6 
mechanism has been demonstrated. "Conjugation-like" transfer is a more general 
mechanism than generalized transduction since generalized transduction is 
limited by a number of factors extraneous to homology. 
Dr. Pat tee asked whether the crystal protein genes are stably integrated since 
they are part of a transposon . Dr. Dean said it is assumed the crystal protein 
gene is stably integrated in the chromosomal loaation; it can be lost from the 
plasmid location. 
Dr. Baltz asked whether chromosomal genes bound by insertion sequences involved 
in illegitimate recombination would be considered legitimate candidates for 
inclusion on Appendix A of the NIH Guidelines. 
Dr. Clewell said conjugative transposons probably hitchhike with plasmids even 
though they can conjugate on their own at a lew frequency? but the issue is 
vhether information demonstrating the transfer of chromosomal genes has been 
published. He said evidence indicating genetic exchange between EL_ cereus 
and Ih_ thuringiensis shews the type of exchange described in criterion 4 (Attach- 
ment III). 
Dr. Friedman asked the working group to comment on the data cited by Drs. Novick 
and Polak for subtilis and amyloliquefaciens (Attachment II). Dr. Dean 
said subtilis and B^ airy loliquef aci ens have been shown to exchange chromosomal 
genes; they are included on Sub list B of Appendix A. 
Dr. Friedman asked the working group to consider the data cited by Drs. Novick 
and Polak for Bj_ subtilis and pneumoniae (Attachment II ) . 
Dr. Lovett said the evidence for genetic exchange cited by Drs. Novick and Polak 
describes transfer of extrachrcmoscmal drug resistance genes. 
Dr. Macrina said a vast amount of information has accumulated in the past 
five to ten years vhich demonstrates widespread dissemination of drug resistance 
genes among Staphylococcus , Streptococcus , and other closely related pathogens. 
These genes are found on transposons, plasmids, and at chromosomal locations. 
A growing body of evidence suggests transfer of drug resistance genes should 
be considered a separate type of genetic exchange. These plasmids exchange 
intragenerically as well as intergeneric ally but are probably not "conjugative" 
per se . The mechanism of transfer of drug resistance genes should probably 
be called "conjugation-like." Drs. Clewell, Dean, and Macrina said they knew 
of no instances where drug resistance plasmids mobilize chromosomal ENA. 
Dr. Macrina said the drug resistance plasmids should more properly be called 
multiple host-range plasmids to distinguish these types of plasmids from the 
plasmids found in gram-negative bacteria. 
Dr. Pattee said seme investigators have reported sane gentamycin plasmids can 
transfer chromosomal ENA, but these results have not been reproducible . 
[ 537 ] 
