11 
bacteria to grow in a nonlaboratory environment. The resulting mu- 
tant. named Chi 1776, met the criteria for EK2 containment developed 
by the XIH Recombinant Advisory Committee and was approved for 
experimental use by the Director. 
Oliver Smithies, a member of the recent Academy panel, discounted 
any possibility of risk with the host organism constructed by Curtiss 
and his colleagues. Smithies said in his testimony : 
* * * the negligible risk of Chi 1776 * * * surviving in the feces 
or of the recombinant DXA plasmid, being transferred to some 
other bacteria becomes less than one chance per 100.000 laboratory 
workers working for 10.000 years without special physical pre- 
cautions. (With the application of) physical precautions, * * * 
the risk is no longer worth considering. 
Several essentially nontransferable plasmids have also been developed 
for use as vectors with Iv-12 Chi 1776. 
Curtiss and others therefore disagree with the suggestion that pref- 
erence be given or experimentation restricted to use of host cells that 
do not normally inhabit human beings. Xot only are the genetic char- 
acteristics of E. coll Iv-12 well known but also substantial evidence of 
its safety is beginning to accumulate. A requirement to use another 
host organism would impede research and raise greater uncertainties 
about potential risks. 
USE OF OTHER HOST-VECTOR SYSTEMS 
The data on mutant strains of Iv-12 do not support a conclusion 
that all recombinant DXA research is without risk. Curtiss argued in 
his testimony that his own findings should not be applied to any other 
host-vector system; even knowledge about other variants of Iv-12 is 
insufficient. He referred specifically to two host cells of potential in- 
terest, Bacillus subtilis 168 and Pseudomonas putida PpGi. Unlike 
E. coll . both of these bacteria are soil microbes and are nonpatho- 
genic : however, there are few if any data on the factors that influence 
their survival in a natural environment or their ability to transmit 
recombinant DXA to other micro-organisms, let alone data on what is 
required to cripple these organisms in order to prevent their prolifera- 
tion. Curtiss believes that such data should be collected on alternative 
host-vector systems before they are approved for recombinant experi- 
mentation. Stuart Xewman of the State University of Xew York at 
Albany in a letter to the subcommittee suggested that once a new 
host is certified, investigators should closely monitor their experimen- 
tal cultures to insure that contamination, type reversions, or other 
unexpected changes have not occurred. 
At present, comparatively little effort is being devoted to non-K-12 
systems with the exception of Bacillus subtilus and a few viral vectors. 
1 et many researchers with commercial applications in mind believe 
that E. coili K-T2 may not be the ideal organism to receive certain 
kinds of genes and recommend development of a varietv of host- vector 
systems. Ronald Cape took this position in his testimony to the sub- 
committee. Even in basic research, the failure of gene expression bv a 
recombinant DXA molecule may be a function of the particular host 
cell environment : and the availability of other host cells would facili- 
tate investigation of a greater variety of DXA functions. For these 
[Appendix B — 271] 
