December 7, 1960

Dr. Yukinorl Hirota
Department of Genetics
School of Medicine
University of Osaka
Osaka, Japan

Dear Hirota:

In my last letter | forgot to mention some very Interesting papers that
| have recently seen by Mitsuhaash! and others which have appeared in the
Japanese Journal of Experimental Medicine 30: 179, 1960. If we take these
literally some strains of Shigella may have an Felfke factor which Is
responsible for resistance to drugs. If you are not already aware of this |
would think that you would find tt very Interesting to see whether this factor
behaves like F with respect to the mediation of sexuality and with respect to
the removal by acridine orange.

Yours sincerely,

Joshua Lederberg
Professor of Genetics