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THE COLLEGE

Laboratory of Microbiology June 17, 1949
Botanical Laboratory
38th St. and Woodland Ave.

Dr, Joshua Lederberg
Department of Genetics
University of Wisconsin
College of Agriculture
Madison 6, Wisconsin

Dear Dr, Lederberg:

I was very stimulated this morning by the arrival of your letter
and the four cultures of A. tumefaciens, Many thanks for your generosity.
The cultures came through in good condition,

Mr, Gordon's manuscript was very informative and I wish you would
thank him for me,

In reference to your letter, I am glad to know of the Aniline Blue
medium, Riker has proposed other media containing dyes about which
br, Braun told me, but they were not too reliable. I will try your
suggestion and use the Aniline Blue,

The mutants you sent, (GI and GII) are similar to the only stable
one I have, in that the deficiency is of a Sulphur compound or ion,
My stable one is a methionine less strain, It showed no growth in
any of the amino acids tested including cystein, L (-) cystine, and
glutathione, However, sulfide ions alone were never tested but I
strongly suspect that these too would prove negative, It might be
possible to use one of your strains together with my M7 (Methionine
less) in stars and make isolations from them, You made no mention
of star formation with the A6 strain so I presume that you had no
difficulty with it, Dr. Brau and myself have experienced some
difficulty in obtaining good stars with the AG so for that reason
we chose the B2, the IIBV7, and the 137 strains for our work, The
M7 is of IIBV7 origin, This is a nice strain to work with because of
its ease in forming stars and its relative stability; it throws off
fewer rough colonies than the other strains with which we have worked,
There is another feature to this strain in as much as we have @ non
virulent (for almost all of the hosts that the sister cell isolate
shows virulence) strain which is an apparent stable mutation, This
could be used as an additional character,
I am in the process of attempting to isolate a mutant of the Bo
strain, It will be several weeks yet before I will have any indica-
tion of the outcome of the present search,

The work with the tetrazolium reaction is more than ever confusing,
When I talked to you it was thought that the "cofactor" would be in
the peptone and could be tested for with cell suspensions, Latter
work has served only to further confound me, It seems that in addi-
tion to pH and peptone, casein hydrolysate, and yeast extract will
also aid the reduction, When the organisms were mixed with various
substrates in Thunberg tubes all substrates and the minimal medium
allowed reduction to the red formazan, This served to further com-
plicate the findings. It is apparently not as simple as was first
thought,

If you and/or Mr. Gordon are planning to continue the work with
tumefaciens please let me know so that I may send you strains and
such information as I might have,

I appreciate the interest and generosity you have shown, Please
give my regards to your wife and thank you again for your help.

Sincerely yours, .
Robert J, Mandle

RJM/aep