May 30, 1956

Dr. Norman Horowitz
Blology-- CalTech
Pasaduna 4, Calif.

Dear Norm:

Some of Marv' Johnson's students and I are trying to work up an interest
in some genetic angles on penicillinase and penicillin action in FE, coli, and
for this it would be helpful to have some penicillinase-negative mitants. We
have in mind to do some searching of our own, but I thought that some of the
material that Rowley had published on would save us some time. I should write
to him, buthhear he is travelling around, and thought anyhow he might have left
his cultures with you. The ones I have in mind are in his 1952 JGM paper, say
A and 4A of tabke 1 (Vol. 6, p. 274), and 2463 meth* of table 2, which appear
to be the most sensitive to penicillin. I am postulating that these mtants
may have considerably less penicillinase than K-12; if you know of any infor-
mation on this, I would appreciate it, and 1f the supposition is wrong, don't
bother about the mtants.

If you can't help me yourself on this, but can pass this request on to
anyone else who can (including Rowley, if you know where he is) I would appre-
ciate that/

With best regards,

Sincerely,

J oshua Lederberg