UNIVERSITY OF LONDON

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POSTGRADUATE MEDICAL SCHOOL

DEPARTMENT OF BACTFRIOLOGY.

 

  

OF LONDON
Telegrams
POSGRADMED CHISK LONDON DUCANE ROAD
Telephone LONDON, W.12

SHEpherds Bush |260 (4 lines)

2nd.December,1°951.

Dear Dr.Cavalli,

About 18 months ago,when you let me have two of the
recombining types of K 12 mutants,I told you I would let you know
if I made any progress with them. I am now enclosing a draft letter
to Nature(which I have since had to reduce to 2/3 its length) which
may be of interest to you. In brief,it shows that 58-161 can still
induce prototroph formation with W 677 after "sterilisation" with .
streptomycin,while similar treatment of W 677 renders it quite
incapable of participating in recombination. Since getting this off
my chest,I have confirmed that small,sub-mutagenic doses of UV
radiation greatly stimulates recombination’ rates, and shown that the
effect of the radiation is on 58-161. If this mutant is irradiated,
washed,resuspended in broth at 37°C and mixed with a young broth
culture of unirradiated W 677,very much larger numbers of prototrophs
arise than with an otherwise similar but unirradiated mixture.
On the other hand,when W 677 alone is treated with UV and then mixed
with unirradiated 58-161,the number of prototrophs is usually no
greater,and is often less,than in the control mixture. It seems to
me that these experiments show that there is a qualitative difference
between the two mutants and that,while 58-161 probably is a gene
donator,W 677 is a gene acceptor. If this is so,it looks as if there
might be mating types among the K 12 mutants but I presume the
geneticists have already looked for this without success. Spicer
is letting: me have some more recombining strains which you sent him
and I will try the effect of streptomycin on them. I hope to
publish what I have done so far in the Jour.Gen Microbiol. in more
detail and will,of course,acknowledge vour gift of the K 12 mutants
there, Incidentally,the supernatant fluid of broth cultures of
irradiated 58-161 is inactive in recombination although the whole
culture,before centrifuging,is highly active. It therefore looks as
if the extruded genetic material remains adherent to the cell and
that the use of filtrates will not prove effective in the case of
K 12 anyway.

I hope life is bein ood to you and that u enjo
being back in Italy. none 8 » vo joy

Yours sincerely, |.
(Dr.William Hayes) pislcame