9 
III. COMPARISON OF NIH GUIDELINES SPECIFICATIONS FOR EK-2 HOST TO 
THE PROPERTIES OF X 1776 AND X* 878 
It is of interest to compare the EK-2 specifications called for in 
the Provisional NIH Guidelines (1976) to what has been possible for the 
Curtiss group to achieve in the construction of x^- 778 an8 X^ 878 * The 
latter strain (xl876) is the designation for X^ 778 carrying the pSClOl 
plasmid (the "vector" for gene implantation), which confers resistance 
of the bacterium toward the antibiotic, tetracycline. The comparison 
made below does not imply an agreement with the contents of the NIH 
Guidelines (for our detailed critique of the Guidelines, see reference 2), 
rather it is illustrative of the biological obstacles tint are being 
encountered in realizing "biological containment" for Escherichia coli. 
Provisional NIH Guidelines : 
"... modifications of the E. coli 
K12 host and/or plasmid or phage 
vector should not permit survival 
of the cloned DNA fragment f in 
other than specifically designed 
and carefully regulated laboratory 
environments..." (Guidelines, p. 18) 
y!776 and y!87 6 : 
Curtiss et_ _al_. point out: "In testing 
X1776, we have not satisfied these 
criteria because that was not possible 
and because we now believe there are 
some flaws in the above stated 
requirements for an EK-2 system." 
(Curtiss _et_ a_l. , p. 3) The. strains 
proposed would have EK-2 status based 
on survival of the host without a_ 
cloned DNA in them. The authors point 
out " . . . one could choose a diversity 
of cloned DNA fragments some of which 
might increase the host's and/or 
vector's potentials for survival 
and/or transmission of DNA and others 
which would decrease these potentials 
and therefore create a false sense 
of safety." (Curtiss et al . , p.3) 
This last statement voices a concern 
shared by a number of scientists, 
namely, that the presence of a foreign 
t All underscorings in this Section arc ours. 
[Appendix C — 197] 
