December 27, 1950.

De. Stan Shapiro,
Dept. BacterfLolory,
Iowa State Colleze,
Ames, Towae

Dear Stan:

I don't mean to be difficult, but I find it difficult to believe
that anythine 16 wrong with your 55-161 and %-1177 cultures, if t ey
confor to what they are eunposed to be. ould you try it once more;
4f they still don't work, please send transfers back to me, and I'll
send you fresh. If you really have picked up infertile derivatives, I'd
be very much interested, because nothing litte that has happened here.

Under this cover, you will find a mimeographed cireular, whieh says
nothing you do not already Imovw.

dell,what was the conclusion of your sex tests on -erobacter’ 24d I
understand that you had tested mutants fron 30-odd different straine in
all combinations without success? Here, I've been sereening a very
larco vunber of straine for crossing with F-12. Of about 140 £. coli
so far tested, there are 8 or ten very gocd pos sibilities, several al-
ready thoroughly verified. ‘ost of them are typical coli (s0-e sucroces;:
one is a “paracolon’ inéésrediate (Imvic ——¢#: Lao-}. I should be in-
terested to test more independently isolated coliforms, serobacter, etc.

If you can send re any (wild types}, your cooperation vould be appreciated.

Your name ic on the railine Met, so you'll cet ali revrints, at inter-
valo of a year or 90. Zether is working fulltine now, on lyscgenkoity
dn te12,

With best wishes,

edincerely,

Joshua Lederberg