meas. on LT~2*

October 6, 1952
Dear Norton:

This letter is in reply to yours of the 2d [if we continue to correspond
with cross-firing, such asformal introduction may be a good idea).

XI am glad to hear that your leb. organisation has progressed to the point
that you want cultures. They will be sent on (if still viable) very shortly.
Actually, not so many cultures have been lost, but only because the beads
extracted from cracked tubes that were sopping wet above the cotton still
grew out. Your comments on the directions of your work at Rockefeller seen
very sound. It is important to remesber that a really adequate proof that
FA = phage has yet to be made. This may be difficult, as it 1s like asking
whether the particle that transduces alight, underwwhatever other circuastances
are critical, indtead have killed. The UV activation may still be « useful
lead.

I'm not mare that I did understand the sentence (p. 2 P.4) that you asterisked:
what system are you talking about "heterologous—donor, sensitive-indicator"?
In this connection, you aay be interested in SW-665 (which I will ship), a
Xyl- mutant of SW-541. Bruce found this strain to give an unusually high yield
of transmotilisations with PLT22/2, and I think the same may hold for the Xy}+
transduction. It gave a (linear at serial dil.) assay of ahout 1 Xyl+ per 10
plaques.*Control assays with SN-435 and SW-666 (a Gal- from SW-543) were not
linear (I don't know why, there should have been enough cells), but roughly 5-10x
leas. SH-665 also seems to be self~lytic, but the plaques were suppressed by
PLT22} Another lead that may be pertinent for you: Bruce and I were impressed
by the relatively high efficiency of transmotilisation as compared with antigen
transduction. I rather suspect this is, after all, due to inhibition by the serum
of the trabsduction itself. The transaotilisatdon of 9N-543 by PLT22/2, which gives
both 1 and b was rather drastically inhibited by the addition of either serum
to the motility agar. There was a 90% inhibition of Xyl+ output from SW-665 by
the addition of .02 ml tymr. serum to the plates 15 alnutes after the celle and
FA were aixed. I would suspect the somatic rather than the flagellar antibodies,
but think this problem belongs to you. Anyhow, I eam checking the advisability
of growing the cells + FA separately some time before inoculating serum-selection
plates.

Concerning the coli galduction, I may have omitted one point. Eether finds
that Lp; Lpo” (which adsorbs lambda) oan be galduced. The usual result is still

immune, but rarely the output is lysogenic! (This does impair the definition of
imauneg but points up the association of galduction with lambda). In at least one
case, the result was unstable jointly for lysogenicity and Gal+, in others the
two functions separated. This pretty well shows that the phhge is essentially
passive, but may or may not proceed into the bacéérium along with the Galt/ Your
interference experiment sounds dngenious but difficult. At any rate, as many
etages as can be tested mist be looked at in studying the assochation of FA with
phage. I don't quite see why you are concerned about a linear FA response at
low multiplicities, Either a constant fraction of the temperate particles are
genetically effective, independently of each other, or plaque formation does not
necessarily mean the loss of the cloge (we have some evidence of this in K-12}/ with
the "contaminated" colonies).

SW-543 1s getting more and more complicated. The serum situation has improved,
allowing some better experiments. For one thing, the spontaneous h reversions
show a second phase (only about 3-5 per small plate) which I have not yet identified.
It will be alittle strange 18 Kauffmann had mislabelled this paraB. I have FA from
a good many other serotypes: PLT22 works very well on paraB's, abony, enteritidis,
gan diego, altendorf, and dublin. I am waiting to have the typing confirmed, but
each of these seems to give its own phase as well as b phases in the transmotilization:
of SW-543. I have been using SW-666 mostly, to check on linked Galt/antigen trahsduc-
tions: 30 far nona. Together with your remarks about SW-572, I think we can forget
about the chance of an intrinsic origin for the non-b phases. I have not had any luek
so far with FA from typhi, stanley, eastbourne, or heidelberg. Can you give me your
setup for typhi? All this seems to point very well to linked transductions of
Pseudoalleles, but I think the explanation is, in its way, simpler. If, in SW-543+
FA(i) [4.e. typhimurium], the i phase is a two-linkedOgene transinduction, then
4t should behave like typhimurium in a genstic test, viz. ite FA should in turn
transduce both b and i. In the one experiment I have tried so far, this was not the
case, and only i phases occurred (tested with the help of b-antiserum selection),
whereasthe controls worked very well: FA from spont, or transinduced b gave only b,
PLT22/2 of course gave makyx both bd and 4. What this means (aad the suspicion of
which led to the sxperiment) is thgt SW-543 is a very pecdlaar strain whose genotype
can be given as AY B. The b tranB@uctions are a® B » the i's are A* BU, each a
one-gene transduction. This can be Intespreted to mean that A~ is inhibited by B-,
or needs B+, reas the other A alleles are not dependent on B+. Presumably other
non-dependent A? alleles will be found, perhaps among the spontaneous b. This hypo-
thesis can be checked further in varlous ways, o.g., a two-step i transduction, obtain
vis A~ B+ should be at B+, and ite FA will transduce Moth b and i to SW-543. I don't
know the details of Alexander's dual transduction, but one should, of course, rely
on genetic tests like this, rather than inferences directly from phenotypes, as to
the genetic basis. ,

We are bound to run into points of technique and material that will be recipro~
cally useful, and I am sure there will be no hesitation about exchanging such infor—
mation. To help explicit statement, why don't we exchange each other's stock lists
from time to time? At least, we can-give precise examples. I hope I haven't left
anything important out of this letter: it is easy enough to forget the frame of
reference.

Your CU's never showed here. Esther will take care of it as best she can when
we arrange the renewals, very shortly. CU mailings generally seem to have been in a
mess this summer.

Sincerely,

Joshua Lederberg

P.S. Why do you suppose SW-435 1s avirulent? How about its prototrophic transip
ductions? Or can you transduce virulence from LT~2?
JL