10 
Transfer of recombinant DN A from E. coli K-12 to other organisms 
A few scientists argue that while K-12 itself is unlikely to be harm- 
ful, its interaction with other E. coli strains could produce hazards. 
Jonathan King of the Massachusetts Institute of Technology observed 
in his testimony that hospitals have been experiencing increasing num- 
bers of infections from E. coli strains other than K-12. This increase 
is attributed in large part to the acquisition of antibiotic resistant 
plasmids by E. coli bacteria in the intestine. King infers that the- 
escape of a laboratory clone or contact between K-12 and Qther or- 
ganisms in the environment could result in the transfer of recombinant 
DXA molecules to a wild strain of E. coli and might induce a new 
form of pathogenicity. He argued that the evidence summarized in 
the Academy report and examined at the Falmouth conference is 
insufficient to conclude that use of K-12 eliminates any potential dan- 
ger from recombinant molecule exchange. 
King and other investigators who disagreed with the majority 
opinion at the Falmouth conference point to the evidence that K-12 
can persist in the human intestine for as long as 6 days. In further ex- 
periments with variants of K-12 enfeebled by a technique affecting 
plasmid transferability, transfer did not occur in the intestine but was 
accomplished in the laboratory; but these researchers suggest that 
while the probability of transfer of recombinant DXA plasmids from 
K-12 is low, it cannot be disregarded. Moreover, they claim that in- 
sufficient work has been done to insure that transfer by mechanisms 
other than direct transformation would not occur; nor have any 
experiments adequately addressed the possibility of gene transfer 
outside the intestine, in sewer systems, soil or via intermediate hosts. 
As yet there is no evidence that transmission of recombinant DXA 
molecules would be harmful, but researchers are nonetheless attempt- 
ing to determine the likelihood of such transfers. Oliver Smithies of 
the University of Wisconsin referred in his testimony to a then unpub- 
lished paper 2 reporting that in a 2-year period of monitoring the 
feces of laboratory workers engaged in nonrecombinant DXA re- 
search, no K-12 bacteria or K-12 plasmids with multiple drug resist- 
ance markers were ever found. The workers in question were using 
plasmids capable of being transferred, whereas in recombinant DXA 
experiments transmission-deficient plasmids are used with a weakened 
variant of K-12. Thus, the paper concluded that if transmission- 
proficient plasmids used without any special physical precautions did 
not appear, there is little if any risk of gene transfer from K-12 plas~ 
mids in recombinant DXA work. This study is widely regarded as a 
significant demonstration of the safety of the Iv-12 host. 
Development of f arther weakened E. coli hosts and vectors 
Even though the available evidence shows “noi-maP K-12 to be a 
very defective organism, even more enfeebled variants have been de- 
veloped to prevent colonization and transfer of recombinant. DXA in 
the event of accidental release of the organism. Kov Curtiss of the 
University of Alabama described his success in producing additional 
mutational changes in K-12 which greatly limit the ability of the 
'-'V. Petrocheilous nnd M. H. Richmond. “Absence of Plasmid of E. coli K-12 Infection 
Among Laboratory Personnel Engaged in K Plasmid Research,” Gene, Vol. 2, Xo. 5-6,. 
December 1977, pp. 323-327. 
[Appendix B — 270] 
