WALTER REED ARMY INSTITUTE OF RESEARCH Lave.

WALTER REED ARMY MEDICAL CENTER
WASHINGTON 12, D.C.

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November 19, 1959

Dear Joshua,

Thank you very much for your letter. I have just recenkly seen the abstract
by Hirota in "Genetics", We have not had any positive results with infective
transfer, with a coli strain or witn a Salmonella strain,

We have started some mouse virulence studies with S. typhosa hybrids (an artif-
icial situation at best). There seems to be some loss of virulence by the
'diploid' type, however, this may be due to the slower growth rate exhibited

by this form. Actually, I should prefer to examine mouse virulence in the
case of 5. typhimurium. Esther mentioned that she had developed some stocks

of TM-9 having a number of selective markers, If available, I would apprec-
iate a transfer of a strain of this kind to try the isolation of avirulent
hybrids from E. coli Hfr x S. typhimurium; virulent hybrids from the reverse
cros s eventually I hope. ~~

I am unable to answer the question concerning derivation from Hfril or Hfrc,
but it would be very helpful if it could be established sone way whether it
was either or neitaer,

I am enclosin» an abstract for comnent (particularly as regards the last sent-~-
ence) which we intend to submit for the S&B meeting in Philadelphia.

Best regards,
Sincerely yours,

(

P. S. I heard from Seymonr thru a friend visiting at Brown that he is 'superbly
married',