. MEDICAL RESEARCH COUNCIL
_ NATIONAL INSTITUTE FOR “MEDICAL RESEARCH

THE RIDGEWAY - MILL HILL ” LONDON, N.W.7.
Cables: NATINMED MILL, LONDON. -

 

PRIVY COUNCIL

- 8th aprsy, 1952 8

the

Professor J. Lederberg, . er
‘4 Department of Genetics ’ ; a
" University of Wisconsin, a
‘ Madison 6, Wiseonsin, i
; . U.S. As oo SF . r

Dear Professor Lederberg,

I was interested to receive your enquiry regarding the
antagonist of streptomycin produced by Ps. pyocyanea. Although I.
have carried the work further, and em still engaged on it, I have not
published anything further.

Ido not think that it would prove of any value for the purpose
you suggest. The antagonist does not appear to have any activity against
cells which have been previously inactivated by streptomycin it would appear
only to protect cells which are growing in the presence of streptomycin.

As far as E.coli is concerned I have had difficulty in showing
that the antagonist is active. I have not pursued this problem far however,
since E. coli does not grow regularly in the system that I am using for
measuring the activity of the antagonist. A further difficulty is that
it is not easy to get a preparation of antagonist free from inhibitory
activity at high concentrations.

If as the work progresses it would appear to be of any assistance
to you I will let you knows ;

Yours sincerely,

) 6. aa
JeW. Lghtbow