'landed' on a specific receptor site, all the tail fibres settle down onto the surface and the base plate become firmly seated on the cell wall, and the tail sheath contracts (the sheath contains ATP
WIKI which is thought to power this contraction). The central tube is pushed through the cell wall membrane and the viral DNA is extruded from the head down through the tail tube and into the interior of the Bacterium cell. The mechanism for this action is unknown. The process by which the injected DNA combines with the host cell process is too detailed and complicated to be explored here, but it is sufficient to say that invasion of a single e-coli bacteriophage will replicate itself up to 300 times and at a very rapid rate - faster than viruses which infect pant and animal cells.


I have produced a 3D model animation of a T4 virus locating and attaching to a Bacterium (below), which I have '
artistically positioned' inside a blood vessel. So please note, this is not where e-coli actually are likely to be found: it just looked cool!



LOOK AT THIS!!!!


If you look carefully at the approaching T4 Virus, you will see I have made the head transparent, so you can see the genetic material inside, and its journey down through the viral tube through the bacterium cell wall and into the interior.

Perhaps one of the most common viruses affecting us humans and causing annual misery is the
Influenza Virus, which we can take a quick look at here...

     
     


Comments to the author
Mol Smith are welcomed.

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Published in Mar 2010 Micscape Magazine.
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