Transduction is another process by which recombinant 
DNA may be transferred from the laboratory to wild populations 
of bacteria. Little is known about the occurrence of 
transduction in the wild. Most strains of E. coli are 
sensitive to the generalized transducing phage PI, but the 
distribution of this phage in the environment has not been studied. 
(F: 711) . Anderson reported that one out of 114 strains of 
E. coli isolated from 38 human subjects was sensitive to 
infection by phage lambda. (F: 686-687) . Lambda lysogeny 
was not observed in this strain. More study is needed to determine 
whether or not transduction contributes to bacterial gene flow in 
the wild. 
Though E. coli K12 and X1776 have vastly different 
capacities to survive in many environments; they have similar 
capacities to proliferate in and kill experimental animals when 
injected into various tissues.— ^ Wild strains are 1,000 to 
10,000 times more virulent than these laboratory strains in 
injection experiments. The LD 50 for K12 and X1776 when 
injected into mice is about 10 ® to 10 ® bacteria; this number 
would be contained in one ten- thousandth of a milliliter of 
bacterial pastes routinely handled in microbiological experiments. 
Therefore, we recommend: 
(a) Phsycial containment levels should not be compromised 
until biological containment is better understood. This is 
especially important in considering the change from P4 to P3 and 
16 / S. B. Levy et al.. Nature, 274 (1978), 395. 
[A-194] 
