ALL CORRESPONDENCE
TO BE ADDRESSED TO
THE DIRECTOR

TELEPHONE
F OAB4

 

’

Che University of Melbourne

BACTERIOLOGY DEPARTMENT

Carlton, 3, 19th September, 19.55,

Dre J. lederberg,
Department of Genetics,
University of Wisconsin,
Medison 6,

WISCONSIN, U,S,4.

Dear Josh,

I was delighted to receive your letter irdicsting your
interest in visiting Melbourne in 1957 and have now submitted your
mame and Esther's to the Unite d States Educational Foundation urder
the categories of Fulbright Lecturer and Fulbright Research Scholar
respectively. Mac Burnet, who wil] probably be writing to you, is
equally enthisiastic over your proposed visit am will be only too
happy to offer you hospitality at the bench during your stey in
Melbourne. He will be acting as co-sponsor to my nomination.

In regard to projects which Esther could work on here this
is a little difficult to forecast exactly what will be problems of
current interest in two veers hence. At the moment there are three
research topics being investigated of direct and indirect genetical

interest. One is concerned with mutants of Aspergillus ugse which
aiffer from the parent strain in producing significantly (6-fold) higher

yields of citric acid then the parent Wisconsin strain 724. We are at
present preparing papers for the Journal] of General Miercbiology on the
nature and fermentative activity of these mutants and describing a
technique of isolation and Girect screening using a paper culture
technique. The latter merely involves culturing isolated spores on
absorbent paper previously soaked in medium containing a pH indicator.
By measuring the size of the cclony and the diameter of the acid zone
produced we arrive at a ratio,

the acid unitage (= Giameter of acid zone),
diameter of colony

Mutants with values greater than 5 are invariably high citrie acid
yielders. We know nothing of the genetics of this mitation. We are

now trying to discover biochemically why they produce such high yields.
One positive statement we can make is that the parent culture and mutants
metabolise citrate at an equal mte so that the lower ylelds of the
parent culture is not due to the utilization of citric acid as it is
formed.

aA
(K; Another line of research deals with mutaticn towards
Lo nonlysogenicity in By mecaterjum. The prophage of this organism is

not firmly built into the chromosome structure so that non-Iyvsogenic
mutants are encountered. Dr. Huybers of tris Department has foun a
mitetion rate (loss of prophage) which may be as high as 4%. He looked
for (A) "mutants of K12 and nomlysceenic Stanhs. but failed to detect
any in each organism. However, out of this he chanced upon 2 suicidal
mutation in which the phage from the normal lysogenic Staph. wil] lyse
mutant cells and the phage from the mitant cells will lyse the normal.
Hence, culturing the normil and the mutant together resultg in yutual

destruction. Vic cael th how attelsf agy (¢ each)

Then, of course, there is the veast work whieh I have no
doubt will still be budding in '57. We are sure te have something going
when Esther arrives.

Next week I shell be seeing Mr. Rossiter whd is in charge
of the U.S.4. Fulbright programme and should anything worth reporting
arise from this I shell immediately let you knowe

Finelly, many thanks for the eulitures which you sent us.
Unfortunately three out of the five tubes were broken, but we recovered
the orgénisms without cross ccntamimtion. It was an excellent ides to
give us agar deeps instead of fluid suspension (this saved the day).

I think you might warn your packer that it is a pretty tough journey to
Australia and a lot of packing is required. Fulbrighters of course are
handled mere gently!

With best wishes to yourself and Esther,

Yours singerely,

Ak

P.Se Last night I lost between the Department and home your reprint
from the Waksren series of lectures on aaa and Genetics.
~rf -

Can I ask for 4 second one if available. i}
fr ; _¢ ¢ f. ?} * f —
‘ ° ; : & f

asmhiK kt VEL Tom,