MERCK INSTITUTE
FOR

THERAPEUTIC RESEARCH

RAHWAY, N. J.

November 15, 1951

Dr. Joshua Lederberg
Department of Genetics
University of Wisconsin
Madison, Wisconsin

Dear Dr. Lederberg:

Your observations on the growth response to air of
the Murray resistant strain of E, coli are not surprising to
us. The published studies of streptomycin-resistant E. coli
strains were on cultures that had been maintained for a long
time (a year or more, in both cases) previous to the metabolic
studies, as was noted in the paper. Since publication of
those data, we have several timesisolated resistant strains
of E. coli, Gratia and Murray, and in all cases the freshly
isolated organisms grew as well as the parent sensitive
strains. However, on continued cultivation with or without
streptomycin, for six months or longer, it has been noted
that some of these resistant strains grew very poorly, and
resembled the orgainsms previously described. We do not know
whether it is a matter of chance that the organism loses the
ability to respond to air, since the phenomenon was not sub-=
jected to detailed study, and we therefore have hesitated to
publish the data we do have. It is important, of course,
that such a study be done, but we are unfortunately not ina
position to carry it out at this time. It would be interest-
ing to determine the effect of continued cultivation on the
Murray resistant strain we sent to you, which was isolated
in August of this year, and was transferred monthly since on
tryptone-yeast extract-KoHPO}, agar (AC agar), at 100 pg strep-
tomycin per ml. It had originally been isolated from this
agar in the presence of 80 pg streptomycin per ml, and was
transferred serially in increasing concentrations of strepto-~
mycin up to 5000 pg per ml, after which it was maintained as
stock culture,

It is indeed the same Pat smith who was at Yale,
but she is now working with Dr. George Wald at Harvard,

Sincerely yours,

A -QQrudk —

ELO: MEM Evelyn L. Oginsky