FOLD SIDES OVER AND THEN FOLD BOTTOM UP ANO SEAL.

NO OTHER ENVELOPE SHOULD BE USED.

Feb. 65 1949.

Dear Jacques,

I have your letter of the 31st.

You can be sure that the findings I wrote you of are as puzzling to
me as to yoy. We tested for galactosidase with K-12 grown on galactose.
Such celis do ferment lactose with acid production; I have not measured
oxygen consmption. It is. of course, possible that our galactose is
contaminated with a small amount of lactose, and we will have to repeat
the experiments with highly purified material. Even so this would not
account for the respoase of Lac)-, especially to butyl galactosdde.

Pardon me for my ambiguity in referring to "utilization". I have not
yet tested for combination of galactose or lactobionate with the enzyme,
and I was, referring to the utilization by the cell. It is, of course,

quite ‘possible that lactobionate unites with the galactosidase, but that

acs

at ds ‘not. split from it rapidly cnogh to allow utilization as aC source,

‘We have repeated many times, “the substrdte experiment (a ha Spiegelma

: ‘that you referred to, The reults are even more striking in the case of
i! the Maly segregation, because the linkage situation results in adaiy about
_' ‘Uf Malf prototrophs, a value which is not influenced by the medium on

which the cells have been grown. The ‘same thing is clearly seen in our

“heterozygote! segregations, where the segregation is followed directly

on the EMB agar carrying the substrate.

incerely,

  
 
  

Joshua Lederberg