May 25, 1962

Dr. Helen Mukel¥
Department of Bacterlolagy
and Serology

University of Yelsink!
Helsinkl, Finkéend

Dear Helen:

| was pleased to find your corrected paper walting for me
@pon our return from Japan. Your suggestions are al! excellent ones
and | think the paper should Just go In substantially as It stands.
1 do not think It Is @o00 long at all by the usual standards of the
Journal. Perhaps the maln comment | should make for eccurate
information concerns the references. £&M agar 1s mentioned by Hirota
In footnote 11 and also by Richter, 1961, page 335. But it Is
probably better to Just replace the reference by ''EMS agar without
succinate’. As for Ann Cook's paper, it should be 1962, and | hope
will be published In Genetics. This can be perfected In the proof.
t will put In the proper designations for the three lac™ cultures In
table 1. {| hope you will not object @0 my changing the symbol tyro~
to tyr™, only because It Is more compatible with our current useage.
There are perhaps Just one or two other minor changes.

On the whole | am very much pleased at the present shape
of the paper and Its further Improvement by your own comments. if
will look forward to seeing the manuscript of the second paper
before too long. However, there would be little point In trying to
rush It before about the third week In June, as | have a very busy
time ahead In catching up with accumulated work.

it is also tery gratifying to see how you have continued your
studies, although as we had already begun to suspect there may be some
serious technical problems In maintaining useful maleness and high
development of flagella at the same time.

in Japan wa had an especially time with Tetsuo fino, who Is
continuing his work along more and more physiological and blochdénical
Vines. 1 hope it will be feasible to errange to remain tn close touch
among all of us. in particular we would like to start sane DNA studies
In connection with phase variation during a brief visit that he may pay
to the States In early September. One of the very useful things If it
could be possible to develop it before that time would be s Salmonella
serratia hybrid in which a serratia F™ has acqulred and can successfully
manifest a small segment from Salmonella Including H1 and Ho. If such
a heterogenote can possible be obtained and if it shows phase variation
Dr. Helen Mékeld 2 May 25, 1962

we would like to make a beginning attempt to discover whether there Is
any difference In the DNA composition of the bacterla fn the alternative
phases. May | ask whether you would be able to offer anything In this
regard? We have been stressing this kind of work very heavily lately
particularly with the Bacillus subtilis transformation system. Gan

has had some very exciting results on the separation of the DNA corres~
ponding to different genes in this system. At the present moment he

is In India revisiting his parents, but he will be back In another
month or so.

To return to our paper, It will probably expedite matters If
| arrange to take care of proof here. Of course, { will see to it that
you are informed about the progress of the manuscript and consulted If
any material questions should arise. 1! will also arrange for a reasonable
number of reprints to be sent directly to you.

With best regards to Ollle,

Yours sincerely,

Joshua Lederberg
Professor of Genetics

JL/je