CARNEGIE INSTITUTION OF WASHINGTON
DEPARTMENT OF GENETICS

COLD SPRING HARBOR, LONG ISLAND, N.Y.

April 18, 1949

Dr. Joshua Lederberg
Dept. of Genetics
University of wisconsin.
Madison 6, wisconsin

Dear Joshua:

I am verymuch interested in your T6 lysogenesis
problem. Enclosed you will find the PIS in which
the experiments on lysis from without are described,

There are several points which should be kept in
mind in using this technique, muxa They are perhaps
not made clear enough in this report. One is that it
makes some difference what stock of T6 is used for lysing.
I have found that some high titer stocks do not work
very well while some of lower titer are better. whether
this is due to the presence of dead phage which can still
lyse cells or whether it is due to other factors has not
been determined. One can easily test lysing stock
turbidimetrically. Incidentally, synthetic medium stocks
are generally better for this purpose since the titers
get higher than in broth.

The other point is that I now use the chilling
treatment with all my experiments, since it was with
this méthod that we found our agreement with sonic
rupture of cells.

I now have single burst data which show that I
am lysing all of the cells (over 90%) with my method,
and not merely stopping a fraction of the cells and gettig
the usual large bursts from the remaining cells.

I would be interested to know how this method
works on 4 lysogenic strain, and would appreciate
it if you would keep me informed of your results.

Sincerely,

burs

A. H. Doermann