Effects of rifampicin on the relationship of R6K replicating forms to the folded chromosomal complex of Escherichia coli.

An examination of the relationship of R6K plasmic DNA to the folded chromosome has shown that replicating forms of this plasmid, when compared to the non-replicating forms, were preferentially associated to the apparently mediated by RNA molecules. In this report we show that inhibition of RNA synthesis with rifampicin prior to pulse-labeling cells harboring R6K plasmid DNA resulted in the release of the replicating forms. Analyses of the single-stranded length of rifampicin-released nascent molecules indicate that continuous replication of R6K plasmid DNA to unit length was not affected by the presence of rifampicin. Thus, it appears that complexing was not required for continued synthesis of this plasmid. Further, the inhibition of protein synthesis does not appear to alter the complexing frequency of R6K plasmid DNA to the folded structure. These results suggest that active RNA synthesis is required for maintaining the association of the replicating forms to their replicational site(s).