THE UNIVERSITY OF MICHIGAN 
DIVISION OF BIOLOGICAL SCIENCES 
Mr. Richard Riseberg 
DHEW Office of General Counsel 
National Institutes of Health 
Building 31, Room 2B50 
Bethesda, Maryland 20014 
RE: Exemption of the bacterium Caulobacter crescentus from the 
recombinant DNA guidelines 
Dear Sir: 
Dr. Bert Ely recently sent me a oreorint of his manuscript 
entitled "Transfer of drug resistance factors to the dimorphic bac- 
terium Caulobacter crescentus " and requested that I conment on the 
data presented. 
I find the material entirely suitable for publication and except 
for very minor changes, mostly in grammar and typing, I would recommend 
its immediate submission and publication. In addition, I have indeoen- 
dently confirmed several of Dr. Ely's observations regarding RP4 trans- 
fer and the Phage sensitivities associated with RP4. 
I therefore submit that it has been shown that Caulobacter 
crescentus freely exchanges conjugative plasmids with other bacteria 
including Escherichia coli , that non-conjugati ve plasmids can be 
readily mobilized by other plasmids like RP4 between Z_. crescentus 
and E^ coli , and that plasmids like RP4 result in chromosomal mobi 1 i - 
zation within C. crescentus. Jollick (J. Gen. Microbiol. 99:325) 
has observed that RP1 wi 1 1 el ici t chromosomal mobilization between 
different species of Caulobacter but that most of the exconjugants are 
unstable and stable recombination seems rare. These observations taken 
together suggest that P type plasmids mobilize C. crescentus chromo- 
somal DNA into other organisms as well, though this remains to be 
demonstrated. 
It is my hooe that these observations will allow C. crescentus to 
be classified within the group of organisms known to exchange genetic 
material with E. coli . 
NATURAL SCIENCE BUILDING. ANN ARBOR. MICHIGAN 4S1Q6 
UNIV. CENTREX TEL. (313) 764-1817 / DIVISION TEL. (313) 764-1440 
September 14, 1978 
Sincerely yours 
Robert A. Bender 
Assistant Professor 
cc: Bert Ely 
[A-149] 
DEPARTMENT OF BOTANY - DEPARTMENT OF CELLULAR AND MOLECULAR BIOLOGY 
DEPARTMENT OF ECOLOGY ANO evolutionary BIOLOGY - DEPARTMENT OF EXPERIMENTAL BIOLOGY 
