YALE UNIVERSITY SCHOOL OF MEDICINE
333 CEDAR STREET - NEW HAVEN : CONNECTICUT
DEPARTMENT OF PHYSIOLOGICAL CHEMISTRY

September 18, 1952

Dr. Joshua Lederberg
Department of Genetics
University of isconsin

Dear Josh,

In the past few weeks we have started
to work with one of the serineless mutants
(¥ 1975} that you so kindly sent me last
Spring and hsve run into certain difficulties
which aré new to me. Usine the Tatum hasal
medium =- which works well for all coli de-
rived from K 12 - and either L-serine or
elvcine, the maximal crowth obtained is
never more than about half that observed for
* 12 or for other mutants such as the
orolineless, methionineless, etc., “e've
carried out our incubations at 30 and at 35°
and have even shaken the incubation tubes
without improvine the rrowth as measured
on the Evelyn,

Have you any experience alone this line
which micht help us? At the moment we are
trying to find out whether 1975 has any
renuirements in addition to that for glycine
or serine, Incidently, a serineless strain
I cot from Rernie Davis acts the same way,
Perhaps this is just a characterisic of serine-
reouiring coli regardless of their origin,

Needless to say, any advice you have to
offer concerning this problem will be most
welcome.

Sincerely,
—T”
le

Sofia simak