June 19, 1952

Dear Dr. Klieneberger—Nobel:

I am indeed sorry to hear of the negative conelusion of your painstaking
work with E. coli K-12, but must admit that my own experiences have been
very similar, and that I have not been able to find any morphological
peculiarity associated with recombination. I am still interested 1a
the problem of L-forms, regardless of their connection with genetic exchange,
which appears now to be very remote. One of my students, as I have mentioned
played a bit with BE. coli B + phage T3, but like yourself was unable to
verify the regeneration of bacteria from "sterile" filtrates. Perhaps
the material for this is going to be found in Hemophilua pertussis,
judging from soma recent publications. And we etill have some lingerging
suspicions on the filtrability of phage-treated Salmohella, although
this seems tonbe unrelated to genetic transfer,

Have you reinterpreted the possible fusion figures, as diagramed
with your letter of Dec. 20th? I have seen a few associ&tions of this
general sort, and wondered whether any meaning could be attributed to
them.

Perhaps an opportunity will develop, in the future, for a closer
discussion of these problems. I hope you will not hesitate to reppen the
question of a visit to this laboratory whenever it seams appropriate $o
you.

Professor Tatum ahd I are writing up a general account of genetic
studies with K-12 of the last six years. Unless some unforeasen findings
develop very soon, we shall have very little to say about the morphology
of the mating, Would you eare to have any of your observations quoted,
regardless of the negative conclusions, or the negative result of your
work itself? I am not sure whether it will fit in or not, but I should
want your explicit permission before making any comment whatever based
on your work,

Yours sincerely,

Joshua Lederberg