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COMITATO Opnivarore
PER IL IX CONGRESSO INTEYNAZIONALE DI GENETICA —
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Segreleria Generale: ie di ‘Genetica dell’ Universita
Vis Celoris 1 - Milano (Italia)

i

16/2/52

Dr.¥. Hayes

Dept.of Bacteriology
Postgraduate siedical School
Ducane. Rd.

Lon dad onn W, 12,

Dear Eayes, _

Thank you for your letter of Feb,l0th and
the enclosed note to Nature 3 I am interested to see that UV
stimulation agrees with,and rerhaps follows fron, fertility
behaviour. I have a strain with a higher frequency of' recombi-
nation that seens to have a higher sensitivity to. UV stimule-
tion than 5°-161 (from which it was derived). As to Spicer's
infertile strain - I think he sent me a subculture of it some
tire ago; I can recall writing him something about infer-:ili-
ty of one of his strains ~ it is probably the fomnth occurren-
ce of the same event, viz.mutation to infertility.The first _
nust. have been in the building of TLB,- jy. one occcurred in a.
Bie strain +hich I treated with Ny in 19493 another to “rs,
Lederberg again ina BM- strain. I have a subculture of this,
which was sent to me by Lederberg.

Re your experiments: I think I ern predict
the result ofk the experiment which you plan,of infecting an
infertile strain with a fertile one,It was discovered by Le-
derbers a month ago,and I was reaching when I heard cf it,e-
xactly the sane conclusion ,that fertility(ratbertself-ferti-
lity) is infective. It is very highly infective. In 4 hours
contact(shorter é@xposures not tested) 9C;) of the cells of
an infertile strain are infected, It is not easy to detabh
the transforming principle off the fertile celis; I hove how-
ever to confirm sone eRppriments which were positive recently.
Infection is nore difficult in the presence of DNA-ase 3; and _
ie enhanced by UV-stimulation,so that sb ane well be that the
transforming principle be the same; anes ne es your irradia~

ted cultures viscid, However, the transforming principle mus;
h -
 

be either insohuble or highly unstable in solution,since is
cannot be recovered easily in filtrates,

When I suggested crossing two streptonycin-sterilised
strains torether, I meant of course using two fertile strains,
I have some idea that gametes -if there are any such things ™
may be formed on both sides. On the present evidence,it may be
that the infarkitityxef inability of streptomycin sterilised .
inferyile celis to cross with fertile strains is due to their
incapacity of reacting to the fertility transfoming principle
by forming gametes. Ome facts haem emerced however,which throws
doubt on the whole recombination storys: in the infection for
Fertility , infection betwee: living cella eccurs,but nothing is
usually found in the filtrates. Does this not look like. what
hapsens for: prototroph’ formation ? I still believe thets is a
fundanehtal difference between ‘tha two phenorena, ‘but I. am not
as sure about it ae I was a month Ago.

I shell be in London for a fev days in the firat week of
sareonh and shall ring you.up 3 I shall take this opportunity for
letting you have the strains which you demand. As to the meeting
te Burope nicro. jbicegeneticists, I think you will hear soon of

£ orfics sal Ty? pe) will be from 1-5 September,tha place is not
yet decided -except that it will be in Italy. Would you please
keep this information private.

Yours sincerely

Pe’. I sball send a copy of this letter to Ledeberg,