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strain of coli . This new information that has been obtained since the 
issuance of the present Guidelines comes in part from, number one, consul- 
tation with scientists having expertise in a number of different areas, 
including bacteriology, virology, infectious diseases, and plant biology. 
In addition, as we have heard today, there have been published reports, or 
there are reports in preparation from national and international scientific 
meetings, that deal in part or entirely with the potential biohazards of 
recombinant DNA research, and these reports have been a valuable source of 
information for our Committee. 
Finally, there is published — and some recent unpublished — results from 
experiments that are concerned with the risk-assessment of E. coli K-12 as a 
host for recombinant DNA, and these results have been a major factor in our 
recommendations. I would like to add that these unpublished experiments — and 
there are a few that are cited — were carried out, these experiments were 
carried out by recognized leaders in microbiological research, and have 
involved generally accepted procedures of analysis. These experiments, both 
the published and the recent unpublished experiments, had been designed to 
test the following: number one, the survivability and colonizing ability of 
E. coli K-12, and EK2 host-vector systems; two, the transmissibility of 
plasmid and phage vectors; and three, the potential of E. coli K-12 for 
pathogenicity . 
I would like to briefly comment on the results from these experiments. 
With respect to the colonization of the intestinal tract by E. coli K-12, the 
earlier published studies on the inability of this strain to colonize the 
intestinal tract of volunteers under ordinary circumstances have recently 
been repeated and extended with similar results by Dr. E. S. Anderson. The 
colonizing ability of E. coli K-12 has also been studied recently in some 
detail by Dr. Rolf Freter. In the studies of Freter, and this was reported 
at the Falmouth meeting — Incidentally, I would like to add that this was a 
meeting, as we have heard, where a group of experts in the field had the 
opportunity to discuss the results that were presented, and to discuss the 
conclusions that were arrived at by the presenters of papers. 
In Freter's study it was demonstrated that the EK2 host cell, Chi-1776, 
which carries some six mutations that affect the colonizing properties of E . 
coli , is unable to become established even in germ-free mice. I took a 
little exception to the analogy that was attempted to be drawn between 
recombinant DNA research and electronic circuitry breaking down in nuclear 
power plants or in spaceships and so on. I think I would like to underscore 
what Dr. Davis has said. This is not a question of the number of things that 
can go wrong; it is a question of how many things can go right in order to 
take a cell which is disabled — as an analogy maybe it has lost some six 
different electronic circuits — and, by probability, to somehow pick up the 
six electronic circuits so that now things can go right. I think that the 
kinds of analogies that have been drawn aren't too accurate. 
In these experiments, and in testing the colonizing ability of E. coli 
K-12 strains, attempts have been made to convert the E. coli K-12 to an 
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