This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Morris, C. F. Articles by Rownd, R. Search for Related Content PubMed PubMed Citation Articles by Morris, C. F. Articles by Rownd, R.

 Previous Article  |  Next Article 

J Bacteriol. 1974 June; 118(3): 867-879
Copyright © 1974 American Society for Microbiology. All Rights Reserved.

Transition of the R Factor R12 in Proteus mirabilis

^a Laboratory of Molecular Biology and Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706

ABSTRACT

When Proteus mirabilis harboring the R factor R12 (a round of replication mutant of the R factor NR1) is cultured in medium containing streptomycin there can be an amplification in the number of copies of r-determinants per cell and the formation of enlarged polygenic R factors containing repeated sequences of r-determinants as well as polygenic molecules consisting of repeated sequences of r-determinants. This phenomenon has been referred to as the "transition." When transitioned cells are then cultured in drug-free medium, within a few generations two distinct density species of R factor deoxyribonucleic acid (DNA) are observed in a CsCl density gradient: a 1.712 g/ml band of covalently closed circular R factor DNA consisting of one transfer factor (RTF-TC) plus one r-determinant and a 1.718 g/ml band consisting of repeated sequences of r-determinants. The RTF-TC component of the R factor appears to control the replication of all the R factor DNA which is attached to it. In the autonomous state, however, polygenic sequences of r-determinants do not appear to replicate under the same control mechanism as when they are attached to an RTF-TC.

¹ Present Address: Department of Biochemical Sciences, Frick Chemical Laboratory, Princeton University, Princeton, N. J.