ISTITUTG BH WILANESE

Feb.8, 1953.

Dear Joshua,

Much of my time is spent on Conrress organization,a very
dull task, but I try to keep as active as I can in the laboratory.
Some thme has elapsed since I got your lesser Christmas letter sthank-
you for it,as well as for the offprints of the fundamental Salmonella
peper,end the very good Lac paper hy Mrs.Lederberg. I am sending under
seperate cover four copies of offprints -the Heredity paper and the
abstract from the Italian microbiology Congress. Tell me if you want
more copies. Dealing first with personal business :

1) I heve not yet prepared the microfilm of the paragglutination
papers but shall do so next week/I hope you were in no hurry/

2) I h@ve sent you under separate cover a complete collection of
the Boll.Soc.Tht.iicrob.Sez.ital.,except years 30-31-~32. Public ation
was stonped in '43. There is no charge for it : we still have a few
copies left.

3) You dom not need to thank me for the sbove. In fact I am alrea-
dy thinking of asking you somethinz on exchange,and exactly,one or
two of the U-tubes which you use for filtra ion experiments.I have
a great difficulty in finding glass filters that filter sterile.

4) A young bacteriologist from Rome, Dr.Calef,has started working
with me on K-12 senetics. He has an #.D. and is an ective and bright
young chap (25) with good experience of bacteriology. He would like

to spend next academic year in your laboratory,and is looking - has
asked Buzgzati to get him one- for a sgholarship to this aim. Can you
°

accomodate him after October / F719 SRe utd also be interested about it
hecause I may be able to offer him a job on his return

5) I doubt that I shall be able to come to the States before the
Spring of 1954. This summer we are busy wwth fConsresses ;the only op-
portunity would have been the CSHS,but I have not been invited. I une
derstand Hayes was invited some months ago. Ihope I shall see you at
the Genetics Congress,although Congress time is the worst for talkine
shop. I wonder if you will be able to stay in Burope some tim after
Sept.the 12th?

6) Hayes has got : 1) an F strain ; 2) an Hfr strain. His Fe
(58-161/S) is very poorly transducible and gives 70% F- protorophs
when crossed to W 677 F+. I should consider it as a weak FT, His
Hfr,obtained spontaneously from an old culture of 58+161/S transduced

to P+ seems from his descriptions entirelywakin to mine. He asks my
Hfr,because his is STAzgr and he cannot test St-resistance of gametes,

I would really see no reason to deny it;I should only ask that it be
not circulated to other laboratories,
 
  

STITUTE $6 WILANES

7) Jim Watson has spent here a few days in January.He has a theory
to explain segregations - but the theory,which may help to explain
some facts,does not fit quantitatively.I understand he is sending you |
copy Of a manuscript about it.

Turning to my work ,

1) FT: there is probably a locus loosely linked with methionine
(but not with B, or colicine B-resistance which are linked with me-
thionine).In fact,crossing FT which is M- to TLB -ST on minStMetB
the M- recombinants are more often F- than B+, rt recémbinantsv tested |
sofar (only a dozen) show : hégmal recombination rate (F has low
recombination rate and high incidence of Becombination of the St-locus
in 80%; segregation into F+ and F-,with 50% frequency,when backcrossed
to TLB,-S*F+,with one exception giving 100% P-., Three such FT recone
binants,including the last,can be trahsduced though with very poorly,
to F+.jaybe FT itself is transducible buta at a very low rate.

When I heard of Hayes's results with his FY I tested samme Py transfer
in recombination using the third f-F- straan in existence,i.e.iirs,
Lederberg's strain ;it gave all F+ recombinants when crossed to "LB.
F+ with one exception. £kxisa This strain has the same canacity of
adsorbing F+ as TLB|-F-. There is probably a correlationhe between

a) transducibility to F+ 3; b) adsorption capacity ; @) % of Fe recome
binants (with complications due to segregation ) with various F- stra-
ins.xk I shallsw see if I can get some quantitative data about this.

