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multiply or doesn't penetrate, it doesn't cause disease. So when you put 
these virulent genes into the E. coli , into the K-12 as a matter of fact, 
or even other strains that you isolate from stools of normal individuals, 
and put this Shigella , the virulent genes into it, the genes that allow the 
Shigella to penetrate and multiply, the E. coli does not penetrate and does 
not multiply. So here two alterations have been done in terms of trying to 
upgrade the virulence of this E. coli to make it like Shigella, and this 
has failed. This is giving large numbers of organisms to volunteers, enough 
that would produce shigellosis if this was a parent organism. 
DR. FREDRICKSON: Dr. Hornick is also a member of the Recombinant 
Advisory Committee, a new member. Dr. Szybalski, who just left this Com- 
mittee, had his hand up too on this same matter. Yes, please. 
DR. SZYBALSKI: First, about E. coli K-12, it does not grow in the 
intestinal tract and does not colonize, and doesn't grow in nature. No 
coli grows in nature. It perishes very fast and that is the reason why 
you use a coli test for recent fecal contamination, because you see only 
recent contamination. A few days later it is gone. It doesn't survive, 
and that is the reason it is an indicator. 
Now, to answer your question, I think the best would be to take a 
quotation from the Gorbach letter, which refers to Dr. H. W. Smith, who 
is really a specialist in this field, and he says that first there was a 
consensus agreement with the concept that E^ Coli K-12 could not be appar- 
ently converted to an epidemic pathogen by inserting DNA molecules. Indeed, 
Dr. H. W. Smith carried the assertion one step further, saying that in his 
opinion not only this would not happen inadvertently, but even deliberate 
attempts to produce epidemic pathogens would require 20 years of full time, 
and it would be an evil effort. 
DR. FREDRICKSON: If we allow the members of the Recombinant Advisory 
Committee to continue this colloquy, I think it may be extremely valuable 
to the members of this Committee if we do that. 
Are there further questions directed to this particular problem or Dr. 
Bock's last presentation? 
Ms. Simring, you are a witness, and we will give you an opportunity, 
Ms. Simring, after this to return again. 
MR. THACHER: I have some comments on this question which I will give 
as a witness later, but I would be happy to state them now. 
DR. FREDRICKSON: You are in the same case, Mr. Thacher, but I don't 
want to be overridingly severe. You have a question for Dr. Bock? 
MR. THACHER: No, on the question of how well we understand the patho- 
genicity of E. coli K-12. 
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