April ll, 1950.

Dr. Frank Davis,

“Woroblology Research Division,
Agricultural Research Center.
Beltsville, Maryland.

Dear Dr, Davis:

Your paper, "The utilization of some organic compounds by one strain
each cf 8. anatun, S. oranienburg, and S. pullorun", J. Bact., 593361,
1950., has just come to my attention. I have sone comments which I
mould Like to bring to your consideration.

On p. 361, Johngon and Rettger are quoted as reporting that S. pullorum
requires thiamine in an amino acid mediun. I have never found such a
requireaent of S. pullorum, and I believe that Johnson and Rettgsr's
paper may have been misunderstood. Most pullorum strains will grow on
medium supplemanted with esrtain amino acids,depedding on the strain,
but usually including cystine, arginine, leucdne and histidine. S. galli-
narum, on the other hand, requires thiamine, almost consistently, and
in fact can do quite qell without amino acids [although Johnson and Rettger
do not mantion the latter]. You may,of course, choose to luzp gallinarum
with pullorum. although for nutritional and epidemiological purposes they
are as distinctive as any Salmonella species.

Elsewhere in your paper, you mention that 5. pullorum failed to utilize
any of the carbon sources which you tested. In view of the well established
nutritional requirements of this type, such a result could only have been
anticipated. Since ths primary objective of your work seems to have been
the determination of the scope of potential energy sources for these Sal-
monella, it would be of some importance to distinguish clearly between
the availability of a carbon compound as an energy source in a synthetic
medium on the basia of its metabolic utilizibility,from the question of
the specific grewth factor requirements of the organism (amino acids, vitamins,
etc.) The history of nutrition research both on animals and aleroorganiams
shows clearly that little progress can be made until this distinction is
Clearly appreciated and presented. In the present instance, the media used
for 3. pullorum should be supplemented with the specific growth factors
required by your strain, before any rational attempt can be made to inves-
tigate the range of organic energy sources available to it.

Yours sincerely,

Joshua Lederberg
Assistant Professor of Genetics