June 12, 1952

Dr. Robert Guthrie

Sloan-Kettering Institute for Cancer Research
410 BE. 66 Street

New York 21, N.Y.

Dear Bob:

T am pretty sure that I have tested W-1177 x ATO 9723. Some
yeors ago, I tried crossing various auxotrophs in this strain,
and with K-12 derivatives, unsuccessfully. I wouldn't say that
it had been completely, exhaustively worked out, but nothing en-
couraging has come up. You might check with Ryan, who has been
using this strain for some time. B has been looked at rather
thoroughly, and has shown no signs whatever of mating in any
system, Lately, I've revised my conclusions about 9 37 (the
"Wakeman" straihg used especially by Bernie Davis). This appears
to be fertile after all, but ah an extremely kow rate (ca 10710)
in the various combinations tested. The fertility is too low to
be useful for genetic work. I'm afraid we don&t have the kinds
of mitants you arg looking for in Kel2, with perhaps one or two
exceptions. Whig don't you go after them yourself? I think Bernie
gust have a slant of K~-12- if not, I'll be gladdto send you one.
If you want to do recombination work, you should best start out
with marked auxotroph strains so that you don't have to rely on
the mitation you're interested in as a selected marker. 58-161
or W-1177 would do the trick. Again, I think you can get them
across the street, —

As to 3B. subtilis, ‘we've made some desultory efforts with it
but have not gotten vexy far tewards a conclusive test. If you have
the material for it, i% certainly ought to be done. DeLamater has
been talking about sex! in B, megaterium, but the evidence (as it 4s)
is purely cytological.s

4

\ Sincerely,

Joshua Lederberg

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