W-1982

May 6, 1952

Dear "Luca" (?)

Your letter of April 28 arrived yesterday. Airmail service from Italy seems
relatively slow- I wonder why? I have received letters from Japan usually much
faster (3-4 days). I had always understood that you would take the responsibility
for the JGM paper [that is, if you accept the sequence of authorship as LC & L
for the Genetics paper]. You exaggerate the rawness of your English, even for
your letters. It has a continental flavor, but is very legible and quite correct

(barring a few minor details). But of course, I'm only an American myself, and no
authority on English.

q

You have raised the mauestion before of the possibility of my attending the
international congresses next year. In addition to the Genetics congress, I believe
the International Congress of Microbiology is also meeting (in Rome.!) Do you have
any affiliation with this group? You mentioned that some sort of special invitation
might be fabricated from the Genetics. If this could be done, and possibly the same
also for the microbiological congress, I think it might be possible to press the
foundations here for some financial support to enable me to attend. If my wife and
I did travel to Europe, however, we would prefer to go not merely for the congresses,
In addition to our personal plans, would it be feasible for us to spend a few weeks
in your laboratory? This is all very tentative, of course.

I am very sorry about the behavior of the last shipment of cultures, and to have
wasted so much time. I will rectify this promptly. The silica~gel looked very good
for a time, but appears to be too unreliable now. If I recall correctly, you xx
wished to have strains 679, 58, W-1305 and W167. I shall send these again, ©.’
and also Wkéitix This last is 58161 Lambda xtteebere F+. We are also sending this
to Hayes to verify whether the UV-stimulation effect depends upon the presence
of lambda. lirs, Lederberg also asks me to send W~1258A, the “prototrophic" NTCC123,
and some auxotrophs from it. Although we are not absolutely certain about W-1258A,
it is reasonably sure that it is a spontaneous mutant of 123. The F-status is still
under study, but probably F-, [Mrs. Gosting here meanwhile has reinvestigated
E. coli isolates hitherto regarded as inferthle with K~12, W-1177 having been used
as the tester. Several of them (still a very few percent of all tested) are fertile
with «-1177F+, and must be regarded as self~incompatible]. The only reason for uncer-
tainty about W-1258A is that the mutation occurred in an old culture not under close
observation, and we are relying on the correctness of the label. There is very little
else in the laboratory that shares its prototrophic, F~, lambdaesensitive quality.

I hope this disposes of most of the very old business. Maas' sterility story has
been pretty definitely resolved. All of his tests were with Waksman-coli derivataves,
and these are all very poorly fertile with K-12 and with each other, although Fr,

The reported effect of the pantothenate-mutation on fertility is based on incorrect
comparisons,

My letter of April 29, which you are possibly reading as I write this, carries some
new details on Hfr. I shall refer to it for details.
1)

2)

3)

4)

5)

6)

I would summarize the current st&tus of the Hfr work here as follows:

Lac+S™ recombinants from W~-1895 (your Hfr recently received) x W-1177.. approach
10% of the tctal population after two-three hours growth. Recombinahion is also
detectable after negligible growth.

The “zygote-colonies" are also detectable as segregating +/- on plain EMB lactose.
They show only the sane patterns as the Lac+S" selections. Usually only two
components, are present: one indisiinguishable from the W-1177 parent; the other

also Mal-S* usually Mtl-Xyl-M+B,-TL-, but Lact and often Vj" and v5. A few TL+

Lac+ ohtained without selection were all v,°. The results support a linkage

sequence V Lac. ...6602-Vy 006.7. ek » a8 in the earlier data. However, the segregation
of TL is not random, but very strongly biassed for TL-, which also perturbs the
segregation of the linked factors. The other factors mkam seem to constitute a
second group, in which thare is a similar perturbation localized at S. From previous
experience, this bias can be identified with the elimination or defect for Mal--s,
for which F+/F- appears to be decisive, I may add that studies of non-Hfr crosses
in which 5, &, and Lec have besn unselected markerg (P- ¥ TL- on methionine-agar)

hs . SP wx, bus =

now support « Linkage of S--M, but net M—Lec, the latter was previously deduced
only from the high*r nroportion of Lac- in M+ (prototroph) selections of M+Lac~ x M-Lac

RHTXM but we may now conclude that something else directs the Lac ratio

M+TL+ occurs about 2-34 as frequently as the main types already mentioned. It has
been noticed without nutritions] selection, but studied more thoroughly in diluted
platings on ninimsl agar. the patterns observed are as expected with the selection
for Ti+. The Lac ratio 1s difficult to assess, however, because ‘nost of the
prototrcephs cre mixcd in varving proportions, unlike the standard crosses. I do
not undesrytuad this unless sueccessiva matin? is involved.

Conditions of high fertility are not very critical. Extremely dilute cultures are
capable of xmk& nating, and the resronse is very rapid. Hfr x F~ is mch more
fertile “hin Wir x Hfr or dfr x F+, The nrogeny of Hfr x Hfr (e.g. Lae+S? from
Lac- x ST) are still Hfr. However, the productivity of H¥rx Hfr is too low to be
very useful for detailed study, although it would be most interesting because of
the symmetry. As far 2¢ Iocan tell, the seprerstion patterns of Hfr x F+ are
similar to those of 2) above; I am studying the selected prototrophs more closely.

I have stsrted sone experiments with azctoiprite ( a much more euphonious hame
than mustard) to mkuxktrx new Hfr or F- types, So far (with linited treatments)
there has bean no success.

Cytologically, nothing new, Kiteneberger—Nobel has been studying §8-161 x W-1177.
She writes about some unique cell forms (not quite 4—forms) that she founds only
in the cross plates. I have not seen anything spectacular yet with Hfr, but am
not auEK whether further development of "conjugants?" occurs later on agar.

Hayes has sent a copy of his talk at Oxford. I see xm we will ccntinue to have
semantic problems, which will make it difficult to resolve the issues. The substance
of his self-reproducing gamete idea is not illogical. (although I think it is cer-
tainly poorly stated and probably incorrect). He is suggesting that F+ transduction
conveys the same vehicle as is involved in recombination, but empty. Your DNAse
experiments may scotch that. The aerathan phenocopy, which is reversible, also
separates the potential from the actual presence of the Ft agent. His second

point, that the gamete is imperfect from the F+ side is np more untenable than my
vagae idea of elimination after fertilization. I think the occurrence of still
hemizygous Mal/S crossovers argues for post-meiotic elimination, but not conclusively.
I hope it will be possible to s&ate the issues clearly,in our paper at least. If you
could try to repeat his sm-treatment experiments, it would be very useful.