December 7, 1949.

Dr. P. R. Edwards,

Communicable Disease Center,
Enteric Bacteriology Laboratory,
Chamblee, Georgia.

Dear Dr. Edwards:

Thank you very mich for the diagnosis of the S. coli strains sent you.
These strains had not been exposed to deleterious agents, and were simply
found in the stock which we had maintained without repurification since
receipt from Borman in Connecticut. It was a relief to learn that we had
good grounds (since both are S. coli 1) to reject the disturbing idea that
the culture was mixed because of our own technical incompetence. The two
cultures have certainly diverggi in an interesting way. I shall try to find
out whether they are ultimately derived from F. coli 134; as I mentioned,
Borman's label read " 54& "gp and he had implied that it was ultimately
gotten from you.

I would be very interested to consult with you concerning the possibility

of phages isolations for diagnostic purposes. Within limits, phages might

be of great value in epidemiological work. My own experience, and what I
have been able to learn from the literature suggests, however, that there
will be only the most general parallelism between phage typings and sero-
types. It probably would npt be possible, in general, to obtain monospecific
phages whose host range would be exactly congruent with the distribution of

a given somatic antigen or complex. However, within a given serotype, phages
might be useful in untangling epideaiological traces. The sort of work that
Lilleengen has been doing with typhisurium should be extended.

I would like to take this opportunity to bring up another suggestion,
which I may, >erhaps, have stated imperfectly to you before. The hasty, and
extensive (rather than intensive) survey that I made on the nutrition of
Salmonella strongly suggested that, within serotypes, there my be a num
ber of distinctive nutritional sub-types. This is especially true of
S. pullorum and gallinarum, which are officially "lomped"; because of their
common somatic antigen, but which are nutritionally and pathologically
distinctive. The few gallinarum strains which I have studied, or heard tell
of, invariably require no more than thiamin as a nutritional supplement,
whereas pullorum strains generally require a number of amino acids, usually
including cystine and leucine. I believe that it is the low cystine content
of most ordinary media which is responsible for the slow growth that is
usually mentioned as a "cultural" characteristic of these strains. This
correlation should be studied more thoroughly, and if supported with

a variety of isolates originally characterized by their diseaee-producing
characteristics, should be the most precise method for laboratory diagnosis
of these non—motile Salmonellas.

But I also feel that possibly less distinctive subtypes of other serotypes
should also be characterizable by their nutritional requirements. I believe
that it is unfortunate that Hohn and Harrmann went so far in their claims
for the "ammonstark" characteristic, especially at a time when the inter-
pretation of bacterial growth on synthetic media was less well understdéod.
Their generalizations concerning the far-reaching biological significance
of auxo-autotrophy are patently fallacious, but I think that theybhave
induced a reaction which obscures a proper consideration of the potential
usefulness of nutritional studies.

As somewhat of a minor corrolary of my plaintive remarks, I would like
to point out something of the significamce of the "citrate" teet as applied,
for example, to the S. coli I sent you. An organism will fail to grow on
a synthetic medium with citrate as sole carbon source under either of the
following circunstances: 1) if it is unable to utilize citrate as a carbon
or energy source, or2@#) if although potaatially able to utilize citrate, it
is unable to grow due to a requirement for an additional growth factor(s). In
the present instance, the S. coli Lac+ is unable to grow owing to a require-
ment for histidine; the typical E, coli is citrate-negative for reason (1).
Even 4f it were felt that a more thorough nutritional examination was too
ambitious a program, I feel that the differential value of the "citrate"
test could be greatly amplified, and put on a more rational basis, if it were
accompanied by a parallel test on a synthetic glucose medium. Glucose-negative
organisms are sufficiently rare in this group that inability to grow on a
glucose-synthetic medium would imply a nutritional requirement (2), while
ability to grow on glucose-synthetic but not on citrate would imply the
incompetence to utilize citrate (1).

I hope that we may have an opportunity to discuss these matters in
more detail sometime— perfiaps at the next national SAB meeting.

rooney ee
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Assistant Professor of tics