March 1, 1954

Dear Doctor Rogers:

I am sorry to have to write that the cultures of E. coli serotypes
055 and 0111 that I hed requested last December have never arrived.
I did not wish to trouble you sconer as you pointed out that it would
be advisable for you to defer shipment until after Christmas, but a
sufficient interval has now elapsed to give me some concern.

As I reread your letter of December 21, it occurs to xe that you may have
been waiting for further word from me, and that I might be responsible for the
delay myself in not having interpreted your letter in this light before. Howbeit,
I should perhaps take thie opportunity te clarify my request.

For an extension of genetic studies, Dr. Bernstein and I would like to
use af representative as poseible gpa set of these serotypes. The distinctive
phage types might help to insure this, but we would be equally interested in
any variety of cultures from dietinct sources or that subsumed a minimum of
overlappkng on any criterion. Dr. Bernstein had suggested that you might have
the full series ef lysctypes as well as additional fresh isolates, whereupon I
wrote to you earlier. I would be grateful to you for any extensive group of
Ee coli 055 and 0111 that you might be able to furntkéh.

Thank you for your offer of the additional types, which I will certainly
keep in mind. For the present, however, it might be beset if we confined our
studies to the types hamed. If we have an opportunity to extend our studies still

further, I hope to be able to turn to you for your proffered asalstance.
Yours ainceraly,

Joshua Lederberg
Associate Professor of Genetics