UNIVERSITE DE PARIS.
FacuLTe Des SCIENCES

LABORATOIRE vr GENETIQUE

43. Rue PieRRE CURIE. PARIS V‘ Nevember 30, 1955

Tél. : ODEon 16-40

 

Professor J. LEDERBERC

Department of Genetics

University of Wisconsin
Madison 5, Wisconsin

Dear Josh,
1) I am sending you today four strains of yeast 3:

wy GF 276/3 br/l a2 mating type -
- 9

? BIS p4 " +
/7 53/19 a " -
'” 53/19 e " +

These strains are those used as testers in our earlier work (Chen, Ephrussi
anc Fettinguer, Heredity, 1950). The first two strairs are "vegetative petites",
The lasttwo were "segregational petites” (recessive r + eytoplasmic factor).
These strains have not been used since 195] and the tests performed last week
did not show the presence of the cytoplasmic factor. This does not surprise
me because our previous experience shows that the latter is easily lost,
converting "segregational petites" into what we called "double mutants", T
presume that these two strains still carry tke recessive r, and that your
student will therefore be able to obtain strains of "secregational petites"
by crossing them to wild type and dissecting a few asci. I would have been
happy to have this work done here for you, but my assistant, who does these
things, is on s maternity leave until January. :

2) Concerning the red pigment of adeninelese mutants : strain 276/3Br/lA
which I am spending you is an example. It is derived from 276/3Br which has
normal respiration and is adenineless and red. lAs is petite and is white on
the usual yeast extract (low glucose) media. However various factors and, in
particular, high glucose content (above 3%) will make it produce red pigment.

The non-production of pigment by petites is due to their inefficient sugar
utilization. Pigment formation requires the presence of sugar after arrest of
growth ; on the usual (low glucose) media the arrest of growth of petites is
caused by exhaustion of glucose, hence there is no pigment formation,

Pigment formation in its last phase also depends more directly on oxy-
dations (via a system which is not the Warburg-Keilin system). Therefore, ade-
nineless strains with normal respiration febm white colonies under anaerobiosis ;
these will repidly turn red on exposure to air./Red pigment formation is inhki-
bited by excesg adenine. The concentration of adenine must therefore be con-
trolled in sypthetic media.
UNIVERSITE DE PARIS DEG 5 1955

FaAcCuULTE DES SCIENCES

LABORATOIREcos GENETIQUE

13. RUE PI—ERRE CuRIE. PARiIs V*

Tél. : ODEon 16-40

 

Lastly, there apparently exist adenineless strains blocked at earlier
stages and which never form red pigment. I think Roman, who is deing some
very interesting and extensive work on ad yeast, has found such strains.*

3) I promise not to take back any part of what I said te you about
your commentary at the Detroit meeting. You can safely send me a carbon.

4) In your last letter you forgot to write about your Salmonella re-
sults which you intended to tell me in Detroit.

5) Your congratulations have been conveyed te Harriett and Anne and
are appreciated (at least by the former),

Kinds regards,

/

Boris EPHRUSSI

x) Reversions from ad requirement to ad independen& are frequent, but have

no selective advantage in petites. An easy way of checking that strain 142
(whick I am sending you)still carries ad is to plate if'on a medium consisting

of Od ~ yeast extract + 6% glucose. It should form red colonies.