130 
1 microbes carrying genes from distant species. 
2 Most of the rest of what I have to say bears 
3 on what I mentioned earlier, namely a rational reconsider- 
4 at ion of potential hazards of recombinant DNA research. 
5 By "rational" I mean related to prior experience. 
6 I think we have had available relevant experience 
7 with microbes that was not well utilized in the development 
8 of the current guidelines, but is more accurately reflected 
g in the proposed revisions. For example, the experimental 
10 evidence that non-pathogenic bacteria like E. coli K 12 
11 are not converted into contagious pathogens by simply 
12 acquiring small clusters of additional genes, even from 
13 donor pathogenic strains. These experimental findings, 
14 of course, have been emphasized at the Falmouth meeting. 
15 We have also had very long experience in the 
16 safe handling of truly pathogenic microbes. In most 
17 cases, simple microbiological methods suffice. For 
18 instance, in our medical microbiology course, where we 
19 have students of medicine, completely inexperienced in 
20 the handling of microbes, we use cultures of Neisseria 
21 meningitidis , a cause of severe meningitis; Shigella 
22 dysenteriae , the cause of dysentery? Salmonella typhi , 
23 the cause of typhoid fever; and many other pathogenic 
24 organisms. Over a 16 -year period I have not been aware 
25 of a single case of disease related to these laboratory 
[222] 
