Department of Genetics
University of Wisconsin,
Madigon 6, Wis.

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‘June 26, 1952.

Dear Dr, Fredericq: :

aN
Thank you for your informative letter of May 24. ©

I was especially pleased to learn of the fac iity of use of the 58-161
and W~1177 strains- there are any humber of problems. to which they may be
applicable. :

May I accept your offer to send back miltiply reaistant mtante of
these strains? I would be esppcially interested in such derivatives from
W-1177, for I believe that its susceptibility to colicins may be responsible
for "gexual# incompatibility in crosses with some new coli isolates, and I
have been using this culture very extebsively as a tester against a large
number of other strains.

If you have already had, or should encounter the occasion to pre-
pare a multiple-resistant derivative of W-1177, I should be very grateful
to have it from you; if not, we shall probably take time to do the job
ourselves. Meanwhile, our main use of colicins has been in the classifi-
cation of new isolates, and we have not studied mtations to resistance
as seen in the laboratory.

Thank you for distributing the strains further. I would appreciate
it very mech if my request to be informed who has obtained them could
accompany the cultures in their further travels. That is, I would be
interested to hear if Professor Winkler distributes them further.

/ Yours sincerely,

| , A feck \ c
| td po : Joshua’ Lederberg,

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