7 
II. INTRODUCTION 
The NIH Guidelines for Research Involving Recombinant DNA Molecules 
will seek to contain bacterial hosts and/or viruses carrying implanted 
foreign genes by assigning combinations of different levels of physical 
and biological containment depending on the specific types of experiments 
to be performed. The term biological containment refers to the use of 
genetically modified or "disarmed" strains of the human gut bacterium 
Escherichia coli as host for the propogation of foreign genes. To quote 
the Proposed Guidelines approved by the NIH Recombinant DNA Molecule 
Program Advisory Committee, the disarmed strain of Escherichia coli K12 
. should not permit survival of the cloned DNA fragment in other than 
especially designed and carefully regulated laboratory environments at a 
—8 
frequency greater than 10 . J ' This strain of E. coli will be designated 
EK-2 and its use as host to carry implanted DNA fulfills the EK-2 level 
of biological containment. 
Dr. Roy Curtiss III and eight co-workers at the University of 
Alabama have worked toward the construction of such an EK-2 strain for 
more than a year and their data were presented to the NIH Recombinant 
DNA Molecule Program Advisory Committee at its most recent meeting two 
months ago. Curtiss e_t ajl. (1976) have summarized their efforts and 
achievements: "... a total of 13 genetic manipulations (were required) 
to obtain a strain that should meet the requirements of an EK-2 host as 
specified in the current proposed NIH Guidelines for Recombinant DNA 
Molecule Research. This strain cannot synthesize the murein layer of 
its cell wall under other than carefully controlled laboratory conditions 
I 
due to two mutations at different map (chromosomal) positions, is unable 
[Appendix C — 195] 
