W.J. Gartland 
- 2 - 
January 11, 1982 
not colonize the normal mammalian gut, primarily because they are unable 
to displace the resident strains; it is not obvious to me that K12 is any 
different in this respect). On the other hand, it has been shown that K12 
can become significantly pathogenic under certain conditions. For example, 
a recent report by Portnoy and Falkow (J. Bacteriol. 148:877, 1981) de- 
scribes the acquisition of mouse lethality by K12 as a consequence of 
receiving a cloned hemolysin determinant from a wild strain of E_. coli . 
In consideration of the above, I would be very pleased to see reduc- 
tion to PI containment of most of the currently regulated experiments but 
I would urge that the guidelines remain in effect with their present force 
for experiments such as those mentioned explicitly above. 
Richard P. Novick 
RPN:cf 
(6531 
