. LonG IsLAND BIOLOGICAL ASSOCIATION
COLD SPRING HARBOR, NEW YORK

THE BIOLOGICAL LABORATORY . October 21, 1955

Dr. Joshua Lederberg
Departnent of Senetics
University of Wisconsin
Madison, Wisconsin

Dear Josh,

I am sending you a summary of the tests on Novick's chemostated 58-141.
For some now unknown reason, I had been assuming that you had this information.
Your suggestions as to the handling of the F-disinfection studies sounds
satisfactory. The first thing I had been intending to do was to try to
disinfect by repeated passage in minimal medium with limited supplement,
i.e. a fluctuating population never exceeding a certain population density.
The use of a chemostat is mach more sophisticated however and should answer
any questions answerable by the other method. I have a number of things in
mind with regard to this problem, but most of them are not directly pertinent
to what had and is being done. One thing,however, is pertinent I think:
Tn none of the motility-disinfection experiments did I have an extensive
series of controls of the following kind. During passage on motag, perpetuate
two lines of descent, one involving constant isolation from the periphery (as
usual), one constantly from the center of the swarm. My guess is that che
both would eventually become highly motile, but that only among the former would
F~ be found. If this has not been done there, and you think it worth doing in
light of what you have found by now, I'll be able to do this.

The B transducing system to be used involves Pl. Involving as this does
an initial emphasis on phagology (isolation of Pl mutants, etc.) progress has
b2en agonizingly slow, despite the fact that Jill Hershey has been working with
me on the sroblem. JI suspect too that the S” auxotrophy at least is due to
mutations at other loci; but, if so, it will still be interesting to test the
large series of independent mutfvants for "microallelism".

I suppose you have heard of the Salmonella "transformations". DNA from
wild-type brings about the appearande of tryp # among
tryp,- (for example), but many of these "transformants" are now déficient at
another tryp locus (tryps for example). The activity of the preparations is
destroyed by DNAase. Demerec suggests that the appearance of an allele presant
in neither donor nor receptor may be due to damage incurred in the preparation
of the DNA (at the ends of small fragments for example). So far as I know, the
eritical control has not been done: Demonstration that DNA from, say, tryp,~
does not also cause the appearance of tryprt uma when applied back upon tryp,- cells.

Ozeki, in Demerec lab interprets a phenomenon in adenine transductions
as analogous to m "trailing" in motility transccutions. Along with large
transductants, he finds small colonies; upon restreaking, these never contain
more than one colony~preducing-c2ll on the original selective medium. Restreaking
from this single colony again shows enly one colony~producing cell present.
If this &s due to an active, non-mltiplying fragment, 1 wonder if some of the
small, non-prototrophic colonies obtained in c°li crosses might be analogous.

 
- LonG ISLAND BIOLOGICAL ASSOCIATION
COLD SPRING HARBOR, NEW YORK

THE BIOLOGICAL LABORATORY

I haven't had a chance to do anything more on the Jacob type experiments,
but hope to very shortly. I think the difference between the two experiments
can be shown to be due to strain differences by the type of experiment we have
already done: Using oru technique and using lysogenic Hayes’ Hfr show that
the order of transfer is L-V-Lac, as already suggested by our meagre results.

I have sent you the culture of nae Hfr Yaren and I used; we obtained it from
Lennox who calls it K15 (M- Az? Ss Thank you for the cultures; I am a little
confused at the moment as to what : lan may have had in mind. what would be most
desirable, J think, would be a well-marked F- Lac~ VF T- Le; is such a strain
available’

Your question with regard to La Jolla is appropriate; and I must admit that,
_after thinking it over, doubts accumulate. Much 68 this is due to my ignorance
both of marine biology and the position itself. I have thought for a long time
that I would like to attempt something on the developmental genetics of a colonial
protist (e.g. Volvocales) and had thought that something of this kind mim might
be appropriately done at La Jolla. However, the Volvocales are not marine and I
really have no idea what organisms might be appropriate. Sponges perhaps but then
these are not microbes. So this is the state of my ignorance. Granting that
appropriate marine organisms exist, that their cenetics is not too inaccesible, and
that such work would be welcome, I think I could honestly predict a considerable
interest.

Sincerely,

“Pare

P.D.Skaar