Dept. Genetics, University of #isconsin, dadison 6, Wis.

Dear Dr. Frederica:
Your interesting paper on the M-colicjn activity of V/1 ete.

(in Antonie van Leeuwenhoek, April,1951), just came to hand. This

seems a most extracrdinary observation. Have you considered the
likelihood the the M-colicin is the result of recombination be tween

a phage-like element of V and TL? This would presuppose that the colicin
V is actually an incomplete or fragmented phage, and that colicin pro-

duetion was a sort of lysogenicity. One point that was puzzling is the
interrelationship of Tl and T7. Resistance to these phages is maakk usually
independent. Is there any difference in the activities of V/1 and V/7
on B/1,5 and B/? ? Are non-colicidal mutants of V known so that one could
determine whether the prior presence of V-colicin igs required for si-colicin
formation with T1?

A specific point of understanding or translation: at the bottom of
p. 104, you refer to "un mitant V/5 lysogene". Am I correct in thinking
that this was a culture carrying residual T5, and not a true lysogenic
strain from which nonlysogenic v/5 is readily isolated?

I hope you will have had time to try your hand at recombination in

E. coli K~12, and will be interested to have your comments. The colicidal
types you sent have been very vakuable in the classification of new types.

Yours sincerely,

Joshua “ederberg