495y Edgemere Avenue
Baitimore-15, Maryland
July la, 1947

Mr. Joshua Leserberg

Osborn Botanical Laboratory

Yale University

New Haven, Connecticut

Dear Josh:

I phoned you em the day we had decided upon, but you
were out of town, so I am writing to pass on the latest results
of the B. anthracis work pius a brief summary of tne material
with which you are already familiar.

1-Separate cultures of rough and smooth B. anthracis
were incubated at 37 and 42°C for 13 days (experine nt
discontinued at this voint) . No morphological changes.

2-Smooth plus rough at 42°C, 4,400,000 rough added to
5,900,000 smooth. After 48 hours 9, Se 20,000 smooth and
no rough vresent.

S- Smooth plus rough at 47 and 42°c, 14 smooth adaed to
15, 900,000 rough.

4 days- 42°= 15,500,000 smooth; no rough.

4 days-37 = 10,400,000 smooth; 4,600,000 rough.

7 days-42°= all smooth pHoweet dilution= 0.1 ml of
7 days-57 = ail smooth 1:10 dil. spread over agar
7 days-42°= one rough colony; others smooth.

7 days-37 — ratio of 1 rough to 5 smooth.

( Loopful streaked on agar)

4-Rough organisi: grown in broth filtrate and in heat
killed Bus pension of smooth showed no change after
6 days at 42°C,

The following may be of interest: The smooth mutation
shows a loss of proteolytic enzymes and of virulence. A reversion
in enzymes can be obtained, but virulence and the original rough-
ness are not regained.

If the above has not bored you, the rest of this letter
may do so. I am anxious to set back to the laboratory to continue
the research but will have to wait until September. Will you te
staying on at Yale or will you return to Columbia? My only useful
deed this summer was reading Luria'ts review on genetics. I enjoyed
nN

it and plan to do some more reading in the same field, for I
have a sneaking suspicion that the geneticists @nd genetics)
are getting tne correct answers in far more instances than

I (let us not say "in my ignorance") have been willing to
admit.

Please say "Heilo" to Esther for me.

Sincerely yours,

 
 

» M. Leise