October 8, 1953

Dear Dr. Hungate:

This is rataer like trying to mke a medical diagnosis by mail, but it appears
to me that the most vulnerable point of your procedure has to do with "post—incu-
bation" [after mitagenic treatment, prior to plating]. fdesepageaB of the mimeo-
graphed vorsion of "Isolation and characterization of b 4a]. mtants"). In
addition, your conditions of treatment might concel ecting against
auxotrophs. \

 
      
 
  
    
  
   
    
     

Yorphologécally typical bacteria (no less than
are mitinucleate, and in fact usually display @
preparations, —

ave as if they
cell in stained

worried about this, I will gend a cul of Y-87 thionine-dependent, lactose—
negative). The incidences of aumotrep after the most effective
mutagenic treatment, may still te one iderably less. I would strongly
recommend that you screen your tion} by means of the replica~
plating techaigue.

On the whole, mtations to a
measuring mitagenic effects.

toxic, I would suggest Novic:
reliable for quantitative me

do not m&e for a very handy system of
rk at P30 ievels which are not too

& methodology as far and away the most
of mitation (See Cold Spr, Harbor, 1951;
i is as free from incorrigible errors.

   
  

If you mist use a
collecting quantitat
troph (like Y-87) as
as to the absence of
reservations |.

trophic mtations, I would suggest that the best means of
data is through the penicillin method, us a@ marked auxo-
standard. Cf. Lieb, Genetics 36:466 , 1953. [Her conclusion
enotypic delay mist be qualified very strongly by her own

Yours sincerely,

Joshua Lederberg

Dr. F. P. Hungate
Hanford orks, G.E. Coe;
Richland, Wash.