YALE UNIVERSITY
OSBORN BOTANICAL LABORATORY
NEW HAVEN, CONNECTICUT

January 14, 1947.

Dr. A.C. Braun,
Dept. Animal and Plant Pa hology,
Rockefeller Institute,
Princeton, Nd.
Lear Dr. Braun:

I have just read your paper , Braun ahd Elrod,
‘Stages in the Life History of Phytomonas Fumefaciens! in
the recent J. Bact. issue, with the greatest of interest.
as the enclosed note will indicate, we have been studying
gene recombination in a strain of Escherichia coli, with
results which appear to us highly convincing. Eowever, our
efforts at characterizing the zygote have been entirely
unsuccessful, and indeed might be expected to be futile
because &kke its occurrence is infrequent according to the
genetic evidence, in this strain. Your suggestion that it
‘will be necessary to bring together in a single star aif-
ferent strains of the same species...and determine from
this cross whether a recombination of chare ters results.!
is of course the sine qua non of a genetic confirmation of
the possibility that these stars are zygotes. I would sug-
gest that to ensure that stars which can be formed in mixed
cultures actually derive from cells carrying different gene
combinations, it would be preferable to use irradiation-in-
duced mutants of a single strain such as Chry. IIB, ina
manner perhaps comparable to the procedure we have used in
Esehrichia coli. I hope that you will be able to continue
these investigations genetically, and would appreciate very

mach hearing how they come out. If I can be ef any assistance,