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