cA 1

April 91956

Dear Seymour:

A fuse finally blew and led to the recollection of some forgotten
experiments that might interest you.

In March 1949, we were interested in finding phages that would be
excluded by Lp” and could therefore be used for experiments on the timing
of lysogeny, etc. We were working on the precedent of Burnet's clder
work on staph bhages— and the system we were looking for is of course
very close to the P22-P22V relations in S. typhimurium. fle did not suc-
ceed in getting lambda mutants with the desired property, so we searched
for new phages. We were also interested in the natural distribution of
lambda.

Chicago sewage was filtered and plated on Lp*. 337 plaques were picked
and tested on Lp vs. Lp®. One showed a clear differential, = "p20", This
wag cultiveted, and the difference in eop confirmed; however, p20 killed
Lp without forming plaques, and we therefore lost interest. It was noted,
however, that E, coli B was p208; B/6 was ™, and then that there was complete
cross-resistance among mtants of K-12 selected on the two phages. It was
concluded that p20 was a Té-related phage that could kill, but not lyse Lp*
and we thought no more about it. Our tabn stock of T6 mst have been r*, as
it did not show this differential.

If it would interest you, we might be able to locate the phage stock of
p20, though we are somewhat disordered owing to remodelling. Let us know if
you would like us to search for it.

Sincerely,

P.S. Alan wrote me asking for some auxo- 4 1a VS
trophic mutants. We could supply some, and wou jen Bt

be hap py to, but most are tied up in various com soshius Lederberg
pl&cated combinations of markers. Bernie Davis mst t

have a much better library for this kind of stock, but

I will be glad to scrounge for anything else.

P.S.