CAN APPARENTLY ALi>0 BE GENERATED NATURALL Y IN VIVO ALBEIT ON 
A LESSER SCALE. SECOND* NEW DATA ABOUT THE BIOLOGY OF E.C0LIK12 
INDICATE THAT (1) E.COLI K12 DOES NOT COLONISE THE HUMAN GUT 
< 2 ) E.COLI IS NOT PATHOGENIC (3) E.COLI K12 CANNOT BE MADE 
COMMUNICABLE OR PATHOGENIC EVEN BY INTRODUCING GENES FOR TOXINS 
AND OTHER PATHOGENIC PROPERTIES FROM OTHER STRAINS OF E.COLI 
BY STANDARD GENETIC METHODS (4) THE PROBABILITY OF TRANSMISSION 
IN THE ANIMAL GUT OF NON-CONJUGATI VE PLASMID VECTORS FROM AN 
E.COLI K 1 2 HOST TO SOME OTHER BACTERIUM IS LESS THAN 10 -16 PER 
BACTERIUM PER DAY. IN SHORT E.COLI K12 IS SO GENETICALLY 
DEFECTIVE THAT IT IS INCAPABLE OF BECOMING A PATHOGEN. THE 
STRAINS OF E.COLI K12 THAT HAVE BEEN FURTHER DISABLED BY THE 
INTRODUCTION IN THE LABORATORY OF MANY MUTATIONS WHICH FURTHER 
RESTRICT THE CONDITIONS IN WHICH THE ORGANISM CAN SURVIVE 
(BIOLOGICALLY CONTAINED E.COLI K12: EK2 HOSTS) PRESENT NO 
THREAT TO MAN OR HIE ENVIRONMENT. 
WHEN THE ORIGINAL GUIDELINES WERE DRAWN UP THIS INFORMATION WAS 
NOT AVAILABLE* AT THAT TIME IT WAS SUGGESTED BY SOME THAT E.COLI 
K 1 2 MIGHT BE READILY CONVERTED INTO A PATHOGEN BY THE INTRODUCTION 
'OF FOREIGN DNA. MOREOVER* NATURAL BARRIERS TO THE EXCHANGE OF 
GENETIC MATERIAL BETWEEN SPECIES SEEMED GREATER THAN WE NOW KNOW 
THEM TO BE. THE NEW EVIDENCE DISPELS MANY OF THESE FEARS AND SO 
THE CONTAINMENT MEASURES INITIALY AND PRESENTLY REQUIRED ARE NOW 
RECOGNISED AS BEING TOO STRINGENT AND SHOULD BE RELAXED. 
[Appendix A — 88] 
