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NOV a} 3 1964
WESTERN RESERVE UNIVERSITY 3 .
CLEVELAND 6, OHIO
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SCHOOL OF MEDICINE

DEPARTMENT OF MICROBIOLOGY

November 9, 1964

Dr. Joshua Lederberg

Department of Genetics

Stanford University Medical School
Stanford, California

Dear Dr. Lederberg:

In my laboratory we have become interested in why K12 bacteria
carrying lambda prophage do not support the growth of T4rlIl bacteriophage,
whereas the absence of prophage allows growth of the T4rlIl. One question
that we have asked is whether the differance between K12(ipt) and K12(lp-)
is attributable to expression of a lambda gene or to inhibition of a gene on
the bacterial chromosome, It is possible that a meaningful answer might
be forth coming if we could obtain a strain of bacteria that has lambda on
the host chromosome and an episome with those host genes that ng saber
the lambda prophage site. Hirota and Sneath described several F particles
with different markers, It would appear that episome Fg or Fi3 state I
(high fertility for gal, try) would be logical episomes to use. | Since the
work was done in your laboratory I wonder if you have retained these strains
and whether you could send them to me,

One preliminary answer I vould need to know or examine is whether
a strain marked lpt/F hp- galt could be obtained and maintained long enough
to test it as a host for T4rlIl or whether the lambda gets on the episome so
rapidly that both host chromosome and episome contain lambda, If there
is a reasonable time interval during which the episome expresses and
does not contain the prophage, I would plan to use a K/4 as episome donor
and F"(lpt) as acceptor, At varying times after mixing the two cultures
I would infect with T4rII and look for progeny phage.

It is entirely possible that similar experiments have been done with
negative results, If you have heard whether this is so 1 would appreciate
this information,

Sincerely yours,

Taz anus Leds l, ac law

Lazarus Astrachan