RUTGERS + THE STATE UNIVERSITY AUG 2: 1962

INSTITUTE OF MICROBIOLOGY
August 20, 1962 NEW BRUNSWICK, NEW JERSEY

Dr. Joshua Lederberg
Department of Genetics

Stanford University Medical School
Palo Alto, California

Dear Josh:
I have your request for information on the effect of polymyxin in

modifying E. coli conjugation, specifically asking for a more detailed
reference than the brief allusion in my antibiotic review. The experiments

involved were done while I was working at Cold Spring Harbor under a ee)
Fort Detrick contract. The observation, made about 1953, showed that as ~
strain 3s-\6\| became progressively more resistant to polymyxin, it ~—
became progressively harder to recover prototrophs from W \\111 matings. UW
After 6-10 gradient plate isolations the matings became fruitless. For S
approximate levels of drug required, see the review, figure ~
—

It seems very possible that my casual reference to episome
elimination is premature. The well-known effects of polymyxin on the cell
surface suggest that changes in the bacterial wall associated with resistance
may be incompatible with retention of the mating potential. I had written
something about this idea in my renewal application for USPHS E-2615, but
soon thereafter your paper with Sneath cane out.

If you are doing no more work along these lines, there are probably
enough differences between polymyxin and periodate to justify some
investigation into the former. On the other hand, maybe you have a student
working on this or related problems. Let me know by postcard whether this
problem is still tied up, and whether, if not, I can use your stocks: W 2324,
W 3064, W 3086, W 6, W 3876, W 3776, W 3780, providing you are willing
to send them to me.

Best regards.
Sincerely,
Vermin
Vernon Bryson

VB:DP