Moselio Schaechter


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« Adhering To The 'Replicon Model' The Sloppy Way | Main | Death Toll to Persisters »

February 06, 2014

Pictures Considered #13. How Many Things Can Be Illustrated In One Picture?

by Elio

This transmission EM of a thin section of a T2 phage infecting an E. coli cell was produced by Lee Simon in the late 1960’s. It is noteworthy for depicting a remarkably large number of properties of the phage and of the infection process. Can you figure out how many such characteristics are illustrated or at least strongly hinted at? I came up with nearly a dozen (see below). How about you?

Figure1 I am grateful to Lee for letting me use this wonderful image.

Phage properties illustrated in this picture:

  1. These phages have a head, a tail, and tail fibers.
  2. The long tail fibers are bent at a sharp angle.
  3. The tail is attached to the head by a narrow neck collar.
  4. The head appears to be icosahedral.
  5. Absorption is tail first.
  6. In virions absorbed to the cell, the tail sheath becomes contracted.
  7. In absorbed virions, the head appears empty, although not always totally.
  8. Apparently empty heads are seen intracellularly.
  9. Phages “mature” intracellularly near or within the nucleoid
  10. The filling of the phage heads appears to be a rapid process (only a few intermediates between empty and filled heads are seen.
  11. The host cell appears to remain intact throughout an advanced stage of infection (although small holes in the envelopes cannot be excluded)
  12. A sectioned infected E. coli looks like a pizza with pepperoni

Comments

Wonderful example of how an image can be highly descriptive and explanatory of natural phenomena and processes! Thanks!

Elio replies:

Nothing could please me more than this comment. This is the whole point of this series, "Pictures Considered!" Many thanks,

Elio

Thank you for this!! My students are preparing for an exam on different types of microscopes -- how they work, how samples are preped, and what can you see with each type -- and I posted a link to this on the course web site. Perfect timing.

Julie Harless

Elio replies:

How nice! I am delighted that you put this piece to such good use.

Elio

It shows the relative sizes of the phage and the bacterium (which are much closer than they were in my mind's eye).
--bks

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