How Many Things Can Be Il­lus­trated In One Pic­ture?

Pic­tures Con­sid­ered #13

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?

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.