2) Heat or acetone killed F- (and F+) cells can adsorb Fs atwattr®,
much as living cells. I am trying to get the F-receptor in a cell-free
condttionsif successful,it should permit to make a crucial test of
the carrier hypothesis by Hayes,which I do not yut believe,ins pite
of the Salmonella mwxidengex analogy. This proof could also be carried
out with dead cells,but a soluble receptor would be cleaner.Of course,
therevmight always be the escape,for Hayes,that the receptor does
not inactivate the F-virus by adsorbing it,but by making its reproduc—
tion in the cell impossible : a rather capntious objection. Yowever,the

exoeriment has yet to be done,
, 3) The quantification of the adsorption experiment,and some other
work which I have started on the kinet#ts (for insitance,there is a
strong dilution effect sless than 10° meixx F+ cells/ml will caase al-
most no infection) are being made possible by t'e use of the StAzT
crossing method.It is now quite reproducible. I use Penassay broth
with 1% Béfico agar in it,and pour plates with 10° “azide,10” T,,104

micrograms St,end bbout 10’ cells from a preincubated mixture. Reco:bi-
nation rates ar= as follows : TLB,-S7F+ x TLBy-Az "TTF, 4x10-7; P-xF+,
ISTITUTO

 

10° «3 F+x r+ ,107| ; F- x F-, 0 or occasionally 2 or 3 colonjes out
of the 109 parental cells plated.Have you started on the kinetics
proper? I should very much like to leave yam the physical aspects,
and consider rather the biological aspects,ugE hife stage and con-
ditions of transfer,and production of F+. LT pdb uh yom wom abe Sf.

a)The only coli-line ,the Feagent of which seems to be pretty
active on FT x FTis the Waksman coli. Unfortunttaly,I am unable to
get a stable F+ infection with Waksman F to any K-12 F- line. I
have had to work with mewmge 4 trois,which is obviously not as clean
as one would like. For instance (cultures enclosed),a methionineless
or homocystineless coli Waksman (1288/33 which I got from Davis ,and
is probably allelic to M- of 58-16l;syntrophy tests not well done,
however ),plus M-S'RFY (original Frs= strain No.219 of which a cultu-
re is enclosed,and corresponds to a StF mutant from strain No.8) ;
plus a recombinant from Fr x F+,which is B,-St°M+Xy1-Mal- ,on mini-
mal streptomycin B,-All recombinants are Ayl+Nal+(with 1% XyltMait)
and a few B.-. The same menage a trois would be sterile or almost so
if the F-donor were an M-&t°F+ of the K-12 line. However,when Fyis
acting as recor bination-determiner,thep pattern of reconbinattdon is
aifferent from that of Fy(from K-12) ;it would seem that Fy, determi-
nes easily the transfer of M+(saemasinnaliyxacesmpanr,never that of
TL+,very rarely that of St and linked genes. It would seem a sort
of "preferential trandduction",although the existence of a low pro-
portion of “co-"transduced markers would seem to make this a aiffe-
rent case altogether from Salmonella and K-12v(admittedly more si-
milar to the last onesnothing is filterable thréaéugh Seitw with the
Fe system). The difficulty of having stable Fy transduction has led
me to stop temporarily this line; however,the finding of other F+
agents permitting PX crossesvweems rather intesesting,eand it
weultd—-be-very seems attractive to try on an Pr ypt your fertile coli-
strains other than K-12. The two FT strains which I have-sent am
sending seem-Father are not ideal,but if the menare a trois “i tn
a SS foreign coli gives higher yield than a cross between the foreign
coli and she M-STFT strain this may be an indication of an effect.
Fould you be interested to have it tried in your laboratory with
other coli strains ? I hope you will . Another question : have you
been able to secure stable F transduction from coli Waksman?

5) Your work with Hfr is very interesting.Could you send me

H 313, and W-1578 ? Incidentally, how did you get F- in the P-G- ?

Was it obtained with nitrogen hustard?
I am also sending: which &s B,-lLac-,and gives 100% F- on crossing,