6 
We recommend that the construction and testing of possibly suitable 
EK-2 host/vector systems, continue with careful and extensive experimentation , 
along lines that reconcile the objections we have raised in this critique. 
Time must be allowed in the construction of an EK-2 host so that sacrifices 
in the construction (such as that of the isogenicity of with its 
parent and the direct use of nitrous acid mutagenesis) are not made in the 
future for the sake of expediency (see this paper §§A1, AI, A3, A4, A5, 
A6, A7) . 
We commend the honesty and candid nature with which Roy Curtiss' 
group has presented their results, and hope that their T/ery impressive 
experimental efforts and frank presentation will serve as -.xamples for • 
other groups attempting to develop similar EK-2 systems. It is with a 
deep sense of admiration for the work of Dr. Roy Curtiss III and his eight 
co-workers at the University of Alabama that we offer our detailed 
criticisms, the highest form of respect that one group of scientists 
can pay to another group of scientists. 
At present, we find that the "weakened" Escherichia c:li strains 
obtained by the Curtiss group have many "strengths" which do not support 
the concept of biological containment. 
[Appendix C — 194] 
