UNITED STATES DEPARTMENT OF AGRICULTURE

AGRICULTURAL RESEARCH ADMINISTRATION

BUREAU OF AGRICULTURAL AND INDUSTRIAL CHEMISTRY
PEORIA 5, ILLINOIS

April 29, 1946

Dre Joshua Lederberg

Osborn Botanical Laboratory
Yale University

New Haven, Connecticut

Dear Dr. Lederberg:

Itm glad to know that you are planning to study the genetics of
Schizosaccharomyces versatilis.

S.» versatilis grows rather poorly on synthetic media, probably due
to a growth factor deficiency, the nature of which we do not knows
It will grow fairly well on a synthetic medium similar to that
which Dr. Burkholder uses.

The Schizosaccharomyces are haploid in the vegetative phase and
conjugate just before sporulation. This is true when the cultures
are grown on agar, and presumadly when grown in still liquid cul-
tures, as evidenced by the shape of the asci. Itm not sure about
shake cultures, for if I remember correctly, I have seen in these
spherical asci, denoting either that complete fusion of the con-
jugating cells has occurred or that no fusion has taken place, the
inference being that diploidization took place when the ascospores
germinated. If such diploidization does occur early in the vege~
tative state, it is apparently rare. a
This yeast is definitely homothallic, and single spore cultures will
most likely sporulate.

I do not lmow of any yeasts which are frankly heterothallic.
I shall be glad to learn how your work progresses.

Sincerely your's,

Lynferd J. Wickerham, Zymologist
Fermentation Divisior
Northern Regional Research Laboratory