even

May 22, 1952

Dear Spicer:

You may be interested that I have just received and endorsed
your WHO fellowship application. I note that you are applying for
a tehure of 3 months. This is somewhat on the brie? side, but ina
view of personal repponsibilities, I can well understand it. I was
& little surprised at the penuricus scale of the stipend for a can-
didate of your auturity, or is this supplemented by your own organi-
wetion? If not, I should be interested to know whether you would be
barred from accepting euxiliary financial support.

In the endorsement, I indicated that you would be welcome at any
tims during the next academic year, except that I shall be away during
February 1953. Sctober—November—December, or perheps slightly better,
November~December—January wili do very walk. As ccon as you Lave setiled
your definite plans, 1 should like to know just when you plan to arrive.

It is probably not to soon to begin detalled discuseions of research
problema. From our experience, I would conclude that a systematic study
of related strains 4a more LikelySto ve fruitful than a more extended
survey. It seems very likely that groups B and D form one connected system,
within which transductions will be fracly pousible, Lialted caly y the
suitability of cvallable phages. Mt "5 (seven Dee) Cincss is orig to oon
sclidate this principle. The nost icgicai further step is the exagination
of the remaining majoxv groups, aspeciaily ¢. If the mechangén of genatic
exchange can bs worked out there, we can then try to relate, if possible,
the behavior of the different groups. Perhaps I aa overoptimistic, but I
am fairly confident that we can find what we are Locking for dia these groups,
by follcwing the methodology alreacy estaslisned, For this reason I suggest
that we study 2 @ munber of atrains cf a eingle “serctypa ahvoge phages nave —
been well defined, ani I conclude that Williams~smith has already done this
kind of praparatory work with S. thompsor. “We ourselves spent cver two years
"preparing auxotrophs...of the comson types iplanning to] foliow up -eny ercss
that seems particularly interesting or hopeful", but it wae not until we
undertook a poncontre~ed study of S. typhimurium that interpretable results
were achieved. way I urge as strongiy as i can that we follow a similar
coursa here; if another type besides thompson seems preferable, lut me hear,
Once the technique of intra-strain recombination is validated,it should be
very easy then to proceed with inter-type studies, with the wain objective,I
suppose, of serotypic recombination.

Not long ago we received a sample of Boulgakov—Sergic's "flagellar
phage", and have been using it to select 0-forms of varying stability,
which have been intereating for our genetic analysie of the flagella.

We find that very few artificial O-forms are completely stable, and have

been surprised at the ease with which OH-"reversions" have been sulected

a such strains as Felixf S$. typhi 0-901. Have you had any experisnce
th this?

Sincerely,

Joshua Lederkerg
*Associate Professor of Genetics
*P.3. Professor Tatum was my counselor for my Ph. “Des but went back
to Stanford University from Yale.