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frequency of transmiss ib il ity . It doesn't take into account the fatty acid 
content of the intestinal tract. Fatty acids clearly inhibit the transfer 
process. It doesn't take into account the pH and oxidation-reduction poten- 
tial in the intestinal tract, all of which further have been shown to reduce 
transmiss ibil ity . In my view, that number is very much on the high side, and 
the probability is probably, in my view, even less than that. 
In addition, the defects in the conjugative ability in the Chi-1776 
strain, this EK2 strain, the disabled strain, have been shown in published 
reports to even further reduce the likelihood that a plasmid vector in an 
EK2 host-vector plasmid system will be transferred by conjugal mating. 
Finally, to conclude my statements on the transmiss ib il ity aspect 
of EKl and EK2 systems — in the case of the lambda cloning vehicles, the 
phage cloning vehicles — the narrow host range and host-dependent mutations 
within these vectors severely limited their transmissibility . 
The increased confidence in E. coli K-12 as a host in recombinant 
DNA experiments also stems from estimates on the probability of converting 
E . coli K-12 to an epidemic pathogen, as has been brought up a number of 
times today. As discussed this morning, the recent Falmouth Workshop on 
Risk Assessment of Recombinant DNA Experiments — at this workshop some 40 
scientists representing a number of different areas of expertise, including 
specialists in infectious diseases and the bacteriology of the intestinal 
tract, came to the consensus conclusion that E. coli K-12 is so severely 
enfeebled in essential properties for survival in nature and for patho- 
genicity that it is incapable of being converted to an epidemic pathogen by 
the insertion of DNA by recombinant DNA techniques. Experimentally it has 
been demonstrated that the deliberate introduction into E. coli K-12 of 
virulent plasmids or chromosomal genes implicated in the virulence of a 
Shigella flexneri strain--both of these kinds of experiments have failed to 
convert E. coli K-12 to an effective pathogen. Thus, even in the case of 
these well-defined systems where intensive attempts were made to convert E . 
coli K-12 to a pathogen, this organism retained its nonpathogenic properties. 
Finally, in considering our Committee's consideration of the safety of 
recombinant DNA research, it should be noted that geneticists in general are 
becoming increasingly aware of the potential for exchange of genes in nature 
by events that do not involve extensive homologies between DNA sequences, or 
to put it another way, by events that do not involve requirement for DNA from 
identical or similar organisms. For example, the recently discovered trans- 
locatable elements, which have been well documented in a number of very 
beautiful papers — the discovery of these elements in bacteria — these elements 
have been shown to promote the exchange of genes between DNA molecules that 
are incapable of recombining by the usual recombination events. 
In addition, there has been recent documentation of the incorporation 
of bacterial DNA into the cells of higher plants. Dr. Chilton, who is 
with us today, and her colleagues, their work is particularly germane to 
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