UNIVERSITY OF LONDON

DEPARTMEN®T. OF

 

BACTERIOLOGY. - SU Bbe

POSTGRADUATE MEDICAL SCHOOL
OF LONDON -

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Telegrams ~

POSGRADMED CHISK LONDON DUCANE ROAD
Telephone .
SHEpherds Bush 1260 (4 lines) LONDON, W.12
10th .February,1952.

Dear Cavalli,

Many thanks for your last letter. First of all I am
enclosing a reprint of my letter to Nature,and also a typescript
of another letter just submitted,dealing with the enhancing effect
of UV on recombination. I thought this piped latter might
interest you. I am quite sure of the results though not,of course,
on the provisional theory based on them. When 58-161 log phase
broth cultures are irradiated and then incubated in broth for an
hour and washed,the resulting concentrated suspension is marked] v
viscid. I have had one such preparation estimated in an Ostwald
viscometer before and after treatment with DNA-ase and the viscosity
is definitely reduced. I shall be doing some more tomorrow. This
viscosity does not seem to be produced after irradiation of W 677
nor of an infertile 58-161 strain obtained from Spicer. This will
also be checked tomorrow,I hope. I am particularly interested in
Spicers strain. His W 677 & 58-161 strains(? obtained from you)
showed recombination just over a year ago. He left them on egg
medium in the refrigerator for a year while he was doing the Dip.
Bact.course and when he returned and tested them,they showed no
recombination. Working on my provisional theory,I suggested to him
that his 58-161 had lost its self-reproducing yeux gamete and ~
had therefore become like W677. On testing them out I found that
his W677 strain showed recombination with my 58-161 but not vice
versa. His 58-161 is completely infertile,even after UV stimulation,
I am now anxious to show: (1) That Spicer's 58-161 is capable of
prototroph formation when mated with a strain that behaves like
my 58-16l,e.g. 58-161 reverted to prototrophism,or a prototroph
from the mating of 58-161 & W 677, or some other interfertile strain
in accordance with your works (2) That Spicer's strain can be made
fertile again. This latter I propose to test for in the following
way: Make 58-161/Spicer S% and also Azide’ as a marker,then allow
it to grow in a fertile 58-161 culture after irradiation;finally to
plate out on streptomycin-agar and pick a number of colonies which
are S° Az’ ,and which presumably are not erwkerezapeg all prototrophs,
and test these for ability to recombine with W677. If these
experiments work out (they probably wo'nt!) I would consider the
evidence very strongly in favour an "infective" gamete which,like

P.T.O.
symbiotic phage,can be lost from a culture but which has no lytic
properties. If one assumes this to be the case it would explain your
findings concerning the absence of interfertility in w 677 and its
existence in the case of 56-161,wild-type K 12 and all prototrophs
since,in cultures of these strains a proportion of cells would lose
their gamete and become "zene acceptors" like W 677. However,I have
now tested 140 colonies from one plating of 56-161 and have not yet
found one colony which is not fertile.

In answer to your question,I have tried to see whether
prototrophs would result if 58-161 and W 677 were both sterilised by
streptomycin. The answer is "No", I would very much like to try
strains other than TLB] ~,however. I have not yet succeeded in
obtaining a back mutation to prototrophism with my 58-16l,even after
irradiation. I would be grateful if you could send me this,one strain
with and another without sugar deficiencies,both of which you say you
have obtained. - They would serve both my purposes. Would you like
58-161/Spicer? Incidentally,55-161 is definitely Biotin +. I find
that my strain grows just as well in basal medium + methionine,whether
or not biotin is added,when glucose is replaced by pure hydrolysed
saccharose which is,I think,certainly biotin-free. Moreover in a
short paper by Davis(J.Bact.,1950-60-507) he refers to 56-161 as
requiring only mettionine.

Incidentally,do you know anything about a meeting of what
I think is called the "International Association of, Vicrobial
Geneticists" which is meeting in Naples in either April or September?
I would very much like to produce some of my results there (as well as
to see Naples!) but do'nt know how to go about it. If you should
-have any information on this,I would be grateful to have it.

_ I think this letter is very diffuse but I thought I would
Like to tell you how things are going with me. I find this recombinat-
ion a fascinating phenomenon, . r

- Yours sincerely,

 

- (William Heyes)

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