March 18, 1952

Dr. Charlotte A. Colwell
Research Bacteriologist

Veterans Administration Hospital
Hines, Dlinois

Dear Dr, Colwell:

Recently, I tried to repeat experiments on the effect of methyl-
naphthaquinone as reported in your paper in J. Bact., October 1946.
I tried the K-12 strain of E. coli (used in my other genetic work)
and looked for the small golony variants. I had no diffdculty in
observing the pronounced bactericidal effects at low concentrations
(.00L5 - .002%) in synthetic madium, but did not find the small colony
variants in platings on nutrient agar.

It might take some time to trace down the immediate cause of this
discrepant reuult, and perhaps it cannot be done at all with my straih.
Would you still be able and willing to provide cultures of a proven
susceptible atrain and its dwarf variant? This would be very helpful
in orienting my experiments to a more compatible conclusion.

I should perhaps indicate the basis of my interest. I should like,
first of all, to look into the question of the selective versus the
indtctive action of the quinone. Secondly, there may be a relationship
between the small coloy variants (if they are indeed induced) and
the acriflavine-induced. "petites" forms of yeast, desribed by Ephrussi.
These are of great genetic interest.

Yours sincerely,

Joshua Lederberg
Asascolate Professor of Genetics