May 12, 1969

Dr. Klaus Mampell
International R&D Incorporated
6303 Waterway Place

Falls Church, Virginia 22044

Dear Dr. Mampell,

It was good to hear from you. I have a very vivid recollection
of your work during the forties on 'Bpidemics" of mutation. It must
be very gratifying to you te be able to feel now that the virus
theory has a much more substantial theoretical basis than it was possible
at that time.

IT am enclosing a bibliography of the most significant items I have
encountered so far on the actions of chlorine. We have confirmed the in-
activation of DNA by chloramine and also found a nice correlation
between radiation-resistance and chlorine-resistance. We are persuing the
question of mutagenesis at the present time.

I do not see any possibility of doubt that chlorine is a potential
mutagenic agent and that everything now rests on the chemical forms by
which it may penetrate the body. For this reason I think it is very
important that you maintain tight control of the constituents of the
medium that you use for cultivating Drosophila as well, perhaps, ae the
associated microorganisms. In fact, unless you are already working with
sterile cultures it is going to be difficult to eliminate differential
antimicrobial effects as part of the causes of the changes you find.
There is little doubt that Drosophila ordinarily get significant parts
of their essential growth factors from microorganisms unless the diet is
especially constructed to be innately complete.

I would be interested to see any material that you develop on the
subject as well as any other literature that you may discover. We have
found it very difficult to collect this in any straightforward way and
from time to time discovered new material that we had not previously
suspected.

Sincerely yours,

Joshua Lederberg
Professor of Genetics

Enclosure
JL/rr

174d WY W