FEDERAL SECURITY AGENCY
PUBLIC HEALTH SERVICE
VADCDOICXDOICAK OR,

 

IN REPLYING, ADDRESS THE
‘UBLIC HEALTH SERVICE

REFER TO:

Tuberculosis Research Laboratory,
411 East 69th St., New York 21, N. Y¥.

April 9, 1952.

Dr. Joshua Lederberg,
Department of Genetics,

The University of Wisconsin,
College of Agriculture,
Madison 6, Wisconsin.

Dear Joshua:

It seems that not only our last letters but also our thoughts
have crossed.

You say that thee is little doubt that the Kl and Klt mutants
were derived from the W strain. Yet they carry a phage which lyses
W-1177 whereas the wild-type W does not. Is that correct?

The history of the Kit - strains is the following: In Sept.
1950, markers were put on the Kit strains, yielding Klt-trl, Klt-p, and
Kit~h2. These 3 strains were crossed with W-677 and 58-161. In these
crossing experiments the strains taken from a 20 h NY culture (YE + NZ
medium) were grown together for 4 hrs. at 37° in NY (0.5 ml of each —»
total of 5.0 ml), before plating 0.1 ml of the unwashed suspension on
minimal agar (incubated at 37°). Appreciable numbers of colonies
appeared on the plates Kit-h2 x W-677, Kit-h2 x 58-161, end Kit-p x 58-161.
Also in crosses among the Kit strains, appreciable numbers appeared on
Klt-trl x Kit-h2 and Klt-p x Klt-h2. On the control plates there were
either 0 or 1 colonies. However, these colonies were not tested further
to see whether or not they really were prototrophs. At a later stage
(Jan.-July 1951) various other Klt derivatives were crossed with the two
indicator strains, but no recombinants were obtained in any of these
experiments. I have no record of recombination experiments with Klt~h2
and Klt-p derivatives (e.g., Klt-h2-pl, etc.) These would be the most
likely ones to recombine. I am sending you the parent strains Klt-h2
and Klt-p.

So far I have two pant” mutants in W-677, but unfortunately one
is blocked in the synthesis of - -alanine, the other in the synthesis of
pantoate. Tough luck!

There was one sentence in your letter that wasn't clear to me.
"These (Klt- derivatives) gave very sporadic results with K-12 testers,
and altogether only a very few prototrophs were obtained so that I cannot
place too much emphasis on my negative results." What do you mean by
Dr. Joshua Lederberg April 9, 1952.

in Me frst plo *

negative results? Do you think that there was recombination?

Best regards, also to Esther,

(ems

Werner K. Maas

WKM/h1

LS. Nauk, fs Me UY 1/17 shes, lal jeoot Arresed -
[As K W- 1426 )