LEDERLE LABORATORIES

A Division of AMERICAN CYANAMID COMPANY

PEARL RIVER, NEW YORK PEARL RIVER 5-5000

August 20, 1962

Professor J. Lederberg
Stanford University
Medical Center

Palo Alto, California

Dear Josh:

Joe Lampen forwarded your request for information on pyrimidine and
citrulline mutants of BE. coli. As you undoubtedly know, I have
strayed from work in this area but will try to supply the information
while I am here between absences due to meetings and vacation.

We have not published anything on these mutants. However, Yates and
Pardee (J. Biol. Chem. 227: 677, 1957) reported some work on a uracil-
requiring mutant 550-460 (A.T.C.C. 9723g, formerly A.T.C.C. 11,548)
and a mutant (185-480) requiring uracil and citrulline. References
to earlier work are cited in this paper. We have two other uracil
mutants (40-482 and 969-434) and another uracil-citrulline mutant
(823-304). According to my records, I gave you a culture of 823-304
in May 1946.

The three uracil mutants have only partial blocks. With all five
mutants either cytosine or isocytosine will support growth in place
of uracil although growth with isocytosine is slower. The four
strains tested (185-482 was not tested) failed to grow with orotic
acid in place of uracil. Tests with orotic acid probably were not
conclusive in view of the report (J. Biol. Chem. 221: 743, 1956)
that some pyrimidine mutants grow extremely slowly with orotic acid.

The two uracil-citrulline mtants failed to show syntrophism with
each other (with either uracil or arginine limiting) or with another
strain (550-462) which requires only citrulline. Tests with the
other uracil mutants were inconclusive because of their partial block.

As you may recall, reversion of the uracil-citrulline mutants resulted
in simultaneous loss of the requirement for both uracil and citrulline
whether reversion is obtained by limiting growth with uracil or with

AUG 27 1962

we
Professor J. Lederberg ~2- August 20, 1962

arginine. However, an occasional reverted culture retained a partial
requirement for arginine (or citrulline, presumably) in which case the
addition of uracil increased the amount of arginine needed for normal
growth.

I trust this information will be of use to you. If you plan to work
with these mutants, we could probably supply you with some which you
are not able to obtain elsewhere. We have had moderate success in
recovering viable cultures lyophilized 12-15 years ago.

With best regards,

Sincerely yours,

oe gis
GA
R. R. Roepke

Chemical Pharmacology Department
Experimental Therapeutics Research

RRR: mak

ec; Dr. J. 0. Lampen
Institute of Microbiology
Rutgers University
New Brunswick, New Jersey